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Fuel Pump Relay or CIS-E Unit??
I have a 1990 560SEL with a warm start problem thats also expanded into short hickups while driving. Narrowing it down with a friend, here is what's happening:
It appears to be temperature dependent since I've had no cold starting problems. I think the cause must be either an intermittent fault in the fuel pump relay or the CIS-E control unit sending a "fuel cut" signal to the relay when it shouldn't. The CIS-E control unit unit has a temp sensor input which is why I'm including that as a suspect. I don't think it is tach signal related, because my tach still works when the motor cuts out on the highway. Please, any ideas or suggestions?
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Dave 2002 Audi S6 Avant 1983 300D 1984 300D (sold) 1990 560SEL (sold) Last edited by biobenz617; 12-01-2007 at 03:55 PM. |
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Have you tried jumpering the fuel pump relay...? That would be my first (and least expensive!) test.
Jonathan
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Blue Ridge Mercedes Jonathan Hodgman http://www.blueridgemb.com/ Enthusiast Service, Restoration & Tuning. Follow Us on Facebook! Located in the Atlanta area Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines. Mercedes Repair Atlanta |
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You mean jumper it when I'm having problems? That would take the relay and the CIS-E control unit out of the equation, so I still wouldn't know what the root cause is. The fuel pumps always run for at least 2 seconds when I switch the ignition off then on again, but they are shut off while the engine is cranking when the problem happens.
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Dave 2002 Audi S6 Avant 1983 300D 1984 300D (sold) 1990 560SEL (sold) |
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Well, no. It will Only take the fuel pump relay out of the equation which I'm wagering is the issue.
Jonathan
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Blue Ridge Mercedes Jonathan Hodgman http://www.blueridgemb.com/ Enthusiast Service, Restoration & Tuning. Follow Us on Facebook! Located in the Atlanta area Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines. Mercedes Repair Atlanta |
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Quote:
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1993 190E 2.3 2001 SLK230 1971 LS5 (454) Corvette Convertible |
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Ah, you mean jumper the fuel pumps when I have the problem
I measured power consumption of the pumps (including the O2 sensor heater) at 7.7 A, within the 6-10 A spec. They've been noisy for over 35k since the car was purchased. At this point I'm also confident it is the relay. I'll pull the relay and open it up before I spring for a new one. Thanks for the solder example pics
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Dave 2002 Audi S6 Avant 1983 300D 1984 300D (sold) 1990 560SEL (sold) |
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No solder joints were bad, but from damage to the plastic housing, it had been opened up at least once before. I just bought a new one and now its all good
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Dave 2002 Audi S6 Avant 1983 300D 1984 300D (sold) 1990 560SEL (sold) |
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Glad you got it sorted...My only Hope is that the unit you purchased was either Genuine new, or a Beckman rebuild. The KAE's are Very poorly made (China) and do not hold up over time.
Jonathan
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Blue Ridge Mercedes Jonathan Hodgman http://www.blueridgemb.com/ Enthusiast Service, Restoration & Tuning. Follow Us on Facebook! Located in the Atlanta area Specializing in all pre and post merger AMG's including Hammers and DOHC M117 engines. Mercedes Repair Atlanta |
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I can't remember, but it was probably the cheap one from worldpac. It did seem like a lower quality part and I barely got it to fit in the plastic holder slot. It doesn't matter though, since the car's days are numbered by windshield frame rust
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Dave 2002 Audi S6 Avant 1983 300D 1984 300D (sold) 1990 560SEL (sold) |
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