fuel tank strainer - Page 2 - PeachParts Mercedes-Benz Forum

funola · #16 11-15-2012, 12:49 AM

Quote:

Originally Posted by pnolet

Mine is a 99 is there anyway besides visual inspection (if that fails) to maybe test if the fuel line has a leak. Why would it only do this on 1/4 tank or lower

Does your 99 have metal fuel lines that can rust? Full tank would put more pressure in the fuel line than 1/4 tank thus less air coming in via the pinhole..

You can try and Mityvac but the results may not be conclusive since the pinhole can be very small.

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whunter · #17 11-15-2012, 12:51 AM

Quote:

Originally Posted by pnolet

Mine is a 99 is there anyway besides visual inspection (if that fails) to maybe test if the fuel line has a leak. Why would it only do this on 1/4 tank or lower

I will try to lay out a full diagnostic of the fuel system.
Each post will cover one issue.
FYI: The fuel sender has been superseded four times, and alternative level verification may be needed.
The current part is MB# 2105424017

* You have replaced the fuel tank Screen.

FYI
MB diesel filtration, how it works.
MB diesel filtration, how it works. - PeachParts Mercedes ShopForum

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whunter · #18 11-15-2012, 12:52 AM

What is this valve and why is it dripping diesel?
What is this valve and why is it dripping diesel?

Fuel tank vent pictures + location
93 300D 2.5L Turbodiesel Power Loss

What happens when a tank vent gets clogged.
What happens when a tank vent gets clogged. - PeachParts Mercedes ShopForum

Imploded fuel tank - so sad!
Imploded fuel tank - so sad!

Why do I have vacuum in my diesel tank.....................?
Why do I have vacuum in my diesel tank.....................? - PeachParts Mercedes ShopForum

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whunter · #19 11-15-2012, 01:21 AM

These include the injection pump.

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whunter · #20 11-15-2012, 01:27 AM

I seriously doubt it could be related to your symptoms.

OM60_series IP delivery valve reseal
OM60_series IP delivery valve reseal

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whunter · #21 11-15-2012, 01:39 AM

The most common issue is bad O-rings.

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The shutoff valve O-ring is overlooked - missed all the time.

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The nylon fuel lines become ugly coffee color due to microscopic cracks/abrasion/age, and the O-rings on each end fail.

Item #26 pre-filter element is known to distort with age, causing mild to no start issues.
Note: The associated O-ring must be replaced at the same time, for similar reasons.

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The screw on fuel filter BOLT has O-rings that need to be inspected at each new filter, and replaced every 2 - 3 filters.

On rare occasion, the shutoff valve may crack.

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pnolet · #22 11-18-2012, 11:07 PM

I've replaced shut off oring also all the dv rings all the fuel lines and much more. I'm pretty confused by this post...how can I specifically diagnose my problem? Old the vent be a symptom?

whunter · #23 11-19-2012, 02:48 AM

Quote:

Originally Posted by pnolet

I've replaced shut off o-ring also all the dv rings all the fuel lines and much more. I'm pretty confused by this post...how can I specifically diagnose my problem? Old the vent be a symptom?

If you know the circuit, you can apply vacuum or low air pressure for leak diagnosis.

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DAR2KMR2 · #24 11-19-2012, 03:35 AM

I'd think about checking or changing out the mechanical lift pump, especially if you have high mileage on the engine and have replaced all the o-rings. I had a similar situation happen to me on my '87 diesel ..... sluggish running and it would quit with about a 1/4 tank of fuel remaining. The lift pump worked but it was weak ... so when the fuel ran low the pump couldn't produce enough fuel pressure to keep everything running. I replaced the lift pump and all was fixed. Additionally, on the OM606 motors it is possible to mix up the fuel lines when replacing the o-rings and then things don't run right either ... so double check that everything is hooked up correctly as per the diagrams previously provided. Good Luck!

pnolet · #25 11-19-2012, 04:55 PM

What is the cost on something like that? In fact are these lift pumps testable?

pnolet · #26 11-19-2012, 05:03 PM

Also I feel this important.... If I am parked at an incline where the tank be higher than the engine, it runs idles but if u level out it dies after minutes

whunter · #27 11-20-2012, 12:50 AM

Quote:

Originally Posted by pnolet

What is the cost on something like that? In fact are these lift pumps testable?

