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Hi Josh, I own a 1994 BMW 530i 3.0L V8 (E34)which was running beautifully. About a year ago, I noticed a slight "miss" on the engine while idling. A mechanic seemed to think that it was possibly a dirty injector or two. I treated this with injector cleaner in the fuel tank but without any success. He also did a compression test and mentioned that it was a bit low (6-7 bars on some cylinders) However, at normal driving speed there seemed to be no indication of this. However, one day, the car would not start. The engine just cranked and cranked and it seemed there was no compression at all (its as if the spark plugs were removed. But with a small push, the engine started immediately. The problem was then gone for a few weeks and then suddenly it would re-appear. With a small push or even a tow (less than 5 meters, the engine would start instantly). could it possibly be faulty hydraulic lifters or what. The engine only has a genuine 130,000km on the clock. I look forward to your response...
Answer -
Cedric,
Does the car have a manual transmission? I'm assuming so, since you said it would start when you pushed it.
Anyhow, are you sure the pressure is off by 6-7 bar? That's 80-100psi difference!!! That is a large problem. I'm not as familiar with the 5-series as I am with the 3-series, but these problems aren't model specific. I know the V8's had some issues with the material the blocks were made from called Alusil (Silicone impregnated aluminum). After the blocks were wearing prematurely, they changed the material to Nikasil, and it solved the problem. I would check to make sure your block is not one of the "bad material" engines. I know they had a recall to fix/replace these blocks, and maybe yours wasn't fixed, and now the block is wearing out, causing the lower compression. I could see 1-2 bar difference (15-30psi), but 6-7 bar.... that's enough to concern me. I would have another compression test done, just to make sure those numbers were correct
It sounds to me like there is an electrical issue with the starting problem, and unfortunately it will have to be searched for, to fix the problem. You can try some forums for your car (E34) and see if those guys could help.
www.bimmerforums.com
www.roadfly.com
Just look for the E34 forum and hopefully someone there will know exactly what your problem is.
Good luck,
Josh
Hi Josh,
Thank you very much for your prompt response..Sorry for the misunderstanding. what I meant was that the current readings for the compression test was between 6 - 7 bars on some cylinders. I think the proper readings should be about 8 bars on a new engine. Also - was Nikasil not the previous material which was giving problems and then later replaced with Alusil?.
One more thing which I failed to mention earlier was that this "hard starting" is more prominent when the engine is hot. However, once again, with a small push, the engine starts instantly.
In terms of the electrical problem you mentioned - it rings a bell now that around that time I experiened starter problems and an auto electrician told me that he had to fit a relay on the starter to correct it. Since then, my problems started. ie My battery would run down when the car stood for a day or two. I now have to disconnect the battery and reconnect it when I use the car - however, I still experience the "non-starting" issue from time to time and have to push it to start...
AnswerCedric,
I may have been wrong on the Alusil/nikasil issue, one of them was bad, and you dont want it.
At least we know that the compression is close on all cylinders. You dont want one or two with way lower compression than the others.
I'm not sure what kind of relay he put on the starter, maybe the solenoid, but I'm confused as to why he put a relay on? Relay's stick sometimes, and drain batteries... so this could be the issue, I would have another electrician take a look at it, or a trusted mechanic.
Hope this helps,
Josh
