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Fuel Pump Relay?
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Posted 8/12/2019 3:25 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: 9804
5000
Fuel Pump Relay?

Does anyone have any thoughts or recommendations on this request from a member in another country?

I still have my green 2000 MB (Puch) G500 Cabriolet. I don't know if you can help me. After 12 years of owning my G, yesterday was the first time it "let me in the street" . When for jogging, when finish started the car drive for 5 minutes and it went off (dead) had all lights on panel, had ignition, started, but did not start, after 5 minutes, tried again, it DID start and arrive home. My diagnosis is Fuel Pump relay, because the fuel pump is new 50,000 Kilometers (31,250 Miles)., The problem is, that I can not find the location of the relay, have no manual that say's so , not even the fuse and relay chart, no one knows in the USA because my G is European version, 2 door Convertible,. etc. Can you give a clue were to look for or if somebody has a diagram for a 2000 4632061X.... Thank you


Any chance this could be a bad CPS or K40 Relay?
#240877
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Posted 8/12/2019 9:21 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: Fuel Pump Relay?

My first place to check would be the k40 relay's solder joints.

However, preventive maintenance says to replace both and see if the K40 can be resoldered.

#240882 - in reply to #240877
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Posted 8/13/2019 6:55 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: 9804
5000
RE: Fuel Pump Relay?

J.R. - 8/12/2019 9:21 PM

My first place to check would be the k40 relay's solder joints.

However, preventive maintenance says to replace both and see if the K40 can be resoldered.



My thoughts, too. Thanks!
#240885 - in reply to #240882
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Posted 8/13/2019 12:24 PM
otiswesty
Expert




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

That must be Freddy with the bright green Cab
I agree the K40 is the likely culprit, I carry a spare for that reason. It would be good idea to alsodo the CPS as you mentioned.
#240886 - in reply to #240885
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Posted 8/17/2019 4:55 AM
David J. Pearson
Regular




Date registered: Apr 2006
Location: Cumbria, UK
Vehicle(s): 230 GES,G500 Classic,300TE 24, 200 CLK Cab. 73 TR6
Posts: 87
50
Re: Fuel Pump Relay?

Had exactly this problem last year. Couldn't trace or replicate the problem at shop as would start every time for them, but thought it was fuel pump. Fitted new one, four or five months later, exactly the same problem. Fitting spare k40 fixed it. Ordered new one and been ok ever since.


Edited by David J. Pearson 8/17/2019 5:01 AM
#240907 - in reply to #240882
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Posted 9/2/2019 9:39 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: 9804
5000
Deteriorated K40 Relay

Attached are some shots of the inside of the K40 Relay questioned regarding the fuel pump relay in the original post.

I would certainly say they these messy solder joints are most certainly the cause of the problem. Anyone agree or disagree?

I've advised him to wire brush away the crap, re-solder any joints that look bad, buy a new one and use the refurbished one as a spare. Agree? Disagree?





(20190831_163337_DxO.jpg)



(20190831_163401_DxO.jpg)



Attachments
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Attachments 20190831_163337_DxO.jpg (128KB - 0 downloads)
Attachments 20190831_163401_DxO.jpg (117KB - 1 downloads)
#240942 - in reply to #240877
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Posted 9/2/2019 11:40 AM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3463
2000
RE: Deteriorated K40 Relay

I just noticed that this problem is on a V8 engine.  The CPS gets cooked in that configuration.  That would tilt the guesses towards CPS.  And they are really cheap to replace, so replace it and see if the problem goes away.  Then look at the K40.

As to the K40: Messy isn't the issue, that brown stuff is just flux that wasn't completely washed off.  The problem is cracks around the pins.  To see those you need a magnifying glass.  Much easier to just touch up (reflow) each solder joint, with an emphasis on the larger pins.  There is a second failure mode where the relay coils develop an intermittent connection.  That isn't fixable. 

#240943 - in reply to #240942
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Posted 9/2/2019 2:22 PM
ewalberg
Expert




Date registered: Apr 2006
Location: Past: San Francisco. Present: Germany
Vehicle(s): 2000 g500
Posts: 1872
1000
Re: Fuel Pump Relay?

If I recall from a long time ago, the crankshaft position sensor is most Iikely the problem if the vehicle starts and runs if started cold but won't start when hot. And that you could theoretically duplicate the problem by just putting a heat gun to the CPS. I had to change mine out, but it never stopped running once started. That's different.
#240944 - in reply to #240943
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Posted 9/2/2019 7:30 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: 9804
5000
RE: Deteriorated K40 Relay

Alan, All that flux between the contacts could be causing some stray currents.

