I'm back after a long break... No Spark

XJOSHX · 08-22-2012, 12:06 AM

So I got my first 944 after a 5 year hiatus. I am pretty happy since I got a good deal. The car has full service records and was well cared for... until it lost spark. The car is an 83 with 120k. It's dirty from sitting the last 10 years. Gas tank has a stab wound, and the gas smells awful! Sooooo without delay, onto the issue...

The car was parked into storage unstarted and untouched for 2 years. The previous owner (Who is a mechanic, but not the best one) went to go start it, and there it was with no spark. He replaced the DME relay, and decided it was the sensors on the bell housing. IIRC they are the reference and speed sensors? I know they time the car using a square wave signal. Anyways, he got brand new ones, and put them in. He said he didn't tighten the nuts, tried to start it, and no spark still. Would that by any chance make it so it won't spark still? It does have power to the coil.

If that don't fix it, I would like to do some diagnostics, so I need to know some values. I need to know what the coil test at, how to test the DME it's self, what to test the sensors and wiring at, and anything else I should look into. I was also curious if there were any safety function that cut off the DME, like FPSS, or OPSS or something. Any help would be appreciated.

FYI, it's an early car. 1983. Here is a picture to make this more interesting...

Guest765 · 08-22-2012, 12:24 AM

The sensors are probably swapped, flip them around and try again.

lupdiesel · 08-22-2012, 06:01 AM

So you have power to the coil, but nothing coming out? Sounds like a coil issue. You said it was not replaced yet?

GGX2 · GGX2's Garage

When I got my 83 it had no spark, PO had said something about replacing the sensors so I swapped their connectors... had spark after that :P Do you have Tach bounce? Because I didn't before I swapped the speed and reference sensors.

XJOSHX · 08-22-2012, 01:18 PM

I literally have not messed with the car at all yet since I just got it last night. I am told there is no tach bounce. Makes me think more and more about the sensors.

XJOSHX · 08-24-2012, 11:29 AM

So I heard people talking about an LED test for the sensors? I can't find any info. I dislike changing parts on a whim.

Guest765 · 08-24-2012, 12:59 PM

Why ask for help and ignore what multiple people have told you to do? Perhaps you misundrstand, tty swapping the POSITION of the speed and reference sensor; we did not mean go out and buy them - yet.

GGX2 · GGX2's Garage

You might not need to replace them, if the PO replaced them both at the same time he may have hooked them up backwards. It's very easy to check, I found a picture online, just swap the connectors in the picture and see if you get spark or tach bounce. Good luck.

VOTS89 · VOTS89's Garage

Quote:

Originally Posted by XJOSHX

He said he didn't tighten the nuts, tried to start it, and no spark still.

Make sure they're properly adjusted and the nuts are tightened. If that doesn't help, I'd swap the connectors like GGX2 suggested.

Bruce

XJOSHX · 08-24-2012, 10:17 PM

Those suggestions were NOT ignored. I have parted out quite a few of the cars before so I am rather familiar with them, and thier parts. I know the sensors, and I know the plugs, I just have not had a spare minute to get out there yet. I am going to wrench on it sunday, but in the event this is NOT the problem I am trying to get more info now so I can track it all down, and get it done sunday instead of waiting for more replies.

VOTS89, I do NOT know how to properly adjust them. Do you happen to know of a write up on here or rennlist that I can check out?

VOTS89 · VOTS89's Garage

Here's the Clark's Garage procedure I've used in the past, I'm assuming it works for all years of our cars.

Clark's Garage Home Page

Click on "Garage Shop Manual"

Then click on the last hyper-link under "Fuel and Ignition" for Speed and Reference Sensors

Cool camera shot of the car by the way!

Bruce

Dave Colangelo · Dave Colangelo's Garage

I had a no spark issue with my 924S (early 944 motor) when I first got it. It turned out that the ECU was bad. The transistor that pulsed the ground for the coil had toasted. I had the ECU rebuilt by some place and every thing was fine after that. I spoke with them and they said it was a common problem with these ECU's. Any way the only way to really check the coil connections is with an oscilloscope, you should see a square wave.

Not tightening the bolts on the sensors could prevent them from working. Not sure how much play is in those sensors as I have never replaced them. If they are lose in there and not at the proper angle to the sensor wheels they will not function correctly. From an electro-mechanical stand point they are designed to be a specific distance from the sensor wheels, if that distance is drastically off it will prevent the magnetic fields from affecting the sensor correctly and thus generating a signal.

Regards
Dave

XJOSHX · 01:18 AM

Quote:

Originally Posted by VOTS89

Here's the Clark's Garage procedure I've used in the past, I'm assuming it works for all years of our cars.

Clark's Garage Home Page

Click on "Garage Shop Manual"

Then click on the last hyper-link under "Fuel and Ignition" for Speed and Reference Sensors

Cool camera shot of the car by the way!

Bruce

Fantastic, thank you a ton! I took one more shot before I pushed it around the house to where I am going to be working on it. Here is another one for ya!

XJOSHX · 08-25-2012, 06:19 PM

I put the stock ones back in today. Tried them, and tried switching them. N tach bounce. I also was not really hearing my fuel pump. Will the DME relay kill the tach bounce too? I will go pick up the new sensors (forgot them at the PO's garage) tomorrow. I hope I can get SOMETHING out of it tomorrow