all that for nothing

[DeathCougar]

Why would you go through all the trouble of removing the fuel pump, when you can test it in-tank in the vehicle? The access panel under the drivers seat allows you access to the plug on the top of the tank. Simply hook power to the larger Blue wire, and ground the White/Black wire.

I have drained every fuel tank on every 3rd gen I have ever worked and parted out doing this very same thing. Super easy.

*edit* You can also follow the above instructions laid out by Kyle

 

[Wayne]

Why would you go through all the trouble of removing the fuel pump, when you can test it in-tank in the vehicle?
-----------------------------

Ahem...I waited a month between the time the problem started and when I dropped the tank, because I was not convinced the pump was the problem and was pretty certain it was not based on the information at hand. No further information was forthcoming on further diagnostic tests so I finally felt no other choice. After all, its a "15 minute job", or so some people say. Haha. I don't blame anyone for this, not even the ____ who told me to get on with dropping the tank because it was "obviously" the pump. I knew that had not been determined with certainty, and ignored him, but eventually had no other ideas to pursue.


Anyway, moving on.


I checked for 12v at the tail light relay and jumped it, bingo tail lights. Did same at efi relay, its getting 12v. I jumped it and checked for 12 v at the fuel pump/circuit opening relay while I cranked it and got nothing. Battery dying so thats where I'm at while I recharge and go to work.

 

[EatonKyleH]

I checked for 12v at the tail light relay and jumped it, bingo tail lights. Did same at efi relay, its getting 12v. I jumped it and checked for 12 v at the fuel pump/circuit opening relay while I cranked it and got nothing. Battery dying so thats where I'm at while I recharge and go to work.

excellent. Well so what you are telling me is represented on this sweet paint drawing I just made lol.



The junction connector and the wire itself are all that stand between the point you now have power and the point you do not. You can take a piece of wire and touch one end it to your paper clip in the efi relay and the other to the paper clip in your circuit opening relay. This would bypass the junction connector and is an easy way to complete the circuit before digging for it. If the wire is broken or junction connector connections are bad your pump will run when jumping power from your efi relay clip to the circuit opening relay.

 

[Wayne]

OK now I'm confused.

Got home from work and jumped the fuel pump/circuit opening relay, which did not have voltage when I tested it. I went to plug in the pump at it's normal socket to get it ready for running the long jump from relay to relay. But the pump ran immediately. Wait a minute-went back and checked for voltage at the fuel pump relay. Still nothing. Is my tester dead? No, still have 12v at the EFI relay. But why not at the fuel pump relay if juice is obviously getting to the pump? This baffles me

Quite aside from my confusion, I hear something else getting activated when I jump the EFI relay. Sounds like its in the engine/intake area but I didnt try real hard to pin it down. Doesnt sound like a click, its more of a tang. Just curious what that is.

OK, unconfuse me

 

[EatonKyleH]

OK now I'm confused.

Got home from work and jumped the fuel pump/circuit opening relay, which did not have voltage when I tested it. I went to plug in the pump at it's normal socket to get it ready for running the long jump from relay to relay. But the pump ran immediately. Wait a minute-went back and checked for voltage at the fuel pump relay. Still nothing. Is my tester dead? No, still have 12v at the EFI relay. But why not at the fuel pump relay if juice is obviously getting to the pump? This baffles me

Quite aside from my confusion, I hear something else getting activated when I jump the EFI relay. Sounds like its in the engine/intake area but I didnt try real hard to pin it down. Doesnt sound like a click, its more of a tang. Just curious what that is.

OK, unconfuse me

So are you saying the fuel pump runs now or that it just ran for a second and shut off and wont turn on again? Also what sort of tester are you using? Like a test light?

 

[Wayne]

I had both relays jumped, getting ready to run the wire between them like you suggested. But the pump ran as soon as I plugged the pump in. They key wasn't even in the ignition. I used my analog multimeter to test the relay sockets for voltage. To summarize, the pump runs with both relays jumped, no wire between the relays (I never got that far), and no key in the ignition. But when I use the meter I can't detect voltage at the circuit opening relay even when the EFI relay is jumped. But the pump runs anyway when both relays are jumped. Confused yet?

So are you saying the fuel pump runs now or that it just ran for a second and shut off and wont turn on again? Also what sort of tester are you using? Like a test light?

 

[EatonKyleH]

I had both relays jumped, getting ready to run the wire between them like you suggested. But the pump ran as soon as I plugged the pump in. They key wasn't even in the ignition. I used my analog multimeter to test the relay sockets for voltage. To summarize, the pump runs with both relays jumped, no wire between the relays (I never got that far), and no key in the ignition. But when I use the meter I can't detect voltage at the circuit opening relay even when the EFI relay is jumped. But the pump runs anyway when both relays are jumped. Confused yet?

Well Gee Golly Mr.
Things are now real interesting and I hope I keeping the explanations simple as this continues might be a little hard.

But ya the pump will run without the key on if both relays are jumped because you are providing power across the relay manually. There is power at all times there waiting for you to turn the key which in turn signals the ECM to close the relay. We are in a sense closing that circuit without it.

Now does the pump run with only the circuit opening relay jumped and the EFI relay installed as normal? You WILL need to turn the key on to check because the ECM will need to close the EFI relay.

Let me know what happens.
I know where this is probably headed but I'll try to keep it one step at a time as to stay on the same page.

 

[Wayne]

W

Now does the pump run with only the circuit opening relay jumped and the EFI relay installed as normal? .

