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2000 G500 Fuel Pump Relay
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Posted 10/8/2019 8:07 AM
DUTCH
Administrator Doppelgänger




Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2000 G500 NMLE,2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9806
5000
2000 G500 Fuel Pump Relay

Is there a fuel pump relay for the 2000 G500? I was of the opinion that it was incorporated in the K40 Relay. If there is a separate relay for the fuel pump, does anyone have an idea where it is physically located?

Asking for our friend in Venezuela.
#241075
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Author
Posted 10/11/2019 10:09 AM
J.R.
Elite Veteran




Date registered: Apr 2006
Location: Southern Maryland
Vehicle(s): 00 G500, 09 911 4S, 11 Cayenne S, 86 280GE (sold)
Posts: 755
500
RE: 2000 G500 Fuel Pump Relay

The fuel pump relay is one of several relays built into the K40. There are no other relays directly related to the fuel pump.

The K40, used in several models of Mercedes. Some folks have even gone so far as to replace the offending relay on the K40 circuit board: https://www.pelicanparts.com/techarticles/Mercedes-SLK230/68-ELEC-K4... "Comments: I opened the K40 like you have shown in the photo. Took it to an electronic repairman. He hook up a 9V and 1.5V battery and tested the relays. The fuel pump replay has no response. He took the relay out and found the hairline copper wire in the coil is broken. He replaced the relay with a spare one he has old part from split type air conditioner circuit and hold it in place with some thick silicone glue. The whole troubleshooting + replace relay need less than one hour. I put the K40 back into the car and fuel pump working and start up no problem.
He also found some minor cracks on the wields. Lead-free stuff won't last, he said. Fix them as well."
#241091 - in reply to #241075
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Author
Posted 10/11/2019 10:47 AM
otiswesty
Expert




Date registered: Jun 2007
Location: Portland, Oregon
Vehicle(s): G500
Posts: 2714
2000
Re: 2000 G500 Fuel Pump Relay

If the K40 is good, maybe he needs to try replacing the fuel pump itself?
#241092 - in reply to #241091
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Author
Posted 10/11/2019 8:01 PM
DUTCH
Administrator Doppelgänger




Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2000 G500 NMLE,2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9806
5000
RE: 2000 G500 Fuel Pump Relay

J.R. - 10/11/2019 10:09 AM

The fuel pump relay is one of several relays built into the K40. There are no other relays directly related to the fuel pump.

The K40, used in several models of Mercedes. Some folks have even gone so far as to replace the offending relay on the K40 circuit board: https://www.pelicanparts.com/techarticles/Mercedes-SLK230/68-ELEC-K4... "Comments: I opened the K40 like you have shown in the photo. Took it to an electronic repairman. He hook up a 9V and 1.5V battery and tested the relays. The fuel pump replay has no response. He took the relay out and found the hairline copper wire in the coil is broken. He replaced the relay with a spare one he has old part from split type air conditioner circuit and hold it in place with some thick silicone glue. The whole troubleshooting + replace relay need less than one hour. I put the K40 back into the car and fuel pump working and start up no problem.
He also found some minor cracks on the wields. Lead-free stuff won't last, he said. Fix them as well."


I copied and sent this to the menber in Venzuela. For some reason he doesn't want to accept that the relay is in the K40. This in spite of the fact I sent him the schematic.
#241094 - in reply to #241091
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Author
Posted 10/11/2019 8:24 PM
J.R.
Elite Veteran




Date registered: Apr 2006
Location: Southern Maryland
Vehicle(s): 00 G500, 09 911 4S, 11 Cayenne S, 86 280GE (sold)
Posts: 755
500
RE: 2000 G500 Fuel Pump Relay

When my first one failed, I had to wrap my head around it and then the proof was when I resoldered that one relay, the fuel pump started cycling normally during the start sequence.
#241095 - in reply to #241075
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Posted 10/12/2019 10:17 AM
paulunm
Regular


Date registered: Jan 2015
Location: Los Angeles
Vehicle(s): 2000 G500
Posts: 86
50
RE: 2000 G500 Fuel Pump Relay

DUTCH - 10/11/2019 5:01 PM

J.R. - 10/11/2019 10:09 AM

The fuel pump relay is one of several relays built into the K40. There are no other relays directly related to the fuel pump.

The K40, used in several models of Mercedes. Some folks have even gone so far as to replace the offending relay on the K40 circuit board: https://www.pelicanparts.com/techarticles/Mercedes-SLK230/68-ELEC-K4... "Comments: I opened the K40 like you have shown in the photo. Took it to an electronic repairman. He hook up a 9V and 1.5V battery and tested the relays. The fuel pump replay has no response. He took the relay out and found the hairline copper wire in the coil is broken. He replaced the relay with a spare one he has old part from split type air conditioner circuit and hold it in place with some thick silicone glue. The whole troubleshooting + replace relay need less than one hour. I put the K40 back into the car and fuel pump working and start up no problem.
He also found some minor cracks on the wields. Lead-free stuff won't last, he said. Fix them as well."


I copied and sent this to the menber in Venzuela. For some reason he doesn't want to accept that the relay is in the K40. This in spite of the fact I sent him the schematic.


He already replaced the K40 with new though, correct?
#241097 - in reply to #241094
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Author
Posted 10/12/2019 10:28 AM
DUTCH
Administrator Doppelgänger




Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2000 G500 NMLE,2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9806
5000
RE: 2000 G500 Fuel Pump Relay

paulunm - 10/12/2019 10:17 AM

He already replaced the K40 with new though, correct?


Yes. It did no good, but replacing the CPS looks like it might have fixed it.
#241098 - in reply to #241097
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Posted 10/14/2019 12:25 AM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3464
2000
RE: 2000 G500 Fuel Pump Relay

Basically, the K40 has a terrible printed circuit board design (yes, I am actually a professional).  A proper resolder job will hold it for another decade.  There are some tricky copper reinforcements one can add, but absent some practice people are likely to just make it worse.

 

The CPS was just put in a poorly chosen location next to the left side exhaust header.  It wasn't designed for that kind of heat.   Replace if in doubt, and carry a spare.

#241101 - in reply to #241095
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