Terry Jamison

OK, I've tested just about everything in secton 28 of the factory manual on my no start 944. I'm down to the reference sensors. I pulled them out and put my ohm meter on pin 8 and 27. The resistance reads 2 kohms, a little above the specs of 0.6 to 1.6 kohms. But, both sensors read the same. My meter is analog. So, I figure 2 kohms is close enough. The second resistance to test is the insulation resistance. The factory manual says to test this resistance on pins 8 and 5 on the DME plug.

Can I check the insulation resistance directly at the sensor as oppsoed to at the DME plug end of the harness? There is no pin 5 on the sensor plug itself. What is sensor 5 at the DME?

I'm curious about the insulation because there are a couple of worn spots on the speed sensor. No wire is showing. Just the insulation is worn away in a half-moon shape in a couple of places where it's been wearing against something metal in and around the cable.

If the sensors test good on both accounts, it's time to re-adjust the spacing between the sensors and the flywheel and starter ring gear.

When I pulled the sensors out of the bell housing, both of them had metal particles picked-up by the permanent magnets. This worries me because this the car that the starter pinion gear and the ring gear don't mesh unless i roll the car in gear to align the teeth. I'm beginning to worry that the no start condition and the starter grinding are related. Perhaps the ring gear is worn to the point that the distance between the sensor and the flywheel is greater than .08 mm +/- .005 mm.

I haven't pulled the starter out yet to get a look at the gears. But, I can see the ring gear when looking through the whole for the speed sensor. It looks like about 1/8th of an inch has been ground from the aft portion of the ring gear. This shouldn't really affect the distance between the speed sensor and the ring gear. But, it does affect how much of the gear passes under the sensor.

With the speed sensor "seeing" less of the ring gear, how is the signal generated affected?

CT944

I'm having the same problem. Tonight I disconnected and removed the reference sensor and it was filthy with dirt and small metal filings. Magnet seemed strong though. I cleaned it off and reinstalled it (the small BG sticker fell into the ref sensor hole...oh well). Car still won't start. Maybe I need to replace the sensor with a new one? I did not take out the speed sensor, should I try that next. Strong smell of gas when cranking the motor. All in all, still no spark. Installed a new Fuel Pump Relay last week as well....

Rob

If I recall correctly, you should be able to measure the resistance across 2 of the 3 pins and get a reading of ~900-1k ohms if the sensor is good. Sorry, I don't recall which of the two pins. Also, be careful switching the 2 sensors will cause a no start condition

Edit: Sorry, I didn't really read the first post untill after I replied.

Waterguy

Pin 5 on the DME plug is simply ground. The reason they suggest testing at the DME plug is that it tests for shorts in both the DME wiring harness and the sensor plug/cable. If you find that pin 8 is grounded to pin 5, you have a short. The next step would be to unplug the sensor and try at the sensor plug (each pin to ground.) If the sensor is still grounded, the problem is in the sensor/sensor cable. If not, the problem is in the DME wiring harness.

HTH

Terry Jamison

Don,

That makes perfect sense. After taking some time to think it through I figured out that they're just checking to see if pin 8 and its related wire are not grounding or shorting out.

Well, both sensos check good. I think that I can live 2 kohm on my analog meter.

Next I have to get am 0.8 mm washer to glue on the end of the sensor so that I can check the sensor spacing.

Now, if crew scheduling will just stop calling me and sending me on these two-day trips. Don't they know that I have a car to fix.