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#1
12-09-2002, 11:05 PM
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fuel issues:runs great for 4 minutes then...
Hey!
You guys have been an amazing resource and I'm in need of advice yet again. My 72 280se has run just once before (sat for ten years) and it chugged especially up hills. You suggested I replace the fuel filter, put in high octane gas and add a supplement (Chevron Techron). Well I did it all and then started it up. Ran well for 4 minutes -- lots of power, smooth etc. Then once it warmed up it started to go back to chugging and stalling. What's up. After about 15 minutes of driving and 10 minutes of idling the radiator cap spewed coolant (the cap had no inside mechanism -- one is on order). One final odd note is that it would periodically idle very high without a foot on the accelerator. When I had a friend revving it, the accelerator cable didn't seem to move at all. Any help is greatly appreciated. 
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#3
12-11-2002, 07:09 PM
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a couple of words...
valve adjustment.
my 250 did the same thing, although a little longer than 4 min...had a tune-up and the valves adjusted and now she purrs. as far as a high idle...i've had the same issues on a few cars, simple injector or carb adjustment, and it was fixed.
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#4
12-11-2002, 07:52 PM
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Probably the idle mixture is out of spec, so that it won't run warm. Sounds as if you are going way lean warmed up.
Check for vacuum leaks, and you need to lubricate the throttle linkage by spraying some white lithium grease in all the joints. DO NOT REMOVE THE LINKAGE TO CLEAN IT, you will have to re-calibrate the pump and linkage. I cannot emphasize this enough, the adjustments are critical to mixture control. Very precise and fiddly, and just taking it apart and putting it back together can get it out of sorts. There is a reason MB changed to electronic injection after 1972! If lubing everything and making sure the linkage is moving correctly doesn't fix it, you will need a manual or an experience mechanic. Under no circumstances should you fiddle with the little brass wheel on the back of the pump with the engine running, you will have to have the pump repaired! Mixture adjustments MUST be done with the engine stationary -- you are turning a screw on the the governor, and the governor spins...... Check for a vacuum leak around the intake hot, too, or binding linkage at the air horn. A broken cold start valve could be a problem, so could a defective or improperly adjusted cold enrichment device. And don't neglect the possibility that the valves are adjusted too tight -- they will stay open when the get hot, giving you all sorts of trouble! Keep us posted! Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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#5
12-12-2002, 07:46 PM
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Steamroller:
I checked with my local benz guru today, and he said if the linkage is sticking, the auxillary air valve (fast idle valve) is definitely stuck open, and this will cause lean running when the engine warms up. Non-repairable, you will need to replace it. It's on the block under the manifold, probably a pain to get to. You cannot adjust the pump to compensate, either. Good luck! Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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