Car not starting not the DME
02-24-2019, 10:21 PM
#1
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Car not starting not the DME
The car is a 1989 944. I was driving the car and it has a brand new DME with less than 5 miles of use. Suddenly the car decided to die with no warning or hesitation while I was driving. Things I have done to check the car are:
Spray throttle cleaner in the throttle body to see if it is a fuel issue and also removed the hose for the fuel rail and cranked the engine and no fuel came out of it (maybe a check valve issue?)
Did a DME bypass
checked the two crankshaft position sensors ( I am not to sure if I did it correctly) The top plug read normal resistance and the bottom one did not read good from the car wire harness. Both the plugs that lead into the bottom of the engine don't read correct numbers which I found weird.
I also hear a buzz from the DME module in the passenger foot well not sure what that means.
Spray throttle cleaner in the throttle body to see if it is a fuel issue and also removed the hose for the fuel rail and cranked the engine and no fuel came out of it (maybe a check valve issue?)
Did a DME bypass
checked the two crankshaft position sensors ( I am not to sure if I did it correctly) The top plug read normal resistance and the bottom one did not read good from the car wire harness. Both the plugs that lead into the bottom of the engine don't read correct numbers which I found weird.
I also hear a buzz from the DME module in the passenger foot well not sure what that means.
02-25-2019, 03:59 PM
#2
Burning Brakes
The only way to properly diagnose the crankshaft sensors is from the DME plug in the passenger side foot well.
They should read about 1000 ohms for each sensor, +/- 200 ohms.
They should read about 1000 ohms for each sensor, +/- 200 ohms.
02-26-2019, 07:10 PM
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What points do I need to test resistance in order to test the Reference sensor and Speed sensor?
Also I noticed that the Tach does not bounce when I am trying to crank the car. It does every once and while but it is very rare for it to do that. Is that a dead give away that it is a reference sensor or speed sensor?
Also I noticed that the Tach does not bounce when I am trying to crank the car. It does every once and while but it is very rare for it to do that. Is that a dead give away that it is a reference sensor or speed sensor?
02-26-2019, 07:46 PM
#4
Burning Brakes
firstly never assume that because a part is brand new that it must be good....especially not DME relays. They are very crudely constructed.
You have told us what you have done but not told us what the result was !... did it start ? did it start and die ? did it not try to start at all ? tell us what the result was of each test you mentioned it will give us some idea of what the issue might be.
With the ignition off and the DME relay removed , test that you have 12v+ on terminal 30 of the DME relay base............ yes?
If you have ........then fit a 3x wire bypass which should force your fuel pump to pump continuously with the ignition off .................does it pump...Yes ?
Do you have an ignition spark at the distributor when cranking ?
if the rev counter needle doesn't jump as you crank it could indicate a problem with the speed sensor but the normal needle jump is very tiny... just a blip and hard to see .
I think it is unlikely to be a sudden failure of your speed sensor as you are driving along its probably a poor connection somewhere .
The more things you disturb and replace the more likely it is to cause additional problems and hide the initial problem . best to follow a set sequential troubleshoot proceedure to establish what is working first
.
You have told us what you have done but not told us what the result was !... did it start ? did it start and die ? did it not try to start at all ? tell us what the result was of each test you mentioned it will give us some idea of what the issue might be.
With the ignition off and the DME relay removed , test that you have 12v+ on terminal 30 of the DME relay base............ yes?
If you have ........then fit a 3x wire bypass which should force your fuel pump to pump continuously with the ignition off .................does it pump...Yes ?
Do you have an ignition spark at the distributor when cranking ?
if the rev counter needle doesn't jump as you crank it could indicate a problem with the speed sensor but the normal needle jump is very tiny... just a blip and hard to see .
I think it is unlikely to be a sudden failure of your speed sensor as you are driving along its probably a poor connection somewhere .
The more things you disturb and replace the more likely it is to cause additional problems and hide the initial problem . best to follow a set sequential troubleshoot proceedure to establish what is working first
.
02-28-2019, 10:35 AM
#5
Drifting
I assume in your title and first post, you are talking about the DME Relay, not the DME itself.
You may want to look at the actual DME. In the following thread, I had a sudden stalling issue. As the only thing that has ever caused running cars to die on me is fuel pumps, I went that route, to no avail. Turned out to be cracks in the DME solder joints. Solution begins at post #96: https://rennlist.com/forums/924-931-...with-me-7.html
You may want to look at the actual DME. In the following thread, I had a sudden stalling issue. As the only thing that has ever caused running cars to die on me is fuel pumps, I went that route, to no avail. Turned out to be cracks in the DME solder joints. Solution begins at post #96: https://rennlist.com/forums/924-931-...with-me-7.html