Finally got my new injectors(waited a whole 2 days WHEW) and the engine passes the cylinder balance test. Now have code 542 and 543 i believe is the numbers. But anyway it says "fuel pump circuit open battery to pcm" and "fuel pump circuit open pcm to motor" Any ideas on the fix for this this? tried to trace it had power at pump fuse and the relay control box. My wiring schematics are a little off i think though. Also anybody have a detailed vacumn hose diagram for 94-95 gt? Thanks for the help in advance!
fuel pump circuit open on KOER test
- Thread starter armyjon
- Start date
I don't have a vac schematic that's available online but am pretty familiar with many of the lines (since they bake and need to be replaced 
).
The FP codes are very common for some reason on 94-95's - if the pump loses power (even for a split second) when it should not, the puter generates a code.
Did you ever try to start it with the inertia switch turned off (maybe before you fired the engine for the first time)? This can spit a code.
Otherwise, though it could be a serious code, I might clear the codes and see if it was a ghost code or not (letting it run someplace safe - you would not want the car to stall while in traffic).
Good luck.
The FP codes are very common for some reason on 94-95's - if the pump loses power (even for a split second) when it should not, the puter generates a code.
Did you ever try to start it with the inertia switch turned off (maybe before you fired the engine for the first time)? This can spit a code.
Otherwise, though it could be a serious code, I might clear the codes and see if it was a ghost code or not (letting it run someplace safe - you would not want the car to stall while in traffic).
Good luck.
H50 from what i know as a tank mechanic and my shadetree knowledge. if a circuit is open it has a short to ground. I disconnected the harness from the pcm and relay module and the fuel pump wire has continuity when tested touching a chassis ground. SO should i further investigate where it is or try to splice in a new wire?
Jon, actually I consider an open to mean that a circuit is open - that there's a bad connection, a cut in the wire, etc. It's something that keeps power from getting to B from A.
In my book, a short is a short (a chafed power wire having continuity at some point to earth). I don't see this applying to you, right now atleast.
If you have no fuel system problems, sans the code, it can simply be that your circuit opened for some reason for a split second. This can happen if the interia switch is on the outs and you go over a stout bump or something along those lines.
FWIW, the FP relay wiring:
CCRM pin 11 is battery power to the FP relay.
CCRM Pin 5 is power from the relay to the pump.
CCRM Pin 13 is the ignition feed for the FP relay's coil.
CCRM Pin 18 is a ground pulse from the computer to the FP relay's coil.
Have you had issue with the FP fuse blowing? If there was a short to ground in the FP fuel pump feed wiring from the CCRM, that fuse should be going out. And if battery power to the CCRM goes, it can take out the CCRM fuse. I'd double check your FP power wire with the meter to ensure that there is truely a short of some sort.
Good luck.
In my book, a short is a short (a chafed power wire having continuity at some point to earth). I don't see this applying to you, right now atleast.
If you have no fuel system problems, sans the code, it can simply be that your circuit opened for some reason for a split second. This can happen if the interia switch is on the outs and you go over a stout bump or something along those lines.
FWIW, the FP relay wiring:
CCRM pin 11 is battery power to the FP relay.
CCRM Pin 5 is power from the relay to the pump.
CCRM Pin 13 is the ignition feed for the FP relay's coil.
CCRM Pin 18 is a ground pulse from the computer to the FP relay's coil.
Have you had issue with the FP fuse blowing? If there was a short to ground in the FP fuel pump feed wiring from the CCRM, that fuse should be going out. And if battery power to the CCRM goes, it can take out the CCRM fuse. I'd double check your FP power wire with the meter to ensure that there is truely a short of some sort.
Good luck.
