--Disclaimer-- before I posted this, I researched for 2 hours and found a million other people on here with code 54 issues--- I learned a bunch of helpful info, but my problem maybe slightly different: I just got an 85 IROC with a 305 TPI last week. The Fuel Gauge is pegged, I get code 54, and when I turn the key, I get no fuel pump prime, but the car will start (obviously because of the oil pressure switch)--- Previous owner, said he just had a shop install a new fuel pump, fuel pump relay, and a new computer. I know that the fuel gauge reading full means there's a faulty ground somewhere--- could all these problems be related or are they specifically seperate areas of the fuel system? When I inspected the 5 pin connector going to the fuel pump relay, I noticed that the 3 middle wires sleeves were totally stripped away exposing bare wires to touch each other! I believe at some point, the ground (black/white) hit the ecm wire(green) at some point and shorted out--- can I buy a replacement connector and solder up some new wires? In the mean time I tested the fuel pump by jumping tan to orange; fuel pump came on fine; then I turned the ignition on, and tested the green; it showed 12 volts--- but didn't go away! Isn't it only supposed to show 12 volts for 2 seconds? (to prime the pump)--- It continuosly remained 12 volts until I shut off the ignition. What does this mean? Also, the engine is idling high at 1000 rpms, and when I rev it, it seems to sputter quite a bit--- vacuum lines seemed fine; could this be all ecm related? Thanks in advance!!!

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can I buy a replacement connector and solder up some new wires?

Yes, you can get some from aftermarket harness makers.
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I get no fuel pump prime

When the wires shorted it might have damaged the ECM.
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the green; it showed 12 volts--- but didn't go away! Isn't it only supposed to show 12 volts for 2 seconds?

It’s supposed to stay on.

The oil pressure switch pressure is a backup.
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Also, the engine is idling high at 1000 rpm, and when I rev it, it seems to sputter quite a bit--- vacuum lines seemed fine; could this be all ecm related?

Yes your performance problem could be ECM related therefore I would verify, then replace the ECM.

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Happy Racing!

Thankyou for your reply, that helps alot!

quick question tho, isn't the green/white wire supposed to supply 12 volts for only 2 seconds (basically prime the fuel pump) when the ignition is on; Like I said, its not going off after 2 seconds, its staying on until I turn off the ignition.

I've read that people testing with a test light, say that the light goes off after 2 seconds; indicating the prime circuit is working; so that kind of confuses me if its supposed to stay on like you said---- if its supposed to wouldn't that indicate the ecm is working?


anybody have a link for where I can buy that 5 pin relay connector that plugs into the relay?


thanks!

it’s true that the priming circuit is 2 seconds then will go off IF the ECM is not receiving pulses.

Therefore if you turn the key to RUN, voltage should go away after 2 seconds.

When the engine is running, the ECM continues to put out voltage.

The oil pressure switch pressure is a backup.

If there is voltage there continuously when the engine is not running there is a problem.

An ECM can have damage in only one function, essentially still being able to function.

It depends what the loss is in determining if you’ll have to replace it.

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Happy Racing!

Ok, that makes sense. so before I fry another relay, I should replace the connector and put in a new computer...

any lead on where I can pick up that new pig tail? the closest thing I found to a similar connector--- is a gm fan pigtail.

thanks again!

I am waiting for my new ECM and relay to come in (should be 3 days); in the mean time I want to fix the fuel gauge; Before I drop the tank, and tear the whole frickin interior out of the car to try and find a bad ground, I heard there is some way to test from the connector plug underneath the car/in front of the rear that is the sending unit harness.

The problem is, I searched and searched--- found a ton of people on here with the same problem--- but nobody finishes out there thread! its like, they fix their problem and forget about everything else--- Once I get this fixed, I sware I'm gonna close this thread out--- Descriptively; with easy to understand typing/grammar so anybody else can read it and fix there car.

So, I got a mulitmeter, how can I test to isolate my bad ground?

thanks!

So I'm a little farther, but still need some help. I jacked up the car and pulled off the 3 prong c313 connector and cleaned it. Then I took the car/interior side of the connector; and with a piece of wire, I touched the black pin (ground wire) to the pink pin (sender wire) ---and turned the key on:

The guage went from being pegged full, to reading empty. Does this mean that my wiring from the gauge cluster to the C313 connector is all good?
(If so, then atleast I don't have to tear the interior appart looking for a bad ground)

However, does this mean my sending unit is bad? I figured there had to be a good ground on the tank side, or the fuel pump wouldn't work (it works fine) ---- does the sending unit and the fuel pump have a common ground? if so, why isnt that ground good enough for my gauge?

I guess I just really need to know the correct way to check those connectors

Thanks for all your help!!! This forum is a lifesaver!

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Does this mean that my wiring from the gauge cluster to the C313 connector is all good?

Yes that’s half the test.

Now get a 47Ω resistor and connect it from that wire to ground.

If the gage reads about ½ you know the gage is good, therefore the problem is the float or the wiring going to it.

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Happy Racing!

