Worst week so far!!

[Ron Sebastian]

So I have had a inconsistant issue of my left saddle tank intermitantly struggling to work, engine bogs when I switched tanks to it. I threw the credit card at it thinking I would muscle my way into it working. Starting with the six port fuel switching valve $65. Worked for a day, then back to bogging down and shutting off. Then I changed the switch in the cab with a new one $12. That did nothing. Then I changed the relay switch in the cab $10. No change. I dreaded dropping the 35 year old tank, but did it. Emptied the fuel and dropped it. New left tank and pump $210. Not only did that not fix it, now my fuel gauge is not working and I still have the same problem. I put the 10 gallons back in it. So today after driving 3 hours this weekend on the right tank thinking it would be empty. The left tank was empty when I went to drop it again to see what I did wrong. Swapped out pumps again. No change in anything. Went to the gas station to fill up the right tank that I thought I had been driving on, it was full. I only could fit 2 gallons in it, jammed it up to the cap with fuel, thinking it had to be wrong. I obviously had been sucking fuel from the left tank, but the switch was on RIGHT SIDE. There is only one way for any connector to fit. Then I filled the empty left tank. By the time I got home fuel was pouring from my charcoal canister in the front by the radiator and out of the fuel cap on the right tank. I don't know what I did wrong. I dicked that job all up, and now it still dosen't run right and the fuel gauge is inop. And I just got the parts to redo the disc brakes up front. My confidence is shot. Not sure where to turn. Whiskey?

 

[dvdswan]

Have you checked the fuel filter? If it's fine, then...

it sounds like a partially clogged or almost all the way clogged line. Hate to say this... but you can disconnect the lines at the switching valve and blow them out with compressed air. The problem I believe is the from the pump to the switching valve. So, dropping the tank, disconnecting the pump and blow out the line from the valve to the pump. As a safe measure I would do the line to the TBI as well.

Remember to do the return lines as well. You probably have junk in there as well. Don't blow through components, you don't want to get the junk in your new items.

 

[Redfish]

I am thinking that either your new 6 port switching valve is messed up or that you connected the tubing back to it incorrectly. It's almost like your fuel return is going where it shouldn't and that your suction line may be wrong. I would start with how you re-connected to that valve.

If you need me to crawl under my '87 and get pics for you I will do so. Just let me know.

 

[Ron Sebastian]

I appreciate the insights guys. Rechecking all connections and blowing out lines, next week. I do think it's electrical and not mechanical, but what do I know. I may have even kinked a line installing the new pump, but it still has the same issue as when I started. Thanks again!

 

[Ron Sebastian]

Would still love to know what I did to screw up my gas gauge?

 

[deerejohn]

sounds like the 6 way valve is not working. my truck was sucking off passenger side and returning on driver side switched out 6 port valve and fixed it. ground wire on sending unit maybe. when you drop tank pull sending unit and plug it in under truck and move it by hand and check fuel gauge is moving in cab.

 

[Ron Sebastian]

Checked the float on the bench, ohms we're in range. Nothing happens when attached to wiring harness. Gauge stays at full for both tanks.

 

[Ron Sebastian]

Does the gas gauge wires go through the 6 way?

 

[deerejohn]

yes it does. here read up on this.

https://www.gmsquarebody.com/threads/dual-tank-operation.20921/

 

[Ron Sebastian]

I'm on it. Everything appears correct. I am missing something and it's very disturbing I can't see it.

 

[scrap--metal]

I appreciate the insights guys. Rechecking all connections and blowing out lines, next week. I do think it's electrical and not mechanical, but what do I know. I may have even kinked a line installing the new pump, but it still has the same issue as when I started.

I've kinked the flexible line above the tank before, but as you mentioned, your issue was there before the work started.

Maybe your flexible line has deteriorated inside if it's still original with the 35 year old tank? I've seen a flexible line fall apart in such a way that there was a flap inside cutting off the flow.

That wouldn't explain the charcoal canister filling with fuel though.

I am thinking that either your new 6 port switching valve is messed up or that you connected the tubing back to it incorrectly. It's almost like your fuel return is going where it shouldn't and that your suction line may be wrong. I would start with how you re-connected to that valve.

^^^ I think @Redfish is on to something.

 

[Ron Sebastian]

Thinking I need to step back from the fuel problem. As far as I can tell, the truck runs on the right tank as it always has. Fuel will start to fill the evap canister if I switch to the new left tank. Still no fuel gauge either side. So I'll leave it for now and not switch tanks. Going to tackle front brakes, hubs, bearings rotors. Hopefully get some confidence back.

 

[Bob25]

I had this exact problem years ago with my '76. The switching valve failed mechanically but the system showed electrically that it had switched tanks. Left me on the road in the middle of winter. Maybe you've already covered that side of the problem, but ...

 

[Ron Sebastian]

Heading in that direction.

 

[chuck13]

Never had ANY luck w dual tanks.Couldn't ya just "T" off the connections and run it like that?I guess the return might be a problem tho...