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Author Topic: Air in fuel  (Read 11471 times)

jens

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Air in fuel
« on: March 11, 2009, 05:57:45 PM »
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« Last Edit: December 26, 2009, 09:57:56 AM by jens »

compig

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Re: Air in fuel
« Reply #1 on: March 11, 2009, 06:12:16 PM »
What type of clear fuel line is it ?
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Wizard

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Re: Air in fuel
« Reply #2 on: March 11, 2009, 06:36:03 PM »
Vinyl lines and stiff plastic hoses are NOTORIOUS for sealing issues,  They would seal up and deform under heat and leak.  Opposite of my problem with rubber hoses leaking/seeping when weather is cold using worm clamps instead of spring clamps (where would I find those?).

Change them to positive sealing system like screw on connectors, silicone with reinforcing mesh with spring clamps.

Cheers, Wizard

compig

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Re: Air in fuel
« Reply #3 on: March 11, 2009, 07:06:09 PM »
Thats the prob with PVC hose , most of the stuff on general sale is not oil resistant regardless of what might be claimed on packaging. Silicone also , unless it is the oil resistant type it will eventually be a problem. There is an oil resistant type of PVC hose available , but trying to identify it is almost impossible. Go for the Tygon brand , expensive but the best. When buying rubber hose go for a well known brand like Gates or Dayco , this will avoid getting rubbish imported junk. Alternatively , use the everyday PVC hose and replace it at least every annually.
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SteveU.

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Re: Air in fuel
« Reply #4 on: March 11, 2009, 07:41:25 PM »
Hello Wizard
For your hose spring clamps go to auto/truck repair shops and offer the mechanics a small amount of money for their take off clamps. There are still quite a few who are pulling them off and replacing them with gear clamps. The small (Japanese) double spring ones are the best. Took me a year or so in OE dealership shops to change my habit too.

SteveU.
« Last Edit: March 11, 2009, 07:53:41 PM by SteveU. »
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Dail R H

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Re: Air in fuel
« Reply #5 on: March 12, 2009, 09:00:45 PM »
   Jens,
   I think what you are dealing with here is one of those universal laws of mechanical things. As ezplained to me by an old sawyer many years ago when we couldn't get the old mill I was working at to cut right.
   " The S O B is just subject ta spells  nan this is one of'em".  I've found that ta be true numerous times in life,some is more subject than others.

rl71459

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Re: Air in fuel
« Reply #6 on: March 12, 2009, 10:25:08 PM »
I agree with SteveU about the clamps. I used to work in the automotive repair field, And I too was a beleiver in worm clamps. After haveing the worm clamps cause
leaks and having solved those problems by improveing the clamps only... I now know that the clamps that provide the best performance are the ones that provide
adequete clamping with the least amount of deformation to the hose.

Not all worm clamps are of the same design... some are better than others. The type that has caused me trouble in the past are the type with the open type
threaded bands. Often these types can extrude the hose caseing thru the slots and damage the hose.  Some worm clamps have a smooth inner band. these seem
to perform better.

I too have had good luck using the spring clamps. The best ones came from the OEM's. I have also had some good performing screw actuated overlapping smooth
band types. Mercedes sometimes uses them.

Not all Barb fittings are equal either. a fitting with an agressive or sharp barb can sometimes damage the inside of the hose, moreso when combined with a
overtightened poorly designed worm clamp.

Good Luck Jens! you will figure it out!
Rob

Geno

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Re: Air in fuel
« Reply #7 on: March 12, 2009, 11:37:44 PM »
What's the fuel flow rate at the IP if you pull the line?

Thanks, Geno

billswan

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Re: Air in fuel
« Reply #8 on: March 13, 2009, 01:14:55 AM »
Jens

I agree with geno's post above if you pull the line at one of the pumps how much flow into a catch can will you get. I did that today with my 10/1 because I forgot to run on straight dino to clear out the WMO . I removed the pump line put a can under and turned on the diesel to clear the lines, after the motor oil cleared the diesel came through the filter pretty fast. Probably about a cup a minute rate, just a guess from memory.

hope you can stop the gremlins  ;D

Billswan
16/1 Metro  in the harness choking on WMO ash!!

