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Okay actually it should read trash in the sock.

I'm in Houston working at a trade show, I drove over from Ms, Sunday nite, and get near to Beaumont, Tx and one of my vac filter blocked switches starts indicating blocked filter on the frame rail pre IP filter, my IP inlet pressure gauge hovering 0-1 psi from it's normal 5 psi. As luck would have it I didn't have a spare filter with me nor none at the 1 autopart store I could find open on a Sunday nite. Being that I have a Racor mount, it has 2 extra ports I'm not using for inlet/outlet, and I was able to come up with fittings/hose to fashion a bypass around the filter element.

The bypass helped some but did not cure the problem; 90 miles out I ring up GMCTD to see if he is going to be up for a while just in case it dies completely & I mite need roadside assist, Diesel gods smiled on me balance of evening, and I was able to limp into Houston 60 mph max before staring fishbiting.

Monday I limp it over to GMCTD's by time I get there both the prefilter hi vac and the on engine filter hi vac alarm are coming on and truck is fishbiting above 40 mph now.

We hit some part stores, grab some new filters, a new lift pump (just in case), lift pump at idle weak flow from on engine manager drain 3-4 psi running sounds are weak. We pulled the on engine filter it was clean, so next obvious possibility is to pull the Racor prefilter, older style elements are not visible without cutting the filter apart, newer style I had just purchased WIX (not actual Racor) have been redesigned so the inlet side flow is visible when removed off of the head.

The bypass I had installed Sunday was removed and the new element installed, reprimed/started the pump with run jumper, (pics will be added when I get home with access to the camera) lift pressure was back up to 5 psi. Priming with the manual prime pump on top of the Racor was difficult (missed clue we came to find out later) so we forced the lift pump to run cheating. I went for a test spin and had to come back still had lites and low lift pump pressure.

Being pressed for time, I opted to replace the lift pump with the new one and also used LP air to blow back through the in tank sock. Life was good I hate troubleshooting by doing 2 things at once, but sometimes one has gotta do what one has gotta do. Anyway I drove around Houston area a couple of days then I started getting the filter light again, low lift pressure 0-4 psi dependings how hard I was running the engine. Yo GMCTD what you doing this afternoon, up for some more work, come on over.

Yesterday the truck up & quit as I was rolling out of hotel parking enroute to GMCTDs it went completely dead on roadside, I crawled under truck, disconnected the Racor inlet line, blew back thru the sock with emergency air source (me :eek: :eek: :eek: ) as luck would have it my tire inflator was in the Burb; It didn't take much effort to clear the sock, I reconnected it started the truck & after a couple of stall episodes before I was able to get it it settled out and I was able to limp to GMCTD's by time I got there I was back to 40mph max speed and both filter vac switches lit up.

When I got to GMCTD's, we pumped out the tank, the fuel removed was clean, dropped the tank and removed the sender unit, the pickup was nearly plugged solid with various types of crud and a sticky tar type residue which I assume to be dead algea & rust congealed together. We cleaned the pickup sock, then mopped out the tank using a cotton foot sock on end of a piece of heavy gauge wire, wringing out fuel and sediment. The tank was mostly clean but sufficient residue in the flow dam baffle & sock pickup area to to crud up the pickup.

Reassembled the tank, plumbing, sender etc. put the fuel back in zippity-doo-dah we had a :grd: moment, all was good on the return trip to my hotel, no filter DP alarms and fuel pressure was never below 4 psi, to about 75 mph, I'll run it out more on my return to Ms this afternoon.

Couple of observations during the troubleshooting, #1 the tech manual for OBD-II is correct the OPS is a backup power supply for the lift pump, the lift pump remains powered with PCM contol or OPS, as verified by removing lift pump relay or unplugging the OPS, remove one or other and pump stays running, remove both and lift pump stops, also with a healthy IP it will pull it's own fuel without aid of lift.

I have doubts however of it pulling it's own fuel through a plugged fuel filter, or in tank sock if weak, combine partial blockage of both you ain't going anywhere fast if at all, so prime suspect to be considered in any fishbite situation is in tank sock, not easiest to check, so do the easy stuff first.

