Fuel pump relay 94 Dodge Van

Tiny
OOPSTIKM
  • MEMBER
  • 1994 DODGE VAN
  • 6 CYL
  • 2WD
  • AUTOMATIC
My fuel pump relay takes a long time to kick in on cold mornings, (-32C). It does nothing for a few minutes then starts to rattle for about 30 seconds then it kicks in. It gets worse each day. I replaced the relay but it still does the same. Any help out there?
94 dodge 1/2 ton van, 3.9 motor
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Tuesday, November 23rd, 2010 AT 3:31 PM

4 Replies

Tiny
CARADIODOC
  • EXPERT
How do you know this? The pump should only run for one second after turning on the ignition switch. Then it will turn on again during engine rotation, (cranking or running). If you're not cranking the engine, the pump should not be running. That's to prevent it from pumping raw fuel onto the ground in the event of a crash that ruptures a fuel line.

Caradiodoc
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Tuesday, November 23rd, 2010 AT 3:36 PM
Tiny
OOPSTIKM
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Thanks caradiodoc, when I first turn on the ignition you do normally hear the fuel pump for a second or two, this doesn't happen now until the relay stops rattling, then I hear a second of the fuel pump and then it will start when I try it. If I don't wait it won't fire at all.
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Tuesday, November 23rd, 2010 AT 3:48 PM
Tiny
CARADIODOC
  • EXPERT
Oh. I would start by looking at the crankshaft position sensor on the passenger side of the transmission bell housing right behind the cylinder head. It is not unheard of it developing "spurious" signals that mimic the pulses it produces when the engine is turning. The Engine Computer will interpret those pulses as the engine is rotating so it will turn on the automatic shutdown (ASD) relay, and the separate fuel pump relay on vehicles that use them. When those pulses are erratic, the operation of those relays will be too. At the same time, the sensor could fail to provide the normal pulses it is supposed to during engine cranking. That can result in a no-start condition.

The camshaft position sensor can cause this too. It's inside the distributor. One thing to try is to unplug one of those sensors, then turn on the ignition switch to see if you still hear that rattling sound. That will set a diagnostic fault code in the Engine Computer and turn on the Check Engine light, but it will erase automatically after 50 engine starts, (about two weeks), after the problem doesn't come back.

Note that if you remove the crankshaft position sensor and reinstall it, the air gap is critical for proper operation. New ones from the dealer will use a thick paper spacer stuck to the end. It slides off when the engine is started and is done doing its thing. When reinstalling an old sensor, get a new paper spacer from the dealer's parts department. Many aftermarket replacement sensors have a thin plastic rib molded onto the end to set the gap. It partially wears away during engine operation. To reuse those, you are supposed to cut off the remaining rib, then use the paper spacer.

Caradiodoc
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Tuesday, November 23rd, 2010 AT 4:06 PM
Tiny
OOPSTIKM
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Thanks for the help, Caradiodoc, I will try this. It only happens when it's quite cold. This morning it even started with the remote start. (-6C) Thanks again.
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Thursday, November 25th, 2010 AT 3:44 PM

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