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  #1  
Old 09-02-2015, 06:58 PM
Paul H.
 
Join Date: Jun 2009
Location: Tahlequah, OK
Posts: 42
87 300D air in fuel lines

I have searched and can't find an answer to this. Probably not looking in right spot. My 87 300D, in winter only or when cold, starts then shuts down in 1-2 seconds. Sometimes we can coax it to run by giving it lots of throttle. When it dies, it does restart after lots of cranking. I know i probably have air in the lines but I've tried to find where it is coming from and can't.
Any ideas on how to isolate different lines so I can find this before this starts happening again?
Many thanks!

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  #2  
Old 09-02-2015, 09:04 PM
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Location: northern IL
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How cold? (Cold enough for gelling?)

Are you using the glow plugs? Are they working?

Do you have low compression?

Air leaks in the fuel line would typically create problems warm or cold. If you are sure it's an air leak, check for bubbles in the clear fuel filter while its running.
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  #3  
Old 09-02-2015, 09:41 PM
Paul H.
 
Join Date: Jun 2009
Location: Tahlequah, OK
Posts: 42
Thanks for the reply.
Yes I have air bubbles. It usually does it if it is below 40 degrees F.
Glow plugs are fairly new and working.
Really need help finding a way to determine where the air is getting in.
Thanks again.
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  #4  
Old 09-02-2015, 10:01 PM
jay_bob's Avatar
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There are a couple common leak spots in a 603.

First thing to look for is the fuel preheater thermostat. This is a barrel shaped device below and behind the IP. This is a simple device and easy to rebuild.

While you are in there replace the black hoses with (edit: 5/16") fuel hose
Steel supply line to pre filter
Pre filter to thermostat
Thermostat to heat exchanger
Heat exchanger back to thermostat
Thermostat to lift pump

And return spout on the primary filter back to the steel tank return

Now let's look at the 3 hoses with banjo ends. If they are dark brown and stiff they should be replaced.
Lift pump to primary filter inlet
Primary filter outlet to injection pump inlet
Injection pump return to primary filter return

That should eliminate any cause of air leak in the fuel system.

Remember the system operates at a vacuum relative to atmosphere, so fuel line leaks will not drip, they suck air.
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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Last edited by jay_bob; 09-06-2015 at 06:31 PM. Reason: fuel hose size error
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  #5  
Old 09-03-2015, 07:28 AM
Paul H.
 
Join Date: Jun 2009
Location: Tahlequah, OK
Posts: 42
Jay Bob,
Thanks for all of the specific spots to check.
I really appreciate your help.
I'll get to that this weekend and then check for air bubbles again.
Is there a kit to buy to rebuild that fuel pre-heater thermostat?
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  #6  
Old 09-03-2015, 07:54 AM
funola's Avatar
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PaulH, where do you see bubbles?
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83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
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  #7  
Old 09-03-2015, 08:00 AM
funola's Avatar
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Quote:
Originally Posted by jay_bob View Post
....................
Remember the system operates at a vacuum relative to atmosphere, so fuel line leaks will not drip, they suck air.
Correct. I'd like to add this is true for the supply line with a lift pump on the IP (not in the tank like on some later diesels)
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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
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  #8  
Old 09-03-2015, 08:04 AM
funola's Avatar
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[QUOTE=jay_bob;351562..........................
While you are in there replace the black hoses with 5/8 fuel hose
Steel supply line to pre filter...........[/QUOTE]

I am not familiar with that engine but a 5/8 fuel hose is huge!
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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
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  #9  
Old 09-03-2015, 12:59 PM
Paul H.
 
Join Date: Jun 2009
Location: Tahlequah, OK
Posts: 42
Funola,
The bubbles were on the return side just before it hits the hard return line.
None coming from the tank.
Thanks for the help.
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  #10  
Old 09-06-2015, 06:32 PM
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Quote:
Originally Posted by funola View Post
I am not familiar with that engine but a 5/8 fuel hose is huge!
It's 5/16" I fixed the post above

That is what I get trying to type from memory while on a plane!
__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech
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  #11  
Old 09-07-2015, 09:46 AM
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Quote:
Originally Posted by Paul H View Post
Funola,
The bubbles were on the return side just before it hits the hard return line.
None coming from the tank.
Thanks for the help.
Air bubbles, no matter where they enter into the fuel system, eventually makes its way to the return to tank line. Once you eliminate air in the return to tank line, you have no more leaks.

In addition to the leak points already mentioned, take a look at your pre-filter. If it does not have the brass sleeve support like the bottom one in pic, they are more likely to leak at the hose connection due to insufficient rigidity, especially if the rubber hose is old and hard. I suggest changing the hose and prefilter with the brass sleeves, get the genuine Mercedes fuel hose (from dealer) so that it fits the Mercedes clamp. A generic 5/16 fuel hose is smaller in o.d. and the Mercedes hose clamp will be not tighten it properly.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
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  #12  
Old 09-07-2015, 11:28 AM
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I have used the all Plastic pre/primarly Filters exclusivly and only had a air leak issue when the Hose was hard (looked like the Hose that came with the Car in 1984).

