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Drive train, fuel, suspension, steering & brakes / M129 idling issues
« Last post by Heckflosse on May 21, 2024, 23:58:37 »Hi from Alberta Canada!
I'm new to vintage Mercedes but not new to the old car hobby, having rebuilt and restored a number of Buicks and Oldsmobiles, yeah, I know, totally different animals.
So the problems I'm having are this; the engine will not idle, and the vacuum at 1000+ RPM is sitting at around 12 inches of vacuum, set the idle any lower and it's like throwing a switch, the car dies instantly. Now I've rebuilt the Zeniths, they were plugged up. I've replaced the fuel pump, filters and cleared out the fuel lines, both outlet and return, and drained off the tank. Screw plug is cleaned, the donut in the tank is clear, and the tank is so far free of rust. I now have fuel aplently, and the car starts right up better than it did before.
So I thought it was ignition; verified that the timing is correct and that the marks on the cam line up with the balancer, and there's no real slack in the chain. Redid the points, had good spark, and then replaced it all with electronic ignition, so now I have better spark and it's on time.
So I have gas and spark. Still no good. Compression is down a bit, 135, 125, 130, 115, 130, 135. Checked and redid the valve lash as per the manual, that is now set. Runs a bit smoother, but still getting backfire through the carb and a pronounced miss out the back.
So now it's looking like it's the cam. I have 2 more cams, both the same number, 1800518601, both with 86 on the back. The lobes on the two spares look a lot better than the one in the car which looks worn. I quick check with a micrometer shows that the one in the car is almost a millimeter shorter than the other two, plus there's a fair bit of wear showing on the lobes. Ok, how about oiling; - yes, the tube still flows oil, made a rather large mess proving it.
How difficult is it to shove one of these other cams in? Would it even be worth a try? Am I missing something obvious here?
Do I have to take the towers off? Or can I just release the rockers, turn out the bolt holding the timing chain gear and carefully waddle it out? Obviously, I'd measure off the journals before installing one of the others to see if it won't knock.
Now, before anyone jumps down my throat, I do intend to rebuild this motor completely, just not at this point. I still have no idea where to source pistons, rings, valves, etc. yet. I just want to get this thing running again so I can get some other issues attended to. The engine has 70K miles on it, and it appears to have spent a lot of time sitting, there's quite a bit of rust on the underside of that cam.
In case anyone is interested, the car is a 1966 W111 230S with a 1967 250S motor in it, standard transmission. The body is completely rust free so I'd like to keep this car.
I'm new to vintage Mercedes but not new to the old car hobby, having rebuilt and restored a number of Buicks and Oldsmobiles, yeah, I know, totally different animals.
So the problems I'm having are this; the engine will not idle, and the vacuum at 1000+ RPM is sitting at around 12 inches of vacuum, set the idle any lower and it's like throwing a switch, the car dies instantly. Now I've rebuilt the Zeniths, they were plugged up. I've replaced the fuel pump, filters and cleared out the fuel lines, both outlet and return, and drained off the tank. Screw plug is cleaned, the donut in the tank is clear, and the tank is so far free of rust. I now have fuel aplently, and the car starts right up better than it did before.
So I thought it was ignition; verified that the timing is correct and that the marks on the cam line up with the balancer, and there's no real slack in the chain. Redid the points, had good spark, and then replaced it all with electronic ignition, so now I have better spark and it's on time.
So I have gas and spark. Still no good. Compression is down a bit, 135, 125, 130, 115, 130, 135. Checked and redid the valve lash as per the manual, that is now set. Runs a bit smoother, but still getting backfire through the carb and a pronounced miss out the back.
So now it's looking like it's the cam. I have 2 more cams, both the same number, 1800518601, both with 86 on the back. The lobes on the two spares look a lot better than the one in the car which looks worn. I quick check with a micrometer shows that the one in the car is almost a millimeter shorter than the other two, plus there's a fair bit of wear showing on the lobes. Ok, how about oiling; - yes, the tube still flows oil, made a rather large mess proving it.
How difficult is it to shove one of these other cams in? Would it even be worth a try? Am I missing something obvious here?
Do I have to take the towers off? Or can I just release the rockers, turn out the bolt holding the timing chain gear and carefully waddle it out? Obviously, I'd measure off the journals before installing one of the others to see if it won't knock.
Now, before anyone jumps down my throat, I do intend to rebuild this motor completely, just not at this point. I still have no idea where to source pistons, rings, valves, etc. yet. I just want to get this thing running again so I can get some other issues attended to. The engine has 70K miles on it, and it appears to have spent a lot of time sitting, there's quite a bit of rust on the underside of that cam.
In case anyone is interested, the car is a 1966 W111 230S with a 1967 250S motor in it, standard transmission. The body is completely rust free so I'd like to keep this car.