When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Since swapping the DME is currently having the biggest effect, I can't help but wonder if the your replacement is in fact not good. It's happened before, fairly recently with one well-know ECU repair outfit: see post #273 on this thread https://rennlist.com/forums/944-turb...troyed-19.html
Perhaps you could source another on a trial basis (maybe contact Elliot from the above linked post)
Dan ... Jacob just sent the ECU back for testing and it was confirmed good
.One assumes that they know what they are doing but perhaps a better test would be to plug it into another early 944 and test it for real.
We are starting to randomly jump between one component and another without any real evidence or diagnosis .I think its important to follow the trail of what we have tested and know for sure
Maybe we should have a recap from Jacob of where we are at currently in terms of what works and what doesn't and the precise details
[QUOTE=peanut;15691249]Dan ... Jacob just sent the ECU back for testing and it was confirmed good
.One assumes that they know what they are doing[QUOTE]
That's exactly what the poster in post #273 of that thread did--and it turned out the DME wasn't good after all. I suspect that they test these things on a bench but that doesn't mean it works in the car. My own experience with a reference sensor that tested good yet caused a no-start has taught me the only way to confirm electronics is via installed in the application.
Yes, it would be very cool if either of these DMEs could be tested in another car. Not so easy, I know.
The other thing that sticks in my mind is how it would keep running when he pulled the FP fuse and stall with it inserted. I still have no idea what to make of that. I feel for the guy: I recall my own mystery issue and frankly, it turned out to be a new "confirmed" part so I'm skeptical of all things "confirmed"
Last edited by Dan Martinic; 03-09-2019 at 02:43 PM.
The other thing that sticks in my mind is how it would keep running when he pulled the FP fuse and stall with it inserted. I still have no idea what to make of that. I feel for the guy:
yeah me too. I know personally how frustrating a no start poor running issue can be. jacob has certainly been meticulous and put a lot of money and time into this
I've learnt everything I know from solving issues with my own 944s2's and other owners cars.
As you point out there are a number of strange anomalies that defy explanation and it is these issues that need to be addressed before anything else really.
I'll run through the threads again tonight and see if I can make a plan of attack for a systematic testing program . I am sure its the only way we are going to solve this.
Well I found a good article that explains how the DME relay works and how to correctly jumper. If this article is correct then I didn’t connect the right terminals. I connected terminal 30, not 86. Which explains why the fuel pump came on, but the car did not fire.
Gonna take out the coolant temp sensor and test it right now.
Ill be pissed if that DME is in fact bad.
By the way speaking to that fuel pump fuse anomaly. With the new DME installed, that doesn’t happen any more. It cranks but doesn’t start. Put the fuse in and the car starts. Swapped the DMEs, car starts and runs without a fuel pump fuse with the old DME installed.
Now with the new DME the only way to get the car to idle is if the coolant temperature sensor is unplugged. It’s like the car won’t run unless it’s on full rich, and then it dies shortly after.
Heres the article I found. I only connected the fuel pump part of the circuit. Not the DME part.
well done for re-checking the DME relay 3x wire bypass and admitting your mistake.
i've maintained all along that there had to be an issue with it if the engine didn't start with the bypass in place and I was proven right . I was beginning to doubt myself lol.
With the sensor test you need to be using a continuity setting on the multimeter not ohms resistance .
basically the engine water temperature sensor is a switch . It makes and breaks an internal switch, depending on the temperature of the coolant in the cylinder head.
If you check your multimeter it will have a setting at the lowest resistance range (600 ohms ?) which has a whistle sound when you put the probes together . It is the whistle sound not the resistance that you are looking for .
Attach the probes to the sensor terminals , place the sensor in near boiling water and then gradually add cold water to bring the temperature down slowly
. see at what temperature the sensor switches on and off as indicated by the multimeter whistle sound going on and off.
By the way speaking to that fuel pump fuse anomaly. With the new DME installed, that doesn’t happen any more. It cranks but doesn’t start. Put the fuse in and the car starts. that is the correct operation
Swapped the DMEs, car starts and runs without a fuel pump fuse with the old DME installed. That must be because there is a short somewhere ,(probably within the old ECU,) which is bypassing the fuel pump fuse and providing the fuel pump with power
Now with the new DME the only way to get the car to idle is if the coolant temperature sensor is unplugged. It’s like the car won’t run unless it’s on full rich, and then it dies shortly after.This suggests that there is still a fault with either the engine coolant sensor or the associated wiring and connections to the ECU, or the air idle control valve . Check the terminals in the AIC valve connector have not been reversed which would reverse the correct cold start operation
I only connected the fuel pump part of the circuit. Not the DME part.mmmmmmmm well as its called a 3x wire bypass I can't understand why you only connected 2x wires but hey you found it in the end which is all that matters.
well done for re-checking the DME relay 3x wire bypass and admitting your mistake.
i've maintained all along that there had to be an issue with it if the engine didn't start with the bypass in place and I was proven right . I was beginning to doubt myself lol.
With the sensor test you need to be using a continuity setting on the multimeter not ohms resistance .
basically the engine water temperature sensor is a switch . It makes and breaks an internal switch, depending on the temperature of the coolant in the cylinder head.
If you check your multimeter it will have a setting at the lowest resistance range (600 ohms ?) which has a whistle sound when you put the probes together . It is the whistle sound not the resistance that you are looking for .
Attach the probes to the sensor terminals , place the sensor in near boiling water and then gradually add cold water to bring the temperature down slowly
. see at what temperature the sensor switches on and off as indicated by the multimeter whistle sound going on and off.
Good morning!
Peanut, I think you're confusing this sensor with the one in the rad. Last time I tested my head coolant sensor, I put it in water in a pot and measured resistance. I can't remember if I measured resistance across both terminals or one terminal to ground, but definitely resistance.
To confirm my memory, I found a post that shows what I'm suggesting:
ok I see what you are saying Dan ..you're correct the engine coolant sensor works by sending a resistance to the ECU rather than acting like a switch as the radiator sensors do .but it doesn't alter the point I was making that this thermister is probably not functioning as it should
The engine coolant temperature sensor that jacob and I are referring to isfitted to the cylinder head not the radiator.it measures the temperature of the engine coolant
Here is a picture of the sensor that we are discussing Dan
#
03-08-2019, 04:34 AM
