lotsofmagnets Posted August 1, 2020 Report Share Posted August 1, 2020 Hey folks, Turns out long time lurker 1st time poster. Figured this would be the place to go with a pretty specialised problem as the m4.4 people are here. Backstory: This is the car I've owned for 12 years now: it's not super sexy but it's mine. i have a 164TE, 1800E, 2 C202s and another almost identical 850 except a wagon (very early production 93 model also) It started life as a 2.0 20V auto which is not bad if you're prepared for the tacho to visit 3PM frequently but through circumstance I got a B5254S and an M56 from a 2.0 (4.45 final drive) and that made the car actually faster than I anticipated. I drove it like that for 6 years but the engine was tired and blowing more smoke than I was comfortable with. About 3 years ago a valve chipped so I threw another head on and drove it for another year but then the week before I was scheduled to fly out to Australia for 2 months it chipped another valve and so I decided the time had come. I already had a B5244T3 sitting aside and I had already rebuilt a 16T turbo for it so last summer I finally put the car on blocks in the backyard and ripped the engine out. Over the winter I did a stage zero on the B5244T3 and rebuilt the steering rack while I had the subframe out to fix a leak and also got access to a full 98 xc70 so took everything relevant to the M4.4 setup from it and worked it onto the B5244T3. Finally, this May just gone I had everything ready and started putting the car back together and after working slowly on it the past 2 months On Thursday I was finally ready to turn the key for the 1st time. My 1st actual attempt to start it failed and so I did checks and the 1st thing I found was that the injectors only pulse for about a second before turning off but then when I release the key an injector or 2 fire once. This happens every time I crank. I tried several very short cranks and the car actually fired up! I ran it for about 20 mins and after about 5 mins the lambda light came on but there's no surprise there as there are no o2 sensors yet as there is still no exhaust and the ecu is an auto one so that might also have thrown the code but the car did run for about 20 mins but then i turned it off and so far haven't been able to get it running again. This is how the engine bay looks right now: So, I think if you've read this far you can probably figure what my question is but I'll ask anyway: Would anyone have an idea what's going on? To recap, when the car is cranking, the injectors fire for maybe a second then stop but then when I stop cranking an injector or 2 may fire again. I've checked power to the ecu and on cranking I get 10.4V which I guess should be enough and I cleaned all of the contacts between the battery and ecu quite well so I don;t think it's an issue of power. Things I'm about to do are check spark to see if I lose spark too or just injectors and then maybe throw a cam sensor and crank sensor in desperation but I'm hoping someone has either encountered this before or has enough of an idea of how the M4.4 system works to help me figure this out. BTW I do have a video of it happening but not sure how to post it here. But yeah, If you have any questions about converting a 2.0 NA auto car to a turbocharged manual then feel free to ask Link to comment Share on other sites More sharing options...
bmdubya1198 Posted August 2, 2020 Report Share Posted August 2, 2020 Nice work! It's cool to see a '93 with a turbo motor. As for your issue, 10.4 volts is a little low. You really want at least 12v at the ECU. What's the voltage at the battery? If that's low, I would replace it. Otherwise, check your wiring to the ECU for power, as well as the grounds. I think what's going on is while cranking, the ECU just doesn't have enough power to fire the injectors. It probably had just enough to get it running that one time, and of course with the charge from the alternator, it was able to keep enough power to the ECU. You'll probably want to find a manual ECU too at some point. The auto ECU will not let you rev over 4k RPM since it thinks it's in park. Link to comment Share on other sites More sharing options...
gdog Posted August 2, 2020 Report Share Posted August 2, 2020 1 hour ago, bmdubya1198 said: As for your issue, 10.4 volts is a little low. You really want at least 12v at the ECU. What's the voltage at the battery? If that's low, I would replace it. Hmm, usually @bmdubya1198 advice is spot on, but have to disagree here; 10.4v cranking voltage should be fine and doubt that's the source of your issue. The threshold is generally considered about 9.6v; see below link for more details: https://www.boschautoparts.com/documents/101512/0/0/b33530c5-f9ca-47d0-991e-1a37933c06e6 Check for spark; IIRC if ecu does not sense spark signal, it will cut signal(s) to injectors to avoid flooding the engine. Let us know how you make out; interesting project. Link to comment Share on other sites More sharing options...
