Hey guys. To make a long story short, I recently bought a 1985 F150 supercab, longbed, 2wd, 302 efi. I got it with a mess of cut off vacuum lines and a seized up air pump with no belt. I got all of the vacuum lines either plugged (air pump related) or to their proper place with no known leaks. When I start it, and sometimes it does not want to turn over, it acts like it misses a bit at idle, idle slightly surges, and if I put it into D or R it almost stalls out then shoots back up to 1000 rpm then goes to about 600. Same if im idling it and turn the a/c on, it will drop to 500 rpm nearly die and then go back up to 650 or so. It has a new fuel pump on it and had trouble recently with loose wiring to the relay causing it to turn over without startup. Now I think I have a fuel problem, but I am suspecting the low pressure pump in teh tank. I will jumper the pumps and disconnect the high pressure to see if I can hear the low, but how do you know if that has failed. The fuel pressure regulator seems to be working fine as if I take the vacuum off, the idle increases. Also, if I wait till morning to start it up, I have to let the pump prime FULLY before starting up or it will just crank.

Also, I read on a forum someone with an 85 that ran all kinds of bad and stalled out and he though it was the fuel pump, but it was the pickup coil in the distributor. Now I am not familiar with that at all. Is that the distributor ignition pickup? Does my truck have this? Where is it located? Also, I took a picture of a strange looking unit labeled "electronic regulator" on the driver fender. Below are pics. What is this? I think I am going to change the pickup if I can just to see. I have on order a new IAC and TPS, but I don't think this is the problem.

Will the truck run with a bad low pressure pump. Why won't it start if I don't let the pump prime for its full time instead of just putting key in and turning it?

 

Do you have dual tanks?
If a low pressure pump is not working then the truck will still run OK at idle no problem. You will hear the high pressure pump whine as it struggles some.
With bad tank pump (or plugged filter) engine will not run well or cut out at higher speeds +50 mph or so.
If you have dual tanks then there is a 2nd fuel filter in the tank switching valve. Easiest way to test is to disconnect the tank fuel line from the selector valve end or at the HP fuel pump and run it into a gas can. I did not have any luck trying to hear the tank pumps run.
I have extensive posts regarding the dual tank fuel system in this forum. Maybe do a search on dual tanks, fuel system, etc.
Doesn't sound like the problem you are having though.

There is an ignition module in the distributor. When mine failed the engine just stalled out in an intersection and never started again. But I am sure that could give any number of problems or symptoms.

According to a diagram in my shop manual ('86) that box is a voltage regulator. However the schematics and text description never mention it.
They do talk about and show the voltage regulator as being integrated into the alternator. I will look more into that.

Edit:
Went and had a look at my '86 and that box is not present. There may be 2 versions one with regulator built into the alternator and one with separate regulator and different alternator.

 

Thanks a bunch, Klricks. Ok, yes it has dual tanks, but the dude who I bought it from didn't say much other than he eliminated the switch to the second pump due to some problem. I had heard about problems to the second tank before so it didn't bother me that it was eliminated. Now I found the selector valve with the in and out ports- IN THE GLOVE BOX! He eliminated it. The only filter I see is a canister looking deal. Is that the fuel filter? I bought a pickup coil for the distributor and I think I am gonna do cap, rotor, plugs, and pickup. I believe he did that not too long ago, but couldn't hurt except the pocket book, right? Again, symptoms are- Starts up at nearly 2000 rpm, drops slowly to around 600. I put into D or R and it nearly stalls out then fires back into about 550 rpm. Idle a bit erratic sometimes more erratic than others. Interesting note. Today I wanted to put some gas in it so I can work with a tank that has some fuel. It was idling at about 500 so just to get to the gas station I opened the throttle screw to about 900 rpm idle. When I got to gas station and let it idle while putting gas (I know bad idea I didn't waqnt to get stuck) it shot up to and stayed at 2000 rpm which caused me to back out the screw. When I leave and put it into gear, it idles low again and tries to cut out but doesn't. I got an IAC and TPS on order even though I doubt that is the problem. New aftermarket fuel pump and relay is in from previous owner. If I remove vacuum from fuel pressure regulator, idle goes up as its supposed to. You think this is low pressure pump failure? The sending unit does not work at all. By the way....when I get to gas station they are nearly out of gas and pump keeps shutting off and I only get 3 gallons before getting frustrated and go home. Over the weekend I will flush radiator and change oil. When my parts come I am going to do everything at one time since I will have manifold off things should be easy. I will put in IAC, TPS, electrical tune up w/ pickup, change tranny fluid, manifold gasket. Is there anything else I should do or consider? THANKS!!!!

 

the little metal box is the voltage regulator the 85 efi has it but the 86 efi doesnt. I have had to replace the voltage regutator on me 85 efi. when the tank pump was out on mine the truck would not run. the high pressure one is on the frame under the hood. The little canister thing you are refering to is the fuel filter, they actually call it a water separator because the water will sink to the bottom of it but it is for sure the filter. I am currently looking for pics of where the vacumn lines go on the motor specifically the ones that come from the firewall if you have those maybe you could help me out too Thanks