Bubbles not welcome -odd air in fuel system - Page 4 - PeachParts Mercedes-Benz Forum

Shern · #46 05-27-2018, 04:19 PM

Quote:

Originally Posted by funola

If I read your post correctly, after you crimped the line, you awoke to no bubble. That means you have no leaks after the crimp, on the engine compartment side. The leak is before the crimp, on the tank side. That's why I suggested you move the crimp one step closer to the tank, to see if the leak in the steel supply line or after that. The supply line is the one that goes to the fuel strainer.

If the clear line is 5/16 i.d. I would not trust it not to blow when the engine gets hot. If 1/4 " i.d. I'd trust it for short term.

Edit: I see you have no clamps on the clear line. Air can get in on the relaxation stroke of the lift pump when it is under vacuum. I already explained to you how to make a clamp with rubber band.

Yeah, apologies this part me be unclear. I haven't isolated the primary filter, that's what I'm trying to express. I pinched the line *directly* before the lift pump so I'll be working backwards, section by section. I'm not convinced just yet that the primary filter isn't the problem.

Edit: the clear line i installed was the 1/4 and boy was it a snug fit. I can certainly wrap some rubber bands around it but to be honest I'm more concerned about when I have to remove it.

funola · #47 05-27-2018, 04:30 PM

Quote:

Originally Posted by Shern

(..............)
The line I crimped, was the rubber hose between the lift pump and the prefilter.
Heading upstream, It seems the next place to crimp is behind the prefilter (the first rubber hose in the engine bay) in effect adding the prefilter to the milieu.

(..............)

I mis-read. You're right, the next crimp should be on the other side of the pre-filter (the steel supply line side).

I never trust those pre-filters without the brass insert support sleeves.

funola · #48 05-27-2018, 04:33 PM

Quote:

Originally Posted by Shern

(................)

Edit: the clear line i installed was the 1/4 and boy was it a snug fit. I can certainly wrap some rubber bands around it but to be honest I'm more concerned about when I have to remove it.

You remove it the same way you installed it. Microwave a cup of boiling water and slowly pour it over the tubing to soften. Yank it off with a pair of pliers.

Shern · #49 05-27-2018, 04:35 PM

Quote:

Originally Posted by funola

I mis-read. You're right, the next crimp should be on the other side of the pre-filter (the steel supply line side).

I never trust those pre-filters without the brass insert support sleeves.

I really appreciate your assistance by the way. This has been driving me nuts for months now.

Where do you find the filter with the brass sleeves? I found a couple on eBay, but seems surprising pelican or any of the other suppliers don't seem to carry them. From the photos, the OEM mercedes filter appears to contain brass sleeves within the plastic tubes, but I'm not 100%.

funola · #50 05-27-2018, 04:52 PM

Quote:

Originally Posted by Shern

I really appreciate your assistance by the way. This has been driving me nuts for months now.

Where do you find the filter with the brass sleeves? I found a couple on eBay, but seems surprising pelican or any of the other suppliers don't seem to carry them. From the photos, the OEM mercedes filter appears to contain brass sleeves within the plastic tubes, but I'm not 100%.

Ebay seems to be the only source now and they're about $10 ea. It used to be everyone had them and they were $1.25 ea. I bought a few back then and rinse them out with soap and water when they get dirty and re-use.

You may be able to sleeve the ones you have with telescoping antenna sections of the correct diameter and a tubing cutter. It has to fit snug to be effective. Use boiling water to soften the plastic to insert.

maclaveau · #51 05-27-2018, 05:54 PM

Pelican did sell them last year, part # PPE-W0133-1641441-HEB. Althought not shown on their online catalog, this was the part# they gave me when I complained about the Febi ones they sent me as their photo in the catalog had brass inserts but the actual product did not.

Alec300SD · #52 05-27-2018, 07:16 PM

Quote:

Originally Posted by Shern

Where do you find the filter with the brass sleeves?

Also available here for $3.97 each.

Shern · #53 05-28-2018, 01:30 PM

Okay, engine bay system has been eliminated... No bubbles this morning. Working back this evening to the short rear supply line.

I realize this is a slow moving narrative with a questionable pay-off. Hoping it's future-helpful.

barry12345 · #54 05-28-2018, 08:28 PM

You did test by clamping the line also just before the pre filter? Common area for a lot of grief. Normally but not always when an air leakage is back farther. You see a tiny stream of bubbles processing through the primary filter. When the engine is running.

