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BMW 735 3.5 1992 - Fuel pump capture (waveforms) #

Posted by Darren Cotton on April 2, 2011, 7:38 am

Year of Manufacture *: 1992
( Optional ) Engine Code or CC: 3500

This has running issues, and many problems, fuel pump i think being one of them......

Blue trace is fuel pressure, green trace is pump current

The lower capture is the pump current zoomed in x272

which appears to have 12 segments...

Fuel pressure seems erratic and on snapped throttle have a difference of around 14psi!
Darren

Re: BMW 735 Fuel pump capture

Posted by Mike Whitworth on April 2, 2011, 8:14 am, in reply to "BMW 735 Fuel pump capture "
Message modified by board administrator April 2, 2011, 3:42 pm

Hi Darren,

That Fuel pump current don't look so good does it?

It looks to me, as though you are losing deffinition, maybe a higher sample rate is needed or personally I would just set a much shorter time base so you can see four or 5 revolutions on one screen.

Mike

Re: BMW 735 Fuel pump capture

Posted by Aidan Birley on April 2, 2011, 8:39 am, in reply to "Re: BMW 735 Fuel pump capture "
Message modified by board administrator April 2, 2011, 3:43 pm

hi Darren

14 psi is approx atmospheric pressure, Is the pressure rise you see a design feature to compensate for pressure difference in the manifold

e.g. has it got vacuum connection on the pressure regulator?

what are the running issues ? Is fuel flow good adn free from air.

Cheers Aidan

Re: BMW 735 Fuel pump capture

Posted by Darren Cotton <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT1876' width='330' height='300' border=0 style='border:none;'> on April 2, 2011, 9:06 am, in reply to "Re: BMW 735 Fuel pump capture "
Darren Cotton

Hi Mike

yep maybe some small set up adjustments could be made, but without those in my opinion the pump proves worn.

I will get it in again and set up different.

Hi Aidan,

The issues with this is poor running when hot, no throttle response when hot and will cut out and not start for a while.

Exhaust manifold blowing, bolts broken in head. engine vac is around 16 in-hg, its running very lean. To be honest its a pile of shite.

yes it has vac controlled regulator, my main concern was not just the pressure difference but also the erratic pressure at idle.

It maybe a feature for the difference in pressure @WOT something i have never seen before.

Well customer has supplied a second hand pump, Great.........

Darren

Re: BMW 735 Fuel pump capture

Posted by Michael Whitworth <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT5568' width='330' height='300' border=0 style='border:none;'> on April 2, 2011, 9:20 am, in reply to "Re: BMW 735 Fuel pump capture "
Mike Whitworth - Administrator

>>>>Well customer has supplied a second hand pump, Great<<<<

I would tell him to fit it himself......

Mike

M.O.M. Miserable Old Manc

Re: BMW 735 Fuel pump capture

Posted by Andy Evans <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT5518' width='330' height='300' border=0 style='border:none;'> on April 2, 2011, 2:49 pm, in reply to "Re: BMW 735 Fuel pump capture "

"I would tell him to fit it himself......"

I don`t think I would be as polite as that Mike!

Andy E

Re: BMW 735 3.5 1992 - Fuel pump capture (waveforms) #

Posted by Darren Cotton <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT1876' width='330' height='300' border=0 style='border:none;'> on April 2, 2011, 6:11 pm, in reply to "BMW 735 3.5 1992 - Fuel pump capture (waveforms) #"

Aidan,

Just thinking about what you said, and of course your right, as there is no manifold pressure @ WOT

So that may be normal. to be honest don't think I
have ever looked at the pressure at WOT until now.

The guy has supplied second hand pump fuel pressure is more steady, AD list it spec as 3 bar, its about 4psi below spec still

Darren

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