No power to fuel pump after engine swap

[PowerAddict]

Hey guys, first post, I searched google alot to help me troubleshoot, and most of the links led me to here..so I thought I'd join. Very nice niche site!

Anyway, I swapped the engine 99 4.0 sohc, was a 99 engine.

I've tested the relays and checked the fuses, and the inertia switch isn't tripped, and I have NO IDEA what to check next.

Any ideas guys?

Thanks.

 

[budwich]

I guess the question is "how did you test the relays" and then it will probably then be obvious about the next question ... "how did you test to see that there was no power to the fuel pump"?

 

[PowerAddict]

power and ground to the coil side of the relay, resitance across the power side of the relay, less than an ohm.

back probed big red wire and big black wire in the harness back by the pump, turned key to both run, and start, No voltage. Pump verified good.

 

[PowerAddict]

Is there a connector for the fuel pump that goes between the inertia switch and the Power distribution block somewhere underneath the hood?

 

[windsors03cobra]

Got power at the relay socket ?

 

[PowerAddict]

yes, test light comes on when key is turned.

 

[budwich]

power and ground to the coil side of the relay, resitance across the power side of the relay, less than an ohm.

back probed big red wire and big black wire in the harness back by the pump, turned key to both run, and start, No voltage. Pump verified good.

good if I understand you... you appear to indicate that you have power going into the coil portion of the relay but why didn't you check for voltage at the "power side" which I think you mean "switched contact"... maybe.... that's the voltage that is "sent" to the fuel pump thru the inertia switch.

 

[PowerAddict]

The relay was pulled to test it, there is power on the "swtiched" side of the relay in the distribution block. There's power for everything in the fuse block, and the relays and fuses are good. Thats why I was asking if there's a connector in the wires that run from the distribution block to the inertia switch.

 

[jakebrake]

sounds dumb but check your wire harness make sure everything is plugged tight and and out of harms way. I put one together once and spent a few pennies trouble shooting before i found a wire that got crimped between a pulley bracket cutting its signal.

 

[budwich]

The relay was pulled to test it, there is power on the "swtiched" side of the relay in the distribution block. There's power for everything in the fuse block, and the relays and fuses are good. Thats why I was asking if there's a connector in the wires that run from the distribution block to the inertia switch.

OK... hope I understand. Then if there is power on the "switched" side going in and out of the relay switched contacts... last question is the relay operated "momentarily" with the Key On action (ie. for a few seconds)????

 

[PowerAddict]

I tested so many things so many times I don't remember, But I know what you're talking about and want to assume yes.

I'm thinking I have 1 of 2 things, either a loose connector or a loose ground. Are there any for the fuel pump that you guys can think of.

I appreciate the help.

 

[Turdle]

Does the check engine light illuminate when the key is switched "on"?

 

[PowerAddict]

yes, all lights come on for bulb check on the Instrument Panel Cluster.

The theft light blinks as it should, stays on for the 3 seconds or so, and goes out while cranking, so I'm doubting security too.

I'm really out of ideas. I just keep thinking that maybe there's a connector for the fuel pump, or a ground for it underneath the hood somewhere....

 

[PowerAddict]

okay, I've got a little bit of progress and I'm going to explain it the best I can.

On the coil side of the relay IN the distribution block, on the terminal closest to the rear of the vehicle, when the key is off position, you can put the test light alligator clip on the postive battery terminal, and put the test light in the terminal slot in the fuse block, and the light will light up. You can then switch the test light's alligator clip to the negative battery terminal, and turn the key, and it is now switched to power...is that right? Thats controlled by the PCM.


So, then, I looked at the other side of the relay's coil side, the terminal closest to the front of the vehicle. I was assuming that since the other side was switching to power, that should have ground. I put the test light's alligator clip on the battery postive, and put the test light in the terminal in the fuse block, and It did not light up.

So, I put a wire in that terminal, and hooked that to the battery, and then I tried to start it...and it started! However, It won't stay running.


SO....what do I do now?!! I feel like I'm so close guys, lets do this thing!

 

[Turdle]

try a different relay.

IIRC there is no "ground" side to the relay coil. One side goes low when that relay is switched on.

 

[PowerAddict]

The relay is not the problem. its been swapped, and tested.

 

[budwich]

okay, I've got a little bit of progress and I'm going to explain it the best I can.

On the coil side of the relay IN the distribution block, on the terminal closest to the rear of the vehicle, when the key is off position, you can put the test light alligator clip on the postive battery terminal, and put the test light in the terminal slot in the fuse block, and the light will light up. You can then switch the test light's alligator clip to the negative battery terminal, and turn the key, and it is now switched to power...is that right? Thats controlled by the PCM.


So, then, I looked at the other side of the relay's coil side, the terminal closest to the front of the vehicle. I was assuming that since the other side was switching to power, that should have ground. I put the test light's alligator clip on the battery postive, and put the test light in the terminal in the fuse block, and It did not light up.

So, I put a wire in that terminal, and hooked that to the battery, and then I tried to start it...and it started! However, It won't stay running.


SO....what do I do now?!! I feel like I'm so close guys, lets do this thing!

ok... that "explains" the "testing"... yikes... Not sure how to explain this and don't take this wrong... but yikes ...

Anyways, without going thru "electronics 101", hopefully you can get thru testing. BUT before you go there, as you have found out, you can get the "thing" started... so IF you at least want to do that, your best bet is to run a wire from the positive battery terminal to the "other side" (ie. pump side) of the inertia switch. This should cause the pump to run and your engine should start and "run forever". IF that doesn't happen, you have other issues. IF it does (ie. "run forever"), then you can back track with testing from there and hopefully, find your issue.

 

[PowerAddict]

okay, we are definately losing something in translation here....Lets put it this way, I know how to basic electrical tests, thats not the problem.

The real problem is that I don't have a wiring diagram, so I have no idea what is supposed to be doing what and I'm just guessing.

does someone have a wiring diagram?

 

[PowerAddict]

OK... hope I understand. Then if there is power on the "switched" side going in and out of the relay switched contacts... last question is the relay operated "momentarily" with the Key On action (ie. for a few seconds)????

I re-checked this, and no, its not momentary at least according to the test light.

 

[budwich]

Anyways, no problem. As I suggested, just run a "jumper wire" to the other side of the inertia switch from the battery (or equivalent) and just start your truck. It had better run "forever"... IF you get that far, then you can troubleshoot the rest fairly quickly... OK