Unofficialbmw.com

[bobstl540]

This weekend was driving on highway when engine inexplicably began to 'bog down' when applying accelerator. Low fuel indicator had come on recently but was certain there was still plenty of gas (based on 6+ yrs of experience with car). Did not get a Check Engine or any other dash indicators. Got off highway and engine stalled when I got to the light. Car would restart but wouldn't idle and choked out when I applied gas to keep RPMs up. Tried several times with same result before decidng to have it towed to my independent BMW shop which is where it now sits waiting for them to open tomorrow. Went back this morning and tried again with same result (i.e. turned over fine, but coughed before stalling out - almost like a lawn mower when the choke is left on). Thinking MAYBE I had run out of gas I put 2 gallons in and tried again... it kicked and coughed but after 5 seconds or so settled into a normal idle. Here is the strange part that I need some help with: fuel gage registerd about 1/3 tank which did not make sense (i.e. only put 2 gallons in) so I let it warm to normal temp and then drove to gas station filled it up. It took 14.4 gallons + the 2 gallons I put in = 16.4 gallons. Tank holds 18+ which means there were almost 2 gallons in tank when problem started so I did NOT run out of gas. Car runs fine/normal but gut tells me something is up and I do not want to have it recurr when I am in middle of nowhwere (again). Car has 85,XXX miles and was in shop last week for new P/S pump. Could it somehow be related? Any thoughts on what might be going on?

[alexgraf]

This car has a transfer pump from left to right of the tank, where the real fuel pump is located. THere could be an issue with this pump not feeding the right side of the tank. That would explain why you had 2 gallons still in the tank but cannot access this reserve.

So, you can repair this, or keep 5 gallons in your tank all the time.
_________________

'95 325is


'99 528iT - a real SUV

[edjack]

Why would you think that the PS pump had anything to do with the fuel gauge? No relationship.

You need to measure the resistance of the two level sensors in the fuel tank. Perhaps one is bad.
_________________


Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.

[bobstl540]

Bad transfer pump makes sense. I'll have my mechanic check it out. Thanks.

[bobstl540]

Update: mechanic put computer on car this morning and there were no fault codes of any kind. Ran Alex's tank transfer pump theory by him but he says computer would (should) indicate 'misfire' fault code if problem was no gas. Drove car 20 miles to/from work with no problems. Guess I will not let the tank get below 1/4 full and hope for the best.

[alexgraf]

Thanks for the update.
_________________

'95 325is


'99 528iT - a real SUV

[edjack]

Best to fill up at 1/4 tank. Fuel cools the pump.

If you run the tank nearly dry often, you will shorten the life of the pump.
_________________


Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.