Heat Soak No-Start

[alsgro]

Hi, all.

I have this pesky problem of my '81 FI not starting after it's been sitting for awhile. Once the car is up to temp and I shut it off, it won't start after sitting for more than 15 or so minutes. If I fire it right back up, it's ok... Or if I just run into 7-11 for a few minutes, it's usually fine. BUt lately, if it sits for, say a 1/2 hr, it just cranks and cranks.

It happened twice today, and the 2nd time I had a buddy hit the key while I looked at the wire from the coil... No spark I could see.

I left the hood open for about 15 minutes, and she started right up.

I've replaced the T sensor and even the thermo time sensor. Anybody got any bright ideas? It's a real PITA when I'm trying to get errands done and such. I should get a medal for having this Spider as my daily driver for the last 3 years. I like to keep it running!

[vandor]

There are only 3 parts in the ignition system that make spark: The coil, the module, and the pickup coil in the distributor.
The first and last have resistance specs listed in the manual. Test them when the car is not starting, see if they are in spec.
Can't really test the module if it's intermittent, but they are not expensive to replace, and you may even find a used one for testing from somebody with a parts stash.

[majicwrench]

You can certainly test module, but realisticly not on the road without nice equipment.

The module is THE most likely culprit. They get hot and fail. Cool a bit and work. Could be lots and lots of things, but first things first.

Like was said, module cheap. I would replace and take it for a drive.

Keit

[courtenay]

I have (what may be a dumb) question regarding the module: If it fails when the car is running and hot, will the engine quit? Or is it only a factor when the engine is hot and stopped? ie it is needed to start the car but once it is running it isn't needed.

[majicwrench]

IF module fails with car running, yes, car will shut off. Module is taking place of points, and opening and closing the circuit thu coil.
Module actually gets hotter when car sits for a bit, thus the often no spark after hot soak.
Keith

[fiatmike124]

Do you feel that you have confidently proved that there is no spark after heat soak. If not carry a spark plug and try again. If you do have spark, consider having the injectors tested/serviced. Heat soak can be a source of deposits in injectors as the residual fuel evaporates.

[courtenay]

IF module fails with car running, yes, car will shut off. Module is taking place of points, and opening and closing the circuit thu coil.
Module actually gets hotter when car sits for a bit, thus the often no spark after hot soak.
Keith

Thanks, Keith. I'm chasing a similar problem that only seems to occur on a hot day after a long run. Now that the weather is cooler up here, it is working fine.

[alsgro]

Thanks so much, all! Since I posted the car has taken to giving up the ghost while in motion, which is something new since I've owned her.

I must confess to not knowing exactly where the module is, but it seems from the comments that it's a likely culprit. I'm assuming it's around or near the coil?? Also, what are the symptoms of a failing coil. I think i'm running the original!

Gonna be replacing the upper control arm bushings this weekend, so I'm hoping to solve this pesky problem while I'm at it.

[divace73]

I had a similar problem and it ended being the ign switch for me. Once it warmed up due to long running or hot days it would not kick over. Cleaned my switch out and bypassed the start with a relay (even though the start solenoid doesn't take up too much power).

[majicwrench]

Like has beens aid, verify again the no spark when car fails to start.

While it is possible for coil to fail when hot, realisticly it is not coil issue.

Keith

[alsgro]

Hi again, all. I did verify that there's no spark during this condition. The wire from the coil to the distributor will not make a spark until you let the car sit for a bit.

[alsgro]

I had a similar problem and it ended being the ign switch for me. Once it warmed up due to long running or hot days it would not kick over. Cleaned my switch out and bypassed the start with a relay (even though the start solenoid doesn't take up too much power).

Thanks, I'll try that. Haven't looked at the wiring around there is quite some time, It's probably due for a cleaning. How did you clean the switch itself?