3-Series (E21, E30)Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.
I know this is very well discussed on all BMW forums....but....we can't find the solution to our no start issue!
We have a BMW Lemons Race car in Houston......its an 87 E30 but it has a 1991 E30 engine (similar for sure). We totally stripped it out and most of the wiring too. We have run and raced the car once already, then swapped the engine and it has been running well since.....until Sunday! It refuses to start....again. We have frequently had to do the ECU reset thing....key in position 1 and disconnect the battery for 15 mins......it usually works but not this time.
We have 12v at the pins 30 and 87 on the main relay and also 30 and 87 on the fuel relay. If I link these out, I can force the in tank fuel pump to run but not the main fuel pump - no volts at the pump. Hot wiring the main pump makes it run but we have no spark!
We do have 12v on the coil LT terminal and the centre pin of the coil itself.
I've changed the crank sensor....
We have 2 ECU's and have tried both.
Following the excellent guides available we have tried to link out the DME relays (force them closed) and checked the various voltages on the ECU main cable....all seem good except no volts on the #37 line? Is this important???
It feels like there is a key bit of info not being sent to or from the ECU to power up the fuel pump and allow spark....but its not obvious! We did have a short through one of the earths on the car wiring loom that goes to the inside of the car from the large round multi pin connector.....the 1991 engine loom was not compatible with the 1987 car harness!!! but I have re-made that wire and checked all earths etc...
It needs a cleverer man than me and my team mates put together, so hopefully someone can suggest what we are missing?
Check the alternator wiring, if they are all there, replace the alternator. I once, had to jump the fuel pump wiring to run. Or, put all the wiring back to place, spray brake cleaner into air intake box to see if it runs. I solve the problem after replace the alternator.
Sharky, thanks for your reply.....let me update you ... butI will also check the alternator stuff too!!!
Okay here goes as to what I think happened
....out of the blue......we got it started at 10.30pm last night......why.....we're not sure!
We did go back and check the resistance on the CPS and the spare CPS that we tried to start the engine with.....both about 540 ohms which depressed me no end as I think thats about spot on? But through reading lots of good threads online….our symptoms would have been caused by the CPS sensor not working, either a dodgy lead or some dirt etc…...
We double checked the 12v to the main relay and to the FP relay....all good.....good continuity to the FP wires to the fuse box and to the pump. Linking the main and fuel relay forced the in-tank pump to run but nothing at the main pump (which I think is important - now). I was looking for a confirmed 12V to the fuel pump under the car, but it turns out, this will only see 12v when the demand for the pump to run is present…..with no leaks and the hoses in place, the pump will prime and then stop and voltage disappears…..so that probably was a red herring in terms of me thinking the fuel pump wasn't get a demand all along….I think it was and we only had a no spark issue? There is a chance the fuel pump is still sticking at times ( I think that was the issue when we put it on the trailer going to MSR - but my other theory is the old breather that came from the charcoal canister (now gone) was closed off (me) and may have created a vacuum in the tank and air locked the pump…..but again, I don't know how well we diagnosed the no fuel, no spark issue…..
We changed ECU's for the one we took apart and ran a wire to monitor voltage on pin 37 (I guess we read somewhere that this pin should have 12v and it did)?
We had no spark at #1 plug for 2 days...... also checked the king lead for spark and same thing.
NOTE: Our wipers stopped working ages ago, so we hard wired them in to a new switch in the car......they had also stopped working recently??? I removed the large black relay in the fuse box a while ago as they ran without it anyway.....I can't remember if this was ages ago as in before it stopped working or closer to when it first failed to start…..I think I took it out during the engine install and we were having all the issues with wires melting etc……and it did start despite that!
Now, I am not sure at what point but we had almost all the wiring laid out, we changed back to the original CPS that used to work on the car and we had been messing around with the OCM relay, the connectors for the pulse #6 lead and the CPS (any idea why those 2 are interchangeable)??? Oh, and I put the wiper relay back in again and the wipers worked?
We tried the engine and we got spark at king lead, but not at #1 plug? Changed the distributer cap and leads over and she fired up! For laughs we put the old dist cap and leads back on....and it still worked? Changed the pulse sensor #6 and CPS connections over and it didn't work.....
Took the wiper relay out and it still works.........
So - Yayyyy its working again......but I am not at all sure if we mended it, or there is something lurking in there that will do this again and spoil a race day perhaps???
I'd still like to remove all remaining bunches of wires from the car and end up with the bare minimum in there......not weight saving just ease of use and removing all the crap that could cause this!
We don't have the OBC plugged in anymore with no ill effects to date......
I think I am learning more about this E30 but man its been a round about route to an unclear solution!!!
