Home›Engines›Kubota V1903B

Kubota V1903B Engine

Name: Kubota V1903B Engine
Brand: Kubota

The Kubota V1903B is a 1.86 L 4-cylinder 4-stroke cycle, indirect injection, water cooled diesel engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the MDKAD and MDKB. It holds 7.6 L (2.0 gal) of oil and 7.6 L (2.0 gal) of coolant.

Also known as: Kubota V1903B

1.857 L

Displacement

Cylinders

1800 rpm

Rated speed

7.6 L

Oil capacity

On this pageService parts Specs Generator sets Maintenance Filter cross-reference FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Service parts for the V1903B

The cheapest captured merchant offer per filter — see the full cross-reference below for every OEM/aftermarket option.

Air intake

1 required

RG64842831Air filtersee priceAmazon

Fuel system

1 required

607Fuel filterfind

Oil system

1 required

87415600Oil filter$8.98PartsGeek

Prices captured from merchant listings; some links are affiliate links. Verify against your serial number before ordering.

Engine specifications

Oil capacity	7.6 L
Coolant capacity	7.6 L
Displacement	1.857 L
Cylinders	4
Aspiration	4-Stroke Cycle, Indirect Injection, Water Cooled Diesel
Rated speed	1800 rpm

Generator sets powered by this engine

Cummins/Onan MDKAD Cummins/Onan MDKB

How to read your Kubota engine serial & model number →

Common problems

HIGH ENGINE TEMPERATURE 1
Fix: 1. Add coolant as necessary and repair leaks (Page 18). 2. Replace the engine thermostat, which might not be opening fully (Page 21). 3. Clean the raw water tubes in the heat exchanger, which might be clogged with scale (Page 22). 4. Flush the coolant system to remove coolant passage fouling (Page 18).
UNDERVOLTAGE 13
Fix: Reduce the number of connected appliances, especially when air conditioners and battery chargers are running.
UNDERFREQUENCY—Engine governor unable to maintain rated frequency CODE NO. 15
Fix: 1. Reduce the number of appliances running at the same time, especially those with high motor starting loads such as air conditioners. 2. Check the fuel tank and fill as necessary. (Note: The arrangement of pickup tubes in the fuel supply tank probably is such that the genset will run out of fuel before the propulsion engines.) 3. Remove any blockage in the combustion air inlet (front grille) or exhaust system. 4. Tighten loose fuel line fittings so that air cannot be drawn in by genset lift pump suction. 5. Drain and/or replace the fuel filter (Page 16) and prime the fuel system (Page 8). 6. Drain and/or replace fuel supply system filters and prime the fuel system (Page 8).
Underfrequency 15
Fix: Check engine speed, loads, governor actuator operation, fuel supply, control plugs fully seated, quad leads fully seated in connector to control, quad winding resistance
THE STARTING BATTERIES DO NOT MAINTAIN A CHARGE (Marginal battery, battery connections or charging system)
Fix: 1. Service as necessary by cleaning and tightening battery connections, recharging or replacing the battery or replacing damaged battery cables (p. 4-2). 2. Check the V-belt that drives the charging alternator and service as necessary (p. 4-13). 3. Check for and disconnect parasitic battery loads.
THE STARTING BATTERIES DO NOT MAINTAIN A CHARGE
Cause: Marginal battery, battery connections or charging system
Fix: 1. Service the battery as necessary by cleaning and tightening connections, recharging or replacing the battery or replacing damaged battery cables (p. 4-3). 2. Check for and disconnect parasitic battery loads.
THE STARTER ENGAGES AND DISENGAGES (Low cranking voltage)
Fix: 1. De-energize the PTO clutch, if so equipped. 2. Service as necessary by cleaning and tightening battery connections, recharging or replacing the battery or replacing damaged battery cables (p. 4-2).
THE STARTER ENGAGES AND DISENGAGES
Cause: Low cranking voltage
Fix: 1. Push the generator set line circuit breaker OFF. 2. Service the battery as necessary by cleaning and tightening connections, recharging or replacing the battery or replacing damaged battery cables (p. 4-3).
The genset shuts down.
Fix: See Troubleshooting (Section 9).
The genset shuts down
Fix: See Troubleshooting (Page 7-1).
The genset fails to start
Cause: Cranking will discontinue in 20 to 60 seconds, depending on how cold the engine is, and the amber status lamp will blink Shutdown Code No. 4 (Page 7-5). See Troubleshooting (Page 7-1) if the genset does not start after two or three tries.
The genset does not start after several tries. Fault Code No. 4
The generator set does not start after several tries. Fault Code No. 4
The e-Series Digital Display and/or control switch status lamp will indicate the numeric fault code.
Fix: See Troubleshooting (Section 9).
The Digital Display will display the fault indefinitely.
Fix: Touch any button to clear the fault. The Digital Display will turn off in 5 minutes after the fault has been cleared.

