92 5.0 low fuel pump volts
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92 5.0 low fuel pump volts
My 92 5.0 was having a intermittent fuel pump , sometimes it would run after turning on the key and other times nothing and the car would not start , I figured the fuel pump needed to be replaced , I installed a new pump and nothing and the relay wasn't pulling in so I checked the voltage at the pump which was only 7 volts ( I should have done this before replacing the pump) also only 7 volts at the relay . Could this be a ECM problem? Bad capacitor?
Last edited by kenn; Sep 6, 2020 at 06:33 AM.
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From: Insane
Ok, so there's this wiring diagram...
http://www.veryuseful.com/mustang/te...nks-ign-ac.gif
(Provided by this site, may be helpful in other ways... http://www.veryuseful.com/mustang/tech/engine/)
It's... fun to follow. And assuming it's correct... You can seen the end point Fuel Pump box on the middle left of the diagram. You'd just follow it 'backwards' through the wiring diagram.
The power for the fuel pump (Pink/black) comes directly from the fuel pump relay.
First, note that the fuel pump relay is switched on by the Engine computer (EEC). The signal power to switch it on comes from the inertia relay from the Red/black wire, which then 'turns into' a solid Red wire, which goes back to the EEC (and is spliced with other things powered on that circuit) eventually winding up at the Power Relay in the computer pin number 37. Going the other way from the relay, the relay signal is grounded via the Tan/LtGreen wire that goes to the EEC on pin 22. So when the EEC wants the fuel pump to run, it will ground that wire and that will flip the relay to 'on', which should then send power to the fuel pump.
So now back to the pump. Again, going backwards, the power we know comes in via the Pink/black cable. The power coming to the relay to send to the pump is coming in on the Orange/LtBlue wire. That wire goes back up to the engine compartment, through a fuse link. On the other side of the fuse link, the wire will be Black, and spliced to other things needing power. The wire on the other side of that splice is now Yellow, and pretty large (10 Gauge, apparently, about the size of a pencil or so) which then goes to the starter relay.
With that, the tests are to check the power at the starter relay on both big terminals, probably need key on for the one that sends power to the fuel pump. It should be 12 volts on both. After that, you're tracing it back through to the fuel pump, one thing at a time, until you find the loss of voltage.
If I'm reading this right, and it's also correct for your car (indications are it is), then the things to look at directly are the fuel pump relay input and output, the fuse link, and the starter solenoid. I suspect the starter solenoid is corroded at the terminal, but it could be anywhere. Also check all grounds for solid connections, without that, you're going to have a fun time figuring any of it out.
Hope that helps, good luck! And welcome aboard!
http://www.veryuseful.com/mustang/te...nks-ign-ac.gif
(Provided by this site, may be helpful in other ways... http://www.veryuseful.com/mustang/tech/engine/)
It's... fun to follow. And assuming it's correct... You can seen the end point Fuel Pump box on the middle left of the diagram. You'd just follow it 'backwards' through the wiring diagram.
The power for the fuel pump (Pink/black) comes directly from the fuel pump relay.
First, note that the fuel pump relay is switched on by the Engine computer (EEC). The signal power to switch it on comes from the inertia relay from the Red/black wire, which then 'turns into' a solid Red wire, which goes back to the EEC (and is spliced with other things powered on that circuit) eventually winding up at the Power Relay in the computer pin number 37. Going the other way from the relay, the relay signal is grounded via the Tan/LtGreen wire that goes to the EEC on pin 22. So when the EEC wants the fuel pump to run, it will ground that wire and that will flip the relay to 'on', which should then send power to the fuel pump.
So now back to the pump. Again, going backwards, the power we know comes in via the Pink/black cable. The power coming to the relay to send to the pump is coming in on the Orange/LtBlue wire. That wire goes back up to the engine compartment, through a fuse link. On the other side of the fuse link, the wire will be Black, and spliced to other things needing power. The wire on the other side of that splice is now Yellow, and pretty large (10 Gauge, apparently, about the size of a pencil or so) which then goes to the starter relay.
With that, the tests are to check the power at the starter relay on both big terminals, probably need key on for the one that sends power to the fuel pump. It should be 12 volts on both. After that, you're tracing it back through to the fuel pump, one thing at a time, until you find the loss of voltage.
If I'm reading this right, and it's also correct for your car (indications are it is), then the things to look at directly are the fuel pump relay input and output, the fuse link, and the starter solenoid. I suspect the starter solenoid is corroded at the terminal, but it could be anywhere. Also check all grounds for solid connections, without that, you're going to have a fun time figuring any of it out.
Hope that helps, good luck! And welcome aboard!
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