2nd observation is as we have said time & again check the grounds, when dropping the tank there is 1 very important gnd lug (again pics when I get home) on top of the frame rail adjacent to the tank sender weatherpack connector, it is the gnd for the lift pump. We were doing some preliminary testing before securing the tank 100% and could not get the lift pump to run, hmnn what is up with that, light bulb I wonder if that removed gnd lug goes to lift pump, reconnected it yup that is what it wuz. So another fishbite candidate to consider is the gnd lug at that point.

I'll be doing full pictorial later as the sender on the Burb is bad and I'll be dropping that tank as well in near future.

Bottom line keep like your mother said change your socks often & keep em clean or you will get a fungus.

With that thought you often hear us recommending to buy from known good fuel sources, you can try even though doing that stuff still happens.

I'm thinking that possibly as a preventative measure one may want to periodically drop the tank to check the sock, since I'm a 98 one could theorize check it at about 8-9 years would be a good periodicity for checking.

More later
 

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Hi Tim,

Great post, and will look forward to the pictures. Good debugging by you and GMCTD.

Sincerely,

Rob :)
 

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I just hate dirty socks.

Sounds like it was "real" fun. The dirty sock would be something to easily over look or not even consider as an issue.

Good advice to check the tank occassionally. :)
 

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Two of the best heads got it done!!!. How long & many parts DOLLARS would it have taken a MR Goodwrench ??? Your warning systems paid off in spades!!! You guys are so good you should post all the ways to contact you when this happens to us underlings,Ha, Ha & a big LOL!!!
 

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these socks serve a purpose, but they're a bad design in that they are not easily accessible for replacement.

What would be the down side to deleting the sock and just using a universal fuel filter before the LP?
 

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Such a colorful thread title. :rolleyes:

Great timing too. Just sprang a fuel tank leak on the Tahoe. Was planning to just drain the tank and patch it in place. After reading this I guess I will drop it and check out the condition of my sock.

I've got a few more years on mine than TD does on his, wonder if the different climates we live in will impact how much crud we find?
 

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joispoi;2000920; said:
these socks serve a purpose, but they're a bad design in that they are not easily accessible for replacement.

What would be the down side to deleting the sock and just using a universal fuel filter before the LP?
My thought exactly. Is there something in the pickup tube-to-fuel line region that has to be kept clean? I'd much rather deal w/ a filter near the LP.

Chaser
 

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That was a good read, and I'm glad you have it all figured out. I was on the edge of my seat at one point; frankly, I could never have been so organized and completed the fix in such an experienced way.

As a diesel newbie I'm now a little scared to take my rig on long trips :(. I'll either have to (a) get over it, or (b) get greasy and become less of a novice! (prolly both!)

Jon
 

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chi2;2001039; said:
As a diesel newbie I'm now a little scared to take my rig on long trips :(. I'll either have to (a) get over it, or (b) get greasy and become less of a novice! (prolly both!)

Jon
.... or have some friends along the way....

Shame it didn't happen while around home, but what better place to have it happen, eh what? You and JD doin' a bench press on a fuel tank on an unplanned trip, but hope you still get some time to do some of the testin' wanted to do together.
 

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Good write up- one to remember when problems arise.

I am fortunate to be able to buy our fuel from a local jobber that sells mostly to big trucks. He moves a lot of fuel through his yard and never a complaint in 12 years.

As far as socks go, I think the old Mercedes had the best set up. IIRC, the fuel line came out the bottom of the tank in the middle of a larger nut ( 27MM I think) that contained the sock. To replace it, you just had to drain tank, unscrew fuel line, then the nut with the sock.

BTW DOc, If you think you got some bad fuel along the way from MS on I-10, lwt me know. I travel that way some times and worry about some of those old in ground tanks,
 

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joispoi;2000920; said:
these socks serve a purpose, but they're a bad design in that they are not easily accessible for replacement.

