Fuel Pump Issue

[Gravy]

First off, this seems to be a ground issue, but than again i'm not 100% sure how, or why. Keep in mind, we tested everything short of using a volt meter testing everything.

(91 Dodge stealth RT/TT fuel pump rewire, remote battery in the trunk with dedicated ground wire going straight to the fuel pump bracket bolted to a clear rust free spot on the top of the bracket though one of the studs)

But it may have started last fall, my fuel pump was cutting in and out and when i started looking, i was getting a knock count of about 30 at idle, and around 70 just cruising. Pulled the knock sensor now i'm getting the right knock count, but my fuel pump doesn't work. I have a rewire done but tried running it with, and without the rewire being on there. Same problem both times. Now, i cleaned a ground, or three on the fuel pump mounting plate, and can get the fuel pump to run by using alligator clips providing a ground to the plate. However, when the plate is bolted to the tank all the way, it doesn't run even with the alligator clips on the tank, studds, bolt, or factory ground wire going to the mounting bracket.

As of right now, with three of the bolts off the fuel pump mounting plate i can get it to run, if i put one on and the MOMENT it makes contact with the plate, i loose ground. I back it off(no pressure, just touching mind you) so that it's free hanging on the top of the stud, it runs. Same with the bolt on the other side. Now, i know this is kinda gheto, but it's late at night and febo and i tried our damndest with neither of us having a volt meter. That being said, electrical tape applied under the bolts preventing them from touching the mounting plate(but still making contact to the studd and fully torqued down) we can get it to start intermitinly, but unsure as to why.

Ground is good from the pump to the fuel pump mounting bracket, and when the pump is hanging over the tank not touching, it runs. But if we put it down and put two bolts holding it down, it works, third one down, it works. Forth one down, no ground even after re-torqing the other bolts down. It is bolt specific as well, bolts 2 and 5 can not be used as the two holding it down, the others can be used in any order/combination and it runs.

If anything isn't clear ask questions, or you have any idea why this might be happening, let me know. I'm open to options, and this has by far been the weirdest thing i've run into with a DSM, or it's retarted cousin. Would love to get it working fully bolted down and ready to run this summer to sell.

Gravy

[s1ngletracker]

back up for a second. What makes you think this problem is even directly related to the fuel pump? I need to go back and read everything you said again... I wish there was cliffs notes for people like me :)

[s1ngletracker]

Now that I read again, it sounds like your power wire has a short somewhere, to the point where if you get a contact between the plate and ground at some points, you short it out. I would carefully look at your power wires. Get rid of the rewire while you're testing as well.

[Gravy]

Removed the rewire and ran straight from battery to fuel pump for testing as well to eliminate anything from point A(battery) to point B(Pump). This post IS the cliff notes. I've tried all three pumps i have(Stock, 190 and 255 walbro) in and out of the vehicle, all three give the same results. And the pump works 100% of the time when the ground wire is supplied directly to the pump, but when the whole assembly is bolted down, i get nothing. Positive is fully covered and there are no exposed wires on it. I've got it working as of now, but with only three bolts holding the fuel pump in the back on, with one more holding it down with electrical tape between it and the mounting plate. Remove it, and the electrical tape it's fine. Put the bolt back down with no electrial tape(metal on metal) and i get nothing. I laughed so hard workin on it i started to cry.

Thanks for the idea though, i'll be checking voltage(resistance and ground) soon as i get a volt meter to rule out a bad wire on either the positive or the ground.

[munchgsx]

Have you tried a different sending unit? Did you do your rewire by the book?
Relay triggered by stock power wire.

[Gravy]

I don't have access to another sending unit, but i know the ground from the factory does work, and i have a secondary ground going to the frame of the sending unit as well.

I did the rewire by the book, and it will run now both in stock format, and with the rewire on there. And with the rewire on if i hook up a stock mass i still get the same issues when it acts up, and works both ways when the problem presents itself. I run with a GM maf and when i start it with the stock hooked up, with out metering the air, the relay clicks on and off like it should. When the car is running with only the three bolts holding it down, i can let it idle, rev it up, and it runs just fine. And it would technically work if i didn't mind the smell of gas following me everywhere.

[s1ngletracker]

I would get a voltmeter and check for voltage from the plate to ground. I still think you've got a short.

[Pushit2.0]

If it was a short to ground it should burn a fuse or melt a wire. I would use a volt meter, go to walmart, harber freight, northern, radio shack, barrow, what ever. Test your voltage in, IE stock fuel pump power wire. Note the 3/S has a High/Low voltage regulator for the stock fuel pump power. Then make sure you have 0 Ohms to ground from the fuel pump ground terminal to the chassis or battery negative. Also check for ohms on the positive terminal of the fuel pump to ground, it should be open or no connection, all of this with the fuel pump sending unit plugged into the chassis harness. Good luck.

~John

[Gravy]

Going to test it tomorrow, if it turns out to be a ground issue, i'm going to drill though the sending unit, and tap in a M6-1.0 bolt and ground out that way though the top of the sending unit. Unless anyone else can think of a reason not to, my stock ground is so rusted i don't think much is making it though there, and this way i can get a good ground, and close up the whole made so that no gas leaks out.

Otherwise, i'll just grind down around all the holes on the sending unit and try several different grounding locations. I know last year i had an issue with the ground, buy my secondary straight to the battery was able to fix it. Even with that spot cleaned up it still doesn't seem to be doing the job any more.


Gravy

[Febo]

Have you tried a different sending unit? Did you do your rewire by the book?
Relay triggered by stock power wire.

He has a bat relocate to the trunk too so it deff is a grounding issue as we were running power straight to the pump, and also grounding the sending unit straight to chassis or the negative terminal to show that it wasnt the pump. It is deff a weird ground issue, havent touched it with a volt meter yet, but we will tomorrow.

Cliff notes are his stealth is possessed.