Yes.

 

[Wayne]

Yes.

And just in case you were going to ask, it runs no matter which relay I put in the EFI slot.

 

[EatonKyleH]

Yes.

Ok. Now we know that the problem lies in the circuit that controls the closing of the circuit opening relay. This is controlled entirely by the ECM. There should be power on the white/light blue wire into the relay and ground on the green/yellow wire to the back of the same relay. If you can get the box apart enough to see which is which great and if not I can get a diagram at work tomorrow to show which hole is each. In the meantime you also might want to check the ground for the ECM. If the ground is bad/has high resistance that would explain why you don't see power at the relay because the resistance of that bad ground would act as a load and therefore consume some voltage leaving you enough to barely run the pump but not enough to be measured with much other than a decent DMM at the relay.

 

[Wayne]

I wasnt entirely clear on what you were asking, but I tested for power with my meter with the key on using the white/blue and green/yellow at the back of the fuel pump relay socket. There were two white/blue wires btw. No power either way. Will go check the ecm ground

Ok. Now we know that the problem lies in the circuit that controls the closing of the circuit opening relay. This is controlled entirely by the ECM. There should be power on the white/light blue wire into the relay and ground on the green/yellow wire to the back of the same relay. If you can get the box apart enough to see which is which great and if not I can get a diagram at work tomorrow to show which hole is each. In the meantime you also might want to check the ground for the ECM. If the ground is bad/has high resistance that would explain why you don't see power at the relay because the resistance of that bad ground would act as a load and therefore consume some voltage leaving you enough to barely run the pump but not enough to be measured with much other than a decent DMM at the relay.

 

[EatonKyleH]

I wasnt entirely clear on what you were asking, but I tested for power with my meter with the key on using the white/blue and green/yellow at the back of the fuel pump relay socket. There were two white/blue wires btw. No power either way. Will go check the ecm ground

Cool ya one of those white/blue wires is the one you should have the jumper/paper clip stuck in. The other one is power from the ECM. Let me know on that ground.

 

[Wayne]

Not finding an obvious ground at the ECM...at least I think its the ECM, under the passenger dash. Just a harness coming out going who knows where...

Cool ya one of those white/blue wires is the one you should have the jumper/paper clip stuck in. The other one is power from the ECM. Let me know on that ground.

 

[EatonKyleH]

Not finding an obvious ground at the ECM...at least I think its the ECM, under the passenger dash. Just a harness coming out going who knows where...

ya that's the area. I'll see if I can get a decent picture of ground locations tomorrow. One thing is though you will need to be able to measure the voltage on your jumper in the closed circuit relay. There is a measurable amount of voltage present if the pump is able to run with the relay jumped. It might not be 12 volts or even enough to illuminate a test light but there is something there and we'd need to know how much is getting to the pump. There is power to the pump as well if it running so measure there. You'll need a DMM if you don't have one. One lead on chassis ground and the other on the paper clip or touching the power wire to the pump.

 

[Wayne]

I think I misunderstood your previous post. I checked again, and I do have power to the white/blue. But no ground on the green/yellow.

It may be a few days before I can get a DMM, unless I can borrow one from someone at work tomorrow. No biggy, its been a month already...

Cool ya one of those white/blue wires is the one you should have the jumper/paper clip stuck in. The other one is power from the ECM. Let me know on that ground.

 

[EatonKyleH]

I think I misunderstood your previous post. I checked again, and I do have power to the white/blue. But no ground on the green/yellow.

It may be a few days before I can get a DMM, unless I can borrow one from someone at work tomorrow. No biggy, its been a month already...

cool so you have power to both white/blue wires correct? the one you with the jumper and the one without? If so the only thing you are lacking is ground from the ECM.

 

[Wayne]

Yep, I have power to both white/blue wires. And no ground on green/yellow.

cool so you have power to both white/blue wires correct? the one you with the jumper and the one without? If so the only thing you are lacking is ground from the ECM.

 

[Wayne]

BTW, there is not just power but a full 12v to both white/blue wires. The mistake I made earlier when I said there was no power to the circuit opening relay (and this is why I was baffled) was that I put one probe on the white/blue and one on the green. I took this as "no power" when all it meant was "no ground". Didn't want you thinking there is a small amount of power but not enough to measure accurately with my analog meter

 

[EatonKyleH]

I know some of you were reading up on this thread before and I wanted to post a little update. I'm sure people find it annoying when reading up threads involving odd problems but never include a resolution at the end.

Well..... This one has been a wild ride!

I've been talking back and forth with Wayne for awhile now via PM after this thread started to get very involved in electrical testing.

Long story short...We found that the fuel pump circuit opening relay was not being supplied a ground by the ECM and with no trouble codes due to a bad ECM ground. He put his fuel pump back in and I talked him through wiring a new ground.

He has told me the vehicle is now running great without issues.

I've still got him doing a couple little tests to pinpoint the exact area of ground failure but we are just about to close this case.

I've honestly had fun on this diagnosis as it is a problem that is EXTREMELY rare and rather complex (I like a challenge). It was really a joy for me to be able to talk a guy with very limited electrical knowledge and a simple analog meter through understanding and resolving a difficult diagnosis. He's also been a really good sport about the whole thing lol.

I've also come out of it learning this fuel pump control side of the circuit and ECM relay controls way better than I ever cared too. Never really had to get involved that deep into it before.

 

[Fishwerks]

[MENTION=94888]EatonKyleH[/MENTION]

You are a wizard