Fuel pump voltage
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Fuel pump voltage
I have a 1992 Ranger with 2.3 engine. Not getting fuel checked fuse got 12 volts. Checked inertia switch got 6.8 volts. Disconnected fuel pump and remove from tank and hooked to 12 volt source and the pump works fine. Don't know why only 6.8 volts to inertia switch, seems problem with voltage is between fuel pump relay and inertia switch. Don't know where fuel pump relay is any help would be appreciated.
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From: SoCal
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From: South Texas
You can probably follow the wire from the inertia switch to find the relay. On my truck (87 Ranger) it's in the engine compartment mounted on the passenger side wall there, next to the airbox. Mine is a square thing with a wire harness plug in it.
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I have found the fuel pump relay.Checked the voltage-12 volts in,6.9 volts out.When i turn key to on position,i get 12 volts out of relay for a couple of seconds then the relay clicks and i get 6.9 volts.How does the engine run if the fuel pump rons on 12 volts and the relay only sends 6.9 volts?I replaces the relay and the same thing happens so that eliminates the relay being the problem.Help please before i take a torch to this thing.
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From: SoCal
Sounds like you're reading voltage on the wrong wire & grounding the relay thru your voltmeter. Thats the click that you are hearing.
Have you got a wiring diagram???
Hers how it works on my 87, yours might be different. With the ignition turned off heres the voltage that you should see at the relay: you should have 0 volts on the red wire, 0 volts on Tan/light green,12 volts on yellow and 0 volts on orange/light blue.
Turn the key to run & you should see 12 volts on red & on tan/light green.
12 volts on yellow & NOW is when you should see 12 volts on orange/light blue which goes to the fuel pump.
Edit the 12 volts on orange/light blue will only be there for 2 seconds after you turn the key to run, and then it times out.
Have you got a wiring diagram???
Hers how it works on my 87, yours might be different. With the ignition turned off heres the voltage that you should see at the relay: you should have 0 volts on the red wire, 0 volts on Tan/light green,12 volts on yellow and 0 volts on orange/light blue.
Turn the key to run & you should see 12 volts on red & on tan/light green.
12 volts on yellow & NOW is when you should see 12 volts on orange/light blue which goes to the fuel pump.
Edit the 12 volts on orange/light blue will only be there for 2 seconds after you turn the key to run, and then it times out.
Last edited by 87 XLT; Jul 2, 2005 at 12:33 AM.
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From: Durham, NC
Originally Posted by 87 XLT
Sounds like you're reading voltage on the wrong wire & grounding the relay thru your voltmeter. Thats the click that you are hearing.
Have you got a wiring diagram???
Hers how it works on my 87, yours might be different. With the ignition turned off heres the voltage that you should see at the relay: you should have 0 volts on the red wire, 0 volts on Tan/light green,12 volts on yellow and 0 volts on orange/light blue.
Turn the key to run & you should see 12 volts on red & on tan/light green.
12 volts on yellow & NOW is when you should see 12 volts on orange/light blue which goes to the fuel pump.
Edit the 12 volts on orange/light blue will only be there for 2 seconds after you turn the key to run, and then it times out.
Have you got a wiring diagram???
Hers how it works on my 87, yours might be different. With the ignition turned off heres the voltage that you should see at the relay: you should have 0 volts on the red wire, 0 volts on Tan/light green,12 volts on yellow and 0 volts on orange/light blue.
Turn the key to run & you should see 12 volts on red & on tan/light green.
12 volts on yellow & NOW is when you should see 12 volts on orange/light blue which goes to the fuel pump.
Edit the 12 volts on orange/light blue will only be there for 2 seconds after you turn the key to run, and then it times out.
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From: SoCal
Maybe the click he's hearing from the relay is just the 2 second timeout?
Ions, heres a real simple trick to keep the pump circuit energized while you check volage. Just apply your own ground to the relay. Check out this link. www.superhighoutput.com/tech_view.php?id=5
Ions, heres a real simple trick to keep the pump circuit energized while you check volage. Just apply your own ground to the relay. Check out this link. www.superhighoutput.com/tech_view.php?id=5
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Why does the relay "time out" after two seconds.My meter is good,still dont understand how fuel pump works if relay times out after two seconds.Torches are in position,ready to light.Thanks for your help and hope to hear from you soon.
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From: Concrete WA
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If I am thinking correctly there are two relays in the fuel circuit, the one with the time out delay is allowing fuel to get to the engine prior to oil pressure. Once oil pressure is adequate the fuel pump is fed from a different source. Need to check a wiring diagram.
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> </o>If I am thinking correctly there are two relays in the fuel circuit, the one with the time out delay is allowing fuel to get to the engine prior to oil pressure. Once oil pressure is adequate the fuel pump is fed from a different source. Need to check a wiring diagram.
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From: SoCal
Originally Posted by Fordteamone
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<o> </o>
If I am thinking correctly there are two relays in the fuel circuit, the one with the time out delay is allowing fuel to get to the engine prior to oil pressure. Once oil pressure is adequate the fuel pump is fed from a different source. Need to check a wiring diagram.
fficeffice" /><o></o><o
> </o>If I am thinking correctly there are two relays in the fuel circuit, the one with the time out delay is allowing fuel to get to the engine prior to oil pressure. Once oil pressure is adequate the fuel pump is fed from a different source. Need to check a wiring diagram.
As you say a wiring diagram is a MUST for fixing this sort of thing.
Ions, did you look at that link I gave you and ground the pump relay yourself??
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From: Concrete WA
87 XLTLearn more every day, mine was on an 83 F250 and the fuel relay did not seam to have a long life, when it died it would not get fuel until the oil pressure came up, lots of cranking. We started carrying spare relay. So If I understand you, ignition pulse comes out of terminal 8 on the wiring diagram you linked to, timing delay gives power during start. Thanks for the lesson.
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From: SoCal
Originally Posted by Fordteamone
87 XLTLearn more every day, mine was on an 83 F250 and the fuel relay did not seam to have a long life, when it died it would not get fuel until the oil pressure came up, lots of cranking. We started carrying spare relay. So If I understand you, ignition pulse comes out of terminal 8 on the wiring diagram you linked to, timing delay gives power during start. Thanks for the lesson.
Not sure which wiring diagram you are refering to for pin 8, the one that i'm looking at here shows pins 16 36 & 56 are wired from the ECM to the ignition module. Pulses on one of these are-i believe- what triggers the ECM to ground the pump relay.
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The circuit pretty simple one pin has power all the time that pin is the power that when the relay is energized goes to the pump. the other is the energize circuit it goes through the coil in the relay through the inertia switch to the PCM this power comes on when the key is turned on. The pcm turns on ground to energize the relay. The 2 seconds at key on is the primer time then the pcm reads that the engine is turning over and completes that ground circuit which sends power to the fuel pump that is pin 22 on the PCM. Now there is a Fuel Pump test port on the EEC test plug. With the key on you can ground the port and the pump will run as long as it is grounded. If you look at the eec test port it has 6 slots turn it up so the the two that are togather are up the Fuel pump test port is the bottom right handed one. If you ground this and it runs then the Fuel pump relay is good. That leaves the inertia switch or the pcm itself and I have seen the Pcm lose the ability to complete that circuit to ground so make sure all your grounds are good. I hope this helps.
jd
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