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Fuel Pump has no power

dreamin-on

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I have searched and read all of the fuel pump threads and am still at a dead end. Please help.

1992 Explorer Sport 4X4 manual transmission will not start. This vehicle had been parked for a year and previously was a daily driver. The motor turns over just fine but I noticed when you take the key to "on" the fuel pump does not run to prime the engine. I have done the following:

-New battery
-Checked for voltage at the fuel pump connector just above the rear axle. 7 volts. I'm not getting power to the fuel pump.
-New fuel pump relay
-New EEC relay
-Checked for voltage at the inertia switch. 6 volts or so--not 12
-Verified the "check engine" light comes on, indicating to me the PCM is fine.
-Attempted to short the fuel pump relay. Nothing.
-Verified 12V at the fuel pump relay and EEC relay.
-Jumped the inertia switch by disconnecting the plug and inserting a jumper wire.

I should have this beast running by now. Please help.
 


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James909

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1994 GMC Yukon 2 Door
Welcome to the forum. With the ignition on try grounding the light blue/orange wire in the self-test connector. If the fuel pump turns on then the fuel pump circuit is fine, but the PCM is not triggering the fuel pump relay.
 








stanleycr1

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I would hang test a new pump assembly if possible to see if it runs when you turn on the key. The fuel gage wires run thru that same plug so there is always power on one pin. NOTE: If you are short on money go ahead an drop the tank before you buy a new pump. There is a good chance that one of the wires have corroded inside the tank an broke off at the terminal. I have seen that twice.
 




dreamin-on

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Thank all of you for the recent help. I have not had much time to work on this rig lately but did get out there the other day. I grounded the light blue/orange wire in the self-test connector and the fuel pump did not run. While I had the wire connected I went ahead and checked for voltage at the fuel pump connector above the rear axle and found 12V.

I am almost certain that it really is the fuel pump now. What do you think?
 




DeRocha

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'93 XLT 4x4
Thank all of you for the recent help. I have not had much time to work on this rig lately but did get out there the other day. I grounded the light blue/orange wire in the self-test connector and the fuel pump did not run. While I had the wire connected I went ahead and checked for voltage at the fuel pump connector above the rear axle and found 12V.

I am almost certain that it really is the fuel pump now. What do you think?

The fuel pump is feed directly from the inertia switch.. If the switch is reading ~6V then the wire you are testing is not the pump wire.

The fuel circuit will only register 12v while the engine is cranking.. Once the tach wire goes to Zero RPMs the fuel circuit will drop to 6-7v (which will not run the fuel pump). I would run a hot wire from the battery to either terminal on the inertia switch to confirm the fuel pump runs and/or starts the vehicle. One member ran his X like that for months before tracking the problem down to a loose ground wire in the EEC.
 




MrShorty

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Thank all of you for the recent help. I have not had much time to work on this rig lately but did get out there the other day. I grounded the light blue/orange wire in the self-test connector and the fuel pump did not run. While I had the wire connected I went ahead and checked for voltage at the fuel pump connector above the rear axle and found 12V.

I am almost certain that it really is the fuel pump now. What do you think?
If you ground the fuel pump test lead, get 12 V at the fuel pump connector, then we can conclude that the circuit seems functional up to that point. We aren't quite at the point yet of definitely saying the pump itself is bad. We could still have a fault in between the connector and the pump, or on the ground side of the pump. At this point, I would probably check the fuel pump ground (On my '92 the fuel pump ground attaches to the body behind the radiator overflow). If the ground looks good, then I'd probably be at the point of dropping the tank.
 




marragtop

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You should get 12v on both sides of the inertia switch. If you don't, then the problem is either the inertia switch or in front of it (PCM relay, FP relay, .etc).
 




dreamin-on

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Today I hung a new fuel pump from the connector above the rear axle. Turned the ignition to "on" and the pump ran like a champ so I dropped the tank and replaced the old one. She fired right up except the starter did not disengage. That's my project for tomorrow. The fuel pump was essentially stuck from sludge in the tank, it was essentially tar.

Thank all of you for your help.

I'll replace the starter tomorrow and she how she runs.

Picture of old pump:

image-1.jpg
 




CountryBoy78

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I think you got your money's worth out of that fuel pump........must have been sitting for some time to get that rusty ....wow.....
 




WickedWindsor

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You may want to change the oil before firing it up if it's been sittng a while. Old stale grimey oil can really mess up an otherwise good engine.
 








stanleycr1

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Glad you got it going. Don't forget the Fuel Filter. :)
 




dreamin-on

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Starter replaced. Drove it about 10 miles today and it runs great. Now on to the next project, brakes.
 




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1992 ford ranger
How's it going guys I know this is an old post but going through the same problems right now. 1992 ford ranger 4.0l manual transmission. Replaced fuel pump fuel filter and relay. Cranks but no start. I grounded the light blue/orange wire in the self-test connector, heard pump turn on and the truck started and ran but only for a little and died out again. Everytime I ground that pin the truck runs. What does this mean and where do I need to go from here? Thank you hope to hear from you soon
 




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