dillon410021

also check reference sesnors

David.N

If your tach is bouncing doesn't that mean the sensors are fine? Also wouldn't those fail from dampness and corrosion not mid driving?

I checked the rotor it spun with the motor, I will go back and check if it spins freely.

Would it really be the timing belt? the motor turns over when i crank it.

I will first try a new ignition coil, then the ignition tune up kit from lindsey racing. then check timing belt.

David.N

Hey guys, So I just took the coil out and put it in my 944S and it started so the coil is fine, and the rotor is on the turbo tight.

If the tach bounces does that mean the sensors are fine?

Next step im guessing is the whole ignition tune up kit.

Would the timing belt skipping a notch actually cause no spark?

ehall

No, it wouldn't. It would cause bent valves and a new head. If you have bent valves and spark, it should still try to crank, but may not start.

audisport

If the tach bounces is means the DME is working IIRC. I would still verify spark, your coil may be working but if the car isn't supplying power to the coil it won't work. After you verify spark, then you should verify fuel. It also maybe saturated/flooded, so pull the plugs and make sure they are clean and let the cyl dry out if there's too much fuel in there since you've been trying to start it unsuccessfully. Also once the plugs are out, I'd do a quick wet compression test just to make sure.

David.N

Alright so I put a new rotor, cap and wires and NOTHING! still wont start.

So know im stuck and I dont know what to do next. The car is not getting spark.

-Rotor turning - Y
-Rotor and cap working (all new) - Y
-DME relay (from other car) - Y
-Coil works - Y
-Coil getting 12 V - ? How do I check?
-DME computer - Y (I think, i smell fuel and tach bounces)
-Speed and reference sensors - ? (would this cause no spark?)
-timing belt jumped a tooth - this wouldn't cause no spark
- Other ideas?

Thanks. A frustrated 951 owner who wants his car ready for the first track day on the 25th.

Bri Bro

The signal going to the coil from the DME should be pulsing between 12V and ground as you crank. Volt meters are slow reacting and may not see the pulse so trouble lights or scopes are a better test tool. No pulse with a tach bounce points to a bad solder joint inside the DME.

9xauto

First. Turn the key half way. You should hear fuel pump whining, If not, your fuel pump relay is dead and no gas being pumped. If you do hear the fuel pump and your engine does turn, the problem is ignition. I would look to borrow a MAF from similar car. Disconnect yours and and see if it starts. MAFs do fail a lot in these cars. If MAF replacement does not work. It is your DME. Check DME relay first. Make sure the fusses are all good. The problem with DME non functioning in 944 is the water damage from above battery tray. The metal is to thin and eventual develops a small crack just above your foot well.

fast951

For the engine to fire you need: Air, Fuel, compression and ignition. Air is always there, so one less thing to worry about.

Your goal is to determine which component you are missing. Fuel, Ignition or Compression.

1- Fuel: You need pressure in the rail and the injectors must pulse.
1.1 - For pressure, the fuel pump and fuel pressure regulator must be working. Ideally you need a fuel pressure gauge to verify. For now, you may be able to hear the pump run when you turn ignition on.
1.2 - For the injectors you need a noid light, LED or a scope. The simple approach is to remove a spark plug and see if it's wet from fuel. If you are getting fuel, move to the next step. note: if the spark plugs are wet, more than likely you need new ones.

If you are not getting fuel: The followings can be the cause: DME relay, fuel pump fuse, fuel pump or DME can be the cause. A short in the wiring can also cause this. Eliminate each, one at a time. If a injector is shorted, it may pull the circuit down. So if all of the above check fine, unplug one injector at a time and see if the car starts..


2 - Ignition: The DME generates the spark signal, sends it to the KLR, which sends it back to the DME which sends a signal to the coil. From the coil you go to the distributor/rotor then the plugs. Any disconnect in this path and you will not get a spark.

For the ignition test, remove the fuel pump fuse out of the fuse box. Keep the 4 spark plugs in the engine. (You do not want any fuel spraying outside the engine!!!).

2.1 - Ignition Path to Coil: Attach a LED to the both poles of the COIL. With ignition ON, one side of the coil should have a constant +12V. The other pole, gets grounded by the DME.
With the LED properly connected, crank the car and note if the LED is flashing. If the LED is flashing, then the PATH from DME to KLR to DME to Coil is functioning. If not, then work your way back and eliminate possible points of failure.

2.2 - KLR: I would start by eliminating the KLR. If the KLR or KLR chip fails (more often than you think), the ignition path will be cut.
WARNING: FOR TESTING ONLY! Disconnect the KLR plug (wiring harness from KLR). On the KLR plug short pin #9 to pin #16. Crank the engine, and check the LED. If it's flashing proceed to next step. If not flashing, the problem is with the DME. (a) if the Tach is bouncing then the problem is with the final stage of the DME (DME to coil). (b) if tach is not bouncing then DME is bad or Speed/Ref sensors.

2.3 - Coil to Spark Plugs: If the LED is flashing, now check for spark at the plugs. Attach a spark plug to the end of a plug wire attached directly to the coil (eliminating cap & rotor). Crank the engine and check for spark. If you are getting a spark, then visually verify the cap/rotor. If the rotor comes lose, then it'll send the spark at the wrong time and possibly to the wrong cylinder.

If you are not getting a spark, but the LED is flashing the problem could be coil.

Once you determine the root cause and fix. Make sure you replace your spark plugs and reconnect the fuse to the fuel pump.

Hope this helps and good luck.

zerMATT951

This is incorrect, the fuel pump does not come on until you crank the engine over unless you jump the relay. To test the fuel pump, you have to remove the fuel pump relay and jump pins 30 and 87b at the relay panel with a jumper wire. That will run the fuel pump and you can further test the pressure at the rail if you have a gauge.

Here's a link to Clark's Garage for a document on testing fuel pressure:

http://www.clarks-garage.com/pdf-manual/fuel-01.pdf

9xauto

When you start 944 you can hear the fuel pump without doing all this job. When fuel pressure is low it will start and die right away. In his case it does not start at all.

David.N

Im not getting spark Fuel is fine. Thanks though.

Thanks for all the input. What and where is the KLR?

black944 turbo

klr is the computer under the passenger footwell with the vacume line running to it

zerMATT951

The fuel pump in a 944 Turbo doesn't turn on simply by turning the key to "on". If your car is doing that, you may want to have it checked as it would be unsafe to have a pressurized fuel system simply by turning the key to the on position.

audiojoe1

Not sure if anyone said this, but check the reference sensor connectors on the back of the engine towards the firewall. There are 3 connectors in a metal retainer attached to the intake manifold. 2 square, and 1 round IIRC.