04.5 sucking air--wont start below 1/4 tank

[Gibbs]

When the tank is that low, I can hear the pump get a lot noiser due to cavitation (which explains why I have to wait and let the pump run a few seconds before I try to start it-- so the system can get primed.) My truck had the fuel canister mounted pump on it when I bought it about 4 yrs ago. I wanted to run a Smarty Jr, so I built my own fuel sytem with a Walbro 392 pump, bypass regulator which returns back to filler neck, and 3/8" marine barrier lined fuel hose. I also relocated the APPS and fabbed a bracket to run a filter base with 3u Donaldson P551313. I'm seeing about 23 psi of pressure at the CP3 at idle. I know this is a little high, so I was going to put a lighter spring in the bypass regulator--but from what I've read it won't cause any problems. I installed the fuel system not long after I bought the truck, but am pretty confident it has nothing to do with no starts below 1/4 tank, because I never dropped the tank or touched anything in it. I used Dorman connectors that adapt the factory fittings at the tank to a hose barb, that way I wouldn't have to fool with dropping the tank. 2003 had basically the same fuel system and it never had any problems.

I know a lot of 05+ trucks have issues when using a draw straw or non OEM pickup, but like I said, I never modified anything inside the tank. Anybody have some pictures or information on the OEM tank module? It seems like it has to be a hose with a hole in it that is not covered by fuel when the tank is getting that low.

I really just need to drop the tank and poke around a bit, but have put it off for a few yrs now.

Thanks

 

[cerberusiam]

Easiest thing would be just get a new canister from Glacier Diesel Power. Probably have a hole in a line from rubbing or a cracked connection, at 12 years old any number of things can happen.

 

[Gibbs]

I finally dropped the tank today and discovered the problem. The mesh filter on the bottom of the module was completely clogged with black sludge. I suspect it is algae/microbial crud, as I had a bout with it a year or so ago that clogged my filters and kept my engine from revving past 1700 RPM. Back then I treated twice with Power Service Bio-Kleen biocide and changed the filters twice and never had any more trouble (or so I thought!) The gunk was really hard to clean off the mesh, as there are actually 2 layers close together and the goo was on each side of each layer, plus it was trapped in between them. I spent about 30 min at the parts washer, along with 2 cans of brake cleaner and compressed air, but I got it pretty clean. I did notice a small tear in the top screen, but I may have done that when handling/cleaning it. The rest of the unit was in good shape. I looked inside the tank and it didn't look too awful bad, so I reinstalled the module and buttoned everything up. I'll give another dose of Bio-Kleen for good measure and run this tank as low as I feel comfortable and see how she works.

 

[cerberusiam]

The black build up is likely asphaltenes, typical problem with older trucks. A constant diet of a good additive will help with that.

 

[p-Bar]

The black build up is likely asphaltenes, typical problem with older trucks. A constant diet of a good additive will help with that.

Good reminder for all of us with these older rigs. Seems like yesterday it was new . Go figure

 

[Gibbs]

The black build up is likely asphaltenes, typical problem with older trucks. A constant diet of a good additive will help with that.

BDaugherty and I were talking on phone about the sludge when I pulled the module, and he mentioned asphaltenes. I knew that was the reason for the fuel filter being black, but I had no idea that gunk could accumulate that much. I learned something new; Thanks.

I had been running Power Service most of the time I've had the truck, but it had 143K on it when I bought it.

 

[cerberusiam]

Once the build up starts nothing short of scrubbing will clean it off. The additives should help limit future buildup.

 

[MJWenrich]

On my 2004.5, with 127K on the clock, I have noticed I hear a gurgling sound as though it might be sucking air and the pump continues to run all the time. Would this be an indication that the pump is failing as well as being clogged? If I drop the tank should I replace the pump due to time and miles? Also, does anyone know of a link to drop the tank? Tried the search function and did not see one that addresses this. A new pump at O'reillys is $230. BTW, I have not been using any additive as I saw posts several years ago that if you use fresh fuel and don't fill just after a fuel dump, it's not needed.