Compiled from service & troubleshooting documentation across every generator set that uses the Kubota V1903B.

Maintenance schedule

Item	Spec	Capacity	Part #
Air filter			—
Fuel filter	Lubricate new element and gasket and fill element with clean diesel fuel; hand tighten		—
Oil filter	Tighten an additional 3/4 turn after gasket contacts mounting pad		87415600	Amazon eBay $14.99 PartsGeek $8.98 KuduParts $18.00
Battery	Sealed, maintenance-free recommended; keep terminals clean and tight		—
Belt	Deflection 0.4 inch (10 mm) at 20 lbs (10 kg) applied at middle of pulley span		—
Coolant	Engine coolant	7.6 L	—
Coolant filter			—
Oil	Lube oil	7.6 L	—
Spark plug			—

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Service intervals

Item	Action	Hours	Months	Notes
Check Engine Oil Level	Check	8 hr
Coolant level	Check	8 hr
Drain Water from Fuel Filter	Drain	8 hr
Engine oil level	Check	8 hr		Every Day/8 Hrs (Table 4-1)
Exhaust system	Check	8 hr
Exhaust system	Inspect	8 hr		Look over entire exhaust system and listen for leaks every startup and after every eight hours of operation
Fuel Filter	Drain	8 hr
Fuel Filter Water	Drain	8 hr
Fuel level	Check	8 hr
General Inspection	Check	8 hr		Daily, 8-Hr; includes Oil Level, Coolant Level, Fuel System, Exhaust System, Battery, and Sea Water Strainer Checks.
General Inspection	Inspect	8 hr		Includes inspection of oil level, coolant level, fuel system, exhaust system, batteries and battery connections; before first start of day and after every 8 hours
General Inspection (Oil Level, Coolant Level, Fuel System, Exhaust System, Battery, Sea Water Strainer)	Check	8 hr		Every day, all models (MDKBH, MDKBJ, MDKBW, MDKB & MDKD, MDDCX)
General Inspection (oil, coolant, fuel, exhaust, batteries)	Inspect	8 hr		every day / before first start of the day
Generator set	Inspect	8 hr		General Inspection before first start of the day and after every 8 hours of operation; includes oil level, coolant level, fuel system, exhaust system, batteries and battery connections
Genset	Inspect	8 hr		Check for oil, fuel, coolant and exhaust system leaks
Oil level	Check	8 hr
Change Engine Oil and Oil Filter - All except MDKBT & MDKBU	Change	50 hr		First service — after first 50 hrs, then every 200 hrs/year
Change Engine Oil and Oil Filter - Only MDKBT & MDKBU	Change	50 hr		First service — after first 50 hrs, then every 200 hrs/year
Engine Oil and Oil Filter (All except MDKBT & MDKBU) - after first 50 hours	Change	50 hr		First service — Break-in oil change; also change the oil and oil filter after the first 50 hours of operation on a new or re-built engine.
Engine Oil and Oil Filter (Only MDKBT & MDKBU) - after first 50 hours	Change	50 hr		First service
Engine oil and oil filter - all except MDKBT & MDKBU	Change	50 hr		First service — After first 50 hours of operation; then per Table 4-1
Engine oil and oil filter - only MDKBT & MDKBU	Change	50 hr		First service — After first 50 hours of operation; then per Table 4-1
Battery	Check	100 hr	1 mo	See battery manufacturer's recommendations
Battery and Battery Connections	Inspect	100 hr	1 mo	See battery manufacturer's recommendations.
Check V-Belt Tension	Check	100 hr		check for slippage, cracking and wear
Engine Oil and Oil Filter (All except MDKBT & MDKBU)	Change	100 hr	1 mo	First service — Perform twice as often when using high sulfur fuel.
Fuel Filters	Drain	100 hr	1 mo	Every Month / 100 Hrs
Genset	Clean	100 hr	1 mo	Do not clean while running
Inspect Battery and Battery Connections	Inspect	100 hr		monthly
Siphon Break	Check	500 hr	12 mo	Monthly, 100-Hr
Siphon Break	Inspect	100 hr	1 mo	Every Month / 100 Hrs
Water from Fuel Filter	Drain	100 hr	1 mo	Every Month/100 Hrs
Water in Fuel Filter	Drain	100 hr		Every Month / 100 Hrs
Water in fuel	Drain	100 hr	1 mo
Zinc Anode	Inspect	500 hr	1 mo	Replace as recommended.
Zinc Anode	Replace	500 hr	12 mo	Monthly, 100-Hr; Model MDKAU does not have a zinc anode to replace.
Brushes & Slip Rings	Check	200 hr		Yearly, 200 Hrs (MDKBH, MDKBJ, MDKBW only); must be performed by trained mechanic; not applicable to other listed models (—)
Engine Oil and Oil Filter	Change	200 hr	12 mo	First service — Every Year/200 Hrs
Engine Oil and Oil Filter (Only MDKBT & MDKBU)	Change	200 hr	12 mo	First service — Perform twice as often when using high sulfur fuel.
Engine Oil and Oil Filter—All except MDKBT & MDKBU	Change	200 hr		First service — After first 50 hrs, then every year/200 hrs