After replacing the Hose with the mentioned 5/16" ID Fuel Hose from the local Auto Parts store I have had no issues for 7 years.
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  #13  
Old 09-07-2015, 11:49 AM
Paul H.
 
Join Date: Jun 2009
Location: Tahlequah, OK
Posts: 42
Thanks to all. Will get back on this soon. Have to work on the bosses car first.
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  #14  
Old 09-13-2015, 10:17 AM
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Quote:
Originally Posted by Diesel911 View Post
I have used the all Plastic pre/primarly Filters exclusivly and only had a air leak issue when the Hose was hard (looked like the Hose that came with the Car in 1984).

After replacing the Hose with the mentioned 5/16" ID Fuel Hose from the local Auto Parts store I have had no issues for 7 years.
A new hose sure helps. Did you use the Mercedes fuel hose clamp (with Phillips head) on the 5/16" ID Fuel Hose from the local Auto Parts store? If the auto parts store hose has a smaller o.d. than the Mercedes 8 mm hose, the Mercedes hose clamp may not provide enough clamping force onto the hose/pre-filter because the clamp closes down to a certain diameter and stops there.

The 2 hose connection on the pre-filter is a weak spot for air leaks. Unlike all other fuel hose connections on the rest of the 617 fuel system, the pre-filter connections are the only ones that is smooth, without a barb, which makes having a pliable fuel hose with the correct size hose clamp and a more rigid pre-filter (with the brass sleeve) that much more important. The pre-filter is under suction, the suction increases with engine rpm. If you see no air bubbles at idle, that may not be true at 3000 rpm.

Here's a real long thread on a documented case of pre-filter (primary filter) issues. His symptoms was pinging at idle and at part throttle, sounds of ball bearings in cylinders when cruising down the road. From Oct 2014 to May 2015, he spent a lot of money and time trying different things on his 617 in a Toyota truck, none of which helped. In the end, he replaced the pre-filter (which has been replaced a few times already with the same type pre-filter w/o the brass insert) with a Facor filter, which is metal, and his symptoms went away.


617 weird behavior diagnoses
"........I think my plastic OEM primary filter was leaking air. Someone mentioned that the filters without a metal insert in the plastic hose barb could crush down and allow air in. I'm thinking this is what happened, as I'd gone through multiple filters with the same issue. The Facor is all metal.

I swear it runs smoother and it has better power. I don't trust seat-of-pants dynos, but I'm now able to accelerate in top gear on hills that before I'd either be able to just hold speed or gradually lose speed on..........."

617 weird behavior diagnoses
__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Last edited by funola; 09-13-2015 at 10:28 AM.
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  #15  
Old 09-18-2015, 01:34 PM
Diesel911's Avatar
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Location: Long Beach,CA
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Quote:
Originally Posted by funola View Post
A new hose sure helps. Did you use the Mercedes fuel hose clamp (with Phillips head) on the 5/16" ID Fuel Hose from the local Auto Parts store? If the auto parts store hose has a smaller o.d. than the Mercedes 8 mm hose, the Mercedes hose clamp may not provide enough clamping force onto the hose/pre-filter because the clamp closes down to a certain diameter and stops there.

The 2 hose connection on the pre-filter is a weak spot for air leaks. Unlike all other fuel hose connections on the rest of the 617 fuel system, the pre-filter connections are the only ones that is smooth, without a barb, which makes having a pliable fuel hose with the correct size hose clamp and a more rigid pre-filter (with the brass sleeve) that much more important. The pre-filter is under suction, the suction increases with engine rpm. If you see no air bubbles at idle, that may not be true at 3000 rpm.

Here's a real long thread on a documented case of pre-filter (primary filter) issues. His symptoms was pinging at idle and at part throttle, sounds of ball bearings in cylinders when cruising down the road. From Oct 2014 to May 2015, he spent a lot of money and time trying different things on his 617 in a Toyota truck, none of which helped. In the end, he replaced the pre-filter (which has been replaced a few times already with the same type pre-filter w/o the brass insert) with a Facor filter, which is metal, and his symptoms went away.


617 weird behavior diagnoses
"........I think my plastic OEM primary filter was leaking air. Someone mentioned that the filters without a metal insert in the plastic hose barb could crush down and allow air in. I'm thinking this is what happened, as I'd gone through multiple filters with the same issue. The Facor is all metal.

I swear it runs smoother and it has better power. I don't trust seat-of-pants dynos, but I'm now able to accelerate in top gear on hills that before I'd either be able to just hold speed or gradually lose speed on..........."

617 weird behavior diagnoses
I just went out and looked; I have the regular US type worm gear type clamps on the plastic primary filter.

When I need a hose clamp I root around in the Box I have of new and used hose clamps and use what is available.

In my case I have had no issues with the US type worm gear clamps on the Plastic filter which I installed like 7 years ago.

In fact now that I think about it the former owner must have changed the clamps as I don't recall the mercedes type clamps on the fuel hoses.

But if someone likes the mercedes type clamps there is similar non-mercedes clamps you can buy. they are just harder to find.

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