latitud39

Hi guys, how much pressure should be for the fuel system for Cherokee 1996, 4.0L, 4x4, automativ tran (AW4)?. Thanks in advance and have a good time.

kearny

if ya got a mpi system 1995 and before it should be 31 psi with vacuum line on regulator and 39 when line is off.go get you a haynes manual.

extrashaky

Don't do that. Haynes manuals are useless.

Download a real factory service manual for your specific year from Pacific Coast Manuals. It's less than $10 for a PDF. Then you can search it and print the pages you want if you need hard copies.

As for the original question, IIRC the fuel rail pressure at idle should be 49 psi + or - 5 psi.

Larry's XJ

Nice first post

Firehawk068

FUEL PUMP PRESSURE TEST - 4.0L ENGINE

NOTE: The fuel pressure test port is used on certain engines only. If equipped, the test port will be located on the fuel rail Fuel Injectors - Typical - 4.0L Shown A sealing cap is screwed onto the test port.
NOTE: The vacuum assisted fuel pressure regulator located at the front of the fuel rail is no longer used on any engine.
All fuel systems are equipped with a fuel tank module mounted, fuel pressure regulator. The fuel pressure regulator is not controlled by engine vacuum.
With engine at idle speed, system fuel pressure should be 338 kPa ± 14 kPa (49.0 psi ± 2 psi)
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO THE ENGINE INTAKE OR EXHAUST MANIFOLDS. PLACE SHOP TOWELS UNDER AND AROUND THE PRESSURE PORT TO ABSORB FUEL.
WARNING: WEAR PROPER EYE PROTECTION WHEN TESTING FUEL SYSTEM PRESSURE.

1. Remove the protective cap at the fuel rail test port. Connect the 0 - 414 kPa (0-60 psi) fuel pressure gauge (from gauge set 5069) to the test port pressure fitting on the fuel rail Fuel Pressure Gauge Installation - Typical Test Port Shown
2. Start the engine and note pressure gauge reading. Fuel pressure should be 338 kPa ± 14 kPa (49.0 psi ± 2 psi) at idle.
3. If pressure is at O psi, connect DRB scan tool and refer to operating instructions in the appropriate Powertrain Diagnostics Procedures service manual.
4. If operating pressure is above 51.0 psi, fuel pump is OK but pressure regulator is defective. Regulator is not serviced separately. Replace fuel pump module assembly.

kearny

i agree,not the greatest, all i got,will be sure to check out pacific coast.i have other issues haynes is useless for.thanks for the help.is my pressure ok at 39?

kearny

so does that mean i should scrap my regulator on the rail since they are not used anymore

Firehawk068

Ah, no, the test I posted is for a '96 (the OP stated '96 fuel pressure)


'96-up 4.0 engines didn't have a regulator mounted on the fuel rail.


'95-earlier 4.0 engines also use a lower fuel pressure.

Mikel Ezcurra

Hello, I have a random starting and stalling problem in my 96 Cherokee. I put a fuel gauge on it and I get 49 PSI at idle and under load it dips below 40 PSI.
When the engine is shut off, it bleeds about 1 PSI per minute. Fuel filter is new. Does this mean that the pump is bad?
Thank you

awg

It could mean you have a leaking injector..I would search for that topic, seen posts on here how to differentiate a bad injector from pump, there is a check valve in the pump too