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Exhaust piping minimum clearance from combustible construction	9	inches (229 mm)
Clearance	Minimum clearance, non-service sides	2	inches (51 mm)
Clearance	Sound shield end clearance for air flow	1	inches (25 mm)
Clearance	Sound shield top clearance to open service door latches	2	inches (51 mm)
Clearance	V-Belt Tension Deflection	0.4	inch (10 mm) @ 20 lbs (10 kg)
Clearance	V-belt deflection	3/8	inch (10 mm) at 20 lbs (10 kg) applied
Clearance	V-belt deflection at 20 lbs (10 kg)	3/8 inch (10 mm)	in (mm)	tension check at middle of pulley span
Clearance	V-belt deflection at middle of pulley span	3/8 inch (10 mm)		with 20 lbs (10 kg) applied
Clearance	Valve Lash (cold) - D1105/V1505/V2003M/V2403M	0.0071-0.0087	in (0.18-0.22 mm)	cold
Clearance	Valve Lash (cold) - V3300-E2B	0.009-0.010	in (0.23-0.27 mm)	cold
Compression	Compression Ratio (MDKAV/MDKAW/MDKAZ)	22:1
Compression	Compression Ratio (MDKBD/MDKBE/MDKBF)	23:1
Gap	V-belt deflection	0.4	inch (10 mm)	20 lbs (10 kg) applied to middle of pulley span
Injection timing	Fuel Injection Timing	12 deg BTDC	deg BTDC
Injection timing	Fuel Injection Timing	13.5-15 deg BTDC	deg BTDC
Injection timing	Fuel Injection Timing	14.25-15.75 deg BTDC	deg BTDC
Injection timing	Fuel Injection Timing	14.75-16.25 deg BTDC	deg BTDC
Injection timing	Fuel Injection Timing	15.5 - 17.5	° BTDC
Injection timing	Fuel Injection Timing	18° – 20°	BTDC
Injection timing	Fuel Injection Timing - D1105	14.75-16.25	° BTDC
Injection timing	Fuel Injection Timing - V1505	14.25-15.75	° BTDC
Injection timing	Fuel Injection Timing - V2003M	13.5-15	° BTDC
Injection timing	Fuel Injection Timing - V2403M	13.5-15	° BTDC
Injection timing	Fuel Injection Timing - V3300-E2B	12	° BTDC
Injection timing	Fuel injection timing	12	degrees BTDC
Injection timing	Fuel injection timing	14.5	degrees BTDC
Injection timing	Fuel injection timing	16	degrees BTDC
Injection timing	Fuel injection timing	16.5	degrees BTDC
Injection timing	Fuel injection timing	18 - 20	degrees BTDC	timing marks line up at 19 degrees BTDC
Other	Battery cable gauge	1	AWG	total cable length 22 ft (6.7 m); approx. diameter 9.43 mm
Other	Battery cable gauge	1/0	AWG	total cable length 30 ft (9.1 m); approx. diameter 9.46 mm
Other	Battery cable gauge	2	AWG	total cable length 18 ft (5.5 m); approx. diameter 7.42 mm
Other	Battery cable gauge	3	AWG	total cable length 14 ft (4.3 m); approx. diameter 6.61 mm
Other	Battery cable gauge	4	AWG	total cable length 10 ft (3 m); approx. diameter 5.88 mm
Other	Compression Ratio	22.8:1
Other	Compression Ratio	24.3:1
Other	Compression Ratio	24:1
Other	Compression ratio	22.5:1
Other	Compression ratio	22:1
Other	Compression ratio	23:1
Other	Firing order (clockwise rotation)	1-2-3
Other	Firing order (clockwise rotation)	1-2-4-3
Other	Firing order (clockwise rotation)	1-3-4-2
Other	Firing order (clockwise rotation)	1-3-5-4-2
Other	Fuel Injection Order (Firing Order, clockwise rotation)	1-2
Other	Fuel pump delivery (test)	2/3	liter per minute	prime test, 1 liter container
Other	High AC Frequency shutdown (Code 14)	70 Hz for 40 ms, or 2% over nominal for 6 seconds		after starter engaged
Other	Low AC Frequency shutdown (Code 15)	90	% of nominal for more than 8 seconds	during normal operation
Other	Maximum Angularity	10 deg Continuous, 22.5 deg Intermittent	deg
Other	Maximum angularity	10 continuous, 22.5 intermittent	degrees
Other	Maximum angularity	10 degrees continuous, 22.5 degrees intermittent
Other	Minimum CCA rating SAE at 32 F (0 C)	360	amps
Other	Minimum CCA rating SAE at 32 F (0 C)	500	amps
Other	Minimum CCA rating SAE at 32 F (0 C)	625	amps
Other	Preheat duration prior to cranking (maximum)	15	seconds	engine temperature dependent
Pressure	Cooling system pressure	10	psi
Pressure	Cooling system pressure	7	psi
Pressure	Cooling system pressure (pressure cap)	10	psi
Pressure	Cooling system pressure (pressure cap)	7	psi
Pressure	Engine oil pressure (normal)	194 - 442	kPa	normal operating temperature

