So my boss asked my brother and me over to do some work on his 66 230SL that has been sitting for about 10 years and only ran maybe once in that time. We replaced some hoses and some various do-dads before moving on to the throttle system.
The return spring was sprung and the links were stiff and the throttle was sticking about half way. We carefully removed the link connecting the fuel injector pump to the rest of the system at the ball joint taking care not to change any link rods. We re-greased everything, replaced the return spring and everything minus the MFI (not connected yet), was working like a charm.
Seeing that we were shining things up, my brother (the actual mechanic) thought it would be a great idea to remove the link and arm from the MFI system without telling anyone. Ok no big deal…needs a tune-up anyway.
Well, we put it all back together and everything seems great! Idles well, revs nicely…no water leaks…(original issue). So my boss takes the car for a spin with my brother as second in command and about 5 minutes later they come putting up the hill just barely making it into the garage before shutting it down.
Turns out the throttle was stuck open. They had to get out and jiggle the links for it to return to idle. They then drove it back to the garage without any throttle (automatic). Anyway, they get back and we look it over…everything moves just fine. Start the car and give it some revs then BAM the throttle sticks half way open!
Grab the links and give them a quick twist and the drop back down to idle position. I looked over the system to see if there was an over-extending link or something but found nothing that made sense seeing it was sticking at about half throttle.
I removed the link connecting the MFI to everything else and lo and behold something internal in the MFI is now jamming. My question (finally) is what could it be? We have a shop manual that more or less ignores this thing so it was no help. After doing some minor research, I found that we have the newer style (I think) going by the pictures of the two types.
The label on the one we have is PES 6 KL 70 B 120 R11 and it has a red oil cap but no dipstick inside. I have no clue if there is any oil inside or not… Everyone tried their hand at resetting the arm and link with no success at all. With the engine off sometimes it sticks, sometimes not. but any time the car is running, it sticks about half way.
The issue here is that it DID work and now it does not. A rebuilt pump is expensive and sounds like a pain in the backside to install, so is there anything else we can try first?