Bad electric fuel pump I think..?! Engine quits

guidoverduci · Oct 13, 2018

Here's the full story... I decided to put a lift kit on myself. I'm not a pro at this stuff, but figured I could swear my way through putting on the lift. I've finished the rear, decided to fire it up... First, I switched the ign to on to prime the pump. It came on, but stopped after about 5-10 secs. It usually stays on the whole time. I then started it up and let it run. I gave it gas to open up the choke, then.. it died. I started back up, ran for a sec, then died. I noticed now the fuel pump doesn't come on, when ignition is switched on. It's a holley red electric pump with a carb setup. I also noticed the aux fuel pump doesn't come on either, but I can't be certain it was working before because I never switched to that tank till now. I'm not sure what I did while lifting it up, but it worked before I put the rear together. Perhaps some relay, or something electrical obviously... but I know NOTHING about electrical. I've got a cheap multimeter from Harbor Freight, but I"m not even sure how to use the thing... Any ideas?

DirtDonk · Oct 13, 2018

Yeah, find the pump relay and check it out. Then find the pumps and check them out.;D
Just kidding, but since none of this is stock we don't know how it's wired or where anything is.
Are there wires running around the rear suspension somewhere? I assume so for the rear pump, but where is it mounted? You'll have to follow the wires and make sure you didn't pinch one and short it out on the frame or something.

Too bad you were not sure that the other pump worked or not before all this, as having both pumps stop working at the same time would maybe narrow it down to the ignition switch, a relay (or relays?) or one of the main power wires.
You may have to apply power directly tot he pump to make sure it works, but if it does then you're just going to have to go down the list one item at a time until you find the issue.

Are the pumps in-tank or external?

Good luck.

Paul

guidoverduci · Oct 14, 2018

Thanks Paul. They’re external frame mounted pumps and the PO put the painless wiring harness in. I thought about the pinched wire, but couldn’t see anything. I sprayed a hose under there to clean out the area and also thought maybe I shorted something out. Now I’m trying to figure where to plug in and see if the pump is getting power. Everything is sealed up pretty good.

SHX669 · Oct 14, 2018

My first suspect would be a burned fuse . If the PO marked what he used the fuse locations for look to see which one it is . If not pull fuses until you find one that has a burned /melted element.
You might have pinched a wire exposing the actual wiring causing a short .

SteveL · Oct 14, 2018

Suspension or body lift? Did you pull a connection apart somewhere? If you were jarring stuff around check your fuel filters too just in case. If a small one clogged up it might let you start up but not run. I run q-jet carbs and if the little inlet filter clogs it will go from running great to cap real quick.

guidoverduci · Oct 14, 2018

Suspension. Would that cause the electric pump to not even turn on?

guidoverduci · Oct 14, 2018

Ok, I gave it some time trying to trace things and check the fuse box. No relays found, no fuses labeled pump and none blown. it's wired clean and tight so I'd have to open wrap to really get into it. I think there are other options before I do that. I looked all over on things I could've potentially pinched... I know I smashed the aux filler tube, but that was in need of replacement already. There was nothing around it that could've gotten smashed. I did noticed some slightly exposed wires where the connection from the harness to the pump is. I'm thinking this has a chance to be the culprit. They are showing from the butt connector more than what I'd say is a pro job. So, how do I use a multimeter to see if voltage is being supplied to the pump? Ground out the black and put the red on the exposed wire, but what do I switch the multimeter to? And if it's zero... there's got to be fuse a relay somewhere... everything leads to the fuse box

gr8scott · Oct 14, 2018

Set the multi meter to 20V DC. If you test that setting on your battery you should see at least 12V.

guidoverduci · Oct 14, 2018

What should I see when ignition switch is placed to on and I’m on the exposed power wire connected to fuel pump?

gr8scott · Oct 14, 2018

You should see 12V. If you don't then the wiring is most likely your culprit.

guidoverduci · Oct 14, 2018

I’m seeing 10...

DirtDonk · Oct 14, 2018

Well that's something, but it's definitely not good. You should not have such a severe voltage drop over even that long-ish distance.
Usually a fuel pump uses at least 14ga wire due to the extra length needed, more than the fact that a pump uses a lot of juice.
Maybe that drop is enough to keep the pump from running though. Not sure it would like only seeing 10v

Did you get a good clean ground for testing? Are the pumps mounted cleanly? I'm guessing so, since they worked up until recently. But it's worth asking.

