John Speake

If it consistantly starts from cold and cuts out with no spark when hot, then this often indicates a CPS problem.

Stromius

I remember a thread like this a ways back that exhibited similar symptoms that turned out to be a cracked CPS connector. Once things got warm, moved around etc, the signal would get "lost" and engine died. Airbox off, MAF off and you should be able to see it well enough. Pain to remove with intake in but doable.

928s4forme

Checked the coils for wandering spark travel night in the dark and didn't see any obvious issues...will be changing the CPS tonight after work. It'll be a joy I'm sure... Cranked her again this morning and of course, she started and ran beautifully. Will post again later tonight with an update...

AirtekHVAC

Hey, post some more info...car, and you....quite a few of us in NC...

Good luck...do keep us posted....

928s4forme

I am in Elkin. The BRP is only a few miles from me in Roaring Gap. Do you come up for the Sharks in the Mountains Meet?

928s4forme

I am near Elkin. The BRP is only a few miles from me in Roaring Gap. Do you come up for the Sharks in the Mountains Meet?

928s4forme

Ok everyone here is the latest...
The CPS is fine...
Replaced original starter
Changed plugs...
Verified alternator is good
Verified battery is good
Checked relays and found issue with the cooling flaps (wrong relay)...
Verified correct relays for each position on ce panel...
Injectors are firing correctly...
Swapped battery ground with new strap...
Cleaned ground points...
All that and I still have the same problem

When she is cold she starts and runs perfect. After she gets hot, she begins to hi/low idle and when throttled she dies. After she is dead, you try to crank her and she acts as if the battery is dead and won't turn over. The starter acts as if it's been heat soaked. Let her cool down an hour or so and she starts right up and runs.

Any suggestions?

Landseer

Are there 12+ volts at the jump post, also, at the CE panel --- when the car is hot and starter won't engage? Did you say the starter wouldn't engage in the hot, stall, can't restart mode --- or won't turn engine over?

Are you certain you got the critical ground points?
How were the valley ground ring terminal solder joints?

Did you indeed swap CPS out? I've damaged a new one on installation because the metal end wasn't well bonded to the plastic.

Am wondering now about your 14 pin connector. Did you unplug, then snap the backs off the two halves to inspect the solder joints. I've seen many of them broken, making intermittent contact. This is where the signal passes to engage the starter. This is probably where I'd put the next bit of effort if you haven't already addressed it.

Did you replace temp II? Are its threads clean so it grounds to the water bridge?





We used to live in Elkin during summer.

Bill Ball

Are you SURE you don't have thrust bearing failure??? Check the crank endplay. If it is >0.4mm OR zero, you have a problem.

I will say, on a possible positive note, that the couple of 928s with TBF that I have seen would still crank, just very slowly, as if the battery was down but not stone dead. Do you hear the solenoid click? Let's say there is an issue with the starter. That still doesn't explain the stalling. TBF would explain that as well as (slow) cranking.

You should check crank endplay regardless of "clean" oil.

Lizard928

You say CPS is fine.
How do you know this, have you tested the signal and the brain with an oscilliscope WHEN the car will not start? Or swapped in a known good one?

Rod Underwood

I had an SL500 that did exactly the same thing and it was the crank sensor. Worth a check if nothing else plays out.

Mrmerlin

OK do this next,
check the crank end play first.

then replace the CPS, put in a new part.

Replace the 4 running relays,
Ignition,
LH,
EZK .
and fuel pump once it dies,

then replace these one at a time , and try to start the engine,

use 53 relays Roger sells em

928s4forme

Will do. I will order new 53 relays tomorrow from Roger and swap out the CPS. Will let you know what comes of it.

Mrmerlin

do the crank end play first as if its grinding up you wont need the other parts

Bill Ball

Colin: Of course, you know the CPS does not interfere with the starter. Just pointing out it may explain the car stalling, but it still should crank. It's hard for me to come up with anything that would cause the car to stall when warm and make the starter not crank over the motor but TBF. Doesn't quite fit that either if the starter is completely dead.