Mechanics

NO POWER TO FUEL PUMP

1994 Dodge Shadow

Ive had the fuel pump replaced and now there is no power going to it. Is there something wrong with the wiring? Please help
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Christa G
November 20, 2011.



Also, where is the relay located? Please need help ASAP. Thank you

Tiny
Christa G
Nov 20, 2011.
What's the symptoms? Have you checked for spark?

Caradiodoc
Nov 20, 2011.
Also, which engine do you have, the 2.5 four cylinder or the 3.0L V-6?

Caradiodoc
Nov 20, 2011.
It is a 3.0L V-6. I took the gas tank off to fix the leak. I got busy so it sat for 3 years. I put the tank back on, then found no power in the wires going to the fuel pump. The car worked just fine before I took the tank off.

Tiny
Christa G
Nov 20, 2011.
I've typed this reply so many times that sometimes I leave important details out so be sure to ask if something doesn't make sense. The ignition coil, injectors, alternator field, and fuel pump OR fuel pump relay are powered through the automatic shutdown (ASD) relay. That's why you have to check for spark. Don't get stuck on the dead fuel pump.

If you do have spark, then we'll work on the fuel pump circuit but first it's important to understand how that one works. With the ignition switch in the "run" position you should not have voltage to the pump. The Engine Computer turns on the ASD relay for only one second after you turn on the ignition switch, (you might hear the pump hum), then it turns it back off. The computer will turn the relay on again during engine rotation, (cranking or running). It know there's rotation by the pulses it receives from the optical pickup inside the distributor. That assembly has a very low failure rate. What's more likely is the timing belt is broken. You can verify that by observing if the distributor rotor turns during engine cranking. Of course if you DO have spark, the timing belt is okay and the ASD relay is turning on. To check for voltage at the fuel pump connector you'll have to measure while a helper is cranking the engine. If you have to work on this problem alone, I can explain how to bypass the ASD relay so you can take your time taking measurements.

Caradiodoc
Nov 20, 2011.
R

Tiny
Christa G
Nov 21, 2011.
Oops, last response was an accident. Thank you! That helps out alot. I also messed up on the make and model. It is a Plymouth Duster 3.0L V-6. I hope there isnt much of a difference.

Tiny
Christa G
Nov 21, 2011.
Nope. The Duster was a model of the Plymouth Sundance, and twin to the Dodge Shadow. The interior trim is the biggest difference.

The 3.0L engine is real desirable and not terribly common in that car. In case you're not already aware of it, you have a really tough little car. My friend who used to own a body shop had one. His girlfriend pulled into traffic and got broadsided in the driver's door by a large GM car going 35 mph. The interior door panel never got touched thanks to a steel beam inside the door. Her only injury was from hitting her head on the door. One used door and a little body work and the car was back on the road. The Olds Cutlass had more dollars worth of damage than the Shadow.

I used a lot of Shadows to create learning exercises for my students. We had six of them, some donated by Chrysler. They were easy to work on and diagnose. If I could find a nice rust-free one, I'd turn that into my daily driver and save my '88 Grand Caravan. The Neon replaced the Shadow / Sundance in '95. No self-respecting mechanic would want to own one of those.

Caradiodoc
Nov 21, 2011.
That is great to know that its a trusty car. : ) I checked for spark and there is spark. Is there any fuse for the fuel pump? I did not find one under the dashboard. What should I check next?

Tiny
Christa G
Dec 3, 2011.
Dandy. Having spark rules out all of the common stuff and just leaves the fuel pump circuit. I can only find a service manual for a '93 model, and I think the fuse box for a '94 is different. Do you have a fuse box under the hood, driver's side, or do you have six relays bolted to the body, three on the left inner fender and three in front of the left strut tower? I'm trying to point out which one is for the fuel pump, ... Woops, I just found my '94 manual and it looks like you have individual relays yet like on a '93 model. If that's right, the fuel pump relay is on the strut tower, closest to the center of the car, of the three.

There's a couple of ways to approach this. You can use a test light back at the tank to test for voltage. As I recall, the connectors are on the right side where you can reach them without lowering the tank. Unplug the fuel pump connector and test on the dark green / black wire. It's important to understand there will only be voltage there for one second after turning on the ignition switch so you're either going to need a helper to turn the switch on or you're going to have to prop the test light up so you can see it from inside the car. You can use a digital voltmeter too but often they don't respond fast enough. Also, voltmeters draw almost no current to do their testing. Test lights draw plenty of current to show up a high-resistance break in the circuit that can prevent the pump from running but be enough for a voltmeter to give an acceptable reading. The test light, in this case, is more accurate.

If you see voltage for that first one second, the relay and wiring to the tank are okay. With the connector plugged in, you should be hearing the hum of the pump for one second when you turn on the ignition switch.

As an alternative, you can bypass the fuel pump relay with a stretched out paper clip. You won't even need to turn on the ignition switch for any of the tests. Unplug the relay's connector and jump between the dark green / black wire and the red / white wire. They will be two of the three fatter wires. Doing that will send voltage to the fuel pump just as though the engine was running. If the pump doesn't run, you can take voltage readings now anywhere in the circuit.

If you find voltage at the pump's connector, either the pump is stuck or the terminal in the connector is spread or corroded and not making a good connection. We have to consider a bad ground wire too. It's fairly common for the pump to not start running due to worn brushes in the motor. Banging on the bottom of the tank will often get them going, and that works even better if you do it while voltage is applied. Once the pump is running, Chrysler pumps almost never quit and let you sit on the side of the highway. They will fail to start up but not quit until the engine is shut off. GM pumps are known to suddenly quit and leave you stranded on the side of the road in a puddle of tears.

Holler back after you've made these tests.

Caradiodoc
Dec 3, 2011.
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