For some reason these last 2 months my fuel pump has its on and off's. I just put in a new engine and transmission into my bronco, and since then my fuel pump has been acting up. I put a new in tank one in 3 years back, but now there are times where it doesnt turn on when starting the car. I'll go underneath with a stick and tap the fuel line and electrical piece leading into the tank and then the fuel pump will turn on. I wanna fix the problem so i dont have to worry about doing that anymore. Could it be the inertia switch? fuel pump relay? or is their some electrical wiring going bad? All i know is it never did this til after the new engine and tranny came into my car, and i have to tap the lines for it to turn on.

Any solutions???

 

Yes, yes, and yes. That said, since it seems to respond when you tap things back by the fuel tank, the inertia switch (located near the passengers feet) and the relay (located under the hood near the passenger fender) don't seem as likely as some loose connection in the wiring near the fuel pump.

Fuel pump circuit is a pretty basic DC circuit. Next time it won't start, get a wiring diagram and a voltmeter and see if you can locate the break in the circuit.

 

Ok. Do you think it could even be that the ignition is not making contact to the wiring going back? It does make contact with the starter when it doesn't want to turn on so that's all good, but then I tap the lines then it turns over and we're good. Idk just a thought. Maybe the problem not in the ignition not making contact with the wiring going back?

 

Not entirely certain how to interpret that post. In an indirect way, the ignition switch could also be at fault. The ignition switch causes the EEC relay to close, which powers the PCM and the rest of the engine management system. The PCM decides when to command the fuel pump relay to close. So, if you determine that the reason the fuel pump isn't running is because the fuel pump relay isn't closing, part of the diagnostic tree at that point will be to check if the PCM is sending the signal to the fuel pump relay to close. If not, then one possibility is to check that the PCM has power, which could eventually lead back to the main ignition switch.

 

OK.. i see where the other guys are right but also I did all the same steps..
I found out that my broncoII had two pumps. one in the tank and one on the drives side on the frame near the wheel well. first thing yu need to have done is a pressure test to make sure there isnt a clog in the line somewhere and then if so I recommend the filter ( you prob already checked that). then if the problem continues check f you have the two pump system. change the front one first ( it's pretty simple) and recheck .. then if you have to ( i hope you dont) you mght haveto change the pump inthe tank. ( that is a lengthy pocess, make sure you ae in a well ventalated area) change out the tank pump. Get the full set of rings and gaskets not just the pump..
good luck.....

 

it`s back there at the tank,my friend

 

And that fuel pump in the back is fairly new at 3 yrs old. My old one lasted 20 yrs

 

i think your problem is at the wires to the pump in the tank, you say when you tap the wires with a stick at the tank she starts up. so that sounds like a connection problem to me. good luck hope you get back on the road.