What would be the down side to deleting the sock and just using a universal fuel filter before the LP?
The sock helps keep water in the tank and out of the fuel system. A water separator can help but the sock keeps the water in fuel at a very low level so as not to overpower the water separator
 

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Nice write up TD. We can add that one to our list of things to check when all else is failing. The pics will be appreciated.
 

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You guys are the best of the best! :hail:

I thoroughly enjoyed reading the story (well told).

Sounds like all that jet-wrenchin' has paid off. I haven't seen the inside of your truck, but I have it pictured looking like the cockpit of a 737 with all the warning lights and gauges!! Kudos on your early warning system you built, -sounds like it was well worth the effort.

I'm glad you were able to get 'er up and runnin'. It couldn't have happened in a more conveniant place havin' JD there to help.

Nice work guys.

Rich.
 

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Scrufdog;2001755; said:
The sock helps keep water in the tank and out of the fuel system. A water separator can help but the sock keeps the water in fuel at a very low level so as not to overpower the water separator
How much water are we talking about?
 

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Good read guys.

Here are some thoughts... I have seen the sock fill up on with rusty crud slime stuff too on 2 gas vehicles. 1 was about 10 yrs old other was 20 ish. Both had different lives and periods of daily driving and and some significant extended resting. Most daily drivers last a lifetime. Also depends on regular fuel source too I imagine.

Yeah initial thought is to take out the sock and run a pre pump filter. But I have had a steel fuel line plug up with the same rusty crud slime on a farm tractor that basically drained out the bottom of the tank. Setup was fuel gravity fed filter and not sure internal to tank. But basically a clot was formed somewhere in line & build up finally plugged the steel line (and could have been some rust from the steel line too). I blew compressed air back through and replace fuel filter and tractor has run fine for 3 years.

I really like the idea of a fairly accessible bottom sock filter like the comment on BMW or Mercedes.

Good fuel/filter practices (which I know Doc does) and the Quality (#1) of the tank are probably the 2 biggest factors to determine life of socks. Seems GM OE tanks are not so good???? This kind of stuff is build up issues mostly and probably not a one time fill up with bad fuel IMO.
 

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Actually - the sock is to reduce reduce entry of air bubbles into the fuel stream - hot Diesel fuel foams easily - when fuel level is low and sloshing around, result is lots of foam, not even welcome at the input to the Inj Pump

You don't want water to take up residence in the fuel tank - Diesel-eating bacteria forms at the Diesel-water interface - it has to travel with the fuel in order for the water separator to function - which is why you don't want to use a water emulsifier - if the droplets are too fine, they pass thru and into the IP - very rustfully damaging in vehicles which are parked for long periods

There is a coarse screened area - ~1/2"dia - on the bottom of the sock intended to pass the heavier stuff off the bottom of the tank and into the fuel manager, with it's centrifugal water\heavy sediment separator - that coarse area was totally plugged with nose excrement - the ~70 micron remainder of the sock was also plugged, as was the filter-bypass valve, intended to supply fuel at incidence of plugged sock

TD's beast could not even be fed due to that sinus-infected sock - the sock and tank is now as clean as we could manage in the short time allowed - prolly will get a new GM sock in the near future
 

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Is there are a way seperate fuel and air if foaming is a problem external to the tank? I've seen some fuel oil supply systems that have air bleeds at the top of a cylinder to vent air. Could a non-clogging version be thunked up?
 

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If the substance was brownish black, and sticky as heck, it is probably sugar. The sugar itself does little to the fuel system, but if it mixes with water, you get the black crud. Had it happen to me on the big truck once. $1000 to clean and rebuild the injector pump.
 

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Jon, who have you been a butthead to?
 

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Any scheme would involve pre-filtration - fill a pre-tank, transfer the fuel to the main tank thru a Racor\equiv - or maybe use an old cotton sock over the end of the nozzle each fillup - would that filter 40gals? - and what would you do with it when done? - pitch it in the trash-can at the island? - certainly wouldn't want it in a baggie under your seat - or in the glove box
 
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