H50 I understand what you're are saying but i'm used to a different mechanical world. I usually build engines with carbs not EFI. But my train of thought is that the fuel pump circuit is open when it shouldn't be so that means it's grounding out somewhere from what i know of electricity. Do you agree or disagree? The car has popped this code about three times that i can remember during the KOER test. And it will do it just idling in the driveway. The engine runs awesome for about 10-15 but then just instantly dies. will have more info tomorrow. I have had no blown fuses yet though and i switched all the relays around so there's no problem there. I had good voltage at the fuse and ccrm when i checked yesterday before i pulled out the computer and ccrm tonight to check connections and wiring.
If you have a simple circuit - a test light across a set of battery terminals - the test light illuminates, right. Now if you remove one leg of the test light, the light goes out but nothing has shorted out. You've simply opened the circuit. That's where I was going before.
With a short, you start blowing fuses.
I didn't know about or forgot about the issue of the car stalling-out-on-you for no reason. What happens when it does this (or direct me to another thread if you're working that aspect elsewhere)?
Will the car restart immediately or does it have to sit for a bit? If it has to sit for a bit, that's a great time to check spark , fuel pressure and injector pulsing while cranking. On 94-95's, the PIP's were a failure item, and that can affect the Fuel pump. A bad PIP is indicated when you have neither injector pulsing nor spark. Then both come back alive as a pair.
EDIT: I see you replaced the dizzy and TFI. I'd still do the above tests if you can (they take all of 2 minutes to do) in case you got a bad part. For instance, when you buy a reman'd dizzy, often times they will not replace the PIP if it tests okay in the shop. Well, the PIP is a major reason to buy a new dizzy and they often fail while hot. I've gotten enough bad parts-store-parts that I'm always suspicious.
Random thoughts.
Good luck Jon.
H50 thanks for all the advice so far. But ye the car dies and i usually have to wait for 30mins-1 hr to restart. I can hear the fuel pump come on, i have pressure at the rail, and i had spark last time i checked and there's definitely air. But iw won't start and the only codes i get are the fuel pump circuit open from battery to pcm and pcm to motor. I'm checking and triple checking everything but can't isolate the problem. Is it possible the pump shutoff switch is gounded out since it's the only thing i have located or removed from the wiring circuit. By the way where is the shut off switch in a 94 gt vert?
also how do i check the injector pulse? they pass the cylinder balance as they are new as of like 2 days ago. I also installed a new stator in the new distributor for giggles about a week before cause the book said that was the problem but after a coil and module still no difference. The book tells me hoe to detect if there's a pip signal but it didn't fix it before it said probe terminal 1 or 4 on the module to see if it pulses. is there another way? Thanks for your patience and time H50.
You'd use a noid light for an injector feed test.
The issue here is that when your car runs, it sounds like it runs well. But something is taking a dump and showing you Mr Hyde. For instance, when the car runs, the cylinder balance test will be great. However, if something is affecting the base signal to the computer for the injectors or ignition, once the component (like a PIP) gets hot and fails, the car shuts off. It obviously won't pass a cylinder balance test now because it won't run.
The biggies I've dealt with that fail after some run-time are PIP's, TFI's, coils and fuel pumps. The quick injector, spark and fuel pressure tests narrow things down quickly and concisely.
joel5.0
Member
Agree with HISSIN50, the fact that you have the fuel pump circuit codes showing up + the no start after time in use, points to a possible FP problem. You may hear the pump priming but, is it providing the minimum pressure required?.....need to check pressure when the no start condition is present. LUK
Well, the morale of this story is even with a fuel pump circuit open code the car still runs so you can interpret that code as you wish cause i drive the car and the code is still active, and just cause you get a new distributor doesn't mean the hall effect sensor is going to be good. After i traced the fp code for a day and then tested spark about 7 times i saw i was getting intermittent spark at times after the car died. But the distributor fixed it, now contemplating installing my own gears. thanks for the advice and help guys i used all of it but, apparently there were more issues than one. H50 i had 2 fp codes 542 543 i bypassed the cutoff switch and one of them went away can't remember which though.
conartist
Member
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