944 turbo wont start

[dkahler]

Hello,

This is my second post. I have a 86 951. It wont start, I have read every post I can find regarding 951 not starting. When I go to start it, it will crank and start to fire up for about a second and then dies. These are the things that I have replaced, all vacuum lines, speed reference sensors, spark plugs & wires, distributor, rotor.

I feel that I have everything hooked up correctly. It is getting fuel, I changed the DME relay.

Any thoughts that you might have would be greatly appreciated.

[968 GUY]

How are you sure it is getting fuel? have you hooked up a pressure gauge?

[John_AZ]

The car ran when you initially picked it up a month ago:
1986 951

Try cleaning the AFM connection. If loose, dirty or not attached you will get the same symptoms.
Make sure the AFM door swings freely.

Then make sure the sensors installation are plugged into the correct wire. DG or BG

Speed and Reference Sensors - Checking, Replacement, and Adjustment

GL
John

[dkahler]

Sorry for the long post.

I know that there is fuel at the rail, however I am not sure of the pressure. That is something I can check. What is a normal range of pressure?

I swapped the reference sensors and cranked the engine, This time there was no fire at all when the engine cranked. I switched them back and again got the engine to fire for about a second. I also checked the AFM connection and door. As far as I can see everything is solid and free from dirt and the door appears to swing freely.

So here is what I did to get the car not to run. As I have gotten to know the car better, it is apparent that it has had a very hard life. I thought that I would remove the venturi valve because I had read that it caused issues. I went ahead and setup the car this way with the venturi delete. Then the car would crank but no fire. Realizing that I had done something wrong, I return everything back to original and the car started and ran fine. However when it was running fine, I had not placed all the hoses back under the intake manifold.

I then placed the hoses under the intake manifold and got the results that I am getting now. In doing this, I realized that the car was missing certain vacuum pieces, "Cycle valve" and other hoses were plugged or not connected at all. I am actually amazed the the car ever ran at all.

As a result, my goal is just to get the car to "stock" condition. I removed the intake manifold and attached a new cycle valve, resoldered the wires for the knock sensor, ISV, and replaced almost all of the vacuum hoses. I used texasblake.com as a reference for where the vacuum hoses attach. I have left the venturi valve in place and as fas as I can tell, everything is connected correctly.

My gut tells me that it is something to do with the vacuum of the car, I am trying to avoid taking into a shop.

Thanks again for all of your insight.

[dkahler]

Well, I have now checked the fuel pressure at the rail and I am getting 39psi. That is with the DME jumpered. It seems to be in acceptable tolerance with the data listed in Clarks garage.

I also tested each spark plug lead to ensure that I am getting spark and each one checked out okay.

Does anybody have any other ideas?

Thanks

[nize]

you mentioned you replaced all vacuum lines, are you sure they're connected correctly? there is one line that runs from the intake manifold to the klr, this should be a separate line. also make sure you have the line that connects directly under the throttle body.

[dkahler]

Thanks for the post. I know that I have the KLR line t'd into the vacuum that connects the fuel dampner and pressure regulator. I will isolate that line. I do have the line connected the throttle body.

Thanks for the tip. I will post an update tomorrow.

[dkahler]

Well, I isolated the vacuum line to the KLR. Unfortunately, no difference in starting. I also installed new fuel injectors. At this point, I am relatively confident that the fuel system is good. Also the ignition system is brand new. I tested the ISV and it appears to be working.

I had my friend crank the engine while I held my thumb over the port on the intake manifold that connects to the KLR and I could not feel suction. Should one be able to feel some level of vacuum doing that?

Other than that, I got nothing. At this point I give up and admit defeat. I am going to take it to a Porsche shop. I will let you know what they come up with.

Thanks for everyone's help and input.

[dkahler]

Hello again,

I have been testing my AFM against Clark's garage procedures for testing an AFM.

Air Flow Meter (AFM) Operation and Testing

In Clarks test he was able to achieve close to 9volts when he was testing the resistance of the swing arm inside the AFM on the resistance track. When I performed this test, I was only able to achieve around 2volts. The resistance was smooth as the volts increased. There were no dead spots in the resistor track.

Since I was only able to achieve 2volts, would you think that my AFM is bad?

Thanks

Doug

[dkahler]

So it seems that my gut feel was correct. My mechanic found out that it was not starting due to vacuum leaks. The biggest issue was the ISV. Apparently it was leaking air causing the car not to start. To add to the issue, they also determined that my ECU was flaky causing the car to start intermittently. So I hope my struggles helps someone else.

Thanks

Doug

[nize]

good to see you've got it figured out!

[Freaky]

New guy here....sorry for being so dumb, but what's an ISV?

[John_AZ]

ISV-Idle Stabilizer Valve. aka ICV-Idle Control Valve.

Good old post:
ICV (idle control valve) or ISV (idle stabilizer valve) O-Ring

Welcome.
J_AZ

[bh912e]

Check that screw is still in the rotor, I blue loctited mine because they can fall out. Also ohm out the ref sensors, you can do it by unplugging the dme. There are threads on it. Then check for spark and finally for fuel by ignition on and either jump dme or press afm flap door in-

If everything above checks out then check crankshaft/ cam timing .....