Hi everyone.
Ihave a 86 944na, replaced the motor in it with a 83na, and guess what....it wont start. I used all the 86 external parts on it,intake, exaust, throttle body, air flow meter,injection,wireing harness, flywheel, bellhousing etc.. It has new speed and ref. sensors, replaced the dme relay as well as the dme itself. I checked all the vacume and wireing conections, made sure the sensors are gaped properly,and going to the right conections for the harness.I then did a continuity check to make sure the wires were not broken inside the harness, and just for good measure checked to see if everything was grounded...it was. I have 2.4 oms in the injectors, 12.5v out of the injector harness,fuel pressure in the rail, a good spark ( new wires, plugs and new coil ). The problem is no signal to the injectors to open and let the fuel into the cylinders. The starter works great, turns over like it means it, the tach bounces when trying to start it, its full of fuel (fresh),oil and water. Put in new timeing belts,made sure all the marks were set up for TDC,including the balance shafts,and ofcourse new cap and roter,and checked the fireing order. After all that guess what....it still won't start. I can deal with the no start thing,but my wife is starting to think IM GETTING OBBBSSSEEESSSDDD with it.

If anyone has any ideas, i would love to hear them. thanks in advance.

 

What year dme are you using with the 83 motor? Also, the AFMs are different from 83-85 than from 85.5 on IIRC.

 

Thanks for the response PorscheDoc;
The DME is an 86 model, I figured if everything on the motor was 86, I should use the 86 DME as well.
No one I have talked to has mentioned the difference in the AFMs to me, I still have the origanal AFM for the 83 motor, I will get that changed on the weekend. But I do not have the DME for the 83 motor, but Ill start with the AFM and see if that does the trick.
I also forgot to mention that the car is an automatic, but as far as I know, that should not make a diferance.

Once again, Thank you.

 

One more thing PorscheDoc;
The only differances I found externaly between the 83 and 86 motors was the opening in the block for the timming sensor test port, and the water temp/ Hi temp alarm sensor beside the DME temp sensor. For the first problem I bored a hole through the flashing at the back of the block,and everything fits fine. The second differance I mentioned, is that the 83 has a single conection point and the 86 has a two prong conection. Not sure what to do about it, because the sensors are much bigger on the 86 motor, I would have to remove the head and bore out a bigger opening, and tap it to fit. Can the two wires be combined, or is there another fix for this.

Thanks again PorscheDoc.

 

Yes, you are correct, they changed the temp sensor on the later model cars to 2 prong, vrs the early 1 prong. I don't know if you are rig something up to make it work or not, i have never tried. Obviously that is the sensor for the temp gauge on your dash. Did you use the 83 wiring harness or did you keep the 86? If you kept the 86, that is good, since it goes with the 86 dme and AFM. I dont know if the 83 harness is different enough to keep it from starting if you used that. Just for ****s and grins, unplug #3 injector and try to start the car. If no go, unplug the #1 injector (plug 3 back in) and see if it will start on 3 cylinders. Let me know what happens.

 

Hi PorscheDoc;
Got home at midnight, and have to be up at 4am so i won't be able to check it till sunday. As soon as i do, i will let you know the results.
Thanks again,talk to you soon.

 

Sorry, can you tell Im tired?
the wireing harness is from the 86( the original). the only thing that is 83 is the moter itself, all the periferals are the original from the car.
thanks again.

 

Hi PorscheDoc;
Tried your advice about removing the connection to the #3 injector,no start. then tried the same on #1 injector, still made no differance. Went looking for the AFM from the 83 motor,and I must have been wrong because I can't find it anywhere. Phoned up a guy I know, and he is going to bring his car over and we'll try his DME and see if it make's a differance.
Thanks Again.

 

I am interested in how this comes out, I have an 85/1 NA that I put an 87 2.5 in. It has the early AFM, manifold, wiring, fuel rail, etc. Just the oposite of what you are doing. The only problem I dont have is the temp sensor. I think if the AFm is causing your problem, mine will cause me a problem. So let me know what happens. Thanks Rich

 

Hi Kinderrich;
Italked to the people at porsche(ONE OF THE MECHANICS) and as far as they are concerend, the car should run just fine if all the external components( fuel rail, throttle body, afm, and wireing harness) are the same year as the DME. So my problem is probably some little detail I have missed. They said that there are some little differances in the early and late motors, but nothing that would cause it not to start.
I was also told that the early and late DME's are not interchangable because of the wireing harness, if you tried to put the late DME into your car, you would have to put in the wireing harness in to match it,(not a fun job).
As far as the temp sensors go, the wide spade post on the late sensor is the lead to the temp gauge, and the narrow one is to the hi temp alarm. As far as i can figure, they don't affect the DME at all.
Question, did you get your car running.
Hope some of this helps you out.