944S/968 conversion HELP!!!

Ross T · 05:09 PM

My mechanic has installed a 968 engine into my 87 944S. I am using the 944S clutch and torque tube. I have the wiring diagram and DME from a 968 istalled. he says he has double checked the wiring allready. I asked him to email me explaining what he has done. I told him I would post my questions here on the board to try and get some help.

Anyone who has any idea please fell free to chime in I have been without this car since the 4th of may. Every time I ask him if things are moving along he seems annoyed that I am asking. I do not know how much patience I am supposed to have.

My mechanic wrote:
OK, so I threw another 2 hours going over the schematics yesterday morning.
All power seems to be there, and I hooked up all red wires, etc, actually
didn't change anything and everything is getting power the way it should be.
I can hear the DME fire up when the ignition is switched on.
At this point I'm wondering if either the crank sensor or the DME itself is
junk. No spark and the fuel pump is never triggered which means that either
the DME isn't getting a crank signal or it just isn't working. I'd kill for
a 968 to check some power on. I have power to the coil and jumpered the
white output from the 14 pin connector. According to the wiring diagrams
the 968 does not use an ignitor, which is odd because every other car
introduced 1987 on does.

Britwrench · 08-19-2002, 03:54 PM

If you are installing a 968 engine into a 944s you would have to use the 968 engine wiring harness and DME computer.
All that would need to be done is to compare the power and ground connections of both cars and ensure that the 968 engine harness is wired as it would be in the 968 body.

If you don't have the wiring diagrams for both vehicles it's never going to happen.

HEAR THE DME FIRE UP????????????????????????????????????

Ross T · 08-19-2002, 03:59 PM

Thank you for the response but my mechanic does have the wiring diagram for both the 87 944S and the 92 968. He has gone over the wiring more than once and is fully confident that all is wired correctly.

Britwrench · 08-19-2002, 04:40 PM

If the wiring is correct and the components all work then it would start and run.

Firstly, have the sensors been checked? with a scope you should be able to check the output of all relevant sensors.

No spark and no fuel is a sign that the DME computer for the 968 is not recieving any signal that the engine is cranking. You will always get 12v to the coil with the ignition "on" as the DME system is the ground.

DME control units rarely fail, I would be looking for incorrect wiring or lack of signal repsonse from a sensor. The engine wil start and run (albeit not that well) with most of the sensors disconnected.

The 968 engine wire harness includes hook-ups to the diagnostic plug. You will need this installed so that the engine can be checked with a Bosch KTS300 tester. Obviously it will also make troubleshoting easier.

Ross T · 08-19-2002, 05:07 PM

my mechanic wrote: "I can hear the DME fire up when the ignition is switched on.
At this point I'm wondering if either the crank sensor or the DME itself is bad.

Is it possible for the DME to make the sound( whatever it is he is hearing that makes him believe it is firing up) if it is not getting a signal that the engine is cranking. If it is a sensor that I need do you know the part # price or how to replace it? is it something I can do?

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by Ross T
Thank you for the response but my mechanic does have the wiring diagram for both the 87 944S and the 92 968. He has gone over the wiring more than once and is fully confident that all is wired correctly.

And what exactly are we to add to such a capable mechanic who not only has both wiring diagrams but the actual car at his finger tips???

Perhaps you could give us the e-mail address of the mechanic and we can converse directly with him. Wouldn't want anything to be lost in the translation.

Britwrench · 08-19-2002, 05:16 PM

I think he is hearing a relay click as I've never heard a DME computer make a noise.

You can check ALL the sensors with a scope. I'm wondering if you have a no-signal from the crank sensor because either;

1. The air gap is wrong.

2. You have the wrong flywheel for this application, I don't
remember, but there is a specific flywheel to be used with
non-dual mass 968 engines. The is a Porsche bulletin about
which one.

Hugh..LMAO

Ross T · 08-19-2002, 05:24 PM

Bitwrench.
Iif the air gap is wrong does that mean going all the way back into the flywheel and checking it? I assume this would take several hours to check this? ..If this is the problem I would hope my mechanic would not charge me. If it is not i will get stuck with a bill. Can i replace the refference sensor with fairly little trouble? I gues it would be best to rule this out first? I can change a reference sensor fairly easily?..?? correct?

