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Old 01-26-2009, 06:01 PM
Registered User
Join Date: Jan 2009
Posts: 5
560sel won't start unless I pull the fuel pump relay?

Hi, I've been tracking down various problems with the fuel system and I think it's almost figured out. I replaced the fuel distributor with a spare and am getting pressure to it, and the piston is not stuck. Everything seems to be normal, and I adjusted the mixture screw so it should at least start. When I try to start it, it runs very rough on maybe 4 cylinders or won't start at all, but if I pull the fuel pump relay out it will start and run perfectly for a few seconds.. Could this be a fpr issue? I don't know what else to check, any help is greatly appreciated.
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Old 01-27-2009, 08:09 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Fuel pressure too high??? possibly the return is blocked OR regulator not allowing pressure to hold 100psi?

Try removing the return line from the A/C line.
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Old 01-28-2009, 05:54 PM
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Join Date: Jan 2009
Posts: 5
Thanks for the reply. I tried that, no change. I guess the next step is to get a fuel pressure gauge to check the regulator. Any ideas on a good one?
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Old 01-30-2009, 10:18 AM
david s poole
Join Date: Mar 2005
Location: dallas
Posts: 1,822
if the car runs fine for a few secs after you pull the fuel pump relay i would guess that you have the mixture set very check pull fuel relay and jump terminals 87&30.this will run pumps with no ignition on.if you are rich you should be able to hear fuel from injectors[high pitched whine].back off [counterclockwise]adjustment on 3mm until noise just stops.then replace relay and start car.if you hear no noise then go the opposite[clockwise] until just before you hear the noise.this gives you a good starting point from which to adjust your fuel setting.
David S Poole
European Performance
Dallas, TX

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
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2000 Mercedes Benz C280
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Old 02-11-2009, 07:52 PM
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Join Date: Jan 2009
Posts: 5
Thanks for the idea, it worked. Got the car started, need to get a multimeter to check the duty cycle. It's doing something weird though, if I go around a turn and step on the gas the car stalls. It starts back up after cranking it for ~10 seconds, it's like the fuel is really low or something but there's plenty of gas in the tank. Anybody have any ideas? I miss driving
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