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-   -   e23 Euro car, 723 power help..... (

redhead 07-04-2012 07:33 PM

e23 Euro car, 723 power help.....
Bimmerfest gang, fisrt, you guys and gals rule, i have had quite a few problems solved by reading the forums, and listening to what you have to say, but, i have a new adventure that i don't see anywhere on here, so hopefully the vast knowledge of the bimmerfest crew can help:

The backstory, this is a 1981 732i, "grey market" brought over from sweden by my wife's god father, he no longer lives here, or drives it, hasn't drove it for about 11 years, sitting in his garage, until he thought it would be a good idea to my father-in-law and i have it, to "get it going" again...... as you know, the 723 was never sold here, the motor never sold/serviced here, and the little documentation i have been able to get from germany is not a lot of help, as this motor didn't last very long in the BMW world. So, here goes:

1981 BMW 732i (e23)
Attempted revival after sitting in garage for 11 years.
Condition: About 140,000 miles on odometer. Starts and runs OK after installation of new Bosch fuel pump and filter. Engine responds to throttle when not under load (out of gear). However, it will not accelerate when driven. It appears that there is fuel starvation when the throttle is applied under load.
Checked fuel pressure at the rail--~28psi at idle. When driving pressure drops to under 10psi when throttle is applied and vacuum drops to near zero inches. Checked fuel pump by brief (very) crimp of hose and pressure rose to 70+psi. So pump seems OK.
Installed new fuel pressure regulator since pressure was somewhat low during initial test and some sludge was removed while being cleaned with carb cleaner.
Same reaction as with the original regulatoróran fine in the garage but would not accelerate on the road and had the same pressure drop with throttle application.
Am I wrong in my belief that reduced vacuum should cause the regulator to increase in pressure in order to increase fuel flow thus causing acceleration? Why the pressure drop?

Please, any good ideas as to why the power just dies will help. We are not going to sink thousands into this car, but want ideas as to why this might be happening, just to have a fun car to play around with and maybe restore fully.

i hope you can help,

redhead 08-17-2012 08:10 PM

So, I finally figured it out, but went the long way around the barn to get there.....

in order of what we did:
replaced fuel pump with a new bosch
replaced all filters, and gas lines
replaced the "sock" that goes on the bottom of the fuel sending/gauge float in the tank
added a 2nd filter in line, just to be sure

tested the pressure at the rail, 30-38 psi at idle and revving while in neutral
ran car on road, with pressure meter attached, ran fine for about 1/2 mile at moderate speed, when put under acceleration in any gear, pressure dropped to 8 psi or less, with no response from throttle. once car sat for 10 minutes, this process could be repeated again with same result.

finally, after a few filter changes, removing the 2nd filter, we decided to test the "flow" of the fuel at a few points in the system, BINGO..... the new bosch fuel pump had a flaw. new pump installed, gas tank removed and sent to shop for cleaning, and problem seems solved. Now on to the fun stuff, new rotors, calipers (2 pistons on each caliper were frozen and missing the rubber) pads and tires.


IEbimmerguy 09-16-2012 09:34 AM

Glad to hear you got her running! There are countless e23's hitting the salvage yards each year. :(

BMWFatherFigure 04-19-2013 01:14 PM

Exlent out come!! Brake rebuilds are easy - seal kits are easy to come by and use rubber grease (Castrol GRR) on the rebuilds.

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