1993 BMW 320i



July, 20, 2012 AT 11:25 AM

I bought a bmw 320i manual. When new the car had Vanos, the engine it had in when I bought it had a s1 non-vanos engine. It ran perfectly for a couple of months (the guy I bought it from had it 3 years) but it had a water problem, when this was checked out it seemed the engine was on its last legs and had so many crap repairs it was a wonder it went at all. I got a good mechanic to find an exact same engine (S1) from a scrap yard that was running and guaranteed for 6 months.
Once the engine was replaced the mechanic started the car and it started to idle fine but would pop and bang if you hit the throttle.
He continued putting everything back together and when trying to start again the car would not do anything but turn over normally without firing.
The fuel was reaching the injection with a great amount of pressure and the plugs were all sparking fine. The compression for all cylinders was fine.
After checking, testing many parts we took the car to BMW who checked it electronically and said the only errors stored were old and nothing that would stop the car from running.
Unfortunately they said they couldn't explain why the car would not go because the engine in the car was not the original engine but from what they could see there was no reason the car should not go. (What a response).
Someone suggested towing the car in case while the engine was sat for so long there could be no oil for the valves to open correctly and towing it would make sure everything was fine with the hydraulic valves.
We towed it down the road and at about 40mph putting it in gear the engine turned over but no firing at first. When the throttle was full on the floor, the popping and farting started. After a mile or so the engine did start and keeping the rev's over 3000 the engine sounded fantastic as if it was ready from a few laps on the racing track, however as soon as the rev's came under 3000 the engine would cut out. When running you could hear the car trying to suck in air between revving like it had just ran a marathon.

We drove the car back from the dealer and once home, for the third time took the injection off to check, it seemed perfect so it was getting fuel.

Off course the mechanic suggested straight away that the timing is the problem, but as this engine has no vanos it should all be done electronically. The engine this new one replaced was exactly the same, so in a normal world it should have ran perfectly, however not to be.

To top it off when we removed the injection system after getting it home we noticed oil coming from the head, so now we had just knocked out the head gasket. After doing another compression test we saw that one cylinder now had no compression, two were a little low. Luckily when we removed the head, the piston's and rings were still fine but the valves were now leaking.

The valves have now been reseated and the engine is yet again back together and the compression is again 110ish for all cylinders, the petrol still has enough pressure to shoot a jet 30 feet and the plugs are all lighting up.

But the car still wont go?

You can turn the engine over on the key forever and it will not fire. We certainly wont try towing the car again.

The mechanic is convinced the timing is out on the engine, which makes sense but this is setup electronically and was perfect for the old engine, of which the new engine is exactly the same?

That we need help is putting it lightly. BMW could not tell us why the car would not go, and of course the minute they saw the engine had been changed gave them a one line out for not fixing anything (it's because you changed the engine to a non-vanos). The fact a non-vanos engine (S1) had been running perfectly for many years in the car didn't impress them as they said it wasn't possible!

The mechanic to be fair has tried so many different parts he is adamant that mechanically the engine is perfect.

I doubt as strange as this is it has never happened before, and I am sure someone will be able to help? I just need to try and connect the dot's before I loose what's left of my sanity!

Sorry for such a long story.


7 Answers



July, 20, 2012 AT 1:18 PM

Unfortunely, we are here and the car is there.

Start with basics, fuel pressure, exact numbers, compression and spark. The front cover will have to be removed to verfiy timing marks are correct.




July, 21, 2012 AT 9:15 AM

Checked fuel pressure 3 bar.
Timing chain marks correct
no1 115
no2 110
no3 110
no4 110
no5 110
no6 110
I cant help thinking that the problem is still timing is it possible that the ECU is playing games as battery was disconected for some time or is it possible that the ECU was not changed from the m52 s3 engine and still thinks its got vanos. Would seem strange as the m50 s1 engine that I took out ran fine and all connetions are correct for the m50 s1 engine.



July, 21, 2012 AT 2:07 PM

The compression is below the minimum requirement of 140 psi.



July, 22, 2012 AT 10:29 AM

The compression numbers showing are for a cold engine turning over with all plugs out, throttle down. No way of testing after engine running without risking another gasket?



July, 22, 2012 AT 10:59 AM

It does not matter if the engine is hot or cold, the compression should be within range. Low compression would cause difficult or no starting. Prolonged cranking would flood the cylinders.

Try the compression test again and this time pump 1 cc of engine oil into the spark plug holes and crank the engine briefly before installing the compression gauge to test.



November, 8, 2012 AT 4:51 PM

It's been a long time to update this but unfortunately I work away for weeks at a time so have been unable to do anything with the car, however here's an update and your "wild" views WOULD be appreciated.

After Towing the car before the rebuild (it did start and ran if the Rev's were kept above 3000) 1-2 cylinders were not firing. The head gasket blew, so we just finished putting everything back together and now we are in the same position as before.

The rebuild went good, all valves were removed and re-bedded, complete new gaskets. No leaking pistons, timing set up exactly as manual stated etc.

Now, we have good Sparking, we have fantastic pressure of Petrol reaching the engine, We have a good battery & Jumping from a second car. But there is still NO firing at all, nothing. The engine turns over very well but NO firing?

The Mechanic has checked every part, lead, cable, connection, pressure and is pretty convinced about two things.

1. The timing is wrong.
2. The fault is NOT a physical part of the car.

He is convinced the problem is Electrical from either the computer itself, an electronic part controlling the timing, or an electronic part somewhere that is "disabling" the car. Preventing it from starting?

How many "if any" sensors can there be on the car that could be sending an "emergency stop" to the computer, and is there a way to bypass them? I know this is out there in "grasping" and "straws" but really, we are both at the stage of spending a fiver on petrol and burning the damn thing.



November, 8, 2012 AT 7:06 PM

Check the fuel injectors for pulsing. Try a little starting fluid to see if it fires up.

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