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My 500 with 72,000 miles stalls after driving awhile, starts right away, but then stalls again after a bit. Only stalls while driving. Cold starts right up, idles well & revs up fine, in park. Warms to 80C in park and runs and revs up fine. But drive for a bit and I can here the fuel pump(s) wine a little and engine drops rpm and stalls. Read on forum thread that the pump relay could be the problem, so got a rebuilt from ProgRama Inc, because couldn't find a new one that would fit socket on a Euro, but does the same thing. New pumps, filter, accumulator and tank screen clean last year at local independent shop with 4 Yelp stars. The mechanic said he used Bosch parts, but they are not, and won't back his work, so he is done. Overload relay checks out, gas is good, vac lines look good, air filter good. Forum post says it might be the crankshaft position sensor, but it is hard to change out. Anyone have any thoughts before I try changing out that sensor or change out the pumps with Bosch or try another FPR. Or does anyone know of a good independent mechanic in the Madison, WI area. Hate to take it to the local dealer$$$$$$ when they know it's your toy. Much appreciated.
 

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Don't know if this will be helpful or not, but my 280SL occasionally suffered from hesitation and then started stalling while driving. Eventually it refused to start at all and ended up on a hook being towed to my indie. Luckily it had got me home previously and the pick up was made from my garage. In the meantime I had replaced the fuel pump relay, plug wires, rotor and distributor cap with no apparent result other than a severe drainage of cash. Once it had failed to start the indie was able to check everything out, as previously on test drives it had always performed beautifully. They quickly discovered that the little booger causing all the trouble and ruining my summer was the ignition module. They recommended replacing this with an after market unit which they claimed was not only technically improved over the OEM part but also 1/3rd of the price. Hopefully they're right. I get the car back tomorrow with at least some summer left for reliable cruising.
 

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I can testify that my 83 500SL and 85 380SE cars have run perfectly for years on the German aftermarket ignition modules, much smaller and cheaper than the old OEM units (about $50 each). They're also very easy to install.
 

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I had a similar problem when I first bought my car. The previous owner's mechanic installed a cheap off brand fuel pump. The car would intermittently lose power and limp along at 10 mph with the fuel pump louldly whining but it never stalled. If I shut the car off for a few minutes the pump would stop whining and the power was back. I installed a Bosch fuel pump and haven't had any problems since.
 

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Discussion Starter #6
How can I test the resistance of the CPS, and what would the reading be? Which wire to the EZL would it be. Thanks
 

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Discussion Starter #8
CPS tested fine , 450 ohms cold, 1000 ohms hot. So installed OEM Bosch fuel pumps and replaced the FPR with a rebuilt from Programma. Runs fine now.....or at least so far. Thanks all for your input.
 
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