72 250c rebuilt carbs, new pertronix, new coil, new fuel pump. Car starts and runs fine. Five minutes into my drive the car looses power and stalls. at times i can shift into neutral and rev it through the storm. Or sometimes it starts to bunny hop like mad. i pull the car over wait a minute and restart the car. and everything is fine again like nothing ever happened. No problem are evident again as long as the car is warm. Let the car sit for several hours and it happens again as the engine warms up somewhere between the cold and hot stage. I think the problem is fuel related but it is hard to check on the side of the road.

has this ever happened to anyone?

any solutions?

choke?
fuel cut off solenoids?
Temp sensor relay?

Take a look at the manifold heat riser valves. They should operate freely. When they work properly they will heat the carb bases to help with the warm-up. You will need to keep after these devils because if they stick, which is very common, they can over heat the carbs and create stalling on hot days. Also check the flex pipe from the exhaust manifold to the air filter neck. This helps keep a constant air temperature to the carbs so the lean jetting can operate reasonably well.

This is a smogged motor so it operates very lean. Both these heating features are necessary to keep driveability fairly reasonable. Back in '72 most cars suffered from some of these symptoms to one degree or another. Mercedes was no exception. Fuel injection cured most of the smog-carb driveability problems but gave us a whole new layer of technical issues to deal with all the inter-dependent sensors and systems.

Good luck,

230/8

Sticky chokes, kinda like they need kicking to get em open at one point of the warmup process? Those heat flaps always struck me as Wintertime gear, not necessarily important this time of year. And if the manifold butterfly valve gets frozen diverting hot air to carbs 24/7 then you risk warping the carbs. Rare to find em fully functional after all these years. After they freeze up lots of people just hammer them into position so they dont roast the zeniths.

I'm not the smartest guy in the world when it comes to ignition systems, but am aware that coils and condensers are heat sensitive too - alot of high-tech ignition gear has its own heat sinks. Have you spoken with Petronix about this?

I would make sure the chokes are opening correctly (watch them), and that the choke pull-downs are operating correctly. Test them with a Mityvac.

If that doesn't help, I would disconnect and plug the dist vacuum lines and see if that fixes it. If it does, something is wrong with the gizmos that advance and retard the timing - probably you are getting way retarded at middle temps for some reason.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe