I have a 91' f 150 with a 302. I bought it cheap from a friend. He quit using it because of stalling problems. He replaced the ignition module-no help. I replaced the distributer cap, roter, plugs, plug wires, distributer, coil, condencer,
had the ingition module tested twice (ok), replaced the battery, battery cables,
relocated battery - cable to a better (less oily) location on the engine, etc..., I replaced things one at a time thinking I would find the bad part but never did.

the symptoms are- starts great when cold. runs for 5 to 20 miles fine, lurches some but not real bad. The problem comes when it stalls trying to pull away from a stop, or I shut it off. Then it won't start. When I first started trouble shooting it, it had spark at first then after some cranking lost spark. Now it has no spark from the first attempt of restart. After about 4 hours it starts fine.
If I try to start in 4 hours, I have to charge the battery. If it sits for 10 hours I don't have to charge the battery.

My 91 has a TFI-IV system which is sending error codes with key on engine off of 63 & 21. continuous codes are the same. I couldn't get run codes because I can't restart when warmed up. If I drive 100' it won't restart.

thanks,
91.mickey

 

Mikey, if you are positive the cranks but no start is attribuited to no spark you should look into to a open or shorted ignition coil, ignition module, or hall effect switch. Now you claim all have been replaced by word of the person that sold you the vehicle. Did he replace these parts or have someone do it for him? Point is, can you difinitivly say these parts have been renewed. Granted, the most common problem for this failure is an ignition module that shorts when hot. Having it tested and finding there is no problem is normall being it has not gotten hot enough to short internally. If you are sure all parts have been replaced i would think you have an intermittant wiring problem between the coil and the ignition module but i would certainly look for a component failure first.

Lastly, are you sure this is a no spark problem? Are you positive there wasnt a dim spark due to low cranking voltage and the problem lies with fuel delivery or the injector controll circuit? I'm not trying to say you havent diagnosed it correctly but you could really waste a lot of time and money thowing parts at something for a single simple failure.

I wish i could provide you with more input but based on your post you have and ignition module/hall effect/coil failure claiming that all are new. If you positive they are all not the culprit the only thing left is the wiring between them.

Hope that helps.

 

I am sure all were replaced. I replaced all but the ignition mod. Autozone tested the mod twice in one setting, the tech who tested it ran the test three times each for a total of six so the mod would be warmed up

thanks,
91.mickey

 

It sounds like my truck (same year, engine, and symptoms). I replaced all the ignition system parts in an attempt to fix the problem. Couldn't pin it down because it would come and go. Ripped up the harness looking for an intermittant short. None of this was causing the problem.

Check the chassis grounds at the small post on the radiator support in front of the battery. The stock Ford arrangement is a little cheesy. Take the nuts off the post and shine everything up thoroughly. Get the nuts back on good and tight.

Check the PCM ground near the driver's side hood hinge. Give it a similar "shine it up" treatment. Double check your battery ground wire on both ends.

Check the screws securing the TFI to the distributor body. They need to be tight enough to get a good ground. Unfortunately you need the special tool or a thin-wall socket to do this.

Check that the distributor hold down bolt is tight.

Fixing the grounds is ultimately what fixed my problem.

Code 21 is normal for a KOEO test with a cold engine. Code 63 can be a symptom of bad grounds -- or likely just be a bad or mis-adusted TPS. This is not related to your "no spark" condition, unless it is another symptom of bad grounds.

 

thank you fefarms for the input. I had already replaced the battery negative cable and relocated the engine end to a better, less oily area. when I did this I replaced the wire going to the grill area. These grounds didn't help. I have not tried the ground by the hood hinge. I have taken the truck to the shop here in my small town. The mechanic there is up to speed on it, as I have picked his brain for the last four days. I will relay the ground info after lunch.

thanks,
91.mickey

 

well bad news the mechanic here in town can't figure it out. He found the starter bad which solved the hard to crank problem, but the no spark problem is still there. I did find that when the truck does run the trouble code reads 98, (hard falt, eec in by-pass). If I understand it right the computer is in a mode that lets you get it to the shop but won't let you drive it normaly. any way we're still stumped. Help......

thanks,
91.mickey

 

The Dali Design reference says that code 98 in continuous memory means the KOEO test has never finished. Perhaps the test was run and you didn't wait long enough. Or perhaps it means "the computer crashed", which is the implication of the Probst reference.

Code 98 as a KOEO code (prior to the separator pulse) indicates a problem with the transmission EPC solenoid. Make sure you know the difference between KOEO codes and continuous memory codes when considering what to do about code 98.

The next time the truck won't start, check to see if it has spark. If there is no spark, pull out the gray SPOUT jumper plug next to the distributor. Try cranking the engine with the jumper removed. See if the spark comes back, the engine starts, or both. If removing the SPOUT jumper restores spark, then the computer is interfering with the ability of the TFI to feed PIP back into SPOUT. This plus code 98 as a memory code would suggest replacing the PCM.

The TFI is capable of generating spark on its own with the computer removed from the truck. In effect, removing the SPOUT jumper accomplishes this, from the TFI's point of view.

"Finding the starter bad" is suspicious. Often the act of removing the wires and installing the new starter corrects the real problem, that of high resistance connections from the battery. The "new starter" works great, but so would the old one if you put it back.