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VEMS Engine management systems, plug & play ECU upgrade

Thanks for the suggestions guy's, I will try the new earth jumper although I've showing a good earth and have already cleaned all the earth points. I'll also try a new earth to the ECU. Not going to get a chance to do anything for a week or so now though :-( Gave her a clean today and she's just sat there growling at me to take her for a thrashing...
 
PhilKent said:
All usual checks are okay, including continuity checks with the wiring harness but currently investigating a poor spark at plugs. Coil spark is okay but possibly a bit weak (new coil, although I've ordered a second just to rule it out)) But at plugs it's either non-existent or very weak (No. 2 being the strongest). This would suggest poor reference signal timing I think.
I have an auto-electrician booked for 6th August to investigate further.
Click to expand...


Why would you bother with an auto-electrician when you most likely have already found the answer?
99% ignition issues on those cars are caused by something wrong with the Speed & Reference sensors.
 
So my no-start saga continues. Had an auto-electrician take a look (have to admit, wasn't sure how competent he was, got another one visiting on Monday), tried earth lines, no difference, spark at coil still appears a bit feeble, but then he noticed that the distributor rotor had high resistance. 1.02Kohms. Thought voila, there the issue.
So he went away, I ordered a new dizzy arm, arrived today, checked it's impedance, 1.02Kohms!, Seems odd...
So, thought I'd try and fix it by throwing all this lot at the problem...

PS. The reason I've not replaced the speed/reference sensors (apart from it being a pita), is they are showing no signs of failure. When the car runs it reads rpm fine. when it cranks I have tack bounce, when I check for signal from both sensors it is present. When I crank, I have fuel delivery, and I have pulsed signal to the coil. All these things would not occur if the ECU was not getting a signal from the speed/reference sensor.
 
how good is the starter, is it cranking fast enough?....when I put my car back on the road my son made up another earth lead for the starter and rang it in unison with the original.....starts much quicker due to this mod...

Pete
 
Actually starter is a good shout, mine failed literally outside the MOT garage recently and the recovery firm would only take it to the nearest garage, I was at first annoyed they wouldn’t fit my spare. However for £240 all in I now have a nice fast modern sounding starter, no idea where they got it from or what make it is but it’s way better than any starter I’ve had in a 944. Probably by virtue of being new and shiny.
Is it not possible to learn much by plugging a laptop in. Mega squirt has a feature to check the timing wheel trace.
 
I have over 200rpm cranking speed.

Is anyone running VEMS who would be willing to either lend me there ECU or connect my ECU to their engine (uploading your own config of course) to rule it out of the equation?
 
WOOOHOOOOOOO! Success. I have a running engine again, thanks to those at the transaxle day with helpful suggestions and brainstorming, but ultimately it turned out to be the ECU. I was ready to send it back to Peep for bench testing, but today I had a really knowledgeable auto-electrician come take a look. He diagnosed a bad signal from the ecu where it wasn't 'pulling down' the voltage to the coil properly. Turned out to be a bad earth connection inside the VEMS ecu itself, cleaned the board and track where pin 5 goes to the capacitor bank and hey presto. Started a ran like it should.

Side bonus is I now also have entirely new wiring harness for the injectors, hall and knock sensors and even the headlights! All for a very reasonable days labour.

Chuffed. :)
 
Great news Phil....hope to see you at another 944 meet sometime in the future...

Pete
 
Quick update on the VEMS ECU issues I was having, just to keep the record going for future reference:
After the Auto-electrician 'fixed' my issue, about a week later the problem returned, so I removed the ECU and sent back to Peep in Estonia. Borrowed DC's ECU and car ran like it should, very handy to be able to swap ECU's and upload your own map.
After quite some time, Peep has diagnosed the fault as a slight/intermittent short in the ignition bank (which I am interpreting as those transistors mentioned previously). He's yet to return the unit as it's still to be tested, but hopefully...... problem solved.
 
PhilKent said:
Quick update on the VEMS ECU issues I was having, just to keep the record going for future reference:
After the Auto-electrician 'fixed' my issue, about a week later the problem returned, so I removed the ECU and sent back to Peep in Estonia. Borrowed DC's ECU and car ran like it should, very handy to be able to swap ECU's and upload your own map.
After quite some time, Peep has diagnosed the fault as a slight/intermittent short in the ignition bank (which I am interpreting as those transistors mentioned previously). He's yet to return the unit as it's still to be tested, but hopefully...... problem solved.
Click to expand...


Are the trigger issues over 5k confined to DC's car?
 
That's a good question, I've not been driving it much and certainly not going for it. I'll have a check before I return it. How's yours running?
 
I can confirm no trigger issues above 5k David....dunno if that's a positive thing for you or not!
 
Rebuild progressing slowly but surely.

Block going to the machine shop next week and then pistons being ordered hopefully.
 
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