1986 Ford Bronco 1986 Ford Bronco fuel delivery problem

LISTER1911

MEMBER
1986 FORD BRONCO
V8
4WD
MANUAL
140,000 MILES

I have a 1986 full size 4x4 Bronco with the fuel injected 5.0L V8. I recently purchased this truck; it had been sitting for approximately 1 year. I changed all fluids, belts, hoses, threw in a new battery and the truck started fine but the gas gauge doesn't work. Previous owner explained that sometimes the fuel pump would cut off and the engine would die. The "fix" was to shake the wiring harness under the hood he said. That turned out to be the fuel pump relay which had been jerry rigged and miswired after a previous engine rebuild-- presumably because the relay was actually bad so they wired around it. I replaced the harness and relay. The Bronco now runs fine until it warms up (roughly 20-30 minutes of driving depending on weather) and then it's as if it's starving for fuel. I can shift into neutral, restart the truck on the move, and usually it will idle until I shift back into gear and it dies again. After sitting for about an hour or two, it's usually good to go again for another 20-30 minutes until the cycle repeats. Any ideas?

1 Reply

KHLOW2008

MECHANIC
41,815 POSTS

Hi lister1911,

Thank you for the donation.

I would suggest testing the fuel pump and its circuit when problem occurs. That is the only way to determne if it is pump or electrical related.

It could be a failing pump that gives way when it is heated up.

If electrical, a relay or some wiring contact could be poor and resistance builds up causing the circuit to fail when heated up.

You can rig a remote wire to the fuel pump and when problem occurs, apply voltage to the pump and if it works, you would have to check the electricals.