Hey guys, first post!

Looking for a little help as to where to start on my girl's Jeep, (89 Grand Cherokee). I'm no stranger to working on cars, but definitely no motorhead. Generally I get a ballpark and start replacing stuff til it's fixed, but money is extremely tight right now and can't afford to throw too much at this thing, so hoping you guys can point me in the right direction.

Symptoms:

1. Couple months ago the temp gauge would occasionally spike to max for a minute or two then drop back down. Obviously impossible for temp to do that so put it on the back burner.

2. Recently oil pressure gauge has been fluctuating, briefly dropping to zero then picking back up (recent oil change as well). Day before yesterday it dropped to zero then would not move, but next time she started it was back to normal.

3. Yesterday stalled on her on her way to work from a stop sign. I started it today and have severe hesitation/almost stalling when giving it throttle in neutral.


My main question right now would be, does the oil pressure sender go through the ECM or straight to the gauge? If it is to the ECM, then I'm hoping the computer is just bad and needs a swap. If there is anyone that knows the color of the wires and optimal voltages in and out of the ecm for temp/oil gauges I could test that easily enough.

I'm extremely hesitant to run more diagnostics with the oil pressure gauge not reading correctly in the event that is actually is the pump not working. Will I know if the pump is not running so I don't blow this engine up?

Would definitely appreciate some advice here guys and open to all suggestions. Just keep in mind the money thing is an issue so cheap diagnostics or solutions are a ++. If it wasn't an issue I'd be throwing a mechanical oil gauge on there right now so I can work on it with peace of mind.

Thanks!

 

I think you'll need to verify these "conditions" - via external measurements - in order to determine valid gauge indications.

Not entirely sure of the '89 Jeep GC diagnostic method but in my '88 RAM, I would cycle the ignition switch key on-off-on-off-on and monitor the "check engine" lamp, it produced a lamp-blink sequence with numerical correspondence to a trouble code look up table.

Example: 1 blink - pause - 2 blink (= 12 = battery recently disconnected), 3 blink - pause - 7 blink (= 37 = non-lockup torque converter), 8 blink - pause - 8 blink (= 88 = end of test).

If any codes are produced then cycle the connections to the ECM (demate/remate) and drive it around to monitor for recurring malfunctions. If any re-occur then respond with greater attention to the issue. If none then it may have been just contamination at the ECM connections - pull them again to clean and apply dielectric grease before reconnecting.

 

There was no GC in 89. Renix doesn't store codes.

Temp gauge goes off of the little sender on the back of the head.

Oil pressure gauge gets it signal from the sender by the oil filter.

Neither one run to the ecu. Check all your motor grounds. Thats prolly the #1 problem with renix.

 

Know where all the motor grounds are so I don't miss any? Also, to the first responder, there is no check engine light.

 

There won't be a check engine light. Renix (Renault motor + Bendix electrical = renix) does not store codes.

The grounds I know of are;

Fender to ground terminal (by battery)
Dipstick to ground terminal
Intake manifold to firewall.

Do you have a big bulky connector on the firewall above the vacuum booster?

 

Vaccuum booster being the cylinder on the passenger side firewall? If so then no i do not see a bulky connector. why's that?

 

Bulky connector near vacuum booster (for power brakes) mounted to driver's side firewall.

 

I do NOT have a connector anywhere near the brake booster

 

If it had a c101 connector (87 had em, but I've seen 88's and 89's have em)

When they wear out and jiggle, since all the sensors are wired through it, it messes everything up.

Start with the grounds.