techno101

So herees the deal. Ignition on... No fuel pump prime... Just happened today. It's been kinda in and out on me for a while though. Got a couple of code 54s but it would still crank and run. Today.... Nothing.
I checked the pump, it works. ( I pulled it and connected it to a battery) . I checked the voltage on the female connector under the car body on the purple wire with a check light first. Nice and bright. I plugged the male connector leading to the pump in and probed the purple wire through the plastic coating and the light barely came on. Then I checked with a volt meter. Around 13 volts at the female connection. The car sat for 7-8 minutes with the ignition still on and the voltage dropped to 9 volts steady. I plugged in the male connector and probed the purple wire and it read 2.5 volts. So is the pig tail male connector screwed up ??

eseibel67

The purple wire is for the fuel level sender, the gray wire is the fuel pump power. Obviously, if the pump runs with direct 12v, power isn't getting there.

Start with the fuel pump relay, not exactly sure where it's located on your model.

vetteoz

iTrader: (13)

Check for 12V on the org wire at relay; if none most likely the fuse is blown
See
https://www.thirdgen.org/forums/tpi/...questions.html

If you have power at relay ,jumper org to grey ; pump should run

]

techno101

Help me help me help me

techno101

Ok the fuse was blown by the battery. Changed it, tried to crank the car, it blew again while engine was turning over. Unplugged ECM, tried again, blew the fuse again, ruling out ECM failure or damaged unit, thankfully. Now here is where it weird.... I unplugged the fuel pump relay, turned the key on, fuel pump primed fine. Engine started fine, turned key off and pump still ran for 3 seconds like it should.... The relay was new 1 month ago

techno101

So what's the deal with the relay?? What's does it actually control??

vetteoz

iTrader: (13)

Did you look at the circuit diagram I put up for YOU

The relay turns on the pump when it is powered up from the ECM and the OP switch wired in parallel to the relay ALSO runs the pump as long as the oil pressure is above 4 psI

techno101

Then why will does the pump come on if the relay is unplugged and there is no oil pressure yet?

vetteoz

iTrader: (13)

From the circuit diagram ,the only way pump can run with no relay is if the OP switch is faulty but then it would run full time ; even when key off ?

rusty vango

did you buy the correct relay?? you didn't get it from auto zone,did you?? having the wrong relay can cause all sorts of profanity.ask me how I know!!

techno101

No I bought it at advance auto

techno101

And I'm not sure why it was running correctly with out the relay either.... OP switch would be easy to change though.

Dakota W.

Turning the engine over with the starter generates oil pressure...So of course the pump is going to run off the OP switch. Did you check wiring from between the relay and your power?

techno101

Full 13 volts at the relay

techno101

But why is the fuse blowing with the relay plugged in? Got a new relay.... Same thing now

Dakota W.

I'm guessing you have a wiring issue somewhere.

techno101

Yeah I just don't know where...

Dakota W.

Better start tracing wires!

bubbazwv

I have the same gremlin...my 87 2.8 v6 runs fine but has the code 54 on all the time I just replaced the fuel pump relay with a acdelco one...I havent run the car for an extended period of time but from what i gather the fuel pump isnt getting the needed voltage for what 2 seconds....if not then it will throw the 54 code....this has driven me crazy...the fuel pressure at idle is 37-40 or so when idle is raised..

dusty91

Ok so here is the issue with this car the two relays tenchno101 is talking about are on the fire wall on the drivers side I have both new the gray I believe really has nothing to do with the problem but whenever I plug the black one in it blows the fuse by the battery. The Orange wire has battery voltage and continuity across to the fuse by the battery.

techno101

So which is which?? I've been told both ways....

rusty vango

you can call up your local chevy dealer and get the part numbers for the correct relays. then you can cross that number at your parts store of choice. there is a tool called a short finder. you need that tool to get to the bottom of your issue. I think you have a short somewhere. your factory service manual has the wiring diagrams in it (you DO have the manual,right?) anyway, I wish you good luck

techno101

Hahaha yeah in a 24 year old car that's been through God knows how many owners....

Veaceonee

iTrader: (1)

There is a 3 wire connector in between the rear seats under the carpet. I think it is the C313 connector. Anyways, they are known for going bad, and can cause shorts. I would check there. It is riveted to the car on the inside.

