Scratching my head (no start) 1990 735il 230k miles

[ChrisRL]

Car died when parked, felt like fuel starvation, i.e. almost started okay, then died, then started with missing. Died again.

So... Started chasing and thus far have

Replaced
Fuel pump
Fuel filter
Rotor
Cap
Wires
Plugs
Master coil
ECU

And still no start (used to start immediately and run very smoothly)
Relays seem good, fuel pump works
Starter motor works fine, engine turns over easily, almost catches, ignites very rough, lots of missing, stalls just short of starting...

So
Scratching.... plus two BMW mechanics also scratching their heads..

Any suggestions, anyone?
I can't be the only one with this problem!

Thank you in advance!

[Avec]

Sounds like a crank position sensor or the main relay.

[ChrisRL]

Avec

Sorry, forgot to mention that I already replaced the crank position sensor as well.
So I'll try the main relay, but having AB'd it with another one that works.... I'll just replace that one too, since the entire chains of gas and spark have otherwise been replaced.
Will let you know what happens!

Thanks!
Best
Chris

[shogun]

checked both fusable links already? One goes directly to the e-box for the Motronic etc. Location pics see my website under reference data>>>electrical>>pdf file Photos and locations of E32 fusible links

[ChrisRL]

checked both fusable links already? One goes directly to the e-box for the Motronic etc. Location pics see my website under reference data>>>electrical>>pdf file Photos and locations of E32 fusible links

Hi!
Long time, Shogun!
Did you mean the ones that are under the rear pax side seat? Connecting from the battery? Never did figure out how to get the seat up... :-)

[shogun]

YES, these you have to check first, under passenger side rear seat. Especially the one difficult to find. Here more pics http://www.bimmerboard.com/forums/posts/377728/
and under the driver side rear seat there are plenty of relays and also fuses.
How to remove a electric rear seat: http://www.bimmerboard.com/forums/posts/62868

[ChrisRL]

Thanks gents! Will investigate further and inform you of progress!

[E32FAN]

If your Fusible Link A is intermittent, then the voltage at post X1540 will be low and fluctuating.

This is easy to measure, at D100 Diagnostic Connector, pin 14. Pin numbers are shown on page 8500.0.20 X1532. And the numbers are molded into the connector.

This is shown on page 1360-01 in the ETM. http://shark.armchair.mb.ca/~dave/BMW/e32/e32_89.pdf

[ChrisRL]

Many thanks, Fan!
Will check it out asap.
Best
Chris

[shogun]

X1540 is in the e-box RH rear of engine http://bmwe32.masscom.net/johan/e_bo..._1987_735i.jpg
other items shown from this 735 e-box, It contains (from left to right):
The Motronic computer or DME
The cruise control unit
The fuelpump (orange) and DME main (white) relays
The ABS computer

20-pin Diagnostic Socket http://www.nmia.com/~dgnrg/diag_s.htm http://pinoutguide.com/CarElectronic...g_pinout.shtml

[whiskychaser]

I know you have replaced a lot of parts, but you still don't know if you have a spark or fuel. Are the plugs wet with fuel? If so, borrow or buy a cheap strobe. That way you can turn the key and immediately see if you have a reliable spark. Don't forget that if you have been cranking it for a while, it may be flooded