Isuzu 4HK1 / 6HK1 — Compression pressure inspection
Testing & diagnosis · Cylinder / compression
For the Isuzu 4HK1 / 6HK1, from the Isuzu service manual.
Applies to: Isuzu 4HK1, Isuzu 6HK1
Before you start
- To keep engine speed at 200 rpm or more, use fully charged batteries.
- ECM records a DTC when the harness connector is removed; clear ECM memory after measurement.
Procedure
- Warm-up the engine.
- Remove the negative terminal of the battery and remove all glow plugs.
- Remove the harness connector for the fuel injector built on the lower head cover.
- Install the negative terminal of the battery.
- Turn on the starter to emit foreign matter within the cylinders.
- Install the adapter and gauge of a compression gauge of the special tool.
- Turn on the starter to inspect compression pressure; measure each cylinder one by one.
- Remove the compression gauge, remove negative battery terminal, install the fuel injector harness connector.
- Install all glow plugs and the negative battery terminal.
Tools required
- Compression gauge 5-8840-2675-0 (J-26999-12) Amazon
- Compression gauge adapter 4HK1: EN-46722 Amazon
- Compression gauge adapter 6HK1: 5-8840-2622-0 Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 4HK1 standard 2.84 – 3.24 MPa (412 – 469 psi) / 200 rpm
- 4HK1 limit 1.96 MPa (284 psi)
- 6HK1 standard 3.24 MPa (469 psi) / 200 rpm
- 6HK1 limit 2.26 MPa (327 psi)
- Differences among the cylinders 294 kPa (43)
Full service-parts list: Isuzu 4HK1 →, Isuzu 6HK1 →
Source: Isuzu service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.