New Fuel System parts, still acts gas starved

[DFNTON]

Having replaced all of the fuel system components less hoses on my '86K100RS, the bike still acts like it's fuel starved sometimes after coming to a complete stop and trying to start off again. The bike hesitates and after a bit catches and runs again.This is an intermittant problem. What can be causing this? HES? Could use a little help with this. Thanks.
Dave

 

[HFbmw]

starved fuel delivery

howdy,
You said you have worked on the system. Is the fuel pump sitting higher in the fuel pump clip in the tank?
My 91 has a slippery mount, I noticed last week the same kind of problem. When the bike was low on fuel there was hesitation. Sooo I figured now what did I forget!
I had the fuel pump out 2 week earlier checking it. So thankfully there was less fuel in the tank for my hands to wade in... pushed the pump further in its mounting device and the problem went away.

tim lindstrom
91k100lt 136,000 miles

 

[DFNTON]

The bottom of the fuel pump is 1/4" from the bottom of the strainer. The problem occured today with over 3 gallons of fuel in the tank. Doesn't sound like the same problem as yours. Thanks.
Dave

 

[DFNTON]

reply from BMW Mick

At 02:07 PM 7/29/2007, you wrote:
>Hi Mick,
>A year ago I was having trouble with my R11RT and we discussed
>sending you my HES and you would send back a reconditioned one. This
>year my trouble is with my other bike a '86 K100RS. Has been cutting
>out like it is fuel starved. Will eventually catch and start running
>well. Thought it might be a fuel problem because of a dirty fuel
>rail. I completely replaced all of the components in the fuel system
>(rail, filter, pump, pump strainer, and fuel injectors) and it is
>still acting up. The bike is 21 years old and was sitting for about
>3 years before I got it in October of 2004. I am wondering if my
>next step is to replace the HES. Do you still rebuild them? If so,
>please let me know as I would like to send mine if you think that is
>the next step. This problem is very intermittant.
>Will appreciate any help you can give me.
>Dave

Dave,
I only repair the Oilhead HES so far. I carry a spare HES for my
K1100LT at 142K miles but
I doubt I'll ever need it. The K-Bike unit hardly ever fails. If
you were only failing when it was
very hot or very wet, I'd lean toward the Hall device. In your case,
I'd go ave the FI and Spark
boxes or their connectors.
Have you tried to recreate the failure while stationary? You
could even have a coil failing which
will take two cylinders out and feel like fuel starvation.

Mick
Tucson


Can anyone give me direction on checking out the coils and the FI and spark boxes? Thanks.
Dave

 

[kayseventyfive]

the bike still acts like it's fuel starved sometimes after coming to a complete stop and trying to start off again. Dave

To confirm or deny a fuel supply problem, buy a tee, a gage and some line. Connect it up and ty-rap the gage where you can see it all the time. Drive and watch it.

 

[jdiaz]

I'm thinking there's a big crack in the rubber intake tube between the airflow meter and the plenum, and the resultant airflow leak is making the bike run lean.

 

[DFNTON]

Air flow meter

very interesting. At another forum someone else suspects that there is a problem with the air flow meter. Thanks, willl be looking at it today.

 

[DFNTON]

Air Box and Meter O.K , what's next?

Checked air intake system and all looks well. No cracks or anything to allow more air in. Looked for vacuum leaks and couldn't find any. The only component in the fuel system that is not new is the fuel pressure regulator. But I see it is after the fuel rail on the return line. How does it work? what pressure does it regulate? I'm confused.

 

[kayseventyfive]

The only component in the fuel system that is not new is the fuel pressure regulator. But I see it is after the fuel rail on the return line. How does it work? what pressure does it regulate? I'm confused.

It regulates the pressure in the line from the pump to the injectors. When the pressure is above about 38 psi (from memory), it opens up and lets some fuel run back into the tank, bleeding off pressure until it stays at 38 or so.

The gage set up I mentioned earlier will check that function. I think Clymer or Haynes describes it in detail.