Mercedes-Benz Forum banner

1 - 20 of 72 Posts

·
Registered
1984 380 sl (currently wkg on 5.0 euro motor swap). 2002 Ford Expedition
Joined
·
821 Posts
Discussion Starter #1
I have read the stickys and searched the forum and I think I have a good basic understanding of the system in theory and I bought the CIS gauge set. To get started I have couple of embarrasingly simple questions (I'm sure many more to follow).

1) I found the fuel pump relay and it is mounted to a bracket behind the glove box. Do I need to unmount it to remove the connector or will the connector just pull off the bottom. It is in a position I can't see.

2) To check pressure at the fuel distributor where do the gauge connections go. I have alldata but the picture is so bad I cant see it. Any one with a picture?

3) As you are facing the engine is the fuel line on the left at the top of the FD what you connect for Control pressure and on the gauge that hose is the one without the shut off valve? where does the other hose connect?

Thanks in advance.
 

·
Registered
1985 380SL; 2004 E320; 2007 GL450
Joined
·
296 Posts
If your fuel pressure gauge is similar to mine (shown in picture 1), then you can do the following:

1. Connect connector A of the fuel pressure gauge to the A port of fuel distributor (show in picture 2).
2. Connect connector B of the fuel pressure gauge to the B port of WRU ( shown in picture 3).
3. Turn on switch C of the fuel gauge.
4. Start your engine. Bleed the gauge briefly by pressing the bleed button (circle D in pic 1) in the gauge. The gauge reading is your control fuel pressure.
5. Turn off switch C of the fuel gauge, The gauge reading is your system fuel pressure.

I did not touch the fuel pump relay when I measured my fuel pressures.

Good luck.
 

Attachments

·
Registered
1984 380 sl (currently wkg on 5.0 euro motor swap). 2002 Ford Expedition
Joined
·
821 Posts
Discussion Starter #3
If your fuel pressure gauge is similar to mine (shown in picture 1), then you can do the following:

1. Connect connector A of the fuel pressure gauge to the A port of fuel distributor (show in picture 2).
2. Connect connector B of the fuel pressure gauge to the B port of WRU ( shown in picture 3).
3. Turn on switch C of the fuel gauge.
4. Start your engine. Bleed the gauge briefly by pressing the bleed button (circle D in pic 1) in the gauge. The gauge reading is your control fuel pressure.
5. Turn off switch C of the fuel gauge, The gauge reading is your system fuel pressure.

I did not touch the fuel pump relay when I measured my fuel pressures.


Good luck.
I cant tell you how much I appreciate the info and the pics. My gauge is the same one. Thanks again.
 

·
Registered
1980 450SL & 1988 560SL
Joined
·
1,667 Posts
Be sure to start with a cold engine and watch the pressure as it warms up. Low #'s = rich and higher #'s = leaner.
 

·
Registered
1980 450SL & 1988 560SL
Joined
·
1,667 Posts
I would have to look at the book to give the correct #'s. But what I mean is the bar pressure #'s on the guage.
 

·
Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
·
9,733 Posts
Good post and great reply with pictures. I nominate for the Encyclopedia.
 

·
Registered
82 380 SL ; 78 450 SLC ; 84 BMW 533i
Joined
·
263 Posts
Do you have the "How to Tune and Modify Bosch Fuel Injection" book? I thought you mentioned that you downloaded it a while back. If you do then just use the procedure outlined in the book and record your pressures at each step. Then go to the troubleshooting section and use the numbers to match to possible issues. The entire test won't take more than 30 - 45 minutes even with hook up and disconnect times.

I have found many problems using that setup on my MB and BMW's.
 

·
It Is What It Is, Dude
Joined
·
22,839 Posts
Good post and great reply with pictures. I nominate for the Encyclopedia.

Crap. Glad you posted that. I had intended to add this yesterday when I separated the D and K Jet links but forgot. It's there now.

If any of you D-Jet guys have threads you think should be linked, please, let us know.
 

·
Registered
1984 380 sl (currently wkg on 5.0 euro motor swap). 2002 Ford Expedition
Joined
·
821 Posts
Discussion Starter #12
Thanks guys.
Sorry but work has got in the way the last few days. Once you showed me where to hook the gauges up everything makes a lot more sense.

1) system pressure is 74 and flutters a little
2) control pressure is 46
3) As soon as I shut off the car the pressures drop to 0 within 10 seconds
Pinched return line and pressure holds so from what I have read the primary presure control valve is shot. I tried swapping one from a spare FD (did not help) and replacing a few o rings but did not help.

4) Car has no power blows smoke and the plugs are carbon fouled and wet with fuel.
The wur seems to be operating as it should.
5)The car is dumping gas and I think the FD needs rebuilding and the pressure regulator need replacing


Am I at the right conclusion or do I need to look a other things too?

