My son-in-law is having fuel problems with his 86 Bronco, 302, Auto, 4X4. Here is whats going on. Truck would did every so often, let is sit a while and would start and run for awhile. About 2 weeks ago it quit and would start for about a minute and die. I put a fuel press gauge on and when starting, pressure would go to about 45 psi, start, stablize at 35 psi, run a minute and pressure would go down to 15 psi and die.

We then jumped the DLC so the fuel pumps would run. Well they would run for a few seconds then quit. The pressure would hold after they stopped pumping. I wasn't sure if I was loosing power to the pumps, so I used an mulitmeter to jump the DLC and we were getting battery voltage and no pump operation.

So we figured pumps were bad. We were going to change them today but I really want to be sure they are bad. We checked the inerta switch and the PO had deleted the switch...don't know why. Anyway while jumping the DLC I would try to move the wires to be sure the splice was good and it was getting pretty hot and pumps were not running.

We repaired some wiring we found to the inerta switch under the hood and replaced the fuel pump relay.

Now the pumps will run by jumping but only for about 45-60 seconds and then both would quit.

I should mention that his fuel gauge will always read full with power on and empty with no power. I don't really know what that is telling me about the low pressure pump in the tank..may have nothing to do with anything.

Anyway I am not sure why both pumps are stopping, they seem to stop together. As it stands right now I am planning on replaceing both the low pressure in tank pump and high pressure external pump. Is there anything else I could check before replacing both pumps.

Any help would be appreicated as these pumps are expensive and it is about 110 degrees out here now.

Thanks

 

Now THAT is the way to put information out so we can help... very nice. Given everything you mentioned, I would be looking at the low pressure (in-tank pump) first. The fuel level sending unit is part of this assembly and it sounds like the sending unit is also malfunctioning. The removal of the inertia switch could have shorted something there. Since you discovered the overheating splice, it is possible that both pumps were adversely affected but I would consider replacing them one at a time. If you are indeed getting "battery voltage and no pump operation" then the pumps are suspect assuming you checked voltage for each pump as close to the pump as possible.