That would certainly be the best route....however....the Lemons 24 hour events here in the USA rules state that the car value (not including roll cage, seat, harness, brakes, tyres and extinguisher) must not exceed $500! And E30's are hated by the judges already for being too good and cheaty!
So a nice expensive, shiney stand alone may be hard to disguise!!!
After getting the car running again last week.....(only idling in the garage as we are still carrying out some body work changes) she decides to stall again and not re-start!
We had power at the coil and good spark! Power to main and FP relays....I coudl link out the FP relay and the intank pump would run, but no main pump or power to the main pump?
If I ran a 12v hardwire to the pump, the car starts and runs perfectly........
So we re-newed the wire to the main pump from the fuse box and all was well for about an hour, then same thing again........whats going on?
I don't think its the fuel pump (I don't mind changing it, but it seems more a power supply thing...or inhibit rather than a faultly wire)?
What about the fuel tank breather solenoid under the throttle body? This is a 1991 engine and we have it in our 1987 car......the old engine didnt have a solenoid.......is the new ECU trying to monitor for leaks in the system and seeing as we have this as an open end right now...does it think we have a huge fuel leak and its cutting the pump???
Should I connect this up to the vent line (we've deleted the charcoal canister) that runs back to the tank? Or can I just plug this vent from the throttle body?
We just ran into the same problem over the weekend and being a fellow LeMons "racer" I was hoping you could help.
Originally Posted by Markdas
We did have a short through one of the earths on the car wiring loom that goes to the inside of the car from the large round multi pin connector.....the 1991 engine loom was not compatible with the 1987 car harness!!! but I have re-made that wire and checked all earths etc...
We have a 87 325e chassis originally with a manual trans and trying to fit a 91 engine that was originally and automatic, but we mounted a manual transmission to it.
We dropped in the 91 engine, hooked up everything and went to turn it over. Turned the key to 2 position and the Main Relay started smoking. The starter did not click and noticed the voltage dropped to 9.4V at the 30 and 87 pin with the key turned on. I don't know whats going on so to the google I went.
Your post mentions the 91 engine loom was not compatible with the 87 harness. What did you check to find the short and how did you fix it?
It seems very similar to our issue.
You're much more electrically inclined than we are and hoping you could help. We've got our race in April so we're cutting it close.
Sorry to hear you are having problems! Sounds very similar!
Basically it appears the engine harness and loom have to be the same year (or at least the same version) so that our 1990/91 E30 engine harness would not work with our 1987 car chassis loom.....its totaly different!
We just swapped the engine harness over and within reason it seemed okay.....
We are now in the situation where we have stipped out almost all the wiring from the engine and re-run our own....ther really isn't many wires needed to run the car (aside from the ECU stuff).....we now have independant 12v supplies going to the areas that need 12v...alternator, coil, main relay, FP relay....so that in the big round connector near the bulkhead (this is the 101 connecter I think) we only have 4 or 5 wires......
Don't worry, we are not that brilliant with electrics at all, but we have spent many an hour pulling out what little hair we have left! If I can send you some pics of what ours looks like now or talk you through some ideas, let me know.
No problem Tim, I think once you swap the harnesses over, the car should be good!
We came 5th at Houston! The car was really good, we had no mechanical outage, two very brief offs due to black flags but our re-fueling sucked and we lost about 4 laps on the leader each time!
We fine with the 325is we can do about 1 hour 45 before getting low on fuel....have you guy run into the lack of fuel problem on long right hand corners!!!
The left hand drive shaft (axle) started to fail on the last hour so we had to take it easy but that didn't lose us any places! So we have some repair work to do and our next race is Eagles Canyon near Dallas!
Good luck later today and contact me if you need some help!
Agree that the E30 has some stupidly complex ignition and ECU set ups....
Our initial problem was the immobiliser kicking in.....
This problem that Tim is having is more around the incompatible engine wiring and the car loom.....we can't mix and match the 1987/88 car loom with a more modern 1990/91 engine.....
Another little problem we encountered was no charge from the alternator after we stripped more wires out one day, including the dash cluster panel.....we discovered that the alternator needs a 12v signal to it, to actually charge, however, if the bulb in the dash that tells you there is a charging fault blows or is removed, it also kills that 12v signal and you won't have any charge going to the battery!
I had a 1979 E20 323i but then I knew even less about cars and thought that was a nightmare.....but I guess it wasn't so bad!
So we got our engine started and its running well.
As Markdas mentioned, our solution was to use the intake and wiring harness from a 87 325i and put that on the 91' head and block.
The wiring does not match up from year to year. The C101 plugs in later vehicles have some extra wires and we fried one going to the chassis. We learned the hard way. I don't know what year BMW changed the wiring but the 87 will not work with 91 or vise versa.
So, but sure to check your wiring diagrams before you do a swap.
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