In trying to solve a problem with my 1986 F-150 302 EFI (166M miles) which eventually turned out to be a map sensor, I recently (two months ago) replaced the spark plugs, distributor cap and rotor, hi-pressure fuel pump, fuel filter, air filter, breather element, EGR valve, EVP sensor, idle air control valve, throttle position sensor, intake air temperature sensor, coolant temperature sensor, and the fuel pump relay.

I also cleaned behind the butterflies in the throttle body and manifold throat with TB cleaner while I had the TB off to install the TPS.

Truck has been running great and mileage improved about 2 mpg.

In the last two weeks, the truck "hiccups" one time in the morning while driving to work on the interstate, a one-way distance of about fifteen miles. I have been unsure if the "hiccup" was electrical-related or fuel-related until this morning. Stopped for gas, filled up, restarted the truck, and it died immediately. Engine would almost "catch up" when trying to restart it. Finally, engine did "catch up" after about ten tries (with me pumping the accelerator peddle a couple of times before each restart attempt) then ran normally.

Am now believing this is fuel-related and suspect either the frame-mounted fuel tank selector (which I have replaced a couple of years ago) or the in-tank fuel pump (which has never been replaced).

Any assistance appreciated.

 

If you go buy a fuel pressure gauge, you can monitor the fuel pressure and verify if you are on the right track. While you are at it, check for corrosion in and around the fuel pump relay. It's mounted in the engine compartment, I believe on one of the fenders.

 

A rule of thumb applicable to ANY vehicle with an in-tank electric fuel pump:

They can act strange when they warm up; when they are getting to their last legs.

They're a huge pain in the posterior to replace (because none of the engineers seem to have the foresight to put an access port in the floor of the trunk, meaning you have to drop the tank to get to them), but in the long run far cheaper than 'point-and-shoot' diagnoses that ultimately lead BACK to the fuel pump because it's the only thing that HASN'T been replaced!

That's my 2 cents.

 

what about watery gas?? When you filled it up, you might have stirred up the water and caused you to stall out.

 

Would the fuel pump make it idle rough at some times when it is just sitting and idling. Because my truck will run fine and then start to idle like it has a huge cam in it. The idle will range from about 2000-300 rpms once it starts to get rough and sometimes die. That is what my truck is doing now and I have replaced the idle air control and some other things like the plug wires and spark plugs etc. I dont know if this is what yours is doing but I thought I would post it just in case.