Sweet, so if the 47ohm resistor makes the gauge read 1/2 empty--- then is there anyway to test the wiring going to the tank without dropping the tank? I'm assuming the guy that I bought the car from put in the new fuel pump (not a new sender) prolly screwed up the wiring or float somehow

I know if the problem is there, I'm going to have to drop the tank anyway, (something I would like to do after I run the 10 gallons out of it first!) But I want to know (by testing) that the fuel pump has a good ground;

The pump seems to work fine (when run off the oil pressure switch; or hotwired from the relay) Since the guage isn't working right and could have a bad ground---- and the fuel pump shares that ground (see where I'm going?!)

If its got a bad ground, I don't want to risk damaging the new fuel pump by driving the car any further; so if there is a way I can test that ground--- and its good, then that will save me the horrible task of siphoning 10 frickin gallons out!


Thanks a million!

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if the 47ohm resistor makes the gauge read 1/2 empty--- then is there anyway to test the wiring going to the tank without dropping the tank?

If the 47ohm resistor makes the gauge read ½, you know the gage is good.

Therefore if it reads wrong with the sender reconnected, you know the sender or the in-tank wiring bad.
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The pump seems to work fine (when run off the oil pressure switch; or hotwired from the relay)

That means the pump ground is making contact.

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Happy Racing!

Roger that! Thanks for all your help, I will post my results for this when its all done; I just decided after I run the tank empty, I'm gonna "hack" me an access hole--- and swap out the sender; I hope I don't die! (lol, don't worry I'm a Jet Aircraft Mechanic; it will be bullet proof; and engineered better than GM when I'm done with it)

im not sure if i have the same problem or not but my car is doing the same thing with the car sputtering when i rev it. my gauge works fine thought.

i sure hope it is not the computer. i dont want to buy a new one. sounds expensive

my temp gauge was peged when i got my car and i thought it was a bad ground also but it ended up being that when i turn the car on it goes the whole way up and gets stuck their. i tore the dash apart and got it un stuck with my finger and it worked. so i drilled a small hole in the gauge and glued a small stiff wire in it so the gauge will go up and hit that and fall back down instead of getting stuck.
maybe that is your problem on the fuel gauge

thanks, but the gauge and interior wiring have already passed their test; by grounding the sender/signal wire, the gauge goes empty; and with a 45 ohm resistor it reads half full; so when plugged into the tank harness and it goes all the way full--- that means the pot on the sender is bad, or the sender wire/plug connection on the sending unit is bad; or needs some cleaning. Either way the problem is clearly on the tank side.

thanks for your comment tho!

JohnnyMonza. DO NOT MAKE A ACCESS HOLE. YOU WILL REGRET IT. Dont be lazy and go the jacked up route. Believe me. A little hole my rear end. The fuelpump is just there under the rear hatch, but you will have trouble trying to take out the pump, wait, you wont be able to take out the pump because of the metal tubes that run all the way across the top of the tank. Look at this picture here that I found in an other thread. You see. It'll be an ugly mod if you go that route. Just lift the rear end up about 2 feet, support at rear end, but be carefull when you drop the axle, dont let it drop too much because you'll snap the rubber brake line. Good luck.

Hey, I appreciate your concern, but rest assured the guy that did that pic you showed me, did a hack job; I've attached some pics of an Engineer's work; this is the right way to do it--- This is the kind of engineering GM should have considered; No loss in structural integrity and makes fuel pump issues gone in a half hour.

I've heard a lot of people that don't like this idea; for what reason I've never understood, (unless you've got a rare car, that should be left stock) they are probably the same guys that can't make their own parts and have to buy all their stuff from aftermarket companies. To me, Kustom Fabrication is the coolest thing in the world--- Even down to a simple fab like this--- just take your time, measure, and use the proper safety precautions when dealing with gas fumes.

and trust me, I've been an F-15 Mechanic for almost 10 years, if I sign it off, your good to fly a 30 million dollar jet... let alone drive a little Camaro!

Checkout these pics:


peace

If you can make such a super clean job just like in the picture that you just provided, then im with you. Thats the cleanest fuel tank access mod that I have seen. Did you do it? Whats your approach?

Thanks, but the credit for that work goes to Scott and his Turbo TransAm:
http://www.turbobuick.com/forums/tur...utes-less.html

My version will be a little different; I'll post pics when I'm done (I'm gonna run that tank empty first before I start cutting; so prolly a week or 2) But yeah, I 've done this before; You just make a template; measure; cut straight; make a gasket; fab a panel; chop a few lines; its easy (check out Scotts thread, for a break down). I just got this IROC to be my daily driver, my real Hot Rod is my 75 Monza; if you want to see some of my fab work check this out; the only thing stock on it, is the body:
http://forums.h-body.org/garage.php?...&image_id=3751
http://forums.h-body.org/garage.php?...&image_id=3762
http://forums.h-body.org/garage.php?...&image_id=3758
http://forums.h-body.org/garage.php?...&image_id=3767

- Jonny

Daaammmmmbbbbbb. The Monza looks like a beast.. Very nice bro.

Thanks, its alot of fun!

I bet it is.