Primary tank good, auxiliary tank spits and sputters

[johnnydefacto]

First I have searched and searched this forum and others hoping to find someone who has had the very same issue, but to no avail. (if this subject is in the wrong forum please move it somewhere more appropriate).

89 c30 dually, 454 TBI. On driver side tank truck runs perfect. I switch over to passenger side and it will die.... UNLESS i pump the throttle pedal slowly, I can keep the engine running forever, in park or neutral, albeit just barely. It dies when I try to let it idle, i depress the accelerator pedal and when I release it the engine revs a little bit, just long enough for me to depress the pedal and release again to keep the motor from dying. I just got the truck, got it from a dealer, had it 2 months before I got it, they put fuel in that tank but never got it to work, so the fuel is not that old, possible mixed in with really old fuel. Knowing this I sat and kept the truck running/reving for 5 minutes hoping to get some of that newer fuel in the mix and hoping the truck would start idling. I need to drain that tank and start with fresh fuel but I do not think that will help.

I am here at work for 2 days and am trying to come up with a game plan for when I get home.

My two thoughts:

I have a selector valve that is not switching over fully (my selector switch is a 2 position rocker switch, it is either in the UP position for the passenger side, or DOWN position for the driver side. It is like a wall light switch in your house, not a momentary switch like I have been reading about, I have no way to "hold the momentary switch for 2-3 seconds" to make sure the selector valve switches all the way).

OR I have a bad fuel pressure regulator that is stuck open or has a weak spring allowing fuel to return to the tank and leaving my TBI with very little fuel.

Fuel filter may need to be changed but I believe I only have one, that both tanks share the same filter, it is post selector valve I think.

Below my selector switch rocker switch, there is another small rocker switch. I have to find out what this does, but i have played with it and does nothing when it comes to my fuel problem.

Any help would be appreciated. Thank you.

 

[foamypirate]

Actually, the more likely (and very common) cause, is a split hose between the fuel pump and the fuel sending unit on that tank. My old 87' had the exact same behavior, ran fine on one tank, and would sputter and barely stay running on the other. When I swapped the tanks and engine over to my 84', I replaced the pumps. When I got the tank open, I found a split hose. Very common issue. It basically pumps all the fuel right back through the split in the hose into the tank.

 

[chengny]

The pertinent part of TSB # 90-6C-89, Dated 9/90 (seems to reinforce what the Pirate suspects is the problem):


Some 1985-90 engines equipped with 2.5L, 2.8L, 4.3L, 5.0L, 5.7L or 7.4L may experience a condition where fuel delivery is interrupted to the engine causing a "no start condition". This condition may be caused by deterioration of the in-tank fuel pump coupler hose located between the fuel pump sending unit and the fuel pump. This condition may be repaired by replacing the original coupler hose with a new VITON coupler hose kit P/N 25028041. The kit consist of a new VITON hose and two clamps.

 

[johnnydefacto]

Actually, the more likely (and very common) cause, is a split hose between the fuel pump and the fuel sending unit on that tank. My old 87' had the exact same behavior, ran fine on one tank, and would sputter and barely stay running on the other. When I swapped the tanks and engine over to my 84', I replaced the pumps. When I got the tank open, I found a split hose. Very common issue. It basically pumps all the fuel right back through the split in the hose into the tank.

The pertinent part of TSB # 90-6C-89, Dated 9/90 (seems to reinforce what the Pirate suspects is the problem):


Some 1985-90 engines equipped with 2.5L, 2.8L, 4.3L, 5.0L, 5.7L or 7.4L may experience a condition where fuel delivery is interrupted to the engine causing a "no start condition". This condition may be caused by deterioration of the in-tank fuel pump coupler hose located between the fuel pump sending unit and the fuel pump. This condition may be repaired by replacing the original coupler hose with a new VITON coupler hose kit P/N 25028041. The kit consist of a new VITON hose and two clamps.

Thanks for the quick reply. Yeah that sounds very likely.... going to have to check that out. Guess now I have to decide whether to drop the tank or lift the bed

 

[highdesertrange]

x2 on the rubber coupler. or it could be a bad fuel pump. don't you have a fuel pump in each tank? highdesertranger

 

[smoothandlow84]

...could also be that the sock screen filter inside the tank (attached to the fuel pump) is either partially clogged, or disintegrated. My square was running the same, figured it was the selector switch...it wasnt. I then dropped the tank and discovered that not only was the sock screen filter clogged, but pieces of it were lodged in the fuel pump. Turns out it was the fuel pump circa 1987....yikes! Replaced fuel pump with a Delphi unit, and also installed a new screen filter, hose and electrical connector. A week later my secondary fuel pump went out. Turns out the screen filter was also clogged. It was easier for piece of mind to just replace the entire unit pump and all since I already had the tank empty and off the truck. Also change the frame mounted fuel filter as well. The frame mounted filter will also collect crap that makes it past the fuel pump mounted filters.

 

[hatzie]

It may be worth noting that almost all the in-tank fuel pumps I've purchased come with the wrong hose that melts and fails in a few months.
Get hose that's rated for submersion in fuel. SAE J30R10
http://www.gmsquarebody.com/forum/showthread.php?t=15026

 

[johnnydefacto]

Actually, the more likely (and very common) cause, is a split hose between the fuel pump and the fuel sending unit on that tank. My old 87' had the exact same behavior, ran fine on one tank, and would sputter and barely stay running on the other. When I swapped the tanks and engine over to my 84', I replaced the pumps. When I got the tank open, I found a split hose. Very common issue. It basically pumps all the fuel right back through the split in the hose into the tank.

Alright, I love this forum. I went ahead and bought that rubber hose piece for around $20, 2" long, came with 2 clamps. I decided that I would rather pull the bed because my tanks have the plastic cover and some of those bolts look tough to get to, plus I am lowering the truck and I needed to grind off the rivets on the leaf hangers...... so I blasted all 8 of the bed bolts with PB blaster, 3 times over 3 weeks. Today I was able to easily unbolt the bed, leaving the rear two loose but still connected, disconnected the filler necks and grounds. My neighbor helped me lift the front of the bed up about 2 feet and I set 2 jack stands on the frame rails to hold up the bed. And the two rear bolts still connected so that the bed would not slide or move accidentally.

Grinding those hanger rivets without throwing massive sparks at the gas tanks was tough but I got them off. Western Chassis hangers and shackles... the hangers mounting holes did not line up correctly so I had to enlarge the holes a bit, no big deal.

I pulled the sending unit out of the passenger tank and boom, that 2" hose had a 1/2" split in it.... I was pumped to see that. The new hose is very stiff and the outside diameter is smaller, so the clamps from the kit had to be used. Quick swap, reinstall... keyed on ignition for a few seconds, then off, did this a few times to prime the fuel lines, and POW, she fired right up, runs perfect with either tank!!! I can switch over and there is no hesitation at all.

Thank you for your help.