jstand22

I think the most the timing can be off is 2 1/2 teeth. After that.....death.

But listen to CPR; speed and reference sensors should do it.

dmalo810

What part of the country you in? Check reference sensors like they are saying. Also, yesterday we had a n/a that wouldn't start, everything was good as you say, then it ended up being the grounding strap was not making contact.

Van

Tell us more about these "2 skipped teeth"...

I have a hunch that something is misdiagnosed...

You don't have "good spark" / "good fuel" / "good compression" and a non-running engine.

You more likely have: "oops, I didn't do the compression test right... you have bent valves because your timing belt failed..."

And, oh by the way, the first red flag of your post was: my mechanic who does not normally work on german cars...

Tinker951

i took the car to the mechanic that normally works on my truck and wife's car. I trust him and I know he does good work. I live in a rural area where the closest porsche/bmw/volkswagen etc is 60 miles away. The compression tests were 125 lbs in each cylinder on both exhaust and ignition strokes. very doubtful there are bent valves. spark is happening at the plug. I suggested he turn the cam 180 degrees and see if the spark was on the wrong stroke. He knew what I was talking about and knew where the sensors were when I spoke of them this morning.

It was driving fine, just sluggish when i replaced the cam on the head and re-timed it. before i took it off, i put the line in the window it was in full view but closer to the right side of the whole from center, just off the notch. when i replaced it, i lined it up in the same spot but tensioning caused it to move to the left side of the notch. thats how i came to the conclusion i was retarded on the timing. the mechanic confirmed it when he took it apart. the fly in the ointment is that while i was trying feverishly to get the cam off and back on to the head, the cam sprocket moved freely. when i got it back on, the mark was in the 10 o'clock position. it could have been 180 out and i wouldnt know and wasnt thinking about it at the time.

thanks for the replies

M758

The reason I said 180 degrees out is that I did that on my 951 7-8 years ago.

I was doing valve stem seals and had the cam tower off. Some how when I put it all back in and set the timing it would not run. I had the same issues. I had fuel and I had spark. Then I figured the cam timing was out since the number 1 plug was not firing on the right stroke. I verified by pull in the cap and watching the rotor approach #1 cylinder. I then watched the piston movement and it was on the wrong stroke.

So I deduced I had the cam 180 degress out and the spark (driven off th cam) was not matching which injector was firing. No bent valves since it was just opening the exhaust vs intake. So I swapped it and all went well.

It should be easy to check since th TDC mark should be up on the fllywheel while mark lines up on the cam gear.

Zero10

The injectors batch fire on 951's so all 4 go at the same time, and if the cam is 180* out the engine will run fine, since you can then turn the crankshaft 360* (180* on the cam) and all the marks will line themselves back up, this happens every second crankshaft revolution. If the cam is not exactly 180* out (which is far more likely in this scenario since there are no timing marks on that side of the housing...) then you will have issues.

If you have fuel, compression and spark (check at all 4 cylinders) then the only thing left to check is spark timing. Check that the cap is on the right way up, and that the set screw is in the rotor.

If you have spark and the tach wiggles when cranking then the speed/reference sensors are fine, the more they are tinkered with the more likely they are to break. Check the connectors over but do not remove them unless it is necessary.

You said the injectors are pulsing okay but did not mention if there was a fuel pressure test done at the rail, or if the rail was removed and the injectors were verified to actually be firing. If the spark timing is right then it sounds like you have no fuel and this needs to be checked.

Mike C.

Does your mechanic have any reference information on these cars? I would hope he at least has the Haynes 944 manual. Finding TDC on number 1 cylinder compression stroke should not be difficult but I would recommend some familiarization before messing with the cam timing on an (expensive to fix) interference engine...

CPR

Nevermind with the S/R's...I just saw where you have spark.

jstand22

swap out the DME relay

CPR

He said he is getting fuel, and spark so the DME should be fine.

There are only 3 components to fire an engine...AIR, fuel, spark....something is being missed. HOW did you mechanic verify spark?

CPR

Wait...you said it is getting spark "OK"...but then say it is not getting spark? Which one? This is important.

Tinker951

I'm not sure how he is determining spark. i know he's got the plugs out to check compression, he may have turned the car over to determine spark or hooked up a test light. he said everything is working like it should but to hear the car turn over, it sounds like no fire, but he's confused because all the components are working separately to provide fire.

ive had the no fire problem once before and it was due to bad spark order, because i misread the haynes manual. he hasnt had time to work on it since yesterday morning when i asked him to give the cam sprocket a 360 spin to change the phase 180 degrees. im hoping he can get to it today.

im confused on a post here, too. do the injectors really fire all at the same time? isnt that a waste of fuel and a backfire hazard?

Funn944

Interference motor, really bad things happen when cam is cam too far out of time (180 ? doubtful) A mechanic that doesn't normally work on German cars, and is stumped wouldn't be my mechanic. At least not for my 944.

JohanvdWalt

I've got no idea on the problem but .............. I'd much rather have a Mech I trust with no knowledge work on my baby than a knowledgeable one I don't trust!

Tom R.

Ditto. My wrench in NY never touched a porsche before my first S2. After he changed the oil cooler gaskets the first time he told me the setup was the same as on the garbage trucks he works on by day.

The principles of all cars are the same. he just needs the reference points.