Hung Like a Stang

Its looking like I simply don't have any power to the fuel pump on a 1999 ford explorer 4.0 sohc. If the relay is #5, I tested it and its got power going to it, and the relay is good. I tested every single fuse in the under hood distribution block, and the one on the side of the dash, all those fuses are good. The inertia switch isn't tripped.


Any suggestions?

petrock

How did you check if the fuel pump is getting power? Make sure it has both power & ground. It needs both. How did you test the relay? You can just swap a known good relay for the fuel pump relay and see if that helps. How did you test the fuses? A visual check of a fuse is only a basic test. The fuse can still be bad. Best way is with a multi-meter or fuse tester. Most fuse kits come with a fuse tester. If your getting power at the relay, are you also getting a good ground? If you have power on one side of the relay, do you have power on the other side?

Good luck...

Hung Like a Stang

back probed the big red and big black wires in the connector by the fuel tank, put a meter, set on DC volts, turned key, nothing.

Relay was tested the only way to test a relay, ignited the coil side of the relay by giving it a power and a ground, and then testing resitance across the power side...all less than an ohm.

fuses were tested with a test light, checked both sides of the relay to for power.

Power was verified in the distrubition block with a test light, when the key is turned, it is ignited.

petrock

If you back probe the red wire (I assume thats the power wire) and touch the ground probe on the multi-meter to a known good ground (like the frame rail), do you get power? If so, you have a bad ground connection somewhere between the fuel pump and the relay. If not, then you have a bad/broken power wire/connection between the fuel pump and the relay. Then just walk up which ever side is the problem till you narrow down where the break is and fix that bit of wire.

Good luck...

Hung Like a Stang

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!

petrock

I don't know the orientation of the relay on your ride. A better way is to use the little letters/numbers next to each pin on the relay itself.

Have you tried swapping the relay out with another one in the distribution block?

Hung Like a Stang

The control wire, from the pcm, to the coil side of the relay (#80 pin at pcm, blue and orange) Has continutiy, however, test light across the coil side terminals in the fuse block does not yeild a test light. So, either my PCM is not signaling fuel pump, bad pcm, or bad connection of that blue and orange wire.

I can check the bad connection, but if that proves to be okay, Why would the PCM not signal fuel pump?

petrock

Don't start jumping ahead and thinking its a bad PCM. Its probably something simple (and cheap).

So the power side of the coil in the relay has continuity to the PCM? Correct? What about the ground side of the coil? Does it have continuity to ground?

Does the power side of the switch in the relay have power? Does it have continuity to the positive battery terminal? the power side of the switch is usually always hot when the car is on. What about the ground side? Does it have continuity to ground?

Have you tried swapping the relay out for a known good one?

Hung Like a Stang

spent all day yesterday tracing through wiring diagrams and testing.

The relay is not the problem, I swapped relays, and tested them 5 days ago after it initially wouldn't start.

On the coil side of the relay, you have the power wire (wire 361, its red) from the PCM, that gives power to almost everything underneath the hood, It goes back to three places on the PCM, and they're all good, all have continuity to the relay terminal. I knew that because that side of the relay works fine, but I tested continuity, and voltage at the PCM.

The other side of the coil is the ground controlled by the PCM, I have checked, checked, and re-checked continiutiy from the pcm to the relay terminal, and voltage at the PCM, and operation. It is dead as a doornail.

I had a guy we know come out and do a two module repogram of the PATS and PCM, it did not solve our problem (as we didn't think it would) but it gave us a P1262 (I think, I didn't look at the code number, he said it aloud), which is a fuel pump circuit malfunction (no s**t), it listed about 8 possible causes, all of these were things I had checked.

The last of these causes being "bad PCM." I hate "bad PCM" because 9 times out of 10 its just a part you're throwing at it that won't end up being the problem.

But me and him went through and checked everything again, and thats the conclusion we came to every time, Every wire is fine, the power control side is doing as its should, but the PCM simply isn't triggering the fuel pump....that list of possible causes did not list any extraneous sensors...as it shouldn't becuase it doesn't even turn the fuel pump on to prime when key is first turned, that should not require any inputs anyway.

So, I know of a known good PCM at the junkyard, (the explorer I got the engine out of I heard it start) and I'm gonna throw it in, and he's gonna come by and re-program it to PATS and see.

Hung Like a Stang

Just so everyone knows, It was indeed a bad PCM, I got one at a junkyard, had my guy program it with PATS, and VOILA!

It started right up, ran great, no check engine lights, I put about 70 Miles on her today.

I took the old PCM apart, and on the back, in the middle, there was a little black mark, something must have burned up...sweet huh...