Roka

'87 S.

I have had this problem for a while now and I have come to the end of my idea list on how to diagnose it.
When starting the car cold (or after letting it cool down a bit), I need to use 2 cranks before the car fires up. The first crank is a long extended one and at the end of that extended crank it gives the slightest indication that it is firing up only to immediately die. On the next crank it immediately catches and fires up. From time to time it takes 2 extended cranks before the 3rd one fires up almost immediately.
Once the car starts it runs fine. It also starts up immediately if you shut it down and restart it.

So far, these are the steps I have taken to try and fix the issue, but to no avail. Some of these were "while you are there" items but I thought it better to list them:

• checked fuel pressure as per Clarks - passed
• checked fuel flow as per Clarks - passed
• jumped the DME relay - still had the problem
• took apart and cleaned intake manifold
• replaced all vacuum lines
• replaced all fuel lines
• replaced fuel damper and fuel regulator
• replaced DME temperature sensor
• cleaned and resealed throttle body
• cleaned and tested ICV
• cleaned MAF meter
• sent injectors for servicing, came back with clean bill of health
• Distributor, coil, spark plugs and wire are new

Any idea on what to do next?

V2Rocket

This sounds like something I am dealing with too. Doesn't want to catch on first try, but when you go back again it start up no problem and runs fine.

In doing some research I came across someone's theory...the first "cranking" is spraying fuel but not enough to necessarily "catch" a cold engine. The sprayed fuel wets the intake port walls and intake valve. Next time you go to crank the injectors are spraying the same amount of fuel but there is extra fuel "left over" from the last cranking cycle - richening the mixture enough to fire a cold engine.

What happens if you remove the vacuum line from your FPR (plug the end of the line for no vacleak)? That would "artificially" raise fuel pressure to the full 944S 3.5-3.8 bar spec rather than the spec minus idle manifold vacuum. Higher pressure should make for a little richer mixture...

Roka

I'll try it this afternoon, and report back.

StoogeMoe

What about the check valve? Sounds like your fuel is draining out of the lines causing the lengthy cranking to fill it back up.

V2Rocket

If so would indicate some level of "lean condition" at cold startup.


Stooge - my ECU "primes" the pump at key on for about half a second, so the lines/rail are full when you go to crank...but I get the same sort of cold start behavior as his. My tune is still being ironed out...

So it may be worth checking the check valve either way but I am thinking it is an electronic issue of some type.

Roka

I thought about the check valve early on in my investigation but the fuel pressure check was ok and so was the leakdown test as per Clarks (http://www.clarks-garage.com/pdf-manual/fuel-01.pdf).

In addition, I jumped the DME relay and had the pump running and priming the lines for 30 seconds before cranking but it made no difference.

StoogeMoe

Well if you're fuel rail is full when cold, you can always try the starting fluid trick. If it fires right up, then you know it's a lean condition. I would test the DME temperature sensor AND the AFM temperature sensor at the DME plug. Make sure they are within spec and are getting through the harness.

968workaholic

Reference sensors/harness integrity? Just a thought since it sounds like you have covered the basic tests/checks

Roka

First off, thanks for all the suggestions.

So I disconnected the vacuum hose from the FPR but still had the same symptoms.

I moved on and disconnected the DME plug and verified that the DME temperature sensor, the AFM temperature sensor and the reference sensor are within spec. Since I was there I also tested the idle contact and full load contact; both were within spec.

I haven't tried the starter fluid suggestion yet. Do I remove the filter and spray it in the airbox?

Any other suggestions would be appreciated.

gtroth

It kind of sounds like it's not doing cold enrichment even though you replaced the temp sensor. I would measure this sensor's resistance at the DME connector. In fact, at times like this, I like to measure everything I can at the DME connector. Follow the DME diagnosis and troubleshooting guide in the FSM.

Roka

All the sensors at the DME connector check out.
Still trying to hunt this down

merope

Did you ever find the solution to this?