Hello all. A fella is wanting to trade me a bmw sedan with the n73 v12 very nice car and runs good, the thing is it is only running on 6 cylinders....

Sandy52

Full member
Points
23
From
Norfolk
Car
BMW X3 30d Xdrive
Start with the easy stuff, are all 6 cylinders that are not working on one side? or are they on both sides. Is there separate ignition for the two banks maybe one side is faulty?
 

obi_waynne

Administrator
Staff member
Moderator
Points
1,137
From
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
If it's been running like this for a while then there could be other faults and issues with the engine (catalysts, uneven wear across the engine banks etc...).

Main issues are
1) Lack of spark - electrical fault
2) Fuel issues - in this case an issue with the fuel rail

On the M70 there was a similar issue, if a plug lead is shorting then the Motronic ECU will reduce or cut the injectors for the whole bank, unburned fuel kills catalysts so to protect the cats a misfire on 1 cylinder will cut the entire bank. I can only guess that the N73 may use a similar setup.

Fault codes may give a clue to what's happening.

If you are lucky then disconnecting all the plugs and lead and reconnecting them could fix the issue.
 

Ardry

Newbie
Points
1
From
Oklahoma
Car
Bmw n73
I made the trade. But.... it is an 89 750il which would make it a m70? It's a v12 with 86k miles on it. No OBD connect, has a round pin connector under the hood.
 

Ardry

Newbie
Points
1
From
Oklahoma
Car
Bmw n73
It's the entire right bank that's not firing. Getting fuel pressure.the car was setting For a number of years, the fuel tank was mucked up in the pumps were badd.the guy replaced the pumps(w chevy pumps) he said he couldent figure it out. Hes a pretty Good old school mechanic, But not Tech savvy. I own a paint and body shop but when I open the hood and seen the 4 computers I figured a man with any sense would try to recruit some help By somebody who might know little about these cars. Not very many BMW mechanics in rual Oklahoma ....
 

Sandy52

Full member
Points
23
From
Norfolk
Car
BMW X3 30d Xdrive
Any input on what its gonna take to fix this issue?
Check you get a spark at the park plugs - cheap tool or just do it the old fashioned way and do it in the dark you wont miss it!
Check the fuel supply? check fuel to the injector pump? then fuel to the injectors-
may need t remove the injectors and swap them with the other side to see if they work- the car runs on the usual side?
Lots of useful advice on YTube on car repairs worth a look.

good luck
 

thexav

Pro Tuner
Staff member
Points
387
Car
2002 Clio 172
Did you go ahead with this trade then? How's it turning out?
 
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