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Ambient	Capacity	Notes
Coolant	50/50 water/ethylene glycol			2.1 L	MDKBH; also stated as 2.2 Qt
Coolant	Fleetguard ES Compleat / EG Premix antifreeze (ethylene glycol based)				Purple coloured viscous liquid; boiling point 107 C, flash point 121 C.
Coolant	Fleetguard ES Compleat and EG Premix (ethylene glycol based)
Coolant	50/50 ethylene glycol/water	ASTM D5345 (prediluted) or ASTM D4985 (concentrated, 40-60% quality water)	above -37°C		Protects to -34°F (-37°C)
Coolant	50/50 mixture of water and ethylene glycol	ASTM D5345 for 50/50 prediluted coolant or ASTM D4985 for concentrated coolant with 40% to 60% quality water	above -37°C		Protection from freezing down to -34 F (-37 C); use fresh low-mineral water, distilled best. Coolant capacity: 4.0 liter MDKBK/MDKBL; 5.0 liter MDKBM/MDKBN; 7.6 liter MDKBP/MDKBR/MDKBS; 13.7 liter MDKBT/MDKBU
Coolant	50/50 mixture of water and ethylene glycol (best quality)	Fully formulated with rust inhibitors and coolant stabilizers; not with stop-leak additives; use distilled water	above -37°C	7.6 L	Good for -34° F (-37° C); ethylene glycol antifreeze is considered toxic
Coolant	50/50 mixture of water and ethylene glycol antifreeze, fully formulated with rust inhibitors and coolant stabilizers	ASTM D5345 for 50/50 prediluted coolant or ASTM D4985 for concentrated coolant with 40% to 60% quality water	above -37°C		50/50 mixture gives protection from freezing down to -34 F (-37 C); use fresh water low in minerals and corrosive chemicals (distilled best)
Coolant	Ethylene glycol antifreeze, 50/50 mixture of water and ethylene glycol	ASTM D5345 for 50/50 prediluted coolant or ASTM D4985 for concentrated coolant with 40% to 60% quality water	above -37°C		Provides protection from freezing down to -34 F (-37 C). Use fresh water low in minerals; distilled water is best. Fully formulated with rust inhibitors and coolant stabilizers.
Coolant	Ethylene glycol antifreeze, fully formulated with rust inhibitors and coolant stabilizers; 50/50 mixture of water and ethylene glycol		above -37°C	2.1 liter	Protection from freezing down to -34°F (-37°C); use fresh water low in minerals, distilled best
Coolant	ethylene glycol antifreeze, 50/50 mixture with water		above -37°C		Good to -34F (-37C)
Coolant	ethylene glycol antifreeze, 50/50 mixture with water for freeze protection to -34°F (-37°C)	ASTM D5345 (50/50 prediluted) or ASTM D4985 (concentrated, 40-60% quality water)	above 37°C		distilled water best
Engine oil	15W40			2.1 L	MDKBH; also stated as 2.2 Qt. Shipped with 15W40 engine oil.
Engine oil	API CH-4 or better, SAE 15W-40 recommended year-round	API/SAE			Synthetic motor oil not recommended
Engine oil	API Service Category CI-4 or better; SAE 15W-40 recommended year-round	API			choose viscosity per Figure 3-1 ambient chart
Engine oil	Multigrade oils such as SAE 15W-40 recommended for year-round use; choose SAE viscosity grade per ambient temperature (Figure 3-1)	API Service Category CI-4 or better			4.0 L for MDKBK/MDKBL; 4.3 L for MDKBM/MDKBN; 7.6 L for MDKBP/MDKBR; 12 L for MDKBS; 10.4 L for MDKBT/MDKBU