Nascar fan thanks for the post, I am going to print it out also.
 

·
Registered
82 380 SL ; 78 450 SLC ; 84 BMW 533i
Joined
·
263 Posts
Right off the bat your rest pressure is bad so you need either an accumulator or check valve or both, the check valve is so cheap it's worth replacing at the same time. That would not cause the problem you have but it will cause warm start issues.

On your control pressures, what was cold and what was warm? I am guessing the 46 is warm. Either way I believe you are correct and you need a new pressure regulator which you can get pretty easily. Once you get that changed you'll need to adjust the A/F ratio.

I would get a new O2 sensor too since it's probably shot now with that much crud going past it. Don't change it until you replace the pressure regulator though.
 

·
Registered
82 380 SL ; 78 450 SLC ; 84 BMW 533i
Joined
·
263 Posts
Yep sounds like control pressure regulator which is pretty easy to change. Just be aware at the number of shims on the old one since the new one will come with probably more than you need.
 

·
Registered
1984 380 sl (currently wkg on 5.0 euro motor swap). 2002 Ford Expedition
Joined
·
821 Posts
Discussion Starter #16
Sorry not trying to be difficult but trying to understand. I know the control pressure regulator is bad and thanks for mentioning the shims and that explains the bleed down.

But the system pressure was a little below spec while it was running (poorly). With all the carbon fouling, black soot, wet plugs and smoke out the tail pipe. Does that not indicate a fuel distributor rebuild in addition to the pressure regulator
 

·
Registered
1980 450SL & 1988 560SL
Joined
·
1,667 Posts
From my time on the system the cold seem somewhat high (lean) and the warm pressure seems spot on. I know that cold lean condition has nothing to do with your other issues.
 

·
Registered
82 380 SL ; 78 450 SLC ; 84 BMW 533i
Joined
·
263 Posts
It's up to you if you want to tackle the rebuild but the indications and the Bosch manual only say pressure regulator.

It would not hurt to rebuild it or just get a rebuilt one from some place like CIS Flowtech;

CISFLOWTECH

When you jumped the fuel pump relay were the injectors making any noise?

I guess I like to know the exact reason for a problem so I can easily identify it in the future that's why IMHO I would replace the pressure regulator and run the test again.

Now it most likely won't start once you fiddle with the FD. You'll need to do an initial setup and then fine tune. A simple way is to jumper the relay and then turn the AF screw clockwise until you hear the injectors start squealing, then back off about 1/8th to 1/4 turn. It will then start and idle.

It's odd though from he way you say it's running my bet would have been on the WUR but you can't argue with the Bosch book:D

Oh yeah, sorry if this is redundant but you did check your air flow plate for centering right?
 

·
Registered
1984 380 sl (currently wkg on 5.0 euro motor swap). 2002 Ford Expedition
Joined
·
821 Posts
Discussion Starter #19
It's up to you if you want to tackle the rebuild but the indications and the Bosch manual only say pressure regulator.

It would not hurt to rebuild it or just get a rebuilt one from some place like CIS Flowtech;

CISFLOWTECH

When you jumped the fuel pump relay were the injectors making any noise?

I guess I like to know the exact reason for a problem so I can easily identify it in the future that's why IMHO I would replace the pressure regulator and run the test again.

Now it most likely won't start once you fiddle with the FD. You'll need to do an initial setup and then fine tune. A simple way is to jumper the relay and then turn the AF screw clockwise until you hear the injectors start squealing, then back off about 1/8th to 1/4 turn. It will then start and idle.

It's odd though from he way you say it's running my bet would have been on the WUR but you can't argue with the Bosch book:D

Oh yeah, sorry if this is redundant but you did check your air flow plate for centering right?
thanks for the tip on getting it to Idle once I replace the FD. I had a spare FD that I could not find at the time when it was time to return the core when I purchased a rebuilt one from Jaytan (which has worked great for 2 years so far). I tried swapping the pressure regulator from that FD to this one with no change. At that point I thought I would try to rebuild the spare since I knew at one time it was ok and then put it on this motor (which I have just purchased and know nothing about). I am trying to deal with some known varables. I have another post on the FD rebuild but am awaiting Orings. As soon as I finish that I will get back to the pressures. I really want to tell ALL of you how much I appreciate the help and advice.

PS the reason I just did not just purchase another rebuilt FD is that I am unsure whether I am going to keep this motor so I am trying to keep the costs down during the evaluation mode.
Thanks again- will post more soon.
 

·
Registered
1997 S320 and 1980 450SL
Joined
·
11 Posts
Where did you get that crazy fuel pressure guage setup? How much? Rent yours? Need to check pressures on wife's 1980 450SL before I start swapping out injectors. Thanks!
 
1 - 20 of 72 Posts
Top