Even if you see one tiny bubble in transit it is too much in your case.

vwnate1 · #55 05-28-2018, 09:13 PM

Waiting to see what the end issues is......

funola · #56 05-29-2018, 09:07 AM

Quote:

Originally Posted by Shern

Okay, engine bay system has been eliminated... No bubbles this morning. Working back this evening to the short rear supply line.

I realize this is a slow moving narrative with a questionable pay-off. Hoping it's future-helpful.

Questionable payoff? Still don't trust the process? I am going to guess you have a bubble this morning after clamping the supply line under the tank.

Shern · #57 05-29-2018, 02:07 PM

Ha, absolute trust. “Questionable payoff” was referring to the end of this story for our readers, not me. I of course have everything to gain.

Last night I crimped the inlet rear fuel line. And this morning?

No bubble still.

This is getting interesting. I’m left with either the rear hose clamp on that same line, the hose clamp on the line from the tank screener, or the tank screener gasket itself.
My money (and hopes and dreams) was on the primary filter. Now I’m really hoping it’s not the screen gasket because that was not a fun job.

Logically this makes no sense, but to be thorough -would a full tank and or a narrower “temp cigar” have any bearing on this? The cigar hose is meant to accommodate surges in fuel, which would mean (in my mind) between surges the flow wouldn’t quite fill the circumference allowing bubbles back? Into the IP return line?

funola · #58 05-29-2018, 04:14 PM

Quote:

Originally Posted by Shern

Ha, absolute trust. “Questionable payoff” was referring to the end of this story for our readers, not me. I of course have everything to gain.

Last night I crimped the inlet rear fuel line. And this morning?

No bubble still.

This is getting interesting. I’m left with either the rear hose clamp on that same line, the hose clamp on the line from the tank screener, or the tank screener gasket itself.
My money (and hopes and dreams) was on the primary filter. Now I’m really hoping it’s not the screen gasket because that was not a fun job.

Logically this makes no sense, but to be thorough -would a full tank and or a narrower “temp cigar” have any bearing on this? The cigar hose is meant to accommodate surges in fuel, which would mean (in my mind) between surges the flow wouldn’t quite fill the circumference allowing bubbles back? Into the IP return line?

The smaller diameter clear hose (1/4" i.d. for 1 ft) is a little more restrictive than 5/16 but not enough to make a difference when running IMO. Static wise, it makes zero difference.

Next thing to try is do not clamp anything and see if you get bubble (this tests the real cigar hose you removed and the 2 clamp connections). If you get a bubble, next thing to try is no clamp again but leave the fuel cap loose to simulate a working tank vent (I do not know if your tank vent is working. If you get bubble, next thing to try is clamp cigar hose (your clear line). If you get bubble, then clamp the return rubber line at the tank.

If none of the above tells you where the leak is, start testing each component with a Mityvac under both vacuum and pressure.

Shern · #59 05-29-2018, 06:42 PM

Quote:

Originally Posted by funola

The smaller diameter clear hose (1/4" i.d. for 1 ft) is a little more restrictive than 5/16 but not enough to make a difference when running IMO. Static wise, it makes zero difference.

Next thing to try is do not clamp anything and see if you get bubble (this tests the real cigar hose you removed and the 2 clamp connections). If you get a bubble, next thing to try is no clamp again but leave the fuel cap loose to simulate a working tank vent (I do not know if your tank vent is working. If you get bubble, next thing to try is clamp cigar hose (your clear line). If you get bubble, then clamp the return rubber line at the tank.

If none of the above tells you where the leak is, start testing each component with a Mityvac under both vacuum and pressure.

What if it is the cigar hose? What would that mean for the T junction at the secondary fuel filter. Something would have to be off...
The funny thing is, everything is running very smoothly at the moment.

About a year ago, I replaced the cigar hose with a regular piece of 5/16 when I found it leaking after a diesel purge. Then I started reading about overflow valves, and shaky idle, etc, and found a compelling case to reinstall one. I haven't noticed an ounce of difference. If anything, running on a restricted hose has been potentially the smoothest running I've had yet.

Shern · #60 05-30-2018, 04:14 PM

Well, it looks like it must be the cigar hose, which is bizarre and to the best of my knowledge, nearly impossible. I didn't pinch anything off last night and awoke to clear lines all around.

I'll reinstall the cigar hose and see what happens tomorrow morning. I really have no idea what to make of this.

*Edit: It only took a couple of hours. An inch of bubble has appeared. This is interesting... There are several channels running through the secondary filter. Some device or another keeps them discrete. Whatever device that is seems to have failed.