carigmbamg

Ok, remodel pretty much done, more time to work on the car. Looking to see if there is voltage at the pump on the driver side, but don't have wiring diagram to determine which wires are which. Can anyone give me the wiring diagrams for the fuel systems so that I can try to figure out the problem?
Thanks.

carigmbamg

Maybe a better question to ask is what service manual do you guys recommend? I will need electrical diagrams to diagnose the fuel problems. I am looking at the "2001 - 2005 Mercedes-Benz 203 C-Class Chassis Star Service Manual Library" from mercedesmanuals.com.

Kansizzle

If you smelled fuel it could be your fuel sending unit, located under rear seat drivers side. Pop the seat out and remove the access panel, if u see fuel when you remove the panel you've found your problem. I believe there is an upgrade for the FSU, you can only get it from MB dealer and runs about $450.

carigmbamg

Back again, remodel done, sick two weeks and played with the car after looking at the fuel system electrical diagram.
I applied 12v directly to the fuel pump with an external battery and was able to run the car fine. I measure ~-10 volts at the connector. Not sure why it is negative, any clues? Applying the correct polarity to the pump runs fine. I need to run 12v across the relay to see if it works. What else is in the system that could be preventing this from running?

lizardjack

Connector on the rear SAM.

carigmbamg

Relay is fine and replacing the fuel filter allows the car to start, but flow is not enough to continue to run. Using external battery and driving the pump ground with +12v and pump driver connector with the ground and the car runs fine and drives. Connectors on the back of the rear SAM all tight. Still perplexed.

lizardjack

It is not about being tight or not. Disconnect the one that goes to the pump and you will see one of the pins/sockets melted.

W203Ramos

do you have a crystal ball of some sort....you diagnosed the prob spot on I stand corrected re the CPS. again, awsome diagnosis of the problem.

John

lizardjack

My pleasure)

carigmbamg

LizardJack, you were correct, removed the rear SAM and the green/black (fuel pump supply) was melted on the socket, providing about 4.5M ohms resistance in the wire and accounting for the drop in voltage to the fuel pump. The SAM looks fine but the connector on the fuel pump wire harness is pretty fried. Do you suggest a whole new harness or fixing the wire with a new connector? Any online suggestions for a new harness? Thanks.

lizardjack

You have a few options there:
Change a connector
Clean an old one
Solder the wire directly to the SAM unit.
If I were you I'd also check the connector inside the fuel tank (right side)
Better safe than sorry.

Charleserion

I have not put the pressure in the needle and without pressure, but the vehicle at the same time. Is the fuel rail to remain under pressure? If this is the case, I think that the fuel is the problem. I check the voltage at the pump and the continuity of the pumps.

lizardjack

W203Ramos

LOL

carigmbamg

I was able to pull the wire and put another connector on it and get it all plugged back in and the car is running. I'm wondering if one of the pumps is out as the massive acceleration is missing. Thanks for all the help.

lizardjack

Pull out the pump, check the connector, check the primary filter (inside tank), replace the main filter (outside). The blockage of the last two could result in a high current on the fuel pumps and connector failure.

carigmbamg

Problem fixed, I put back another relay in the wrong spot that was shutting down the super charger. Car is back! Thanks for all the help, now I can start work on the old '85 BMW 635 CSi.

lizardjack

Good luck)

sandrajolly

It could be multi things could be spark plugs, fuel pump, fuel filter could be air in the lines etc. etc. With out really seeing what the car is doing it will be hard to diagnose. You can place a clip on you tube for people to help you out and diagnose the problem.

lizardjack

late dude))