My DD let me down

[LJ851]

I was driving home from work this eve and stopped to buy a pint . So far so good. I got back in the car ( 85 carrera) to leave and no fire. Cranks fine , no action. This has happened before but only briefly , it usually fires after a minute. This time no fire , and i got a tow home. I carry a DME relay and tried that in the parking lot with no fire.Now at home no spark . im still testing, any ideas ?

[pkracer21j]

Cylinder head temp sensor? or is it the knock sensor? I'm not the most familiar with the EFI Carreras

[Neel]

Have an extra cd unit?? 'Check with a known good part'.. Your car was telling you something when "this happened before but only briefly", but you knew that already..

[LJ851]

Haha... update. Went downstairs to do more diagnostics and it fired right up . this is annoying. Before it would not fail for long enough for me to diagnose it , this is the first time it has failed for an extended period of time.

[Sirius Driver]

Good Luck! I'm hoping to figure out a random hot start issue myself. How many miles a year do you drive?

[schamp]

Wild guess here but could be the ignition switch.

[stlrj]

Originally Posted by LJ851

Haha... update. Went downstairs to do more diagnostics and it fired right up . this is annoying. Before it would not fail for long enough for me to diagnose it , this is the first time it has failed for an extended period of time.

It may have been flooded. Next time it happens, try the "clear flood mode" by flooring it while cranking.



Cheers,

Joe

[Dan J]

It was saving you from the DUI Police
Since you already tried the DME relay if your car was in my shop with this complaint I'd probably change both crank sensors and the CHT

[Drisump]

This sounds like textbook faulty DME relay behavior, maybe your spare isn't well either....but it could be the flywheel sensor. The DME relay gets power only if it senses that the engine is actually rotating. Cheers

[LJ851]

I did try flooring the throttle last night, even tried to push start it . The other times it has not started for a brief period, it was fully warm and then turned off for a few minutes. For example getting gas on my way home from work. Im leaning towards the speed and reference sensors, my good multimeter is at work so i couldnt test them last night. The car has never acted up while running. Oh, and DanJ i was purchasing not consuming .

[dshepp806]

Make sure that damned starter isn't up for changeout.......you're just gonna have to get the sensors checked and try to catch them when the failure occurs..intermittents are a beeitch.....sometimes I don't mind spending the $$$ to changeout (in my case) 10, 15, 20 year old parts (sensors included) just to avoid lengthy intermittence......

,..maybe something to "measure", still?



Doyle

[zippy_gg]

Originally Posted by LJ851

Now at home no spark . im still testing, any ideas ?

When you say "no spark", did you actually pulled at least one plug and saw no spark, or are you using the term generally to mean "no go"?
Your issue could be fuel related, such as filter being clogged or a pump going bad.

[juanbenae]

at least you had a pint to wait on the tow rig.....

[E Sully]

Possible bad cold solder joints. DME repair

[LJ851]

Thanks for all the suggestions, guys. Yes i actually checked for spark with a plug outside the motor. It seems to be a situation where i am getting no fuel and no spark becuase i cant smell raw gas even after extended cranking and when it does fire back up its like nothing ever happened. Judging by the patina on the flywheel sensors id say they have been on there for a while so i went ahead and ordered both sensors and the cylinder head temp sensor as well. I think they probably have lived their useful life even if they are not the culprit. dshepp806 why the comment about the starter? im not following you... car ran like a top today BTW

[nesslar]

Did you try a third DME relay? Maybe we should all carry half a dozen! Your problem sounds very similar to one I had back when; got it started the only time it acted up, luckily I got home, but then nothing more. Swapped it out. Bliss. I certainly like the idea of changing out the sensors too.

[Hugh R]

Just for the PP Brain Trust, my 84 quit dead once on the way to work. No spark, nothing. Towed it to TRE and after two days they figured it was an internally shorted fuel injector, it was sending a screwy signal back to the DME, said they'd never seen that before.