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01 mounty - question about fuel pump wiring harness connector

bryanhbre

Member
Joined
January 3, 2008
Messages
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City, State
Elkhart, IN
Year, Model & Trim Level
2001 mountaineer
2001 v8 mountaineer. Have had the same intermittent issue for the last 4 winters. Never does this in the spring/summer/fall. Any time the temp drops, say under 32° or so, every now and then the car won't start. Not often, but it gets more frequent the colder it gets. Maybe once every 20-30 starts when it's moderately cold but when it gets down into the single digits, like the last couple days, it can be every 3rd start. Can't hear the pump prime when it does this, but if I turn the ignition on and off several times, I will eventually hear it prime & it fires every time at that point. Have had it into a shop, no codes, the truck runs absolutely perfectly. Have changed the fuel pump relay twice (different manufacturers just to test - have a napa one in there now), hasn't seemed to change anything. Also have new plugs, wires, coils this year just as a test. Still doing it. I had gone under the truck to check the pump wiring harness on the frame rail & everything's clean - no corrosion. I did notice a black box or something that was also plugged into that same fuel pump harness & I'm not sure what it is. Have had this in the shop & pulls no codes. Check engine light comes on when truck is started & goes out just like it's supposed to so I'm assuming no computer issues. Fuel pump cutoff switch is OK. Would assume fuel pump is OK since it never does it during the summer & when it does start, it runs absolutely perfectly with no problems whatsoever. I suppose it could be a loose wire but I would have no idea where to start on that - wires looked good underneath the car. I'm wondering what that little black box is supposed to do under there on the frame rail. I would change the pump, however, from what I've seen on here that doesn't necessarily fix it & I would assume since it's been doing it for 4 years the stupid pump would have died by now. Don't drive it much in the winter so I don't think about it for most of the year until it gets quite cold out. Thoughts?
 



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my '00 Mountaineer does the same thing (not as often though). never had a problem until it got cold out. has now done it twice in past 2 months. same exact symptoms you describe. eventually you hear the pump prime and then it'll start and runs perfectly. i've swapped the relays and checked the wiring. at 180k, i'm 99.9% sure it's the fuel pump. you don't say how many miles you have, but i'm sure you're getting up there with an '01. i'll be changing my fuel pump next week.

for those of you who believe a fuel pump either works or it doesn't, you obviously don't have much experience with electric motors. intermitant function of an electric motor (before it dies completely) is absolutely possible. w/in the past 12 months i've had a starter motor and a convertible top motor work intermittently and i've seen this happen many times over the years.
 






I had the same issue. Eventually I got stranded not too far from house, tow it on platform (AAA) and decided to replace the pump before I get stranded somewhere else further.
Installed a Bosch pump and new Bosch strainer (from Amazon). Since then not a problem...

PS: The pump is installed on the same assembly as the fuel level sender, but it can be disconnected really easy once all assy is out of the gas tank. The pump has another small connector INSIDE the tank. Bosch one comes with an pigtail adapter to their pump connector.
 






123k miles on my mountaineer. I would be OK if it's the pump but would it really do this same thing every winter for 4 years & run absolutely perfectly otherwise? From what I've read, when the pump starts to go, it will cause rough running, etc. Never had a problem at all with that. Always runs fine after it starts.
 






123k miles on my mountaineer. I would be OK if it's the pump but would it really do this same thing every winter for 4 years & run absolutely perfectly otherwise? From what I've read, when the pump starts to go, it will cause rough running, etc. Never had a problem at all with that. Always runs fine after it starts.

well, i don't know what else to tell you other than checking for voltage (and ground) at the pump when it fails to run and working backwards from there. i know that one way to make a suspect electrical component fail is to subject it to cold.

if you're handy, and want to spend the time, you could wire in an indicator light on the pump's plus and ground wires and have it in the cabin to easily let you know any time the pump isn't getting a connection. me, i'll be changing my pump next week.
 






You can check the pump voltage at the fuel cut-off inertia switch. Is located inside cabin, the passenger side kick panel. The switch has two wires that carry positive voltage to the pump. You need to measure the pink/black to ground.
My voltage was good at that point (when turned the key, a +12V appeared for a few seconds).

2006-08-29_210045_Fuel_pump_94_Explorer.gif
 






2001 v8 mountaineer. Have had the same intermittent issue for the last 4 winters. Never does this in the spring/summer/fall. Any time the temp drops, say under 32° or so, every now and then the car won't start. Not often, but it gets more frequent the colder it gets. Maybe once every 20-30 starts when it's moderately cold but when it gets down into the single digits, like the last couple days, it can be every 3rd start. Can't hear the pump prime when it does this, but if I turn the ignition on and off several times, I will eventually hear it prime & it fires every time at that point. Have had it into a shop, no codes, the truck runs absolutely perfectly. Have changed the fuel pump relay twice (different manufacturers just to test - have a napa one in there now), hasn't seemed to change anything. Also have new plugs, wires, coils this year just as a test. Still doing it. I had gone under the truck to check the pump wiring harness on the frame rail & everything's clean - no corrosion. I did notice a black box or something that was also plugged into that same fuel pump harness & I'm not sure what it is. Have had this in the shop & pulls no codes. Check engine light comes on when truck is started & goes out just like it's supposed to so I'm assuming no computer issues. Fuel pump cutoff switch is OK. Would assume fuel pump is OK since it never does it during the summer & when it does start, it runs absolutely perfectly with no problems whatsoever. I suppose it could be a loose wire but I would have no idea where to start on that - wires looked good underneath the car. I'm wondering what that little black box is supposed to do under there on the frame rail. I would change the pump, however, from what I've seen on here that doesn't necessarily fix it & I would assume since it's been doing it for 4 years the stupid pump would have died by now. Don't drive it much in the winter so I don't think about it for most of the year until it gets quite cold out. Thoughts?
Next time you have a no start condition, smack the bottom of the fuel tank with a plastic/rubber mallet. Worked for me when the fuel pump quit. And the pump gave absolutely no warning it was failing. Just wouldn't start after being parked for about 20 minutes. By hitting the bottom of the tank, the vibration caused the pump to move slightly thereby making contact and start running. After changing the pump, I cut it apart and found a black substance on part of the armature where the brushes ride.
 






After changing the pump, I cut it apart and found a black substance on part of the armature where the brushes ride.
That would be the worn carbon from brushes...
What happens is that, at cold, the springs that push the brushes against the armature shrink. With the worn-out brushes (shorter), there is not enough contact pressure left to allow the voltage to pass to the armature.
In warm weather, the springs expand just enough to make the pump work - for a while, till brushes wear even more.
how-to-repair-major-appliances-8.jpg

carbon-brush.jpg
 






Wiring harness color code

my '00 Mountaineer does the same thing (not as often though). never had a problem until it got cold out. has now done it twice in past 2 months. same exact symptoms you describe. eventually you hear the pump prime and then it'll start and runs perfectly. i've swapped the relays and checked the wiring. at 180k, i'm 99.9% sure it's the fuel pump. you don't say how many miles you have, but i'm sure you're getting up there with an '01. i'll be changing my fuel pump next week.

for those of you who believe a fuel pump either works or it doesn't, you obviously don't have much experience with electric motors. intermitant function of an electric motor (before it dies completely) is absolutely possible. w/in the past 12 months i've had a starter motor and a convertible top motor work intermittently and i've seen this happen many times over the years.
 







did you mean to ask a question?

if it's fuel pump wiring harness color codes, the pump positive 12V wire is red and the ground is black. the fuel level sender is yellow.

free wiring diagrams: http://search.ebscohost.com/. Use RRCC and rebsco when signing in
 






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