Ok, I bought a new fuel pump, I have not installed it yet because I am trying to make sure it is not an electrical problem. With my test light and the key off I am testing the connector under the driver seat where the fule pump relay conects to. Now, on the Pink/Black wire which is the power to the fuel pump has constant power. There should be no power to that at all. When I check the Orange/Light Blue there is no power which is supposed to be the constant hot. I am confused. Electrical stuff is my weakest field so any help would be great.
Just to get some history on your problem. Were you having issues with you old pump or were you just upgrading? I'll assume you are having problems. Have you replaced the relay under the seat? These fail from time to time, mine did. If you are getting voltage where you are not suppose to, this could be a short, verify your wiring diagram with a second one. Fix this before replacing anything.
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93 LX Notch 4 cyl conversion, Vortech SQ, TF TrackHeat, AFR 185 heads, .125 over Boss Block w/3.25 stroke, COMP blower cam, MAC 1-3/4 shorty, 3550 Tremec, 3.73s, Tokico Struts, Steeda Sport Springs, etc...11.3 at 129.9 through the cats.
Here is everything I have replaced and what I have found.
- Ignition Switch
- Ignition Module
- Fuel Pump Relay
- ECU Power Relay
- Fuel Filter
After dropping the tank the electrical connection on top of the fuel pump was melted on the ground side(Black) but the Tan/Grn (power) was ok. When I removed the pump from the tank the inside terminal was also cooked on the ground side. I tested the old pump out of the tank by hooking it to the battery and it worked fine. Now what, do I replace the pump/harness and hope for the best or should I bypass the ECU and install a manual switch to the fuel pump and see if the car starts and runs. I guess that would rule out if the ECU is bad and save my new fuel pump from being fried. Let me know where I should go from here.
most likely it was the pump connection which was at fault, i would replace the pump and harness and go! make sure when you put the new one in that the connections are tight.
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Sr. Master Ford nerd.
saludos caballeros del ovalo azul
Can something like this really fry the ecu? Can the ecu really fry your fuel pump? Any one know if damage is caused to the ecu if a connected tweecer would suffer too?
Its not possible for the ECU to fry the fuel pump. If an internal short to 12 volt occurred the pump would stay engaged. A short to ground and the pump would not work. So - you can rule out the ECU as the cause of damage.
I also cant imagine the fuel pump cooking the ecu because a replay isolates them.
I would guess it is most likely your pump was starting to fail, pulling excessive current - which resulted in the electrical failure. Its also possible the electrical failed because of a bad connection and that the pump is perfectly fine.
Thanks Blade for the reply, I feel confident now that the ECu is not bad. Phew, save some money. I have found out though that I can not buy a new harness but I did find a place that supplies OEM Ford Connectors that i can order a new connector from and splicE into my harness. I tested the old pump and it still works, but, it is from the era of Stone Temple Pilots so i might as well replace it now while I have it all apart. Thanks!
well it is a relief to hear that the ecu isnt damaged. But what would cause my fan not to come on? I aso noticed that when I was in the engine that my vacum line for the fuel regulator was not hooked up, could this have cause damage? I hooked it up, but nothing changed.
Fuel Pump Woes - Please Help 
