Engine lean at high rpm

[srisant]

Hi,

After several attempts to tune my engine. It is now running well at idle and below 4000rpm. However anything above 4000 it will choke like not enough fuel. My fuel pump is full overhauled from Buds Benz so it must be from something else. I also have disconnect wire to CVS as it start much better without it. Also my mechanic check lambda it is now 0.9 at idle but gone up at high rev which is too lean according to him. Please advise

[Tyler S]

Check the linkage adjustments first. You also want to verify fuel pressure even with a new pump as the pressure regulator in the FIP could be at fault.

[Garry]

As Tyler suggested, you need to do the Linkage Tour that is set out in the Technical manual but only available to Full Members. 

Maybe its time to consider becoming a Full Member, it will pay for its self in just this one process to get the car running correctly.

Garry
Membership Administrator

[srisant]

After adjustment all linkage and throttle body, I managed to get my car running proper at idle and low rpm. Lambda read .9 which my mechanic said it is acceptable from original 0.7. However when the acceleration go beyond 4000rpm engine is struggle due to too lean. My injection pump is newly rebuild from Buds Benz, wondering what else should be the cause of this?

Best,

[wwheeler]

The idle mixture is the easiest to change. The individual mid and upper range adjustments require much more effort. You could try to richen the entire range first, and then go back and lean the idle and low rpm. Easiest way to change the entire range is by shimming the barometric compensator. There are other ways, but are again more effort. To make the mixture more rich by this method, I believe you would remove shims. It is very sensitive and remove/add a max of .003" thick shims each time.

Might also check the barometric compensator to see if it is still working. There is plenty about that on this site also.

[Tyler S]

One more thing to check is the screen in the tank (large hex bottom of tank) and make sure its not plugged up. Will cause fuel starvation.

[ja17]

Connect a fuel pressure gauge to the fuel supply. I like to connect at the cold start valve line at the intake. Check the fuel pressure during your high RPM problem. If the pressure drops off too much, you may still have a fuel delivery problem.

[srisant]

Just check with my mechanic today he said that alignment on linkage are all off. Will test the car tomorrow after linkages are fixed.