1988 Ford sometimes won't start

I"m looking for a second opinion. I have a 1988 F-350 with a fuel injected 351W. Used it around the house for a month or two with no problems. I went out to start it on a real cold day about three weeks ago and it wouldn"t start. The fuel pump in the tank would just run and run. Later that day I went out turned the key to the On position, the fuel pump ran for a second or two like it should and the truck fired right up. Since then, sometimes it will start and sometimes the pump will just run and the truck won"t start. I figured the fuel pressure regulator was getting stuck open sometimes and just bypassing all the fuel back to the tank. But everytime I hook up a pressure gauge, the trucks starts fine. I just want to make sure I"m not overlooking something or that it"s really an electrical problem somewhere. I don"t know what the spec"s are for fuel pressure, but would guess about 35 to 40 lbs.

I would hook gauge up at the shrader valve and turn switch on but not crank, when pump stops you should have roughly 40 psi. Has this truck been sitting up or not used much lately?. You mention first started when it was real cold day and I just wonder if there is small amount of water in the gas tank that is freezing and thawing.

1.) It's COMMON for the fuel pump relays on those Fords to fail and stick "ON", often running the fuel pump 'til the battery is dead. Simple to replace, though.

2.) It is VERY unlikely that your "no start" is due to the fuel pressure regulator sticking "open". Next time it won't start, check for spark first.

edj, I had a similar experience with a 1987 F250 carburated 460 engine. The trouble was traced to a defective fuel pump relay. Some times the truck would start and run, but often would turn over and not fire. The relay in my case is located on the left inner fender. Easy to replace. Hope this helps, Pete

The fuel pump relay and socket has already been replaced due to some bad wires.

If I turn the key to the on position and the pump runs and shuts off after a second or two, the truck will start. If I turn the key to the on position and the fuel runs and doesn't shut off, the truck won't start.

What made me think that it was the pressure regulator is the fact that the only time the truck won't start is when the pump runs continuously. I figured that if the regulator was stuck open, too much fuel would be bypassed back to the tank and there wouldn't be enough fuel for the injectors.

Lucky guys, wish I could hear electric pumps run. Only one I ever heard was bad and real loud.

There were two things that kept my '86 fuel injected F150 from starting.

First it had a high voltage ignition system that would blow microscopic holes in the distributor cap, then it wouldn't run on foggy days. A new cap and rotor fixed it for a few years.

But what got it worst was the fuel pressure regulator that split the diaphragm and filled the engine with gasoline through the vacuum lines. Trying to turn it over with too much liquid in the cylinder did nasty things (I didn't take it apart to find out the details), and it didn't have the second fuel filter so the pump kept rated pressure on the injection supply line even though a lot was going to the intake manifold.

And that was back in 1999. I'd replace the fuel preessure regulator before it wrecks your engine like it did mine. Just on general principles.

If the pump runs long, its not building up pressure for the pressure switch to shut it off. Either the pressure switch, the pressure regulator, or the pump isn't working right. The pressure switch and pressure regulator are a lot easier to replace than the pump.

Gerald J.

The fuel pump was replaced just before I bought the truck (I was the one who put it in) and I put a regulator on it today. Where is the pressure switch located? It would make sense that if the computer doesn't see pressure because the switch isn't working, the computer would not give the signal to the distributor to spark.

I don't know where the switch is, but there has to be a switch or sensor to make the pump start and stop.

Gerald J.

There is no "Pressure" switch. Fuel pressure sensors didn't come about until the returnless fuel system was developed. Fords do have an inertia switch that is a safety shut off in case the pump relay were to stick closed and a fuel line were severed in an accident. It takes a significant bump from another vehicle to cause it to open. Since the pump runs even when the truck won't start, that isn't your problem. One problem they did have back then on dual tank vehicles, and there was a recall (93S68) for it, was they would transfer fuel between the fuel tanks. The fix was install a check valve on each fuel pump in each tank and a new fuel pressure regulator.
When the truck won't start, check for battery voltage on the coil primary feed from the ignition switch. Fords with EEC4 are the worlds easiest vehicles to hotwire. Run a wire from the battery to the coil positive and it will power up the ignition and engine control. I'm thinking you will find either a PCM problem, or a wiring issue. The fuel pump relay is controlled by the PCM, not at all by the ignition switch. The only time the relay will engage is during cranking, or when the PCM sees a tach signal (engine running). Look closely at the PCM relay and fuel pump relays. They are on the fender next to the starter relay. An O.E. fuel pump relay will be green. Look the wires over closely for shorts to power since the supply for the fuel pump and PCM are live at all times. Fords of that era have very durable and dependable PCM's, so check the wiring first.

I'm going to add to my prev post, if the ignition switch turns the pump on and off when it won't start, and you said the relay wires and socket were replaced, definitely look very close at the wires for the relay. Could be the signal wire for the PCM relay is shorting over to the pump and pulling the volts down too low for the ignition to fire.
Fords TFI ignition will work without the PCM. It will only have fixed timing. When the engine starts, the PCM takes over timing advance only. The ignition switch directly powers up the coil, the ignition module, and the PCM relay.

Gerald, the PCM controls the fuel pump relay. The PCM turns the relay on when cranking and engine running. Newer vehicles without a fuel return line run the pump only when needed. Old stuff, the pump runs all the time the engine does.

I have a 1988 F250 that acts the same way sometimes. If I engage the starter and keep turning the engine it would never start. I discovered by accident that if I engage the starter and turn the engine 5 or 6 times and let off, and then turn the starter again, it will start every time. I have started it that way for 2 years and never had it fixed. No one has ever figured out why it does that but as long as it starts, it doesn't bother me.