Got any pics of the pumps so we can see?

Paul

guidoverduci · Oct 14, 2018

Tried a few different spots for clean ground, best I got was 10.4. Both pumps are mounted well on the inside frame rail, drivers side. What gets me is there’s nothing I see that I could’ve came close to smashing. The poor connection on the butt connector is definitely not good, but seems likely that it was always like that. The pump is currently unbolted from the frame in the pic, my next step is to pull apart the connection and see if the power side is still showing 10ish and then making a better connection.

DirtDonk · Oct 14, 2018

An imperfect butt/crimp connector can fail intermittently, or all at once with no warning. But for both pumps to have the same problem still leads back to something else.

But for one thing, your pumps should absolutely be run off of relays. If they're not, then they're extra load constantly on the ignition switch that should not be there.
Pumps don't use all that much current, but any extra current that can be removed from the ignition switch is a good thing. Our old Bronco switches are not super heavy duty after all.

It's possible that the voltage drop is from corroding connectors somewhere. There must be a splice somewhere up near the front because I don't think the additional Painless circuits are long enough to reach a fuel pump on their own. Perhaps the main splice is failing and just decided it was time. Maybe you didn't do anything at all and it was just all in the timing.

Paul

DirtDonk · Oct 14, 2018

Bottom line though, is that with only 10v showing, you're going to have to trace the wire all the way to it's source to find out why.
It's not impossible for it to be a fault in the Painless connection at the fuse panel, but that would be low on the list of possibilities.

You looked under the hood to make sure there were no relays there, correct? Not just along the frame?
One more test you could do is literally run a jumper wire from the battery positive to the positive terminal of the pump. If it fires up like a big dog at that point, you at least know the pump is working.

Paul

guidoverduci · Oct 14, 2018

Thanks! The jumper idea is great. I went out to the garage to give it a shot.. the pump was burning hot... oops.. left the ignition on while I watched the second half of the football game. Doh! Not sure if the hot pump tells you a thing, but I’m gonna call it and re-attack tomorrow.

guidoverduci · Oct 15, 2018

No luck on the jumper, although I used cheap wire. I have thicker gauge speaker wire, but not sure if that would work even if a temporary connection. I pulled apart the connection and the power going to the pump is 11.6. Once spliced together, it dropped to 10ish. I’m going to order another pump. I might have fried this one regardless after leaving power to it for so long.

DirtDonk · Oct 15, 2018

Very possible. The heat is not a good thing because there is no fuel running through it constantly to keep it cool.
It might already have been fried though. After all, you said the other one did not work already and did not know the reason. Maybe this one just decided to die while you were working on other things, in one of those "coincidental mass parts suicides" I mentioned earlier.

If you connect your jumper again and measure the voltage at the other end just sitting there, you should see an accurate representation of any voltage loss over it's length. The smaller wire may have lost some at the far end, but you can easily see it with a volt-meter.
Measuring 11 at the pump may indicate some drop from the load of the frozen pump dropping the voltage. I think it works that way, but one of the electrical gurus can tell you that.

But the fact that you were getting a higher reading with the new wire vs the old does indicate to me that your existing wire is not sufficient. Whether it's due to a bad/corroded connection, or just the fact that the wire is too long, too small, and not using a relay is hard to say from here.
More messing about is in order when the new pump arrives.
With luck you'll see the full 12v at the business end with the new pump. But if not (and even if so) you should add a relay and it's own dedicated circuit from the battery and the pump.

Good luck.

Paul

guidoverduci · Oct 15, 2018

Thanks Paul. I might have misspoke. The existing wire when not hooked to the pump is showing 11.6. When I hook up the pump and measure at the connection, it drops to 10. I tried to trace all the wiring, but I was unable to see any relays. However, it's taped / wrapped really good and then zip tied tight under the dash. I won't say 100% there's no relay, but with how clean and tight everything is, I wouldn't expect the PO to hide it if there were one.

guidoverduci · Oct 15, 2018

side note... I ordered the Carter P4070. It says it has a built in regulator. Should I remove the regulator that's installed up near the carb then?

Bad electric fuel pump I think..?! Engine quits

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