Fuel pump

Tiny
BILLZY70
  • MEMBER
  • 1997 DODGE TRUCK
  • V8
  • 4WD
  • AUTOMATIC
  • 220,000 MILES
What would cause no power to fuel pump
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Tuesday, November 30th, 2010 AT 4:46 PM

11 Replies

Tiny
CARADIODOC
  • EXPERT
Check for spark.

Caradiodoc
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Tuesday, November 30th, 2010 AT 4:48 PM
Tiny
BILLZY70
  • MEMBER
Has spark @ plug wires. Runs on sterting fluid
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Tuesday, November 30th, 2010 AT 4:52 PM
Tiny
WRENCHTECH
  • EXPERT
This is a computer controlled, variable pressure system that is very complicated and requires a professional scan tool to diagnose the problem.
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Tuesday, November 30th, 2010 AT 5:03 PM
Tiny
WRENCHTECH
  • EXPERT
Check fuse #9 inside fuse box and fuse #8 outside fuse box
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Tuesday, November 30th, 2010 AT 5:06 PM
Tiny
CARADIODOC
  • EXPERT
Dandy. That rules out the circuit that causes 90 percent of the fuel pump problems. What you are left with is the pump, its relay, and the wire in between. At the mileage you listed, it is fairly common to have a pump motor with worn brushes that cause it to not start up. Unlike GM pumps, Chrysler pumps almost never quit while running.

Try banging on the bottom of the tank while a helper cranks the engine. Often that jar will get the pump started.

By the way, there will only be voltage to the pump when the engine is rotating, (cranking or running), not just with the ignition switch turned to "run". Depending on the model, that voltage comes from the fuel pump relay or the automatic shutdown (ASD) relay. Those are turned on by the Engine Computer when it sees engine rotation. It knows that by the pulses from the crankshaft position sensor at the rear of the right cylinder head, and the camshaft position sensor in the distributor.

Caradiodoc
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Tuesday, November 30th, 2010 AT 5:10 PM
Tiny
WRENCHTECH
  • EXPERT
I'll let you guys sort this out. Please ignore my first post as I was confusing this system with the Ford system.
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Tuesday, November 30th, 2010 AT 5:13 PM
Tiny
CARADIODOC
  • EXPERT
Hi Wrenchtech. Yup. I can never remember which ones use a separate pump relay. When they do, like in this diagram, it is wired in parallel with the ASD relay. Some older cars run the pump right off the ASD relay, and I remember seeing one model years ago that ran the pump relay's COIL off the ASD relay, but that might have been a mistake in the service manual.

Caradiodoc
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Tuesday, November 30th, 2010 AT 5:33 PM
Tiny
WRENCHTECH
  • EXPERT
Yeah, Chrysler does it both ways. You never know which one you have.
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Tuesday, November 30th, 2010 AT 5:35 PM
Tiny
BILLZY70
  • MEMBER
Fuel pump is 2 years old. Could a bad pcm still let it start and run with starting fluid but not let the fuel pump work.
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Tuesday, November 30th, 2010 AT 9:06 PM
Tiny
CARADIODOC
  • EXPERT
Nope. If you have spark, the pump should be running too. To quickly check the relay, even though they don't fail very often, swap it with a different one like it. The starter relay and AC compressor relay should be the same. You can also pop the plastic cover off the fuel pump relay and watch the contact move when a helper turns the ignition switch to "run". The relay should turn on for one second, turn off, then turn back on when the engine is being cranked.

You can also squeeze that contact by hand. A quick trick is to watch that contact for a very tiny spark when you squeeze and release it. That spark means voltage is going to the pump and the wiring is good. If the pump still doesn't run when there's that spark, the pump motor is locked up. If there is no spark, the pump motor could have worn brushes, (try banging on the tank to get it going), the wire could be broken, or there's a bad connection in the electrical connector at the tank.

Caradiodoc
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Tuesday, November 30th, 2010 AT 9:20 PM
Tiny
BILLZY70
  • MEMBER
Thanks
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Tuesday, November 30th, 2010 AT 9:29 PM

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