Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSJEEP1987WAGONEER BASE, 4.0 M, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMFUEL INJECTION SYSTEM - DIESELTESTINGINJECTORS
1987 Jeep Wagoneer Base, 4.0 M, Automatic
Fuel Injection System - Diesel: Testing: Injectors
1987 Jeep Wagoneer Base, 4.0 M, AutomaticSECTION Injectors
- Remove injectors from engine. Check injectors for erosion (due to unfiltered air particles), carbon build-up, or Blue-colored tip (caused by excessive engine heat). Replace any damaged injectors as necessary.
- Fill reservoir of Bosch Nozzle Pressure Tester (EFEP60H) with clean test oil. Connect injector and holder assembly to tester. Close pressure gauge valve. Quickly operate tester lever 8-10 times to bleed air from tester.CAUTION: DO NOT allow test oil to be sprayed onto hands or fingers while testing. High pressure from nozzle spray can penetrate skin, which could cause blood poisoning.
- Open pressure gauge valve 1/4 turn. Slowly operate tester (one pump/second), noting pressure required to open nozzle. Nozzle opening pressure should be 1885-2001 psi (133-141 kg/cm2 ). Injectors with incorrect opening pressure should be replaced.
- Slowly operate tester and note spray pattern of each injector. Spray should emerge at a straight angle, and should have an even, finely atomized pattern. Replace any injectors that do not have correct spray pattern. A "whistling" sound, produced during testing, is a normal condition.
- Slowly operate tester until pressure reading is 290 psi (20 kg/cm2 ) below normal opening pressure. Hold pressure at that point for 10 seconds. No fuel should drip from nozzle. If leakage occurs during 10 second period, replace injector. A slight wetting of nozzle tip is normal.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.