95 GMC Topkick hesitating and miss firing...

Have a 95 GMC Topkick with the 6.0L TBI engine. Put a new distributor in last year and then new fuel pumps this year. Was running great but started to sputter so figured was getting low on gas (fuel gauge isn't accurate). Put some gas in and seemed OK for a bit but started sputtering again and getting worse. Started and idled great but no power when trying to drive. No check engine light came on. After finding a mouse nest on the engine (complete with live mice, ewe) and remnants in the air filter and intake tube thought wires or something were chewed. Blew mouse nest and all the crap out with a long air nozzle and didn't see any damage. Noticed the TBI injectors appeared to be dripping/leaking the other day so got a can of Seafoam thinking they're dirty. After letting it run for a few minutes could now get 2500-3000 RPM. Put air cleaner back on to take a test drive but acted up again in about a minute.

Limped it back to shop (took forever) where tools are and removed line to fuel filter to check fuel pump. Lots of gas when key turned on. Went underneath and noticed red fluid dripping from filter. Took other fuel line off and removed filter (filter was new with fuel pumps). Rust crap almost like a paste in the filter. I rinsed the fuel tanks a few times when replacing the fuel pumps but must have still had some rust and crap in the tanks. Interesting it got past the strainers on the fuel pumps. Poured some clean gas in the filter and blew it through several times removing a lot of the rusty fuel. Put filter back on and it was like a new engine with instant throttle response and no hesitation or sputtering. Went for a short test drive and problem appears to be solved. I'm so glad it wasn't something electrical where I would have had to get someone with experience to look at it. I don't use the truck too much so will see how it behaves before getting a new filter. I figure I'll trap more of the rust crap and then change the filter. Sometimes you get lucky.

nowadays you need to use fuel stabilizer all the time in occasional- use equipment and vehicles

My mechanic friend said to use premium gas to help eliminate fuel/ethanol related problems. The passenger tank was the dirtiest and it just pumps fuel to the drivers side tank. I think getting low on gas caused more rusty crap to be sucked up. Will see how it behaves in the next couple of days.

EFI TBI systems did NOT like ethanol and do not deal well with water intrusion as the ethanol places the water into solution(polar Solvent) where sends it into the delivery system. Would consider having tanks cleaned by a radiator shop IF will do it to acid burn the rust out, then full cleaning to remove acid residues. Will not ever remove it all where will require more frequent filter changes for the foreseeable future. I agree on the premium gas or using a additive to offset the ethanol, sea foam has a isopropanol component is still alcohol and absorbs, moves water.

What would be a better additive to use or just add premium gas? Apparently the Petro Canada 94 octane gas here has no ethanol in it.

No ethanol 94 is fine. Would look thru the additives available try to find something Not alcohol related, I prefer Lucas for Gasoline.

The other thing you might consider is eliminating the tank you don't need. Since it is an occasional use truck, you probably don't need two tanks worth of fuel at a time. If the passenger tank is the one with the most crud, I would just unhook it and clean your drivers tank and move on.
I am in a similar situation. My tank is pretty clean except where the drain plug is. There is rust in there, but it doesn't appear to be loose. I am going to use non ethanol premium in mine as well, as this truck wasn't made for these new fuels.
I took the fuel filters off this and one on the mechanical fuel pump had some large chunks of

When first put the fuel pump in the drivers side tank it ran great but excess fuel (TBI) went to the passenger tank so after awhile it quit because the passenger tank pumps fuel to the drivers side tank. Mechanic friend said it could be a pain figuring out all the fuel lines in order to bypass the other tank.

Any decent mechanic can determine the lines purpose

DMiller said:

Any decent mechanic can determine the lines purpose

Click to expand...

^What he said!

I wouldn't think there would be that many lines. You probably have main fuel line out, and return lines, possibly to both tanks. There could be a link line that connects both tanks together. I am not sure if both tanks have fuel pumps in them, or just the drivers. Either way, you should be able to disconnect and plug the lines going to the passenger tank. If you have a return line to the pass tank, re-route it back to the drivers.
I am sure there are other concerns as well, but I think it would be better to simplify the system and not have to change fuel filters over and over and ruin pumps with trash getting in the system.

DMiller said:

Any decent mechanic can determine the lines purpose

Click to expand...

I'm sure the fuel lines could be figured out fairly easily for a single tank set up. It's not as simple as just plugging lines to the other tank though. You'd have to cut fuel lines and T into other lines and do a bunch of jerry rigging to make it work. It would also be a lot easier if you had a nice shop to do the work in. Both tanks have a fuel pump but the passenger tank pumps to the drivers side tank and is a different pump. My main objective was to get the truck running properly. If I keep having a problem then maybe removing the tank and having it steamed or professionally cleaned would be a good option or then consider eliminating the 2nd tank.