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  #1  
Old 05-30-2008, 09:10 AM
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fuel pressure regulator

Hi all,

I was changing the oil in my 1970 280SE V6, and noticed a strong smell of gas as I was draining the oil. After some research, many pointed to a faulty fuel pressure regulator, so I went out and got one. It does not resemble anything I could see in the fuel system on the car. So I checked the part against few other suppliers and all had listed the exact same thing. It is a bosch product made in Germany. So now I wonder if I'm looking at the wrong parts of the car. Could someone please help me with the exact location of the fuel regulator?
I have to mention that the car runs very well (fuel mixture is good, no smoke,very smooth) and I realize the stem seals could be bad too but, I still like to solve the pressure regulator mistery.

Thanks for any help

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1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #2  
Old 05-30-2008, 09:38 AM
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Location: Florida / N.H.
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You may want to clarify the engine type, as there is no V6 for that chassis.

Is it an in-line 6 or a V8 ??? ...you have a typo in your post and which engine will make a difference. The 6 is Mechanical FI and the V8 is Electric FI, so they are completely different fuel systems.
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Last edited by Arthur Dalton; 05-30-2008 at 09:47 AM.
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  #3  
Old 05-30-2008, 10:40 AM
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Sorry about the typo, it is an in-line 6 FI.
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1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #4  
Old 05-30-2008, 11:44 AM
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Quote:
Originally Posted by 3BENZER View Post
Sorry about the typo, it is an in-line 6 FI.
OK
That would be MFI.
First suspect on fuel/oil contamination on that system is the Cold Start Valve is leaking by..
It is the valve at the midpoint of the intake plenum. On the valve, you will see a 7mm hex plug. That is leak Test Port. Unscrew that plug while the key is in the RUN position [ energizing the fuel pump] and see if there is any fuel coming out of that test port..there should be NONE..if there is, it is either leaking and needs a cleaning or reseating of the plunger, or it is getting power from the relay when it should not. Disconnect the single wire to determine which condition it is.
There are also other suspects, but that is the first, most common fault on those systems ,so check it.
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  #5  
Old 05-30-2008, 01:09 PM
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Arthur,
Thank you very much for your reply, I will check the cold start valve this evening and keep you posted.

cheers
__________________

1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #6  
Old 05-30-2008, 05:28 PM
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OK,
I checked the cold start valve as instructed, and it looks to be functioning properly. No fuel came out while taking the plug out.
Any other suggestions would be greatly appreciated.

Thanks
__________________

1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #7  
Old 05-30-2008, 05:34 PM
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< >>



...and the key ON ??????
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  #8  
Old 05-30-2008, 07:27 PM
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That is correct.
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1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #9  
Old 05-30-2008, 07:57 PM
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OK

On top of the FI pump there is a device with 2 coolant hoses going to it. This is the Warm Running Device and it enriches the fuel for cold starts and leans out the mixture as the engine warms up.[ that is the reason for the coolant hoses]
On the rear of this is a small can air filter. When the car is cold and running , take a hose and put one end on the filter intake and the other end in your ear. You will hear air being drawn into the filter..as the engine coolant reaches normal temp, this device will cut the intake air OFF and you will no longer hear it. It it works, that is not the problem..but if it does not , then the engine is running rich b/c the device is dirty and sticking open. It can be cleaned and oiled.
These filters also become blocked with dirt, so I always just unscrew them before doing this test to make sure they are clear [ I think it is 22mm/ or 7/8th]
That is the next test.
There are others, but there is a sequence...
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Last edited by Arthur Dalton; 05-30-2008 at 08:05 PM.
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  #10  
Old 05-30-2008, 09:53 PM
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Thanks Arthur,

I will check that filter next and post the result in the morning.
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1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #11  
Old 05-31-2008, 08:04 AM
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Well, I checked the little air filter and I could clearly hear air being drawn into it. I let the engine reach it's operating temperature and checked it again, I could still hear the air being drawn into it but not as much as when it was cold. I guess the next step is to take it out, clean it and try again, is that correct?
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1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #12  
Old 05-31-2008, 10:04 AM
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What was the coolant temp at????
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  #13  
Old 05-31-2008, 10:31 AM
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Just a hair under 175 mark.
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1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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  #14  
Old 05-31-2008, 10:36 AM
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Quote:
Originally Posted by 3BENZER View Post
Just a hair under 175 mark.
That is borderline, so I want you to let it idle for about 5 min and then retry the air test before you take it apart. It takes time for the coolant heat to get up to temp at the WRD thru the hoses.
All air should cease at approx 170, but the element in the WRD may not have reacted yet, so idle it for the 5 min. and post back, just to be sure.
It is working if it is deminishing as temp increases , so we know it is not stuck [ which is usually the problem]. It may just need adjusting for full shut off.
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Last edited by Arthur Dalton; 05-31-2008 at 10:47 AM.
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  #15  
Old 05-31-2008, 11:16 AM
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OK, I let it idle for a while till it reached just above 175 mark and holding steady. then I checked it again after few minutes and could hear it pulling air again but not as much as start up.

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1994 E320 94k
1991 300TE 105K
1985 SD 184k
1983 SD 167K
1970 280SE 54K, sold
1981 SD 271k, sold
1984 300D 145K, sold
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