Both fuel pumps bad?
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Both fuel pumps bad?
I have an 95 F-150 300ci. duel tank. Lately it has been hard to start, like it was having fuel problems. The other day I went to start it and the pump would not come on. I grounded the DLC and can hear what I believe to be a relay but no pump. After reading in my trusty repair manual, I find out that I have 2 pumps, one for each tank. Makes since, but when I flip the switch to the second tank, still nothing. I find it hard to believe that both pumps went bad at the same time. Any ideas? I guess it can be the inertia switch or the selector switch, but the only way I know to test the pumps is to drop the tank and check for power to the pump. Since the truck is stranded outside and in 20 degree weather, I would like the quickest test possible to find out the problem before I freeze to death. Many thanks in advance. Ron
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From: Sand Lake, MI
A bad relay should be easy enough to check with my trusty volt meter.
Yes it would be!
The "Dk Grn-Yel" wire at the fuel pump relay should show bat voltage when the relay closes. Might prove easier to test for it at the inertia switch, that way you don't have to get in under the power box and can test with the relay in place.
Yes it would be!
The "Dk Grn-Yel" wire at the fuel pump relay should show bat voltage when the relay closes. Might prove easier to test for it at the inertia switch, that way you don't have to get in under the power box and can test with the relay in place.
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Well so far no go.
First of all, the inertia switch is not where my book said it should be. After doing some reading on this forum, I believe it to be behind the passenger side kick panel. I hope it is there when I look tomorrow. Also neither my repair book nor does the fuse box lid show me which relay is the fuel pump, and my owners manual is completely wrong. All 4 relays in the box are the same, so I guess I could just swap them around and see what happens. I was also told by a mechanic that it could be in the selector switch. My question is, if I can prove power is going to the enirtia switch and then to the selector switch (i dont know how to do that) can I use my power probe in a convenient location (such as the selector switch) to put power to the pumps to test? If that is not a good location, then where? Below is a pic of my box. Thanks Ron
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Lead Driver
Joined: Aug 2006
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From: Sand Lake, MI
Fuel pump relay is second one in from the fender.
Inertia switch is after the relay, before the tank selector switch (IYNA).
If you have juice at the inertia switch, yea you can test at the tank selector switch.
Red-yellow wire should be hot from inertia switch at the tank switch.
Tank switch set to front tank, red wire is hot. Tank switch set to rear tank, brown-white wire should be hot. Fuel pumps/senders use "Ground E", left front of engine compt, top of upper rad support.
Inertia switch is after the relay, before the tank selector switch (IYNA).
If you have juice at the inertia switch, yea you can test at the tank selector switch.
Red-yellow wire should be hot from inertia switch at the tank switch.
Tank switch set to front tank, red wire is hot. Tank switch set to rear tank, brown-white wire should be hot. Fuel pumps/senders use "Ground E", left front of engine compt, top of upper rad support.
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Holly Cow! Im still reading posts and came across one that says,"Sound like the ground wire coming off the NEG post of the battery and going to the relays and the computer." I never gave it a consideration, but I replaced the battery and connector with new ones. And now that I think about it, it has not started since. There are two ground wires in the Neg termanal. I know I got them both back on, but I didnt like the looks of the wire when I replaced the terminal. Maybe the little ground wire is not making connection?
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From: Sand Lake, MI
The Blk-Wht wire grounds the computer at ground "B" right next to the battery, a black wire runs from the neg bat terminal to that same point.
Make sure the cable from the battery is good and the connections on the inner fender is clean and tight.
Make sure the cable from the battery is good and the connections on the inner fender is clean and tight.
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Many Thanks
After going through the recommended testing, I ended up pulling the fuel pump.And yes Virginia, both fuel pumps can and did go bad at the same time. lol. Many thanks for all the help. Ron