Hello All. I'm at wits end regarding my 88 Bronco with the 302 engine and AOD tranny. It's been sitting up for a while (as I was busy playing in the sandbox over there) and it really hasn't been driven alot in the last couple years. My father who was storing it for me would start it up ever month or so just to keep the engine fresh and oiled. About 6 months ago, I drove it around for a few miles and cycled through all the controls (ac, 4x4, etc.). About 3 months ago, I tried to start it again but it would just crank until I drained the battery. This weekend I decided to throw some effort into it but haven't had much luck. So far here's what I have:

The engine will run on ether so I know I have spark. No fuel in rail so I figured the fuel pump(s) are not running. When I turn the key to on, the frame mounted pump doesn't run so I took it off and tested it with a battery where it runs like a champ. When I hook the pump back on it's connector, it doesn't run but instead just 'thumps' once when the key is turned on and then 'thumps' again when the relay lets go a second later. I measured the voltage between the yellow and brown wire in the relay socket and got the 12.5v. I then tried to short these two wires out to get the pump to run continuoulsly but it just did the thump on when shorted and thump off when I pulled the short. I measure 12.5v at the pump connectors when shorted but 6.8v when not shorted. Why the 6.8v? It's almost like I have a weak connection somewhere that's allowing the voltage to go through but not enough current to run the pump. I looked at every relay connection and they are fine. I even repaired the little black wires on the negative battery terminal (both were pretty rotted) but no help. Oh, I even messed with the inertia switch but no luck. ??? Any thoughts or suggestions?

And another question, with the frame mounted pump off the tank fuel line just dangling, should fuel be coming out when the key comes on due to the tank pump? I have no fuel coming out and I thought these Bronco had two pumps. Maybe my tank pump is bad and it could be affecting the frame pump???

 

I know that you need the tank pump (low pressure) to get the fuel to the frame pump (high pressure). The frame pump cant suck very well. Sometimes if the tank is full, it will run with the tank pump dead. Both pumps should get power when you first turn on the key. They will shut down after a few seconds. (about five)

 

Huh. Don't quite understand what happened but my situation got better, sort of. Since I figured my in tank pump was shot along with the hi pressure pump, I decided to drop the tank and check it out. After a few minutes of cursing and groaning, I dropped the gas tank and yanked out the whole tank pump/sending unit. It looked like it was dipped in asphalt and hung out to dry!!! NASTY! I'm going to get a whole new unit from Ford in the morning. So I went back and shorted the brown and yellow wires from the fp relay and now I have the full voltage at the hi pressure and low pressure connections. My new hi pressure fp works and the relay turns it on/off as it should. Now I just have to clean my tank, install the new pump, put in new filters and I should be good to go. I'm keeping my fingers crossed...