Engine oil	Premium Blue E 15W40			2.1 L (2.2 qt)	Lubricant oil - Premium Blue E 15W40
Engine oil	SAE 15W-40 (multi-grade recommended for year-round use)	API Class CG-4, CF-4, CF or better		7.6 L (MDKAD, MDKAE)	Choose viscosity grade per Figure 2 for ambient temperature range; MDKAF capacity 13 qt (12 L)
Engine oil	SAE 15W-40 (multigrade recommended for year-round use); choose viscosity grade for ambient temperature (Figure 3-1)	API Service Category CI-4 or better
Engine oil	SAE 15W-40 (multigrade) recommended for year-round use	API Service Category CI-4 or better		2.1 liter	Choose viscosity grade appropriate for ambient temperatures expected until next scheduled oil change
Engine oil	SAE 15W-40 multi-grade recommended for year-round use	API Service Category CI-4 or better		2.1 liter	Choose viscosity grade appropriate for ambient temperatures expected until the next scheduled oil change (Figure 3-1)
Engine oil	SAE 15W-40 multigrade recommended; choose viscosity grade per ambient temperature (Figure 3-1)	API Service Category CI-4 or better			Lube oil capacity: 4.2 quart (4.0 liter) MDKBK/MDKBL; 4.5 quart (4.3 liter) MDKBM/MDKBN; 8 quart (7.6 liter) MDKBP/MDKBR; 12.7 quart (12 liter) MDKBS; 11 quart (10.4 liter) MDKBT/MDKBU. Add 1 quart (0.9 liter) when level falls to ADD mark.
Fuel	Gas Oil (red diesel, fuel oil, type A1 or A2)	USCG TYPE A1 or ISO 7840-A1 fuel hoses
Fuel	Grade 2-D diesel fuel	EN 590 or ASTM D975			Use Grade 1-D diesel fuel if fuel tank is exposed to temperatures below 40 degrees F (5 degrees C); cetane number not less than 45; sulfur content not more than 0.5 percent by weight; lubricity min load level 3100 grams (ASTM D6078) or max scar diameter 0.45 mm (ASTM D6079 or ISO 12156-1)
Fuel	Grade 2-D diesel fuel (Grade 1-D if tank exposed below 40 F (5 C))	EN 590 or ASTM D975; Cetane number not less than 45; sulfur content not more than 0.5 percent by weight			Fuel lubricity: minimum load level 3100 grams per ASTM D6078 or maximum scar diameter 0.45 mm per ASTM D6079 or ISO 12156-1
Fuel	Grade 2-D diesel; Grade 1-D if tank exposed below 40°F (5°C); Cetane ≥45, sulfur ≤0.5% by weight	EN 590 or ASTM D975			B5 Bio-Diesel meeting industry spec is suitable
Fuel	High quality Grade 2-D diesel fuel; use Grade 1-D below 40 F (5 C)	EN 590 or ASTM D975			Cetane number not less than 45; sulfur not more than 0.5 percent by weight; cloud point at least 10 F (6 C) below lowest expected fuel temperature; lubricity min load 3100 grams per ASTM D6078 or max scar 0.45 mm per ASTM D6079/ISO 12156-1; ULSD and B5 bio-diesel suitable
Fuel	High quality Grade 2-D diesel fuel; use Grade 1-D if fuel tank exposed to temperatures below 40°F (5°C)	EN 590 or ASTM D975			Cetane number not less than 45; sulfur content not more than 0.5 percent by weight; fuel lubricity min 3100 grams per ASTM D6078 or max scar diameter 0.45 mm per ASTM D6079/ISO 12156-1
Fuel	No. 2 diesel				Grade stated for fuel consumption ratings; recommended fuels are in the Operator's Manual.
Fuel	No. 2 diesel (ASTM Grade 2-D)	ASTM			Cetane number not less than 45, sulfur content not more than 0.5% by weight
Fuel	No. 2 diesel fuel				Typical fuel consumption values are for No. 2 diesel fuel

