View Full Version : 1990 750il ignition failure after storage period

10-01-2005, 05:07 PM
I recently took the car out of storage. During the storage period the battery lost all power. After replacing the battery I discovered the absence ignition fire prevented the engine startup. Has a anti-theft device kicked in due to the absence of power or is something else the problem?

10-02-2005, 07:51 AM
Did you set an anti-theft alarm when parking the car the last time?
But I assume that it is something different.
Do you hear the fuel pumps running when ignition is on position 2 but engine still off, at least for about 5 seconds?
If not, check the fuel pump fuses and teh relays.
Have you checked all relays and fuses? Did you attach the battery correctly? Ot could you have damaged a main fuse?
If no fuel supply, no sparks.
Any possibility to bring the car to a shop for a diagnosis? Otherwise you have to test and I hope that you have a Bentley Service Manual.
Any other things which you noticed now?
First of all, check all fuses, also the ones under the drivers rear seat. I know that this a PITA with the electric rear seats, but with a bit of experice you can do it in 30 minutes to remove the seat and to attach the seat again.
If you do not know how, go to my website below and then to e38.org, there is a detailed instruction from David Cecil.

10-07-2005, 11:38 AM
The fuel pump is working in accordance as mentioned. The fuel vapor was noticed at the end of the tail pipe. It's just not getting a spark.
I have removed the rear seats. Fuses were inspected under the hood and in the rear seat compartment. All fuses were fine.
I have not checked the main fuse. Could you please tell me what am I looking for and how do I check it.
Thank You.

10-07-2005, 04:19 PM
The 750 has 2 fuel pumps.
If there is not enough fuel pressure, the ignition will not fire.
Also, have you checked the battery voltage and the cranking voltage? These car are very sensitive to low voltage. Pls measure the battery voltage.
Also here a link to the site of Johan and Sean, look under engine, where you can check the fuel pressure and other items.
Do you have a PEAKE tester? That would allow you to check for faults and you could read it.
Easiest is of course to ask the dealer to do a fault diagnosis.
Any possibility that ignition wires could have been destroyed by some rodents or similar?
Enough fuel? How long was the car stored? Could there be condensation of water in the fuel tank. Water settles at the bottom of the tank and the pumps could have sucked it and the mixture is not burnable in the engine.
Battery test:
Find a digital multimeter and stick the probe into the cigarette lighter socket in the center console.

The following are the detail figures I use for my own evaluation:
With key out of ignition switch, should see 12.4V or above. 12.0 V is getting low.
With key inserted and turned to position 2 (don't start car), should see 12.0V or more. 11.6V would be too low.
Crank car, catch the lowest voltage reading during that couple of seconds. Should see 10.0V or above. 9.5V would be marginal.
The above just consider the health of battery itself.
Car running at 1500 RPM or more, should see 13.7 to 14.3V, 13.6V or below means the charging system is weak.

When the battery has lost power, all power in the ECU's is also gone. That means that the engine will first run terribly bad until it has re-learned and the 2 throttling valves have synchronized.

Also, when you notice the fuel vapour at the exhaust, that does not mean that both fuel pumps are running.
The V12 can also run on 6 cylinders in limp mode.