fuel pump problems on my 93 yj

rossy44 · 07-10-2010, 01:13 PM

i just replace the fuel pump on the yj and it will only work intermittently. illturn the key to the on position and i will hear it come on and then ill shut it off and do the same thing but it wont turn on. Sometimes it will turn on 3 or 4 times in a row but then proceed to not turn on again. Could the relay be bad or the fuel sending unit wires be faulty?

Jakers09 · 07-10-2010, 01:19 PM

I ran in to a similar situation when rebuilding my 91. The issue was actually related to a bad ground for the fuel pump. The wire itself is black/yellow and attached to the emergency brake bolt.

Roadyy · 07-10-2010, 01:19 PM

It's suppose to shut off til the engine cranks then it will run again unless your CPS is faulty or going bad then it wouldn't run the pump after the initial prime. Disconnect the CPS and clean the connection and check for burnt spots, if all good then reconnect it and try again.

rossy44 · 07-10-2010, 01:39 PM

I replaced the CPS recently so that cant be the issue. Jakers theres a ground on the fuel sending unit itself, on top of the tank thats rusted pretty bad could that be it?

**idaholtby** · 07-10-2010, 03:15 PM

What was the original symptoms that lead to the pump replacement and have they changed any with the new pump or are these issues the same? As Rick stated, the pump only comes on momentarily to prime the rail, then shuts off until the engine is running, but your problems sounds to be more than this. If you have a ground issue, you should also see your fuel gauge peg when the fuel pump problem is active.

rossy44 · 07-10-2010, 03:53 PM

i replaced the original fuel pump a month ago, then a few days ago i went to move it in the driveway and the fuel pump wasn't turning on momentarily to prime the rail and wasn't turning over. so i figured the pump was faulty so i got another with my waranty. Now the pump will turn on to prime the rail sometimes andd turnover but other times it wont turn on to prime the rail at all. the connections on the pump and fuel sending unit are all tight and there are no burn marks on the weather pack connection. The fuel gauge works fine. so im leaning toward a bad ground somewhere

tarjeta · 07-10-2010, 03:58 PM

it is bad ground

**idaholtby** · 07-10-2010, 04:11 PM

Seeing how your fuel gauge is working properly, I don't believe this is a ground problem. The sender for the gauge and the fuel pump share the same ground. If the ground was bad/intermittent, you would see your fuel gauge peg everytime it acted up. Your problem appears to be power related. Check for power at pin 30 and 87 of the fuel pump relay. You can jumper pin 30 to pin 87 to test to see if the pump stays on. If you have power at pin 87 and the pump does not stay on, then the problem is between the relay and the pump and you need to trace it out. If no power at pin 30, then check F1 30amp in the PDC.

Roadyy · 07-10-2010, 05:56 PM

I agree with Idaholtby. If it were the ground or even an intermittent ground issue the gas guage would peg intermittently aswell. I also know several ppl who have bought a faulty CPS or one that lasted a couple months. Just trying to help.

rossy44 · 09-14-2010, 03:31 PM

Ended up being a bad fuel pump relay... hasnt stalled for a 1000 miles since i've changed it. thanx for the help guys

jbeebe · 09-14-2010, 03:43 PM

thanks for the update. this thread is good to keep in mind if it ever happens to me

snakeroo · 02-08-2011, 07:09 PM

Heyas, So I am trying to determine if it my fuel pump that is bad, before going thru the hassle of pulling the gas tank. My problem actually started back in Sept, after I was super low on gas, and then seemingly ran out. For 3 days, I tried everything from changing the distributor cap, rotor and wires....to swapping the horn and fuel pump relays(Horn worked no matter which way). Checked all the fuses under the dash. Then I came across a thread, where someone said to turn the key to the ON position and go back and hammer on the gas tank with a mallot. Did that, hopped back in and cranked it, and it started!

Then on my way home, I stopped into Autozone, ran over the curb, going into their driveway and instantly, my engine started knocking very loudly.I was told by a few local shops, my engine was shot and needed a rebuild or replacement($1,600 - $2,400). So, I hadn't driven it for 4 months, while trying to save up. Only starting it a few times to move it for street cleaning. Well, after revisiting the threads here, turns out my bump stops were eroded, axle slammed into and dented oil pan, when I ran the curb!

I pulled the pan off a week ago, hammered out dent, put back on. Started and engine is now sounding great! Went to restart it about 5 mins later...no start. No fuel pump prime. Well, next day, I decided to put in a new fuel pump relay and cleaned the block where it plugs into also. No luck. SO then decided to a friend hammer on the gas tank as i cranked with the key....wah lah! sputter sputter..vroom. Started and ran just fine. drove around the block. Shut it off. 20mins later..no start.

Is this my fuel pump for sure? I also read about how some wires going to the pump, get pinched somewhere against the frame? Where exactly should I look for that? Cause, I am wondering, if the hammering action, could be bouncing those wires, freeing them from the frame, allowing it to start? Thanks!

yj98joe · 02-08-2011, 07:26 PM

snakeroo, most likely its the pump. Thats pretty much how I have always checked mine out. Beat on the tank if it starts after that ....Fuel pump.
All that being said, sure it could still be something else and the shock from hammering on the tank has moved the wires or whatever. But if you dont get in there and trouble shoot it you wont know until you've swapped out the fuel pump and it strands you again. Any thing is possible.

snakeroo · 02-09-2011, 02:49 PM

Okay, I will still try to trace the wires to find the area where they tend to get pinched. I checked with Autozone. They have two different kinds of fuel pumps. One that PLUGS in and one that SCREWS in. They said I won't know the type I have until I take mine out. Is this true? Or? It's a 1993 YJ, 6 cyl, manual.
One is $81.99 and the other is $71.99. I assume this is just the pump and not the sending unit etc too? Also, the cross member that my gas tank is bolted to looks pretty rusted. Does that usually have to get replaced too? Is that and the tank usually pretty difficult to get off or is it pretty easy??