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Severity	Action
1	One blink	Shutdown due to high engine temperature	Shutdown	Open sea valve; clean sea water strainer; check coolant level and repair leaks; check/replace raw water hoses; readjust a loose pump belt (p. 4-9); replace worn raw water impeller (p. 4-10); clean heat exchanger (p. 4-12); check through-hull; drain/clean cooling system (p. 4-6); replace coolant thermostat (p. 4-8); tighten coolant sender E2 ring terminal; test/replace sender E2; check continuity Pin 9 to E2
12	Overvoltage	Output voltage jumped to more than 125% of rated for 75 ms or more than 115% of rated for 3 s after voltage regulation enabled	Shutdown	See an authorized Onan service representative.
13	Undervoltage	Output voltage fell to less than 90% of rated for 5 seconds after voltage regulation enabled	Shutdown	Turn line breaker OFF, disconnect PTO, reduce loads; fill fuel tank; check fuel fittings and filters; replace fuel filters.
14	Overfrequency	Frequency jumped to more than 70 Hz for 40 ms or more than 2% over nominal for 6 seconds	Shutdown	Reset breaker after starting, tighten fuel fittings, prime fuel system
15	Underfrequency	Frequency fell to less than 90% of nominal for more than 8 seconds during normal operation	Shutdown	Turn breaker OFF, de-energize PTO, reduce loads; fill fuel; prime fuel system; remove air/exhaust blockages; check fuel fittings; replace fuel filters; check for contaminated fuel.
17	Overprime	Prime mode exceeded 5 minutes	Shutdown	Remove object holding control switch in prime position
2	Two blinks	Two blinks indicate shutdown due to low oil pressure.	Shutdown	Check oil level; tighten sender E1 ring terminal; check sender E1 resistance and replace if necessary; check continuity Pin 10 to E1; replace sender with a gauge and service the engine lubrication system if oil pressure is less than 14 psi (98 kPa)
22	Governor Overload	Maximum allowable time at full-duty cycle was exceeded	Shutdown	Reduce the number of appliances running at the same time; check the fuel tank and fill; remove any blockage in the combustion air inlet or exhaust system; check fuel fittings for leaks and reprime; replace the fuel filters and reprime.
23	Faulty Oil Pressure Sender	Controller sensed grounded sender	Warning	Tighten the ring terminal on sender E1; check continuity between Pin 10 and ring terminal E1-1; test sender E1 and replace as necessary; replace the genset controller
24	Faulty Temperature Sender	Controller sensed open sender	Warning	Tighten the ring terminal on sender E2; check continuity between Pin 9 and ring terminal E2-1; test sender E2 and replace as necessary; replace the genset controller
27	Loss of Voltage Sense	The genset Controller lost VAC sensing during normal voltage regulation when the field was functioning normally and frequency was at least 40 Hz	Shutdown	See an authorized Onan service representative.
29	High Battery Voltage	During startup the genset Controller sensed that battery system voltage was greater than 19.2 volts	Warning	Check battery voltage, battery connections, battery charge rate.
3	Three blinks	Three blinks indicate shutdown requiring service by trained and experienced service personnel.	Warning	See Troubleshooting in the Operator's Manual
32	Starting Fault	The genset Controller could not detect cranking speed (quadrature zero crossings) for 3 seconds	Shutdown	Have the propulsion engines running while trying to start the genset; service the battery; change to oil of proper viscosity for the ambient temperature.
35	Control Card Failure–EE	Microprocessor EEPROM error during self-test	Shutdown	Verify fault.
36	Unknown Shutdown	The genset Controller declared this fault because engine speed fell below 1000 RPM for 0.5 seconds, though not by genset or engine control action	Shutdown	Reduce the number of loads on the genset; check fuel level and refill; prime the fuel system for at least 30 seconds; check fuel fittings for leaks and reprime; replace the fuel filters and reprime.
37	Invalid Set Configuration	The genset controller is not configured properly for the genset	Warning	See an authorized Onan service representative.
38	Field Overload	High field voltage induced by high rotor temperature or low power factor loads	Shutdown	Remove generator air flow blockages; reduce appliances; have air conditioners and other appliances checked.
4	Overcrank	Shutdown due to a failure to start within the time allowed for cranking	Shutdown	Push line circuit breaker OFF; check fuel tank and fill; remove combustion air or exhaust blockages; open closed fuel valves; prime the fuel system at least 30 seconds; service the battery; check all fuel filters and fittings and reprime; replace fuel filters; change to proper oil viscosity; conduct fuel pump test; inspect glow plugs; service fuel injectors and worn engine
41	Grounded Rotor	F+ grounded	Shutdown	Verify fault.
42	Processor Failure	Microprocessor ROM error during self-test	Shutdown	Verify fault.
43	Processor Failure	Microprocessor RAM error during self-test	Shutdown	Verify fault.
45	Speed Sense Lost	Controller lost speed sense (quadrature zero crossings) for 0.25 seconds after start disconnect	Shutdown	See an authorized Onan service representative.
46	Genset Overload	The genset Controller shutdown the genset because engine load exceeded 135 percent of genset rating for 10 seconds	Shutdown	Reduce the number of loads on the genset.
48	Processor Failure	Controller unable to sense field voltage	Shutdown	Verify fault.
5	Warning—Shutdown Due to Vessel CO	Shutdown due to Vessel CO	Warning	Get everyone out into fresh air immediately and seek medical attention.
57	Overprime	A local or remote control switch was held in the Prime position for more than 5 minutes	Warning	Remove object holding switch in prime position, replace faulty control switch
58	High Exhaust Temperature	Exhaust temperature rises because of loss of water	Shutdown	Reconnect/replace raw water hoses, replace impeller
59	Low Coolant Level	The engine coolant level fell below the optional coolant level sensor	Warning	Add coolant, repair leaks
61	External Shutdown	The generator set was shut down by a fire suppression system or other external control	Shutdown	Make necessary repairs and reset the external control which shut down the genset
7	Seven blinks	Water stops flowing	Shutdown	Open the sea cock; check for and clean a blocked sea water strainer; check for kinked or leaking hoses; check/replace the raw water impeller; check the hull through-hull fitting for blockage.
Code No. 5	Warning - Shutdown due to Vessel CO	Shutdown occurring due to the vessel CO detector	Warning	All status indicator lights in the control circuit will also blink the fault code. See Troubleshooting Chapter of the Operator Manual.
Code No. 61	Emergency Shutdown	Shutdown occurring due to external emergency shutdown device	Shutdown	All status indicator lights in the control circuit will also blink the fault code. See Troubleshooting Chapter of the Operator Manual.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

