I have tried to post this may times before but it never seems to post.
I have a 1989 460. It doesn't start after it has run for a while. We put in a new cat. Then changed the gas tank low pressure pumps. Then the fuel regulator. Cleaned out the lines going to and from the tanks. Replaced the 6 way switching valve to the gas tank. The EGR. The throttle body. Then the distributor. wires , distributor module, and the spark plugs. It still will not start when it gets hot. Any suggestions?

 

By "not start" when hot do you mean it will or will not crank over?

 

No it will crack but it won't start. At first I thought that maybe it could have been a timing issue. That maybe the timing ws advanced but when we put in the new distributor it was retimed.

 

Id re verify the firing order is correct and rotating in the right direction, clock or counter clock wise Im not sure.
Once your confident that thats right make sure the rotor is pointing to #1 on its compression stroke. Line up the mark on the vibe damper and see if it all jives. A remote starter switch is a great tool to have for this.
Now crank it. Verify you have spark. Use a spark tester.
If you have spark and its timed close enough to fire and its not then it has to be fuel related.
Is this a TBI or carbureted engine? Id imagine its TBI? Can you see fuel coming out of the injector(s). If not could be a bad pump, or something in the fuel system...filter, lines, pick up etc....
If you have been doing a lot of cranking on the spark plugs they could be gas fouled. Replace them. Us Autolites. I have seen fouled plugs do this and cause the spark tester to not indicate spark.

 

Moved to 1987 - 1996 F150 & Larger F-Series Trucks forum.

 

Try the following as a test.

Run engine until warm, like a ten mile drive,

Before shutdown, use a very small screwdriver, flashlight, and go under dash on drivers side, find the inertia switch to cut off fuel in the event of an accident.

The red button of the switch can be tripped by pulling up on the underside of the button very gently.

The truck will run a few seconds then shut down after the fuel rail empties.

Reset button.

Wait a couple of minutes, then try to start truck.

This is if you have a scenario that the truck starts great cold, but after warmup, cranks good, but won't restart hot for a while.

We're working a similar problem here on a setup identical to yours.

 

I read the list of stuff you replaced in you original post(under #1) you don't list the coil. I have read of a bad coil doing this. Did you replace the coil?

 

Tobacco- thank you for that I will try it in the morning.

88n94- I did replace the coil. I wrote that post so many times I started leaving stuff out. Since I was new I think they weren't posting it.

 

Bad pickup coil in the distributor will cause this as well.

 

Thanks to all I think we may have found the problem. It may have been the MAF sensor. It was letting too much gas in and over pressurizing the system. Since we changed that it appears to be workign normal for the past few days. I'm keeping my fingers crossed.

 

There isn't a MAF sensor on your truck, but a MAP sensor, yes. Did you mean FPR?

 

FPR = Fuel Pressure Regulator, in case you were wondering.

 

I am going by what my mechanic had told me. If there is no MAP sensor as you say then maybe I am getting ripped off. But it may have been the MAF sensor.

But each time it is the same thing. When it gets warm it shuts down. Then when it cools down it starts and runs fine.

 

Your 1989 model year truck uses a Manifold Absolute Pressure (MAP) sensor. Many 1994 and later trucks use a Mass Airflow (MAF) sensor.

For reference:

Fuel Injection Technical Library » Manifold Absolute Pressure Sensor (MAP)

Fuel Injection Technical Library » Mass Air Flow Sensor


Your issue sounds more like a PIP problem as noted before.

 

Ok then it sounds as if somethings breaking down with heat load.
Go get yourself a high quality spark tester. The type that has a flashing light and connects between the plug and wire or cap and wire. Induce the problem and use the tester on any of the 8 plug wires. No sparky = ign. Sparky & no run = fuel, likely the pump motor.

Does this thing have the duro-spark ignition? If so Id suspect the dist pick-up (as mentioned) or the brain box...likely.

With a bad MAP you will still have spark and fuel and it should start and run but not well. Been a while since I've messed with a MAP or A duro-spark system.

A bad MAP will allow the engine to run. If its faulty its just not gona give the right feed back loop to the OBC which will effect timing and fuel delivery. A MAP senses engine load and intake pressure which varies with throttle position. A bad MAP signal will cause a rich/lean, advance/retard condition but it should still run.
Symptoms are Surging and idling problems, loss of power, fouled plugs etc but it still should run.

My moneys on the fuel pump or Duro-Spark Module (if equipped). If not equipped then the pick-up in the dist.