He's ordered a K40 Relay. Hopefully, that will solve his problem.
#240945 - in reply to #240943
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Posted 9/2/2019 10:10 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: Fuel Pump Relay?

When I compare his board to my failed board, it almost looks like someone has already gone around and touched up the joints.

Here is a pic of my solder connections from my first K40 failure. I would still be suspicious of his K40 and the CPS.

Edited by J.R. 9/3/2019 12:03 PM




(k40-3.jpg)



(k40-2.jpg)



Attachments
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Attachments k40-3.jpg (31KB - 0 downloads)
Attachments k40-2.jpg (32KB - 0 downloads)
#240946 - in reply to #240877
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Posted 9/3/2019 1:56 PM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3463
2000
RE: Deteriorated K40 Relay

Flux isn't an issue.  Even if it were conductive it would be in the pico-amp range, not even enough to trigger a false relay actuation.  The problem with the K40 is their insistence on saving $0.50 on the board by making it single sided with unplated holes.  This leads to stress at the large solder joints as they heat and cool.  The stress eventually fractures the solder joint and prevents current from getting to the ECU (or sometimes ABS).

Those rough volcano shapes shown in the picture are a result of localized heating that occurs as the joint is deteriorating.  Temps have to get up to 300C for that stage to happen.



Edited by AlanMcR 9/3/2019 9:31 PM
#240948 - in reply to #240945
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Posted 9/7/2019 3:09 PM
David J. Pearson
Regular




Date registered: Apr 2006
Location: Cumbria, UK
Vehicle(s): 230 GES,G500 Classic,300TE 24, 200 CLK Cab. 73 TR6
Posts: 87
50
RE: Deteriorated K40 Relay

Looks like flux to me too. When soldering I always clean off excess flux with a cotton bud dipped in alcohol. I was always led to believe it's corrosive if left on.
Just to reiterate, on fitting my spare K40 that I carry with me, it started immediately after previously refusing to do so. CPS was changed afterwards as a precaution. With mine it was a case of it started from cold, ran for a minute or so, momentarily faltered, stopped and would not restart.
My old K40 is on my bench. I'll have to have a look inside. It was last swapped out as a precaution in 2009.
David
#240958 - in reply to #240948
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Posted 9/12/2019 7:36 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: 9804
5000
RE: Fuel Pump Relay?

A new K40 Relay did not fix the problem. With the new K40, the engine ran for 10 minutes and died.

I suggested that he replace his CPS next.
#240977 - in reply to #240877
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Posted 9/13/2019 1:43 PM
otiswesty
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Date registered: Jun 2007
Location: Portland, Oregon
Vehicle(s): G500
Posts: 2714
2000
Re: Fuel Pump Relay?

Good call on the CPS next. It's also a good idea to carry a spare K40 relay on this generation G500. So that is a plus to have.
#240989 - in reply to #240977
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Posted 9/14/2019 12:53 PM
FredyG
Regular




Date registered: Oct 2007
Location: Venezuela
Vehicle(s): 1993 Defender, 96 Camel Trophy, 2000 G500 Cabrio
Posts: 78
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Re: Fuel Pump Relay?

Thank you guys for your good suggestions and you were right, otiswesty, Its me Fredy. Dutch is doing an excellent job helping me in solving this electrical issue Thank you Dutch. As I said, my diagnosis is a fuel relay, but I haven't found it yet and I don't think its behind the center console. Any way I order one.... also order the Crank Shaft Position sensor, now waiting until its arrival. This is a trial and error thing. Being an 2000 European version of a G500 doesn't have much electronics, just minimal. So , I'll keep you guys posted as I install the CPS start the vehicle and see what happens. TY PS. change the K40 and same thing.



(K 40 new and old resized.jpg)



(New K40 Installed.jpg)



Attachments
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Attachments K 40 new and old resized.jpg (165KB - 0 downloads)
Attachments New K40 Installed.jpg (175KB - 0 downloads)
#240990 - in reply to #240989
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Posted 9/15/2019 7:54 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: 9804
5000
Re: Fuel Pump Relay?

Fredy,

Glad to see that you made it back over here. I feel quite certain that a new CPS will solve your problem.

Please keep us posted. Thanks.
#240991 - in reply to #240990
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