Hi Guys,


I’ve bought my ​​​​​self a nice locking stock 87 Cherokee and I love the his thing. After struggling a while with the renix ralated stuff, I’ve done mostly all the good tips given on cruisers website. This stuff is totally great and thank you cruiser for the effort.

However, I’ve found a problem I am not able to solve and need some advice.

There are normally 4 Relays next to the coil, one for o2 sensor heating, one for the fuel pump, one for the power latch (ecu?) and one for ac. The one for the power latch is missing in my jeep since I’ve bought it one year ago. Problem: I’ve now switched the ac Relays to this port port just for checking what will happen. When I do so my engine can’t be stopped anymore with the ingnition switch. After pulling the fuel pump Relays it stops.

1. question: what is the problem on driving without the power latch Relais?
2. why isn’t my engine turning off with the relays attached? Maybe the prerowner rewired or shorted something to fix some problem.

Thanks in advance,

David

Cruiser thank you for weighing in. After having another look into the engine bay it’s getting more confusing because I compared the attached pic with my configuration and it turns out my fuel pump relay is the missing one.



Is this possible? Engine runs, though.
So I have to revise my questions:

1. question: what is the problem on driving without the fuel pump relay ?
2. why isn’t my engine turning off with the fuel pump relay



Update, when installing the fuel pump relay, the pump won’t stop priming during key on. I think the PO somehow jumpered the relay, but I see no non stock wiring.

What I think could be wrong is the fuel pressure regulator not building up enough pressure that the fuel pump stops, maybe anyone could tell me how the fuel pump in my rig is able to run without the relay?

Again, it runs without the FP relay, with FP relay attached priming with ignition on (no running engine) doesn’t stop.

Thanks in advance.

I’ve found this discussion regarding relay, ecu, etc. Issues. https://www.cherokeeforum.com/f2/198...jumped-227111/

especially this statement seems interesting:

„You should hear the pump prime when you turn the ignition key to RUN. If the ECU doesn't get a crank signal (like when it's in RUN), it shuts the pump off after 3 seconds. If the key is in the START position, the pump runs continuously. Remember that the ECU is king on the RENIX so if it doesn't see what it wants to see, it won't let the engine run at all or if sensor inputs are erratic due to corrosion/grounds it will run very poorly as the inputs will be telling it bad information.“

so it might be an ecu related issue, I will clean ecu contacts and report...

Thanks for your reply, but running just fine would be too much of a compliment for my beauty. Symptoms I am dealing with since beginning is a very low idle - under 500 RPM and hesitation during load changes.

After first rebuying everything, I’ve found cruisers website and did mainly everything of the list. Except ecu contact cleaning and additional fuel pump ground.

And I have still an open relay port, even if my relay order differs from the attached picture. And if a relay is attached to this port, FP doesn’t stop priming and engine can’t be switch off by key.

So I am convinced there is something to fix.

Thanks cruiser for the info. I have made progress btw. I’ve changed the ecu - from a 89 I had laying around for upgrade reason, see cruiser tip #40. so now my fp relay works again, no nonstop priming anymore. That’s a success. However my rpm is still too low resulting in stuttering.

As my header seems rusty it might be cracked, can low rpm be the result of an exhaust leak?

thanks guys.

ah another question, is it necessary to adjust my TPS again after installing the new ecu? Just thinking.

Oh sorry to hear that, wish you all the best for recovery. Elbow is totally necessary for wrenching! I’ll adjust my TPS tonight, if this doesn’t work - injector swap!

I’ll do it right before TPS adjusting, I’ve renewed all grounds, though. Thanks cruiser!