Early 944 wont start :(

[many944s]

Story: 1983 944 engine turns, and gets gas, but no spark! I have replaced the DME relay, and tested the DME itself in one of my other 944s... Still no spark. The Porsche workshop manual doesn't have any pin-out tests for the relay board? Any ideas on how to track down the issue? P.S. already "hotwired" the factory alarm unit. Thanks, Nick

[NKN84944]

First off, welcome to the forum. I had this same problem a few months ago, and found the "Ignition System Troubleshooting" steps in the Garage Shop Manual of http://www.clarks-garage.com/ extremely helpful. My problem turned out to be the reference sensor, which is very easy to check along with the speed sensor with a volt meter. The description for how to test the speed and reference sensors can be found by following the link in the third row of the No Spark Condition table. Basically I would just follow the steps in this guide, starting at the spark plugs and working your way back until you find out what the problem is. Good luck!

[many944s]

I had pondered that, but didn't know how to go about testing. I'm out the door to the garage as I type! Thanks, I'll let you know how it goes. P.S. Thanks for the welcome!
-Nick

55 Ford Fairlane
69 Triumph Spitfire MK III
74 VPJ Indy Car
83 944
85/1 944
95 Ford Mustang

[many944s]

Ok guys.. I just tested both the sensors (ref and speed) and both of them ohm out as open? Has anyony seen both of these die @ the same time before? Anyway, anybody know who has the best prices on these? Thanks, Nick.

55 Ford Fairlane
69 Triumph Spitfire MK III
74 VPJ Indy Car
83 944
85/1 944
95 Ford Mustang

[NKN84944]

Well it sounds like you found it. Its kinda crazy that both went at the same time. I am assuming that you followed the procedure correctly, and found that you had infinite resistance between the poles that are supposed to have the following resistance.

Speed Sensor:
600-1600 ohms between terminals 8 and 27
Infinite resistance between terminals 27 and 23

Reference Sensor:
600-1600 ohms between terminals 25 and 26
Infinite resistance between terminals 26 and 78.

If so, you are going to be in need of both of these expensive little buggers. The part number is 944 606 115 00 (they are both the same sensor with the same part number). I just looked it up here on Pelican and it was $194.53 I paid about 60 less than that from a local German Auto parts shop, and they could be had for about $90 a piece from other online retailers. I would maybe ask Pelican if they accidentally put a 1 in the front, cause that just doesn't seem right. If it is right, there are a host of other retailers (Vertex etc) that you could check out. I also toyed with the idea of a used one from a parts car, but opted against it. Glad to hear that you seemed to have found the problem and good luck getting her up and running again.

Nate

[many944s]

Thanks for the encouragement Nate! Yea, I even triple checked I was testing the right pins when I saw both of them were bad. In a brief moment of self doubt I even popped the hood on my 85/1 and got about 598 ohms on each. I found I can get them from Eightyone motorsports for about $105 a pop. Better then a new DME I suppose

[SoCal Driver]

Very, very seldom do both sensors go bad. Me thinks you didn't check them correctly.

[SoCal Driver]

Do this:

Turn the key on and check for battery voltage at the coil and at one of the injectors (pull the plug on one of the injectors and check each pin to ground -- one will have battery voltage the other may read a little low because the circuit passes through the other injectors).

If there is no voltage at the coil then the ignition switch is bad -- or the wiring to it. Check the ten gage cables at the battery.

If there is voltage at the coil but not at the injectors then the DME relay is bad -- or the socket it plugs into.

If both have voltage then the ignition switch is good and the first set of contacts in the DME relay are good.

Pull the wire off of the first spark plug, stick a spare into the wire and lay it on the intake maifold. Crank the car and see if it sparks. If there is no spark then it can be the reference sensor or rotor. The screw on the rotor can come out but this usually just messes up the spark timing. The cam belt can break or strip off teeth and then the rotor will not turm.

If this does come back to the sensors then check them again. From the center to one side is open. From the center to the other side is resistance.

[Razorback1980]

Hey Nick,

Welcome to the forum. I agree with SoCal...you don't usually lose two sensors at once unless there was an electrical short of some sort.....before you spend the money for new sensors, try his methods. If you read this long enough, you will find he knows as much as anyone and more than most of us, so following his advice is always a smart thing to do.

Good Luck

[many944s]

Thanks for the info SoCal, That's pretty much the procedure I went through (minus testing the injectors) as I pulled the fuel rail to test the pressure and all of the injectors before I started resurecting her.
Here is the Deal:
A friends neighbor needed money, he had the 83 944 parked in his garage since 01. I looked at it and decided to get it (not bad for $350!!) I'll try to get a pic of it posted soon. Anyway, I always keep an extra set of belts in the garage as I have friends in town that have 944s and I usually end up doing their belt jobs as I have the tensioner. So, I decided instead of tempting fate, I would go ahead and replace the belts... not a prob. (P.S. car wouldn't start before this either), All of my marks made before the old belts were removed DO line back up after the new belts are on)
When it wouldn't start, I began at the coil. The (+) wire is energized when the key is turned to the "on" position. No spark when cranking. I then examined the DME relay & swapped it for a new one.. No spark. (also checked voltages at the relay socket, all tested good, as did continuity to ther final destinations in the harness) I then defeated the factory alarm unit behind the stereo, try again.. no spark. Next I removed the DME and installed it in my 85/1 944. She fired right up! I checked connection between the DME harness to the coil connection, it is good. When I got the info from the post about the sensors I pulled the connectors and tested them. From center pin to BOTH outside pins they read wide open. I then tested the ones on my 85 the same way, and they showed the proper resistance.

I appreciate the double check on my testing... but all fingers point to these two sensors.. I even double checked them today, and put the scope on to see if there was any pulse when the engine is cranked, none to be found.

I will definitely let the list know what happens..
Thakns guys!

55 Ford Fairlane
69 Triumph Spitfire MK III
74 VPJ Indy Car
82 DeLorean (lost in divorce)
83 944
85/1 944
87 924S (wrecked @ Speedway)
95 Ford Mustang