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Warm Up Regulator diy kit vs Pro refurb

Started by SteveDuNord, 24 June 2023, 03:55 PM

revilla

Hi Steve,

Before you go into all that effort.
Through several experiences when my CP=SP it ended up being the little oring inside the hex nut chamber inside the fuel pressure regulator. The one where you need to remove the famous clip that holds the spring to the main shaft. What I have seen is that oring is either loose out of its round slot or broken. When that happens the flow from the return line coming from the WUR gets blocked/clogged giving the CP=SP condition. It makes total sense. It can certainly be misleading to straight tackle the WUR. I've been there. But Your WUR is probably ok. Yes, it makes sense to recondition it with the kit and cleaning the aluminum cell plate. Yes, it makes sense checking your return line. Yes, it makes sense cleaning the screens (fuel input at FD, at fuel tank and the one in the WUR). Citric acid is perfect to dissolve all that brown/orange dust. Ultrasound can be used to for optimal results. I wouldn't pay a company big money and/or wait 5 weeks to get a refurbished WUR. No way.
Chances are high that's your problem based on my own diagnosis with mine kjetronic systems. But of course it could be a combination of things.
Good luck and keep us posted please.
Robert
W116 1977 280SEL & 1979 280SE
[img width=150 height=100][url="http://revillagodfroy.com/MB%201977%20280%20SEL/album/thumbs/IMG_0371.JPG"]http://revillagodfroy.com/MB%201977%20280%20SEL/album/thumbs/IMG_0371.JPG[/url][/img]

SteveDuNord

Quote from: revilla on 02 July 2023, 08:50 AMHi Steve,

Before you go into all that effort.
Through several experiences when my CP=SP it ended up being the little oring inside the hex nut chamber inside the fuel pressure regulator. The one where you need to remove the famous clip that holds the spring to the main shaft. What I have seen is that oring is either loose out of its round slot or broken. When that happens the flow from the return line coming from the WUR gets blocked/clogged giving the CP=SP condition. It makes total sense. It can certainly be misleading to straight tackle the WUR. I've been there. But Your WUR is probably ok. Yes, it makes sense to recondition it with the kit and cleaning the aluminum cell plate. Yes, it makes sense checking your return line. Yes, it makes sense cleaning the screens (fuel input at FD, at fuel tank and the one in the WUR). Citric acid is perfect to dissolve all that brown/orange dust. Ultrasound can be used to for optimal results. I wouldn't pay a company big money and/or wait 5 weeks to get a refurbished WUR. No way.
Chances are high that's your problem based on my own diagnosis with mine kjetronic systems. But of course it could be a combination of things.
Good luck and keep us posted please.

I benefited from this experience through the forum search function and recently replaced the o rings on the PR. Unfortunately for me, the problem persists. It could, however, have helped with my original issue which was warm start related. We'll see.
Either way I'm happy to have done the job while the air filter was off. :)

The two obvious variables remaining are WUR and Tank strainer. The good thing is that throughout this process I've learned a fair bit, replaced my injectors, a failing fuel pump and filter, serviced the PR, replaced the inlet filter etc. None of which can be a bad thing. 
'77 280se

revilla

I understand. Been there. You can do the following test. Put a rag to absorb the exiting fuel under the 12mm connection of the WUR return line on the side of the FD right to the left of the main return line. Run the pump by disconnecting the FD blue connector (key in position 1 but engine not running). Unscrew the 12mm nut a bit until you see the first drops of fuel. Pressure gage valve open (reading CP). Does your CP go down as you unscrew that nut?
If yes, your problem come actually from the pressure regulator and not your WUR. Check that little oring is still in place. If id and od not correct it will pop out of its slot blocking the 3 holes where the fuel suppose to return to the tank resulting is a high reading of your CP.
If after this test your CP remains high and no fuel exists that line, the problem is your WUR. That test will at least tell you where to focus your efforts.
Good luck.
Ps.: I've heard some of those pressure regulator kits don't have the right oring sizes. Worth checking the little one is still where it supposes to be.
Robert
W116 1977 280SEL & 1979 280SE
[img width=150 height=100][url="http://revillagodfroy.com/MB%201977%20280%20SEL/album/thumbs/IMG_0371.JPG"]http://revillagodfroy.com/MB%201977%20280%20SEL/album/thumbs/IMG_0371.JPG[/url][/img]

SteveDuNord

Quote from: revilla on 03 July 2023, 11:05 AMI understand. Been there. You can do the following test. Put a rag to absorb the exiting fuel under the 12mm connection of the WUR return line on the side of the FD right to the left of the main return line. Run the pump by disconnecting the FD blue connector (key in position 1 but engine not running). Unscrew the 12mm nut a bit until you see the first drops of fuel. Pressure gage valve open (reading CP). Does your CP go down as you unscrew that nut?
If yes, your problem come actually from the pressure regulator and not your WUR. Check that little oring is still in place. If id and od not correct it will pop out of its slot blocking the 3 holes where the fuel suppose to return to the tank resulting is a high reading of your CP.
If after this test your CP remains high and no fuel exists that line, the problem is your WUR. That test will at least tell you where to focus your efforts.
Good luck.
Ps.: I've heard some of those pressure regulator kits don't have the right oring sizes. Worth checking the little one is still where it supposes to be.

I ran the engine for these tests. Here's what I did: unscrewed the PR - little to zero change. Then unscrewed the line going to the WUR (feed or return?) at the FD. Same deal.

Basically nothing I've tried so far has altered the cold CP. It sits around 5.2 bar, same as system pressure. I keep checking that I have the gauge set up correctly but everything seems fine on that front.

For the PR, I just bought some o rings and refitted them with the closest sizes. Seems to be ok.
'77 280se