Mechanics

NO POWER TO FUEL PUMP

1995 Jeep YJ • 150,000 miles

4.0 L motor
Manual transmission
20 gallon tank

Would just crank (it started and stalled after a second a few times making me think a fuel problem was present)
Fuel relay clicked, fuel pump fuse is good, battery was good
Swapped relay with starter relay and no change, swapped with the relay that's in the fuel circuit (automatic shut off? No change either)
Checked fuel pressure at rail, there was none
Fuel filter was not very old, and there were no obvious leaks
Fuel pump was not priming
I dropped the tank and took apart the fuel sending unit
Put 12 VDC on the pump and it functioned

When the key is on (during the first 2 seconds, no voltage at the fuel sending unit harness, however there are 7 volts at the fuel gauge sensor pin

I jumped the relay (the high current one.30 I believe) to 87
There is 12 VDC at the fuel harness when the pins are jumped
The fuel relay still clicks when the key is just turned on

Ideas would be appreciated
Avatar
Aaronmcd
August 14, 2012.




So while cranking is there power to both sides of the fuel pump fuse?

Saturntech9
Aug 14, 2012.
Seeif your automatic shutdown relay is stopping it from getting power it could also be the pcm not sending power to relay

Hmac300
Aug 14, 2012.
I just checked to see if I had spark, and I do
While cranking I was getting about 11 volts on both sides of the fuel pump fuse

How do you want me to check the automatic shutdown relay? And the PCM?
Thanks everyone
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Tiny
Aaronmcd
Aug 14, 2012.
The blue/yellow wire goes to relay see if it gets voltage or not

Hmac300
Aug 14, 2012.
I checked the 3 pins on the autoshutdown relay and they have voltage
The 4th obviously wouldn't have voltage without the relay
I'm unsure how to check that wire?

Tiny
Aaronmcd
Aug 14, 2012.
That wire probably is the ground. But see if it goes to the fp relay if not you have a bad wire or connector someplace.

Hmac300
Aug 14, 2012.
Hey hmac300 doesnt the power go thru the fuel pump relay then thru the fuel pump fuse on that one?Because they have power thru both sides of the fuse. So that would mean the relay was working?I dont have a wire diagram in front me iam not home so I cant check that myself.

Saturntech9
Aug 14, 2012.
I'm confused guys

What and how would you like me to do?

Tiny
Aaronmcd
Aug 14, 2012.
See if the darkgrn/black wire going to fp is getting power then check the blk/orange wire near dist, that is ground, and seeif its making good contact. There is a fuse in fuse block fuse 5 tht goes to asd relay and fuse 1 in powr dist box, make sure both of those are ok. Those are for the relays I still think it's a shortsome place.

Hmac300
Aug 14, 2012.
All fuses In the power distribution center are good

I still don't know what you mean about the wires
What do you mean by dist? (Distributor or power distribution center?)
Should I remove the power distribution center?

Thank you

Tiny
Aaronmcd
Aug 14, 2012.

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