Adjusting High-Idle Speed adjustment

⚠ Keep your hands away from the engine belt and pulleys.

⚠ The actuator could overheat if the battery is left on more than 10 minutes.

⚠ Be prepared to clamp off supply and return fuel lines to stop the engine.

Tools: strobe or injector clamp-on tachometer, 12 volt battery, battery switch

Adjust the speed control lever stop.
Measure engine speed with a strobe or injector clamp-on type tachometer.
Remove the front and top access doors and loosen the front/left side panel assembly for access to the speed adjusting screw.
Disconnect the actuator leads and connect a 12 volt battery to the actuator terminals using a battery switch.
Switch the battery on, start the genset, measure engine speed (rpm) and stop the engine by switching off the battery.
Loosen the lock nuts on the two bottom screws and back out the clamping screw if speed is not between 3300 and 3400 rpm.
To increase speed turn the speed adjusting screw in 1 turn clockwise; to decrease turn it out 1 turn counterclockwise.
Repeat until high-idle speed is between 3300 and 3400 rpm and set the lock nut.
Run the clamping screw in by hand until snug, back it out 1-1/2 turns and set the lock nut.

Adjusting Speed Control Lever Stop adjustment

⚠ Accidental or remote starting can cause severe personal injury; disconnect the negative battery cable.

Remove the front and top access doors and loosen the front/left side panel assembly so it can swing left.
Loosen the stop screw locknut and back the screw out a few turns.
Turn the stop screw in until it just makes contact and set the locknut.

Adjusting V-Belt Tension adjustment

⚠ Accidental or remote starting can cause severe personal injury or death.

Disconnect the negative cable at the battery.
Remove the belt guard or enclosure top panel and access doors.
Loosen the alternator pivot bolt first, then the adjusting bracket bolt on top.
Pivot the alternator out to tighten belt tension.
Check tension by applying 20 pounds (10 kg) to the middle of the pulley span.
Tighten alternator bolts when deflection is 3/8 inch (10 mm), secure guard and reconnect cables, negative last.

Adjusting Valve Lash adjustment

⚠ Do not use the fuel injection timing marks when adjusting valve lash.

Rotate the engine clockwise (looking from the front) until the intake valve push rod just stops moving down (valve closed).
Turn the engine one half turn more.
Adjust lash for both intake and exhaust valves of that cylinder.
Repeat this procedure for the other cylinder.

Adjusting Voltage Using Control Switch adjustment

Tools: separate voltmeter

Start the genset and let voltage and frequency stabilize for 5 to 10 seconds with all loads disconnected.
Rapidly press START 6 times during the first minute after startup to enter voltage adjust mode.
To adjust voltage up, press and quickly release START (about 0.6 volts per press).
To adjust voltage down, press and hold START for about 2 seconds (about 0.6 volts each press).
Wait about 20 seconds for the amber lamp to stop blinking, then press STOP to save the adjustment.
Restart the genset and check voltage.

Adjusting Voltage Using Digital Display adjustment

Start generator set and let voltage and frequency stabilize 5 to 10 seconds; disconnect all loads.
Rapidly press START 6 times during the first minute after startup to enter voltage adjust mode.
Press and quickly release START to increase voltage approximately 0.6 volts per press.
Press and hold START about 1 second to adjust voltage down.
Wait about 20 seconds for status to change from Volt Adj to Running, then press STOP to save.
Restart the generator set and check voltage; recalibrate AC voltage on the digital display.

Adjusting Voltage Using Optional Digital Display adjustment

Tools: Separate voltmeter

Start the genset and let voltage and frequency stabilize for 5 to 10 seconds; make sure all loads have been disconnected.
Rapidly press START 6 times during the first minute after startup to put the genset controller into voltage adjust mode.
To adjust voltage up, press and quickly release START; voltage increases approximately 0.6 volts each press and release.
To adjust voltage down, press and hold START for about 1 second; voltage decreases approximately 0.6 volts each press and release.
Wait about 20 seconds for the Display to indicate a Status change from Volt Adj to Running, then press STOP to stop the genset and save the adjustment.
Restart the genset and check voltage.
Recalibrate AC Voltage on the Digital Display as instructed in the Operator's Manual.