lotsofmagnets Posted August 2, 2020 Author Report Share Posted August 2, 2020 7 hours ago, bmdubya1198 said: Nice work! It's cool to see a '93 with a turbo motor. As for your issue, 10.4 volts is a little low. You really want at least 12v at the ECU. What's the voltage at the battery? If that's low, I would replace it. Otherwise, check your wiring to the ECU for power, as well as the grounds. I think what's going on is while cranking, the ECU just doesn't have enough power to fire the injectors. It probably had just enough to get it running that one time, and of course with the charge from the alternator, it was able to keep enough power to the ECU. You'll probably want to find a manual ECU too at some point. The auto ECU will not let you rev over 4k RPM since it thinks it's in park. Cheers for the thoughts. I cleaned up all the contacts but the battery had already done quite a lot of work so it is possible it´s still undervoltage. i´m going to throw the battery on charge overnight and try tomorrow with the battery fresh and i might jumper another battery on as well, perhaps straight to the fuel injection relay to make sure it´s getting the full 12v. At least this way I´ll be 100% sure the voltage either is or isn´t the issue. As for the ecu my plan is to just get the car running right now and get the exhaust done. Once that´s done I can organise inspection and then relax a bit. when that´s done I was planning on getting a Vast tune as I´m confident he knows what he´s doing and will just get an ecu with the correct configuration and specs to deal with a manual lpt with a 16t. I´d love to do it myself but I have a wife, kid and job, not to mention all my other project cars and would prefer to keep at least most of those so I think 400 pages of the m4.4 tuning thread and me messing around would be the end of me... 6 hours ago, gdog said: Hmm, usually @bmdubya1198 advice is spot on, but have to disagree here; 10.4v cranking voltage should be fine and doubt that's the source of your issue. The threshold is generally considered about 9.6v; see below link for more details: https://www.boschautoparts.com/documents/101512/0/0/b33530c5-f9ca-47d0-991e-1a37933c06e6 Check for spark; IIRC if ecu does not sense spark signal, it will cut signal(s) to injectors to avoid flooding the engine. Let us know how you make out; interesting project. I am worried that the ecu is getting voltage and my issue is something more complicated so as said above I´ll do one more test to see if I can get the voltage right up to at least eliminate that factor. I have enough crap lying around to throw at it so if it´s a sensor or something like that then I´m covered, otherwise I could be in trouble. My next step was indeed to check spark as that will at least give me another indicator what is going on. When I get everything sorted out I plan to do a write up so anyone else who might be as stupid as me to attempt something like this at least has a starting point. I have pretty detailed spreadsheets of things like wiring diagrams to convert and auto lh3.2 car to manual m4.4 and add things like obdii (i already had that asthe car has a full x70 interior with p2 seats (fronts anyway, working on the back atm but on hold while the car is off the road - engine is higher priority.) Regardless, once the problem is (hopefully) solved I´m going to post it here as there´s nothing more frustrating when you have an issue and search online and find someone with the same issue only for it to remain unresolved as they never posted what solved it... Link to comment Share on other sites More sharing options...
bmdubya1198 Posted August 3, 2020 Report Share Posted August 3, 2020 Ah, I glossed over the part about 10.4v on cranking. I thought it was with key on... thanks for pointing that out! Link to comment Share on other sites More sharing options...
lotsofmagnets Posted August 5, 2020 Author Report Share Posted August 5, 2020 Boring update: charged the battery over nearly 2 days on trickle charge and in the mean time discovered I'd forgotten about the spark plugs and the ones that were in there were quite old. got some new ones and tried to see if i could get spark by hooking them up to the leads and grounding them but over several attempts couldn't get any sign of spark. put them in and wired everything up and still the injectors fire for about a second then stop and this time it didn't seem there was any spark at all. next step is to swap the coil and crank sensor out and see if that makes a difference. Link to comment Share on other sites More sharing options...
bmdubya1198 Posted August 7, 2020 Report Share Posted August 7, 2020 Hmm, no spark? That's interesting. You're on the right track with the crank sensor, you may want to change the cam sensor as well. Link to comment Share on other sites More sharing options...
lotsofmagnets Posted August 8, 2020 Author Report Share Posted August 8, 2020 ...and just like that the problem is solved! Of course it was the ballad of the bad ground connection. The ground rail in front of the battery wasn't really optimal design and one of the connections is for the coil and the impedance was up to 34k ohms. Also, I read elsewhere about swapping the wires for the crank sensor so I did that as well. I swapped the wires for the crank sensor first and I noticed that the injectors would pulse for a moment and then cut out but then after about 2 seconds would cut in again and fire for a while and cut out again and cycle like this. Once I saw this I realised I had a new issue with the spark and threw a bunch of stuff at it and only then thought about the ground, which turned out to be the problem. With that fixed the car started right up and actually ran a lot better than the 1st time I got it running as it was barely responding to the throttle and occasionally running rough. now it starts and idles straight away and throttle response is as it should be. I suspect with the exhaust on and the O2 sensors it will be running great. Plan after the exhaust is to put the plates on and get the car inspected then a tune from vast to take advantage of the 16t. exciting times ahead. Link to comment Share on other sites More sharing options...
gdog Posted August 8, 2020 Report Share Posted August 8, 2020 Good diagnostic work! Link to comment Share on other sites More sharing options...
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