Cold Start Problem
 

Having a problem with cold start on my project ’83 944 (non turbo). By cold start I mean first time each day – not necessarily air temp.

I know there have been many threads before this one concerning starting issues and I believe I have read all of them. Any suggestions are appreciated at this point!

I can get it to start by giving it a shot of starting fluid. Once it starts it runs fine and after it warms up it you can turn it off and it will start up again. That makes me think it is a fuel problem.

Short history - I acquired this car several months ago. It had not run in 6 years. The previous owner was experiencing intermittent start issues which caused him to stop driving it on a daily basis. It had no spark and no injector pulse. By replacing the speed and reference sensors (connectors were crumbling) I was able to get spark and injector pulses. 3 of the 4 injectors had no fuel output. Cleaning the injectors took care of that problem.

Here is what else has been checked/replaced:
Compression is 175 – 180 psi
New distributor cap, rotor, wires and plugs
Drained gas tank and refilled with fresh premium
New Fuel filter
Timing belt and balance shaft belt replaced
Checked mass airflow sensor
Checked mass airflow temp sensor
Replaced DME engine temperature sensor
Checked auxiliary air valve
Found and fixed vacuum leaks – including resealed throttle body
Checked throttle body switches
Fuel pump pressure 29 psi @ idle, 35 psi with vac hose disconnected
Fuel system leakdown - 30 min after shutdown fuel pressure has not dropped 1 psi
Fuel pump volume - 1600 cc in 30 sec

2 items seem kind of funky to me. First - idle speed is high. By turning down the brass idle screw to ½ turn from seated I can get the speed down to 900 rpm. But according to the reseal kit instruction it should be closer to 2.5 turns from seated – which gives a little over 1000 rpm. Second – if I pinch the return hose closed the fuel pressure shoots up to 80 psi. Supposedly it should be no more than 58 psi. I replaced the fuel pressure regulator but the diaphragm started to leak. The 2nd FPR has the same pressures when running. I hesitate to pinch the return line completely closed (I wonder if that’s what ruptured the diaphragm in the first FPR?) but the pressure starts to rise over 58 psi as soon as the line is pinched.
According to Clark’s, if you disconnect 1 injector and the engine starts the fuel pressure is too high. I did that once and the engine started but of course ran like crap until the injector was plugged back in.

Is this a fuel problem? Why is the idle so high with idle screw at 2.5 turns? How is the FPR supposed to work?

gizmoe107;

Verify Your Engine is grounded. With a digital Volt meter measure the resistance between the passenger Strut mount screw and the intake manifold. If should read less than 1 ohm. If is higher, run a 10ga wire 2-3ft from one of the Intake manifold allen screw bolts to a strut mount screw. Be sure to make good contact (use emery cloth 80 grit) for each end before tightening it down on either end.

Big problem with the Porsche especially the water cooled cars...

Later...

Thanks for the reply guru944. What do you mean by the "Strut mount screw"? One of the bolts holding the strut mount? I assume you're basically looking for a good connection to the body. I just checked from that bolt to the intake and resistance is less than .1 ohm. Also checked from the intake to the battery and it is also less than .1 ohm. I've read a lot of other posts that mention ground issues so tonight I'll pull the ground straps at the back of the engine off and clean them up anyway.

Cleaned the battery ground to body, and the grounds that the back of the engine (pain in the neck to get to). Still no cold start. Any other grounds that should be checked?

Could this be an ECM problem? I forgot to mention the first time that I have already gone thru an re-soldered one of the boards per this link:

Early DME repair write-up with pics. - Rennlist Discussion Forums

He says you just need to do the upper board. Is it worth doing the lower board as well?

Finally Fixed! After tracking down every last vacuum leak (at least that's what it seemed like) and checking all the grounds the cold start problem was still the same. The only thing left was the DME computer. Bought a guaranteed used one of of eBay and fixed the problem! Just wanted to follow up in case someone runs across this thread with the same issue in the future.

That's exactly what happened to me. I replaced the DME and she's been running great!
I think I had a post a year or two ago asking the same questions. Congrats!