Carl Presseault

Hi Everyone,

I'm a longtime lurker in there, just recently signed in and this is my first official post. Sadly it's not an happy one.
I own a 944 Na 1984 since August 2017. I was looking for one for a while and this one was the perfect match I was looking for. The Idle was never really smooth but it was running and I was happy. Until November, when the car started to run only on 2-3 cylinder when cold to finally run ok when hot. The only event I could recall before those symptom appeared is driving in a rain storm for 300km and stalling in a parking lot. I stored it for the winter and when I started it the following Spring, she was running fine like when I got it.
Then I changed the oil (Brad Penn 20-50) and the filter and suddenly, she don't want to start anymore. Here's the list of what I did or replaced so far:
-Tested reference sensor (ok)
-Replaced Oil and Filter
-Replaced 4 injector
-Replaced DME Relay and Fuse
-Replaced DME (went that far...)
-Inspected and tested Distribution Cap (has spark)
-Inspected and replaced Ignition wires for BERU
-Replaced and gapped spark plugs (copper)
-Cleaned ground
-Inspected every vacuum line
-Replaced Alternator for a Bosch unit
-Replaced battery
-Replaced fuel pump (cleaned the strainer while I was in there)
-Replaced fuel filter

At this point, she is cranking, I've a tach bounce and a smell of petrol when I do. But when she do try to start, it's only on two or three cylinders... I'm puzzled and I'm a little bit tired to trow parts at my car for zero result.

Any inputs?

Thanks!

C

Carl Presseault

I tested compression and i'm at 130psi-130psi-130psi-135psi

Van

Are you sure the plugs wires are in the right order? Sounds like you have the firing order off.

mikehayes

Hey Carl,
It sounds like you might be well beyond this, but I usually find it helpful to verify the absolute basics if my engine won't start. Have you verified that the injectors are delivering fuel to all cylinders? Have you verified that each plug sparks at the correct time? And finally have you verified the the AFM is delivering the correct air flow measurement to the DME? If you have air, fuel, and spark (at the correct time, as Van points out) then your engine should at least fire on all four, if not start roughly.

Dan Martinic

Smell of petrol? Whatever you do, pull the fuel pump fuse while diagnosing

Get a cheap little 12v LED from an electronics supply and use it to test for injector pulse for each cylinder plus ignition coil

Carl Presseault

I've tested everything.
Today I pulled out the dipstick and I gat a smell of gas. Weird...

T&T Racing

This is normal if cranking the engine for extended periods of time and no spark to ignite raw fuel from the injectors. I would focus on why no spark timed to when it should occur in the cycle. Maybe after testing speed and reference sensors, they were reversed when plugs reconnected. Or connection pins are corroded, that was the issue with my no start problem. Use electric contact cleaner.
Check if the DME is collapsing the 12V at the coil to produce the high voltage spark or if the spark plug is firing. Clark's Garage has procedures

Otto Mechanic

Hi Carl -

I have to vote with Van on this; check the plug order. If that doesn't work, take a look at the distributor again. Mine had a nearly invisible crack in it with a faint carbon trace that was causing a misfire. It's not an expensive part and it's pretty easy to miss even after you think you've inspected it. Definitely check and recheck, then check again, the plug wire sequence. It's really easy to get backwards.

PS: Rain storm and stalling in a parking lot. There's a clue that points to the distributor. Humidity and water will make a marginal distributor turn bad on you.

Best Regards,

Carl Presseault

Perfect! I'll recheck this morning. But the thing is that before, I was able to start it after some time and it was running fine. Now I can't start it without keeping my foot on the pedal.

Carl Presseault

I did check and I'm pretty sure everything's at the right place. I'll replace the distributor tomorrow to see it this change anything.

T&T Racing

Sounds like you have a AFM is in failure mode, sending a signal to ECU/DME that falsely indicates more airflow than actual, pulsing the fuel injectors more frequently, causing a rich A/F ratio. Holding the throttle wide open compensates for the rich fuel mixture and adds more air. Contact Bavarian Restoration

Carl Presseault

Here's the updates.
I replaced the AFM for another one and the problem is still there. I replaced the Distributor cap and rotor and there's still a problem.
My car start when it's cold in the morning but never once the temperature hit above 80F. ICV? I made sure that I had no vacuum leak again. I'm just throwing parts at it right now....

T&T Racing

I read your list of parts replacement and your other threads. Your last thread was significant because the symptom is the engine does not start when the outside temperature is not.
I believe the one part that was not replaced is the fuel regulator located on the fuel rail
You purchase without testing or you can test it by following the procedure from Clark's Garage
The fuel regulator failure mode is closed, increasing the fuel pressure above spec. When it fails, no fuel is returned to the fuel tank and the fuel rail is pressurized to the maximum output pressure of the fuel pump. Consequently, no enough mass of air flowing into intake header for the mass flow of fuel, mixture too rich. The AFM is a volume device and as the intake air temperature increases, the density of the decreases, the air volume is constant, BUT the mass of decreases

Carl Presseault

Exactly what I thought it was but everybody keeps steering me away from this option. I'll order a new one.

Dan Martinic

Ooh I'm curious now!

Say, what's the purpose of the fuel dampner (the other piece on the fuel rail)? Could that play a role here?