how does the fuel distributor work in a 117?

[CzarFC]

On a 560 V-8 117:

Is fuel sent to the injectors in a steady stream or is it sent to the injectors timed to the intake valve?


Thanks!

Scott

[AusMBtech]

That engine will have CIS/Kjet injection. The fuel is constantly flowing through the fuel injector even when the valve is closed. That's one reason why these engines have higher HC emissions.

[CzarFC]

Thanks for the reply. Now this thing is confusing me... My car will sputter out when trying to crank it up unless I press the throttle pedel. At an idle, it will sputter out. The throttle linkages appear to be okay. Before I took the heads off, everything worked fine, (was an oil consuption issue due to worn guides and 4 bent exhause valves) Now the only think I can think of would have been fuel being inject out of sync, but you just shot that thought down... pondering pondering...

what would be other causes of this symptom? Could bad fuel injectors cause this?

At a throttle range where I would typically have 1500-2000RMPs I have something on the order of 700-1000.

Thanks again for the info and happy holidays!


Scott

[AusMBtech]

This thype of fuel system is VERY sensitive to fuel pressure changes and vacuum leaks.

Because you said you have just changed the head then I'm be inclined to say you have a vacuum leak.

Did you replace the seals for the injectors when you pulled them out? check your vacuum hoses and listen for leaks. Some people like to use some carby cleaner to find leaks by spraying copmponents and if the engine running changes then there is a leak in that area.

Is the engine running ok at higher revs (3-4k)?

[CzarFC]

The engine runs like a champ at higher revs, just as long as I stay on the throttle. I'm seriously considering replacing my injectors. 2 of the injectors had been replaced by the prior owner (the other 6 were origional steel, while 2 were brass) so I'm wondering if some of the older ones are finally giving out. Also all the seals above the head gaskets were replaced. I actually replaced all the fuel injector holders. Some of the plastic was poorly casted and I used a hot exacto knife to trim off all the over-casting material before installation. With the new injector holders came new seals and such.

The car does not hold an idle. I have to hold the thottle at a position which I would guess would normally be 2k RPMs to get it to stay running. Oh, could springs be an issue? On the 126 chassis CD it shows 3 springs in the throttle linkages. I only remember removing 1 and I only had one in my parts pile. That was the spring which goes down to the plate in the throttle body. Did I lose the other 2? I would have checked my "before" pictures, however that CD died on me and I lost the pics

[wbain5280]

There could also be issues with the EHA valve, which varies the fuel pressure depending on the O2 sensor reading. Do a search on EHA. Larry Bible and Stevebfl are two techs who have posted lots of info on this subject.

Make sure there are no vacuum leaks. Make sure fuel pressure is within spec. More searchs to perform.

This FI system is faitly simple, CIS with a simple computer system wrapped around it for adjustment.

I'd prefer a real EFI system, with OBD-II, on my 300SE.

[AusMBtech]

I would suggest that you replace the fuel injectors at some point (not until you find the source of your current fault) because the steel colour injector do give some trouble with the pintle falling out while the brass coloured ones are the modified version to solve this fault.