96 Bronk 302 fuel pump power source appears to be intermittent

stumped

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My Bronk just stops on the road and in a few minutes will start again. Also, getting harder to start because fuel pump cannot be heard energizing. After cycling key switch several times I hear the pump start in the gas tank and it starts. I installed a **** switch a year ago and this is when the problem started, but may be irrelevant. I thought the **** switch was getting hot (now switched to a 50 amp toggle switch) and stopping the fuel pump. Is there a switch that may be going bad that constantly supplies power to the fuel pump when engine is running? Could it be the key switch be going bad? Replaced fuel pump 3 years ago. Stumped again...
 

Tiha

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It could still be a bad fuel pump. Don't rule that out yet.

There is the fuel cutoff safety switch. In the passenger side kick panel I believe.
Bad fuel pump relay Maybe?
 

Motech

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If you can access the pump connector and have some long leads, try this quick and simple loaded volt drop test with engine running:
  • Red voltmeter lead on battery positive, probe pump side of pump positive lead
  • Black voltmeter lead on battery negative, probe pump side of pump ground lead
  • The values you record are your "Volt Drop" measurements.
  • Industry spec back there through several switches will be around .12 volt max.
In reality, double that on each leg and you're OK.

Consider: If you measure 2.5 volt drop on positive and 2.1 volt drop on negative, combined loss of voltage to your pump is 4.6 volts. No pump will be efficient operating at 8-9 volts.

If you do measure high values, post them up here for tips on tracking those volt drops down
 

goodO1boydws

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My Bronk just stops on the road and in a few minutes will start again. Also, getting harder to start because fuel pump cannot be heard energizing. After cycling key switch several times I hear the pump start in the gas tank and it starts. I installed a **** switch a year ago and this is when the problem started, but may be irrelevant. I thought the **** switch was getting hot (now switched to a 50 amp toggle switch) and stopping the fuel pump. Is there a switch that may be going bad that constantly supplies power to the fuel pump when engine is running? Could it be the key switch be going bad? Replaced fuel pump 3 years ago. Stumped again...

I'd start by checking the fuel pump safety shut off switch.
(Then start checking ground connections.)

I had a very similar problem with my B2 a few years back, it started happening once in a while and then more and more frequently. To the point where I'd get maybe 5 minutes down the road before dying. Let it sit for 5-10 minutes and it would start up again, and run just long enough for me to hightail it up a hill and back to the garage. I had figured that it was something that was heating up, but I was stumped as to where to start looking, because it could well have been a loose or poorly connected ground wire that got a tiny bit looser once the engine heated things up.

The connector at the safety switch was bad.
It was shorting intermittently. The heat from doing this had partially melted the connector. My supposition is that in the process of melting, the 2 wires were getting closer and closer together and hitting bumps on the road would jiggle the wires and connector just enough to make the short.
 

paul rondelli

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I would expect the cheap fuel pump replacements life span to be around 3 to 5 years. The amount of gas you keep in the tank effects how cool the pump remains. With gas prices going crazy for the last few years .... keeping the tank level under 1/4 could effect how long the pump lasts.

Lets face it .... probably the most replaced part on a Bronco is the fuel pump. I have owned two Broncos for 17 years and have yet to replace an alternator..... but both Broncos have had the fuel pumps replaced. Switches and electrical connectors can go bad/ fail ..... but not even close to the amount of failures from the pump just letting go.
 

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