Pelican Parts - Automotive Parts and Accessories - Porsche & BMW

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DAR2KMR2 · #28 11-20-2012, 09:17 PM

I'm sure there is a test proceedure out lined somewhere along with a special guage to read the pressure output of the pump ..... but if the car idles fine on a negative incline (fuel in the tank higher than injector lines) and dies with the fuel level below the injection pump, plus the fuel filters are new and the lift pump has more than 150k miles on it, that would be enough evidence for me (shade tree mechanic) to replace the lift pump. Good Luck!

pnolet · #29 11-21-2012, 09:55 PM

Any specifics on howto apply vacuum for a leak check? Does tank need to be empty? Please this car is 500 miles from home and it's stranded!!

Mark Rapier · #30 11-21-2012, 10:56 PM

Quote:

Originally Posted by pnolet

Any specifics on howto apply vacuum for a leak check? Does tank need to be empty? Please this car is 500 miles from home and it's stranded!!

Sounds like you are chasing too many tails at once. The first thing you need to determine is if the problem is with the fuel supply/input or the IP/lift pump/filter system. The easiest way to do that is to separate those two elements where the fuel inlet line and the fuel return line connect to the fuel supply side of the system.

Get a couple of 3' sections of clear vinyl tubing I'm pretty sure 3/8" ID will fit, Home depot sells 15' rolls for about $5. Then you get a couple liter empty clean soda bottle or some similar sized plastic container, clear if you can because that will allow you to observe both the rate of fuel return and whether it is a solid stream or filled with bubbles.

Mark the hose and the steel fuel lines so you can get them back to where they belong when your done and separate them where they meet in the engine compartment. Be ready to plug the fuel inlet line because if there is much fuel in the tank it will run out until the level drops low enough. A short 3 inch section of hose that has been plugged with a bolt or even a whittled stick will work fine. Get that apart and close off that line with your plug. Do the same with the fuel return line.

Now you have the fuel supply separated from the engine.

Now you take your clear vinyl hose and using about 3 feet of it connect it to the fuel return outlet up at the secondary filter. Should be a hose bib and a hose clamp attachment there. Then take a second 3 foot section of clear vinyl and attach it to the inlet of the primary filter, should be a hose clamp that attachment there also. Then get your soda bottle or whatever plastic vessel you have that you can squeese into place along side the engine on that IP side area, might need to use a piece of wire, string, duct tape ariound the neck of the bottle to secure it from falling down too far or falling over and spilling. But figure out the how and where placement of it.

With that done pull the bottle out and fill it about 2/3 with fresh diesel, place the bottle into the pre-determined position and secure it from falling or dropping. Place the two clear vinyl hoses, one from the return and the other one to the primary filter, place their ends down into the diesel. You probably will want to use a bit of tape, wire, string to hold the tubing in place at the bottle mouth particularly it the engine starts and runs and you want to drive around the block.

You effectively created a alternative mini fuel system attached to the engine, with that hopefully you can get the car started and determine whether your problem is with the IP/filter/lift pump system or with the fuel delivery system.

If the car starts and runs you should be able to drive around the block (actually a couple miles) with it set up like that. If you find the problems with running and dying that you've described have not been eliminated then the problem is not the fuel supply side of the equation.

But you need to separate the two systems to identify where to focus your efforts. With the bottle of fuel you know that the fuel supply is not in question so it can by seeing if the engine runs and drives eliminate the engine side of the equation.

If you get that done then you can focus the future effort on what needs to happen to get things right.

To answer the specific question you posted, as far as testing the steel underchassis fuel supply line, you plug one end and apply vacuum to the other end, and see if it holds vacuum or not. For your vehicle you would need to clamp off the flexible hose attached to the tank's fuel strainer, remove the hose clamp securing the other end of the flexible hose to the steel underchassis fuel line and separate the two, disconnect the flexible fuel hose between the end of the steel line and the primary filter, then remove the fuel from the steel line by blowing it out using just a couple foot section of hose to attach to the steel line and blow in catching the fuel at the other end, fashion some type of plug and seal one end of the steel line and then apply vacuum to the other end and observe whether it holds the applied vacuum.