First you need to be sure you have fuel pressure. Measure it at the rail. Or at least turn the key and listen for the 1-sec whine of the fuel pumps pressurizing the rail as you go from OFF to RUN (not START). The fuel pump's power wire, the inertial relay, and the relay socket hanging off the computer are suspects.

On my 302 I had a prob with no-starts a couple of times then it died completely. It was the timing chain. I don't know how I got a no-start at one point yet were later able to get it started and run for a considerable trip. Seemed like just letting it sit for an hour and it restarted. But then it really slipped and it really wouldn't start.

 

I get the 1 sec. whine. What is the inertial relay? I replaced the fuel pump relay, but it was at the inside fender next to the battery. I am suspecting the computer may be at fault on this go round.

 

The inertia switch opens on impact or big bump and you have to manually reset it.

Note the input to the Fuel Pump Relay may be a yellow wire with its own fuse link.

 

Do the interia switches go bad? The van runs until shut off, then will not start without time and coercion.

 

Maybe but I think a lot of good ones get replaced. They will not fix them self’s with time so no I do think the interia switch is your problem.

 

If you hear the fuel pump whine, the fuel pump is getting power so the switch is good. Next check the pressure on the rail. Turn it on and off to make it pump it up to pressure (don't run the engine). Put a tire gauge on the valve and look for ~40 psi, or really if you just stick something on the valve and if it sprays out then you know you have some kind of pressure that should have started the vehicle.

 

OK. If I have pressure, then what? If I don't, then?

 

Spark. Take the lead off the center of the dizzy, put it VERY close to a ground, and see if you can draw a spark off it. Or take a test lead, clip one end to gnd, another to a screwdriver, unplug the spark plug wire off the coil, hold them close while cranking. The only thing is you don't want to let that coil spark without something closeby to spark against, it will develop too high a voltage if a spark doesn't form to burn the current off.

Or just take out a spark plug, plug it back into the spark plug wire, make sure the spark plug's metal case is touching ground.

 

Checked pressure at the valve. Just a dribble. Checked flow thru pump-GOOD. Checked flow thru filter-GOOD. Reconnected line to rail. Checked spark-OK. Re-checked pressure at rail after turning pump on and off w/o start-GOOD pressure. Engine started and rough idled before stalling. Re-started and disconnected the vacumm to the fuel pressure regulator and then the idle smoothed out and continued to run smooth. Put my finger over the vacumm port openning at the manifold where the fuel pressure regulator would be connected to and experienced the rough idle situation again. Does this signify a bad fuel pressure regulator? It was replaced with the fuel pumps at the end of March.

 

Hmm....
Well if you take the vac line off the fuel pressure will increase. If the problem were the fuel pump or filter (a delivery issue) taking off the vac line won't increase fuel pressure. So in the case of a delivery prob the engine would be unaffected by removing AND PLUGGING the vac line- which you experienced. But it might also mean nothing.

Introducing a big vac leak will lean out the engine. This may compensate for any number of problems though. Like if your Idle Air Control valve is stuck closed, this will reintroduce some idle air and may make it run again.

 

Would a closed ISC cause the no start situation? Is there a way to test it? It was replaced in March as well.

 

It would start and run if you held the gas open a bit. It will either idle high or won't idle at all if the IAC valve is stuck.

Once you know you have fuel pressure and spark:
Ignition module, vac leaks, computer ground, throttle position sensor, MAP sensor, timing chain, Air Charge Temp sensor... basically in that order.

 

OK. I had no pressure when initially checked. Checked flow at pump and filter and reconnected fuel lines and THEN had pressure. Is this significant? Almost seems that air is getting into the system. Could there be a air leak as the system is de-pressurizing? At the fuel reservior? Just wondering..

Ignition module--replaced 3/11, is there a test to check?
Vac leaks--haven't found any
Computer ground--tightened yesterday
TPS--replaced 5/2
MAP--replaced 5/14
Timing chain--How do you check this?
Air charge--4/14

 

Shouldn't be possible. It's under pressure and a leak would make it spray out.
Now there is a low pressure fuel sump pump in the tank itself. In my experience the vehicle can run just fine without it even being connected. It can make it difficult to prime if there's no fuel in the system. It also means the high pressure pump pulls a slight vacuum between the tank and pump. But if there was a leak here, once you turn off the vehicle I'd expect fuel to drip back out through the leak.

Ignition module--replaced 3/11, is there a test to check?
Check for spark.

Timing chain--How do you check this?
Take off fan & fan clutch, take off distributor cap, put large socket & big wrench on the harmonic balancer bolt. Rock the crank back and forth through that bolt. The rotor should follow its motion with little slack. In an '88 the TC may be close to death if it hasn't been changed yet.

You'd think a slipping TC would be one slip and it won't run, but actually I had several no-starts that happened, left it for an hour or two, came back later and it started ok. I can't explain how that could have happened.

 

No timing chain on the 4.9L. Checked for slop. None noticeable. Swapped out the ISC for a new one--no charge, still under 3 month warranty. Replaced fuel pressure regulator with one with a different part number. First one fit, but may not have been correct. No repeat of no start symptom--yet. Will hold judgement until next hot day drive. Also changed gas cap. Had a locking one that had some mileage on it. Will let you know. Thanks for the help.