Strange 944 Running/ No Start Issues....
02-23-2019, 07:53 PM
#106
Burning Brakes
I can't see how that could be significant or indicative of anything I'm afraid.
I have only owned late 944 and 944S2 models so I have never needed to familiarize myself with the early models so I am struggling a bit too.
The only other thing that occurred to me was that sudden switching on or off could be due to a faulty relay or relay coil supply. I'll have a look through the electrical schematic tomorrow and see if anything shows up.
The other thing that we have not got to the bottom of yet is your DME relay fault .!!! ......there is no way in the World that a DME relay could fire up the engine but a 3x wire bypass couldn't Something is screwy there for sure.
Connecting the 3x DME relay base terminals together does exactly the same job as the DME 2x relays do so why is the result different ???
It would be useful to see a picture of the electrical wires on the underside of the DME relay connector and its associated fuse board connector which on a 944S2 is connector E from memory. I did a video some years ago about bypassing immobilisers that shows the connector .
I have only owned late 944 and 944S2 models so I have never needed to familiarize myself with the early models so I am struggling a bit too.
The only other thing that occurred to me was that sudden switching on or off could be due to a faulty relay or relay coil supply. I'll have a look through the electrical schematic tomorrow and see if anything shows up.
The other thing that we have not got to the bottom of yet is your DME relay fault .!!! ......there is no way in the World that a DME relay could fire up the engine but a 3x wire bypass couldn't Something is screwy there for sure.
Connecting the 3x DME relay base terminals together does exactly the same job as the DME 2x relays do so why is the result different ???
It would be useful to see a picture of the electrical wires on the underside of the DME relay connector and its associated fuse board connector which on a 944S2 is connector E from memory. I did a video some years ago about bypassing immobilisers that shows the connector .
02-23-2019, 08:16 PM
#107
Gotcha. I’ll do my best to try and get some pictures of the wiring behind the fuse/ relay board. On the early cars it’s tucked underneath the dash in the drivers side footwell.
These are the only wiring diagrams I have for the 83 ignition system.
In this post I was testing the sensor that I moved to the position of the speed sensor. It used to be my reference sensor but the two sensors are the same. I was originally getting good readings from it. Now I’m not seeing any resistance readings at all. Does this confirm that this sensor is not functioning properly and needs to be replaced?
02-24-2019, 08:33 AM
#108
Burning Brakes
In this post I was testing the sensor that I moved to the position of the speed sensor. It used to be my reference sensor but the two sensors are the same. I was originally getting good readings from it. Now I’m not seeing any resistance readings at all. Does this confirm that this sensor is not functioning properly and needs to be replaced?
IMPORTANT
Jacob if you take the car to a garage to get this test done they will not have the equipment to do the test.
Garages can only test modern cars that have an OBD2 connector, ECU and and associated software . You need someone who knows how to use a scope with probes to probe the sender and ECU connector terminals
If you do take the car to a garage be sure to make it completely clear that you do NOT want them to do extensive testing to find the fault otherwise they will order and fit loads of unnecessary parts that will cost you hundreds of dollars probably with no result . You will be giving them an open cheque or license to print money
What you need first of all is for someone to check the senders and terminals 8 & 27 on the ECU connector for a 2.5v Sine wave with the engine running .
02-24-2019, 11:26 AM
#109
Drifting
Do you know what brand of speed sensor is in there? If it's the FAE, I'll bet you're having the same issue I did where the sensor's outer shield would have continuity with one of its connector pins. This caused the sensor to display a half sine on the 'scope and the DME to reject its signal. A known problem with some FAE sensors.
Switch the two sensors and try starting
Switch the two sensors and try starting
02-24-2019, 11:54 AM
#110
Burning Brakes
What I'm suggesting is for you to switch the sensors and their connections so that the current speed sensor is now the reference sensor and vice versa. I suspect when you crank the car, it won't start at all, proving the speed sensor is at fault. If it starts and runs as it does currently, then that sensor is likely ok
02-24-2019, 04:11 PM
#111
Drifting
02-24-2019, 04:51 PM
#112
Burning Brakes
02-26-2019, 07:04 PM
#113
02-26-2019, 07:16 PM
#114
By the way I had an idea that I’m sure someone else has thought of that I’d like to run buy you lot to perhaps explain why it would/ wouldn’t work.
Both sensors send a magnetic impulse out as a voltage signal. Which is why you need a scope to test them. With the engine rotating if the sensors are working correctly they send a peak voltage over time and cycle. Hence the sine wave.
If the peak voltage is about 2.5volts everytime there is a pulse, why couldn’t I simply remove the sensor, connect the leads to a voltmeter and pass a magnet near the sensor to see if any voltage briefly registers on the meter?
Im just curious and I’m sure someone else has had this thought so I figure now would be a good opportunity to explain and enlighten as to why that wouldn’t be an effective testing method.
Both sensors send a magnetic impulse out as a voltage signal. Which is why you need a scope to test them. With the engine rotating if the sensors are working correctly they send a peak voltage over time and cycle. Hence the sine wave.
If the peak voltage is about 2.5volts everytime there is a pulse, why couldn’t I simply remove the sensor, connect the leads to a voltmeter and pass a magnet near the sensor to see if any voltage briefly registers on the meter?
Im just curious and I’m sure someone else has had this thought so I figure now would be a good opportunity to explain and enlighten as to why that wouldn’t be an effective testing method.
02-26-2019, 07:26 PM
#115
Burning Brakes
yes you could do that ....its often done using a high speed drill or router but you would still need a scope to be able to see the sine wave voltage level/
A multimeter isn't capable of showing a voltage 50 times a second
A multimeter isn't capable of showing a voltage 50 times a second
02-26-2019, 07:34 PM
#116
Thanks for the info peanut.
02-26-2019, 08:04 PM
#117
Burning Brakes
well the sensor is a magnet when it has a voltage passed through it. The normal way of doing it would be to attach the sensor wires to a 9v PP3 battery and then pass a thin strip of metal past the sensor with a high speed drill .
https://www.speedwaymotors.com/the-t...-sensors/28754
https://www.speedwaymotors.com/the-t...-sensors/28754
02-26-2019, 09:02 PM
#118
I’m just trying to do as much as I can without any immediate access with a scope.
For sh*ts and giggles I unplugged the speed sensor entirely and the car didn’t start. Plugged it back in and the car started.
Does that hat mean anything to anyone? Next thing I’m gonna try is swapping the sensors like dan suggested. Unless I don’t need to after that new bit of information.
For sh*ts and giggles I unplugged the speed sensor entirely and the car didn’t start. Plugged it back in and the car started.
Does that hat mean anything to anyone? Next thing I’m gonna try is swapping the sensors like dan suggested. Unless I don’t need to after that new bit of information.
02-26-2019, 09:28 PM
#119
I’m just trying to do as much as I can without any immediate access with a scope.
For sh*ts and giggles I unplugged the speed sensor entirely and the car didn’t start. Plugged it back in and the car started.
Does that hat mean anything to anyone? Next thing I’m gonna try is swapping the sensors like dan suggested. Unless I don’t need to after that new bit of information.
For sh*ts and giggles I unplugged the speed sensor entirely and the car didn’t start. Plugged it back in and the car started.
Does that hat mean anything to anyone? Next thing I’m gonna try is swapping the sensors like dan suggested. Unless I don’t need to after that new bit of information.