Attatched is the schematic for my car..yours should be roughly the same thing.

vetteoz

iTrader: (13)

Look for the wire colors from the circuit diagram I gave you above , only one relay should have that combo ( tan/ wht wire to pump might be grey ? )

vetteoz

iTrader: (13)

Back to basics

Established facts
The pump runs fine on the OP switch circuit only so that means there are no wiring faults from the battery to the pump
Fuse blows when the relay is plugged in
New relay does same so that eliminates the relay as a problem

Only leaves the relay connector as a possible problem
Plugging the relay into the connector causes something on the pump power circuit to short straight to ground and blow the fuse
Check the terminals in the connector

dusty91

So I have been looking at the connector on the relay everthing looks good there are a few wire that are exposed coming out of it made sure they weren't grounding or shorting out on each other, but the problem is still there.
Now the next question how hard is it to get the this 3 wire connector at the rear seats? And how do I make sure I have the correct connection?

techno101

The connector at the rear of the car is located above the rear differential, mounted on the car body. It's got a good connection, and I have an extra connector also. If the pump will run, you've got a good connection.

rusty vango

pull the right hand seat bottom ,and its right there.the fuel sending unit grounds to the floor pan in that area too,now from under the car its a lil harder to get at.you may have to drop the tank to get at the wiring that connects to the sending unit

techno101

Also I tested the pump in the tank. And the old pump was still good too. You can run a temporary wire from the positive post on the battery and connect it to the grey wire in the three prong connector at that location under the car. You'll hear the pump come on.

vetteoz

iTrader: (13)

You should have started your own thread instead of hijacking this one.

We are now trying to solve 2 different pump problems from 2 different people and it is just getting confusing

techno101

It's actually the same car... I sold it to him

vetteoz

iTrader: (13)

So refer my post # 26 above.

If the pump runs on the OP switch circuit and nothing blows ;
there is NOTHING WRONG with the wiring to the pump or the rear connector he is concerned about
The problem has to be at the relay / or it's connector

techno101

And it only blows the fuse after the engine is warmed up.

vetteoz

iTrader: (13)

Never said that before
Up top he states
"whenever I plug the black one in it blows the fuse by the battery".

So which is it ?????

Blow the fuse after engine warms up is a completely different scenario to what we have been discussing so far.

techno101

We've just noticed this correlation.

dusty91

And really it's not even that warmed up the car only gets.to about 110-120 then it blows the fuse

vetteoz

iTrader: (13)

So we now have ,
install new relay and it runs fine for a period of time until the fuse blows ?

Does it do same with the relay unplugged and running only on the OP switch ?

dusty91

With what I believe is the fuel pump relay (the black relay ) the will start and run (not well) for a short period . But it won't blow the fuse

vetteoz

iTrader: (13)

I'm confused.
We have gone from
Plug relay in and fuse blows
to plug relay in and it blows fuse when engine warms up
to now
it doesn't blow fuse with relay in .


As I said above , check the wire colors to confirm you are dealing with the pump relay

The MAF burnoff relay next to it is powered from the same fuse

techno101

Car is Speed density setup

techno101

Car was originally TBI converted to 90-92 TPI

techno101

The pump relay is has red wire, a black and red wire, a dark green, a tan and white wire, and a purple wire... Correct? This being the gray relay in the pic.

techno101

This being the pic

dusty91

So here is a pic of the connector that plugs in the black relay that keeps blowing the fuse. The wire colors are red, orange, tan, black w/ white stripe and green w/ white stripe. The Orange wire has continuity across the car to the fuse that is blowing.

vetteoz

iTrader: (13)

Looking at the state of the wires I would say replacing that connector would be a good starting point as I observed above
Even looks like it has burn ( short ) marks on the tan wire

86T/A_Ram_Air

I agree with vetteoz here. You need to replace that connector. Rockauto carries them

techno101

Oh yeah that looks bad... But I'm confused. I thought that was the cooling fan relay.

vetteoz

iTrader: (13)

As shown in the fuel pump circuit diagram I put up for you in post # 3 that I keep telling you to LOOK at so as to identify the pump relay !

So far this thread is a waste of bandwidth.
An essential item on the circuit giving you problems is a POS and needs to be replaced , regardless what circuit it is on

techno101

Well that clears up a lot about which relay is which.