So i have built an m42 powered 1984 318i lemons car. The car was a shell when I started with a roll cage so the wiring was created from scratch. The wiring was done to mimic oem wiring through a c101 with switched fuses. At last years race we had 1000 miles on the car and had nothing but problems at the race. Rust in the gas tank was the main problem. I changed the tank and did another test day so the car has over 2,000 miles on it now but at the recent test day kept shutting off and caused us to withdraw from the race next weekend. After 4 laps on track, the engine just shut off and I coasted to a shot to a stop. After a tow back to the pits, the car fired up right away. I went back out and it happened again. After 3 times the track wouldn't let me go back out on track so I worked on it and worked on it and had intermittent problems restarting the car and about 2 miles from the track it shut off and did not want to restart. After a 20 minute sit, it restarted and drove the 50 miles back from the track without problems. Then once home it wouldn't restart.
Here is the build thread: https://www.r3vlimited.com/board/for...e-car-with-m42
Symptoms/ things done:
- The fuel filter had some debris so I assumed it was a clogged fuel filter. Changed that out and on the next session during lap 2 the same thing happened.
- I had added a low pressure lift pump in the later tank to solve fuel starve. So I verified the lift pump was flowing to the 318is fuel pickup on the passenger side.
- Added 5 gallons of gas to full, just in case the lift pump wasn't working
- Bypassed the fuel pump relay and wired the pump directly to constant power and the engine still would not start the first try. (this tells me the problem is upstream of the chassis harness)
- had previously replaced the cps with a new oem CPS last fall
- had previously replaced coil on plugs with known good coils last fall
- swapped the ecu with 2 others and intermittently, it might start but might shut off while idling
- replaced both fuel pump relay and o2 relay and problem did not go away
- replaced the main relay with a good one and thought maybe that was bad and even bypassed/jumpered it with wiring and still the car shut off
- seems like the engine ground is solid, seems like connections at the battery are tight on power and ground.
- stomp test shows 1222 if the check engine light comes on and it is running a wideband oxygen sensor
- upgraded and replaced wiring form teh fuel pump relay c101 connection to the fuel pump and even wired the second pump on a second wire to avoid and pump problems with the wire gauge
Thoughts
So it appears possibly there are 2 or 3 more things it could be. At this point everything that seems logical has been changed out (ecu, afm, coils, oxygen sensor, main relay, fuel pump relay, fuel pump, fuel filter, etc.) It seems the car fires up and runs weel in the cold and does not do well when hot. This is distinctly different from the 'hot restart' afm wire problem which I found years ago on a different 318is and have not connected.
1 - There are a couple thread of the harmonic balancer separating the toothed wheel from the rubber. The one on the car seems solid. Any way to test this besides just separating the wheel? I do have a spare engine with one I could swap. But the car seems to run well then abruptly just shut off does not seem to be the likely cause.
2 - Wiring - The wiring was from scratch so I wonder if wiring upstream of the fuses is shorting out or something. I could check this wiring at the c101 or the wiring in the m42 engine harness for problems. The engine harness does not appear to have been modified. Anything downstream of the fuses has been working just fine.
3 - Grounds - Looking at the wiring diagrams, it appears the CPS, ECU and main relay are the most critical parts to starting the car. I have verified these three items but found this wiring diagram posted by bmwman91 which shows the m42 wiring in great detail. It appears that fuel is not the problem and it is coming from either the c101 or upstream of that. Looking at the diagram, I started wondering about G-103 ground junction connection near the battery tray. Last night I looked at it on the car and the bolt was kind of dirty and the cable itself was not very clean. Here is the interesting thing. With that ground disconnected, the car would still start and idle. I believe this may be the problem but need to do some driving around to test it and I think that means hot weather and hot conditions. Is there a better way to ground this wire than this screw hole at the battery tray? Directly the battery ground? I cleaned the terminal last night and when going to tighten, the bolt didn't seem to tighten all the way, like it was partially stripped or something. Its on the battery tray right behind that shock tower. You can almost see it here in these 2 photos. I think this is the problem but wanted to get other opinions. Since it is an m10 based car, the chassis is slightly different.
Full wiring diagram here, I downloaded in case this link gets broken in the future.
Does anybody have any thoughts on what I may be missing that could be the problem?
Here is the build thread: https://www.r3vlimited.com/board/for...e-car-with-m42
Symptoms/ things done:
- The fuel filter had some debris so I assumed it was a clogged fuel filter. Changed that out and on the next session during lap 2 the same thing happened.
- I had added a low pressure lift pump in the later tank to solve fuel starve. So I verified the lift pump was flowing to the 318is fuel pickup on the passenger side.
- Added 5 gallons of gas to full, just in case the lift pump wasn't working
- Bypassed the fuel pump relay and wired the pump directly to constant power and the engine still would not start the first try. (this tells me the problem is upstream of the chassis harness)
- had previously replaced the cps with a new oem CPS last fall
- had previously replaced coil on plugs with known good coils last fall
- swapped the ecu with 2 others and intermittently, it might start but might shut off while idling
- replaced both fuel pump relay and o2 relay and problem did not go away
- replaced the main relay with a good one and thought maybe that was bad and even bypassed/jumpered it with wiring and still the car shut off
- seems like the engine ground is solid, seems like connections at the battery are tight on power and ground.
- stomp test shows 1222 if the check engine light comes on and it is running a wideband oxygen sensor
- upgraded and replaced wiring form teh fuel pump relay c101 connection to the fuel pump and even wired the second pump on a second wire to avoid and pump problems with the wire gauge
Thoughts
So it appears possibly there are 2 or 3 more things it could be. At this point everything that seems logical has been changed out (ecu, afm, coils, oxygen sensor, main relay, fuel pump relay, fuel pump, fuel filter, etc.) It seems the car fires up and runs weel in the cold and does not do well when hot. This is distinctly different from the 'hot restart' afm wire problem which I found years ago on a different 318is and have not connected.
1 - There are a couple thread of the harmonic balancer separating the toothed wheel from the rubber. The one on the car seems solid. Any way to test this besides just separating the wheel? I do have a spare engine with one I could swap. But the car seems to run well then abruptly just shut off does not seem to be the likely cause.
2 - Wiring - The wiring was from scratch so I wonder if wiring upstream of the fuses is shorting out or something. I could check this wiring at the c101 or the wiring in the m42 engine harness for problems. The engine harness does not appear to have been modified. Anything downstream of the fuses has been working just fine.
3 - Grounds - Looking at the wiring diagrams, it appears the CPS, ECU and main relay are the most critical parts to starting the car. I have verified these three items but found this wiring diagram posted by bmwman91 which shows the m42 wiring in great detail. It appears that fuel is not the problem and it is coming from either the c101 or upstream of that. Looking at the diagram, I started wondering about G-103 ground junction connection near the battery tray. Last night I looked at it on the car and the bolt was kind of dirty and the cable itself was not very clean. Here is the interesting thing. With that ground disconnected, the car would still start and idle. I believe this may be the problem but need to do some driving around to test it and I think that means hot weather and hot conditions. Is there a better way to ground this wire than this screw hole at the battery tray? Directly the battery ground? I cleaned the terminal last night and when going to tighten, the bolt didn't seem to tighten all the way, like it was partially stripped or something. Its on the battery tray right behind that shock tower. You can almost see it here in these 2 photos. I think this is the problem but wanted to get other opinions. Since it is an m10 based car, the chassis is slightly different.
Full wiring diagram here, I downloaded in case this link gets broken in the future.
Does anybody have any thoughts on what I may be missing that could be the problem?
Comment