Ross T · 08-19-2002, 05:29 PM

SoCal, I am not real sure it would be right to give out his email. I am almost affraid to ask as he is always treating me like I am a bother. I have already given him $2,150. I feel I am in a difficult position. It is as if I am in a argument with a cook who has not brought my meal to the table yet. If he gets bothered I am not real sure what would happen. Know what I mean?

Britwrench · 08-19-2002, 05:36 PM

The air gap can be easily checked, either by actually measuring it or by using a scope. If you mechanic does not understand Porsche technology, I would think about buying a Honda to drive around in for a while.........................................

The crank sensor air gap should always be checked anytime the flywheel is worked on, so that means it was his responsiblity to ensure the sensor, gap and flywheel all were checked and correct before installing the motor = no charge to check it.

AFJuvat · 08-19-2002, 05:42 PM

You can change the sensors with the engine in the car, you need a little contortion to get at them, but it isn't too difficult.

Before you go tearing everything apart, also make sure the sensors are connected properly and not reversed

Britwrench makes an excellent point: You make reference to using a 944S clutch and torque tube, but what kind of flywheel? one from the 968 or one from the 944S? My magic helm of all seeing omnipotence is a little hazy today, but if you have a 944S flywheel, I don't think it will work. I believe you have to have the 968 flywheel.

Britwrench, please correct me if I'm wrong, but aren't the fuel pumps different as well, I seem to recall the 968 pushes more fuel.

88 NA 944.608.102.02
88 S 944.608.102.03
Turbo 944.608.102.05
968 944.608.102.06

Also, since the PS pumps are different (higher pressure) wouldn't you have to change the steering rack as well?

AFJuvat

Britwrench · 05:54 PM

AF, the fuel pumps all seem to supercede to Bosch 0 580 464 042
according to our supliers catalog. This wouldn't stop the engine starting anyway. The power steering pumps are different, but I believe that is only because the 944S has the idle switch installed. The pump pressure is regulated by the rack.

I will try and find the bulletin about using a normal flywheel with the 968 engine. But there is no point changing anything until you know what to change..and what the actual problem is........

AFJuvat · 08-19-2002, 06:00 PM

Quote:

Originally posted by Ross T
...I am almost affraid to ask as he is always treating me like I am a bother. I have already given him $2,150. I feel I am in a difficult position. It is as if I am in a argument with a cook who has not brought my meal to the table yet. If he gets bothered I am not real sure what would happen. Know what I mean?

One thing though, do try to remember that he is working for you.... You are paying him for this service, therefore he has a responsibility to YOU to either finish the job as agreed upon or to say "I can't do it"

When I am working in the garage I dislike the "pest" customer as much as the next guy, but I also remember that I have the responsibility to answer his questions because he is paying me. The only time I really have the right to say (nicely) "go away" is when he is affecting my job or violating the safety rules.

AFJuvat

Stuttgart951 · 08-20-2002, 09:05 AM

If he is "hearing the DME fire up" that might be your problem right there.

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by AFJuvat
You can change the sensors with the engine in the car, you need a little contortion to get at them, but it isn't too difficult.

Before you go tearing everything apart, also make sure the sensors are connected properly and not reversed.
AFJuvat

If the 968 flywheel sensor is like the one in my 944S2, there is only one sensor (so you can't reverse them). I know other 944's had two sensors, a reference and speed sensor.
When the engine and transmission were seperated the sensor bracket may have been removed. In that case, the sensor gap would need to be (re)set. Like everyone said, you check the signal from this sensor using an oscilloscope. If your mechanic is a Porsche mechanic this would all be old news to him. He would already have an old sensor with a .8mm washer glued to the end just for doing this.
-Chris

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by ChrisBennet

I know other 944's had two sensors, a reference and speed sensor.

-Chris

Recently took apart an 86 automatic and it had 3 sensors. The two for speed and reference and a shorter barreled one for what looks like true TDC.