Fuel Pump Relay Problem
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Logistics Pro
Joined: Mar 2011
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From: Central Wisconsin
Fuel Pump Relay Problem
So this problem dates back to about a year ago.
1989 F250, 351w, rest of the info is in the sig, but just in case the sig ever changes and somebody needs the info.
Truck wouldn't start one day because the fuel pumps weren't turning on. After a quick investigation the fuel pumps weren't turning on, and I traced that back to the relay also not functioning. I thought, quick fix, put in a new relay.
So I got a relay out of a parts truck (this truck didn't run so the part was of questionable working order) and it didn't fix the problem, so not a big deal. Bought a new relay from the parts store for a few bucks, and still not fixed. I thought it could be the plug for the relay, corrosion or something, so I replaced it. Still wouldn't flip the relay on.
Now, here's what i do know. I'm getting power up to the relay, and have temporarily been running a wire from the plug to a switch and back into the plug to turn the fuel pumps on, and that has worked fine thus far.
I'm wondering if anyone has any insight on what could be going on here.
1989 F250, 351w, rest of the info is in the sig, but just in case the sig ever changes and somebody needs the info.
Truck wouldn't start one day because the fuel pumps weren't turning on. After a quick investigation the fuel pumps weren't turning on, and I traced that back to the relay also not functioning. I thought, quick fix, put in a new relay.
So I got a relay out of a parts truck (this truck didn't run so the part was of questionable working order) and it didn't fix the problem, so not a big deal. Bought a new relay from the parts store for a few bucks, and still not fixed. I thought it could be the plug for the relay, corrosion or something, so I replaced it. Still wouldn't flip the relay on.
Now, here's what i do know. I'm getting power up to the relay, and have temporarily been running a wire from the plug to a switch and back into the plug to turn the fuel pumps on, and that has worked fine thus far.
I'm wondering if anyone has any insight on what could be going on here.
Fleet Owner
Joined: Aug 2005
Posts: 23,668
Likes: 301
From: Easton,Ks
You do not say what color wires have power at the relay plug with the key on.
You say you are running a wire from the plug to a switch and back into the plug to turn the fuel pumps on. From that I take it you are saying you are bypassing the contacts in the relay with a switch from the yellow wire to the Brown wire at the FP relay.
You need to remove your jumper and ground pin #6 of the self-test plug and see if the fuel pumps run then with the key on. If they do you have a bad computer or the wiring from the self-test plug to the computer.
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You say you are running a wire from the plug to a switch and back into the plug to turn the fuel pumps on. From that I take it you are saying you are bypassing the contacts in the relay with a switch from the yellow wire to the Brown wire at the FP relay.
You need to remove your jumper and ground pin #6 of the self-test plug and see if the fuel pumps run then with the key on. If they do you have a bad computer or the wiring from the self-test plug to the computer.
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Cargo Master
Joined: Jul 2009
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Likes: 54
From: Des Moines
I agree with Subford.
If you're getting power at the yellow wire (which you should be, even with the key off as it's supposed to be hot at all times) but you're not getting anything when you turn the key on, something in the circuit is preventing it from completing. My thoughts are to check and clean the grounds, but it may not be that simple.
If you're getting power at the yellow wire (which you should be, even with the key off as it's supposed to be hot at all times) but you're not getting anything when you turn the key on, something in the circuit is preventing it from completing. My thoughts are to check and clean the grounds, but it may not be that simple.
Fleet Owner
Joined: Aug 2005
Posts: 23,668
Likes: 301
From: Easton,Ks
Yes as DBGrif91 said above check the computer ground as I forgot to say:
If the fuel pumps run when you ground pin #6 with the key on and DO NOT run when you short pin #6 to pin #2 of the self-test plug with the key on then check that small black wire with a green stripe at the Neg post of the battery.
This happens a lot when someone replaces the Ground battery cable.
If the fuel pumps run when you ground pin #6 with the key on and DO NOT run when you short pin #6 to pin #2 of the self-test plug with the key on then check that small black wire with a green stripe at the Neg post of the battery.
This happens a lot when someone replaces the Ground battery cable.
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Logistics Pro
Joined: Mar 2011
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From: Central Wisconsin
Hey, thanks for the quick responses guys.
I know I'm getting power at the yellow wire for sure, as that's what I'm getting power off of for the switch.
I will check and see what your guy's suggestions let me find out this weekend and post back here.
I know I'm getting power at the yellow wire for sure, as that's what I'm getting power off of for the switch.
I will check and see what your guy's suggestions let me find out this weekend and post back here.
Thread Starter
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Logistics Pro
Joined: Mar 2011
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From: Central Wisconsin
Gotta revive this thread.
Finally got to investigate the fuel problem after 6 months of pushing the truck aside to work on other stuff.
Disconnected my jumper and switch and put a relay in and to my surprise the relay that i put in works, or at least appears to be. However, I stopped my investigation shortly after this because the volt gauge was throwing itself around and clicking.
Does that sound like a bad ground issue? With the switch it was not doing that minutes before and only started after I put the relay back together.
Finally got to investigate the fuel problem after 6 months of pushing the truck aside to work on other stuff.
Disconnected my jumper and switch and put a relay in and to my surprise the relay that i put in works, or at least appears to be. However, I stopped my investigation shortly after this because the volt gauge was throwing itself around and clicking.
Does that sound like a bad ground issue? With the switch it was not doing that minutes before and only started after I put the relay back together.
Thread Starter
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Logistics Pro
Joined: Mar 2011
Posts: 4,197
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From: Central Wisconsin
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Fleet Owner
Joined: Aug 2005
Posts: 23,668
Likes: 301
From: Easton,Ks
What do you want us to address?
A volt gauge was throwing itself around?
A clicking volt gauge or was it the fuel pump relay or starter solenoid?
Have you checked the wiring under both relay sockets?
That is were the problem is most of the time with an 88 or 89.
A volt gauge was throwing itself around?
A clicking volt gauge or was it the fuel pump relay or starter solenoid?
Have you checked the wiring under both relay sockets?
That is were the problem is most of the time with an 88 or 89.
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