Engine seems to be starving for fuel...

[awg]

the FPR on a 95 is up beside the fuel rail.

I dont know much about them, I think they have 2 lines

must mean you have an OBD1 vehicle (no OBD2 port adjacent to left knee)

You can search how to diagnose this item probably by searching this forum, one of the US forums, or Google

Have you free downloaded the 95 FSM ?

[Classic Boy]

Originally Posted by tazwegion

Fuel pressure confirmed at 45-50psi at idle and higher RPM (FP tester arrived today), pressure drops off quickly when engine shut off, pressure drops quickly even when fuel line clamped (2 pairs of pliers) attempting to hold pressure in fuel rail.

They should be able to hold pressure for a few hours to a few days, a very minor drop off is ok but the rail should stay pressurized for a reasonable time. The pump maybe not up to the job anymore.

[tazwegion]

Originally Posted by awg

there seems to be a conflict in your answer, as you say "the original pump/sender was re-used", but the '96 has an integral in-tank sender/regulator

You seem to be suggesting there is an external regulator as well ?

The '96 unit is unique to that year

No conflict, the manufacturers design the auxiliary tanks to re-use the OEM fuel pump assembly.

Originally Posted by awg

the FPR on a 95 is up beside the fuel rail.

I dont know much about them, I think they have 2 lines

must mean you have an OBD1 vehicle (no OBD2 port adjacent to left knee)

Actually there's no FPR on the fuel rail (only 1 fuel inlet as well) see picture below, additionally there is an OBD port under the driver's side dash.


I checked the build sheet by VIN and it's listed as a 1996 XJ Cherokee, I do remember reading once (don't recall where) that too many Cherokee Chassis were found to have been built in late 1995 so Chrysler held them over till 1996 parked in the factory lot.

Originally Posted by Classic Boy

They should be able to hold pressure for a few hours to a few days, a very minor drop off is ok but the rail should stay pressurized for a reasonable time. The pump maybe not up to the job anymore.

That is why I pinched off the fuel line whilst I had someone shut off the engine, theoretically the rail should hold pressure when isolated unless an injector has stuck open, my next test will be to disconnect the fuel line and pressurise the fuel rail and injector assembly.

[LuluBelle]

check your sensor electrical plugs the 96 has a unique plug oval with round pins and 3 plugs going to the pcm earlier models had one pcm plug that should tell you if it's a real ob2 96 model

[tazwegion]

My PCM does have 3 plugs, additionally when I went to replace the Cam Position Sensor (under the distributor) the variant I required had 3 round pins not the square pin type on offer at Autobarn.

[LuluBelle]

Originally Posted by tazwegion

My PCM does have 3 plugs, additionally when I went to replace the Cam Position Sensor (under the distributor) the variant I required had 3 round pins not the square pin type on offer at Autobarn.

a 96 then

[tazwegion]

Well managed to independantly pressure test the fuel rail/injector assembly (holding 48psi), obviously I didn't adequately clamp the fuel line on the previous test, as the hose was hardened and beginning to perish it has now been replaced.

Next test (pump prime ignition on no run state) failed to achieve more than 10psi, following that I completed another idle test and pump only achieved 40psi (which bleeds down to zero on shutdown).

Verdict appears to be FPR with a weak but barely functional pump.