10/1 OMEGA failed that nasty WMO ash ate it

By the way what is your cylinder index?

AdeV73

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Re: Air in fuel
« Reply #9 on: March 13, 2009, 05:12:11 PM »
I'd start with (c). Funds permitting, I'd consider adding an additional (in parallel) fuel filter, rather than replacing.

Then I'd look at (b); the potential downside being, if the fuel's not coming through the filter fast enough, will pressurising it just break the filter?

MikeyT

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Re: Air in fuel
« Reply #10 on: March 13, 2009, 06:23:02 PM »
Jens,

You are not going to gravity feed through any decent filter (unless it is the size of your basement) and supply enough fuel for this engine; there must be a suction from the pump to draw it through. Fix the possible sources of air leaking into the system where it is under vacuum, ie between the filter and the pump. As some others have mentioned, worm drive clamps are notoriously bad for vacuum side applications.

AdeV73

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Re: Air in fuel
« Reply #11 on: March 14, 2009, 12:03:27 AM »
Is your fuel cold when it goes through the filter, or have you already heated it at this point? If not - is that worth a try?

A site I found through Google (Goldenfuel.com) does heated filters (albeit for an eyewatering amount of money); if your filter has a metal can, or you have some metal pipework leading up to the filter housing, you could wrap heatrope around it for the poor man's equivalent? And if it works... it's acceptable bodgination ;D

AdeV73

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Re: Air in fuel
« Reply #12 on: March 14, 2009, 12:35:45 AM »

I didn't realize that there was such a thing as 'acceptable bodgination' :)
Alas, the fuel is already at about 60 C.


Sure - anything that has absolutely no right whatsoever to work, and was thrown together with parts which were absolutely never intended to be used in the manner to which you bodge them, is acceptable bodgination ;D

Hmm, does 60c give a noticable reduction in viscosity? I've been thinking I'd need at least 100c, probably more... happy to be proved wrong. The only other thing I can think is that your filter has become blocked. 2 microns is not very big, would it be possible to clog it with something that's not obviously visible?

I'd still be tempted to install a second filter in parallel with the first - that would, as a minimum, double the amount of fuel available.

billswan

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Re: Air in fuel
« Reply #13 on: March 14, 2009, 12:59:43 AM »
jens

I would try the 10 micron filter. The waste motor oil I am using is run through an engine oil filter first then a primary diesel filter then a secondary diesel fuel filter it is a 6 micron. The oil is then put in a 5 gallon tank about 5 feet above the 10 micron engine filter which is heated with 195 degree fahrenheit  bypass water. Even straight 15- 40 used engine oil goes through with ease.  The thick oil takes about 15 psi to push it through my 3 filters I described above though.

A 2 micron is plenty small, have you a clean filter to install, it is probably plugged up ???

Billswan
16/1 Metro  in the harness choking on WMO ash!!

10/1 OMEGA failed that nasty WMO ash ate it

By the way what is your cylinder index?

oliver90owner

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Re: Air in fuel
« Reply #14 on: March 14, 2009, 07:59:37 AM »
heated filters (albeit for an eyewatering amount of money);

There are thousands of heated fuel filters out there; most modern diesel cars were fitted with them(post 1980?).

Two filters in series will probably be needed if 2 microns is the target.

Rotary IPs are probably much more prone to wear than the simple reciprocating IP.

I wonder what the original 'snake' filters achieve.

You cannot pressurise the tank if the spill return goes back there.

Air entering a pipe (which should be under positve pressure) would indicate a leak and an under-pressure situation.  I have a diesel car which will operate only on the top half of the tank.  I know it draws air in as soon as the tank runs below half.  Been like it now for about 70000 miles; I just keep the tank topped up.  The pipes are ludicrously inaccessible to check them out.  One day I will stream clean everything and pressure test with less than half a Bar and see if I can find any leaking fuel........

RAB