Changing Frequency adjustment

The genset control box has jumper leads marked HZ SEL and 60 HZ.
Connect for 60 HZ; disconnect for 50 HZ.
Apply the appropriate reconfiguration label over the 'As Manufactured' block on the nameplate.

Changing Generator Set Frequency adjustment

⚠ When changing frequency, make sure the line circuit breakers are suitable for the new output.

Remove the control box cover.
Connect J5 to P6 for 60 Hz.
Disconnect J5 from P7 for 50 Hz.
Apply the appropriate reconfiguration label.
Replace the control box cover.
Check and adjust voltage as necessary after the frequency has been changed.

Configuring the Controller Using Control Switch adjustment

⚠ In configuration mode the control will not start, prime or display faults.

Remove the insulating connectors from harness connectors CONFIG 1 and CONFIG 2 and connect them together.
Press START to increase the code number or STOP to decrease it one unit each press.
Set the configuration code number to 19 for this genset.
Verify the status lamp blinks one blink, pause, then nine blinks.
Disconnect CONFIG 1 from CONFIG 2 and re-install the insulating connectors.

Disabling Battery Charger adjustment

Disconnect the leads marked B1, B2 and B+ from the quick-connect terminals on battery charging voltage regulator.
Insulate the end of each lead with several wraps of listed electrical insulating tape and tie them neatly into the wiring harness.
Secure the access cover when done.

Drive Belt, Water Pump - Adjust / Replace adjustment

Disconnect and connect battery cables, engine wiring harness, fuel lines, exhaust hose, coolant hoses
Drain and refill engine fluids
Remove and install soundshield as needed
Remove and install pump drive belt
Adjust belt tension
Test run unit

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Connection	Leads	Notes
50 Hz: Disconnect J5 from P7	J5, P6, P7	Frequency selection jumper leads in the genset control box
60 Hz: Connect J5 to P6	J5, P6, P7	Frequency selection jumper leads in the genset control box
HZ SEL / 60 HZ jumper leads in the control box	HZ SEL, 60 HZ	Connect for 60 Hz; disconnect for 50 Hz. Apply the appropriate reconfiguration label. Generator reconnection per schematic on Page A-2.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Filters for this engine

Air filter: Kubota RG64842831 Kubota R141142289 Donaldson P821575 Donaldson P822858 Wix 46438NP Wix 42985
Fuel filter: Kubota 607 Donaldson P502161 Wix 33507
Oil filter: Kubota 87415600 Donaldson P550939 Wix 51307 Ac Delco PF13

Cross-referenced via Donaldson + OEM/engine-maker interchange — options to verify against your serial number, not confirmed for every exact variant.

Also used in

Kubota L3600DT — Tractor
Kubota L3600GST — Tractor
Kubota L3710DT — Tractor
Kubota L3710GST — Tractor
Kubota L3710HST — Tractor
Kubota L4310DT — Tractor

Other equipment known to use this engine, via filter-application cross-reference — useful for sourcing parts even when your exact machine isn't listed elsewhere on this page.

Common questions

What is the oil capacity of the Kubota V1903B?

The Kubota V1903B engine has an oil capacity of 7.6 liters.

What is the displacement of the Kubota V1903B?

The Kubota V1903B has a displacement of 1.857 liters with 4 cylinders.

Which generators use the Kubota V1903B engine?

The Kubota V1903B powers 2 generator set(s), including Cummins/Onan MDKAD, Cummins/Onan MDKB.

What oil filter does the Kubota V1903B use?

The Kubota V1903B uses oil filter part numbers Kubota 87415600, Donaldson P550939, Wix 51307.

What fuel filter does the Kubota V1903B use?

The Kubota V1903B uses fuel filter part numbers Kubota 607, Donaldson P502161, Wix 33507.

What air filter does the Kubota V1903B use?

The Kubota V1903B uses air filter part numbers Kubota RG64842831, Kubota R141142289, Donaldson P821575.

What is a common problem with the Kubota V1903B engine?

A commonly reported issue on generators using the Kubota V1903B is: HIGH ENGINE TEMPERATURE. Fix: 1. Add coolant as necessary and repair leaks (Page 18). 2. Replace the engine thermostat, which might not be opening fully (Page 21). 3. Clean the raw water tubes in the heat exchanger, which might be clogged with scale (Page 22). 4. Flush the coolant system to remove coolant passage fouling (Page 18)..