Confirming a Fuel pump problem
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Joined: Apr 2019
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Mercedes W123
Confirming a Fuel pump problem
I have a 1981 W123 with the M102 fuel injected engine
So the problem is I go to start the car prime the fuel pump and start it
It starts fine and runs fine but after 10 or 15 minutes of driving it starts getting weaker and have trouble accelerating it idles fine but won't accelerate so what I found out was that if I stopped the engine and primed the fuel pump a few times and then started the car it starts fine and runs fine and keep repeating that action every 10 or 15 minutes of driving
*I've replaced the fuel injectors with new Bosch ones and I've replaced the fuel filter as well*
I suspect the fuel pump or the fuel pressure regulator but I need some confirmation on that or a way to test the fuel pump pressure
Thank you all in advance
So the problem is I go to start the car prime the fuel pump and start it
It starts fine and runs fine but after 10 or 15 minutes of driving it starts getting weaker and have trouble accelerating it idles fine but won't accelerate so what I found out was that if I stopped the engine and primed the fuel pump a few times and then started the car it starts fine and runs fine and keep repeating that action every 10 or 15 minutes of driving
*I've replaced the fuel injectors with new Bosch ones and I've replaced the fuel filter as well*
I suspect the fuel pump or the fuel pressure regulator but I need some confirmation on that or a way to test the fuel pump pressure
Thank you all in advance
Junior Member
Joined: Jul 2006
Posts: 63
Likes: 4
From: Sunny So. Cal. , land of RUST FREE cars !
'80 300CD , '81 240D , more..
Fuel Starvation
Interesting .
There's a screen inside the fuel tank that occasionally gets clogged up, a serious PIA to remove and clean .
There's also a fuel pump safety relay that cuts off the fuel pump's power if it thinks the engine has stopped .
I don't know where it is on a W123 but they caused us lods of problems on old VW's back in the day......
I hope you get this fixed .
There's a screen inside the fuel tank that occasionally gets clogged up, a serious PIA to remove and clean .
There's also a fuel pump safety relay that cuts off the fuel pump's power if it thinks the engine has stopped .
I don't know where it is on a W123 but they caused us lods of problems on old VW's back in the day......
I hope you get this fixed .
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Joined: May 2022
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2006 cls55 amg
2006 cls55 AMG has the same problem and shuts off
My son has a 2006 cls55 AMG and it is having the same issue where it will start for about 10 seconds and then shuts off. Read it might be the cps so I replaced the cam position sensor and the crank position sensor. Not the fix. Had a friend come over to help diagnose and seems to be a fuel issue. Fuel relays click when key turns on so they seem fine. Opened the back seat and the fuel pump turns on and right before it shuts off, he said that it feels like it stops pumping fuel. Sprayed starting fluid into the intake and didn’t shut off. So now it seems to be confirmed as a fuel issue but not sure where to go from here. Do I replace the fuel pump and if so, the drivers side or the passenger side. Or do I start somewhere else because clearly it’s not getting fuel
