85 c15 fuel delivery issue

[85 SQ]

Fuel tank rusted out replaced with new tank, sending unit and new rubber lines from sending unit to fittings under bed . Drove truck 50 miles the day after no issues . Couple days later truck wont start due to not getting fuel up to filter pull fuel pump ( had a busted spring )replaced with new one have reinstalled twice to make sure rod is setting on fuel pump arm correctly . Still no fuel . Disconnected line to carb before filter . Just a trickle of fuel while cranking . I have also tried to siphon fuel thru what should be the main line from the tank to the pump with no luck . I'm kinda stumped here any ideas ? I should also mention it has dual tanks so it does have the switch over valve

 

[1987 GMC Jimmy]

I would try sourcing fuel from a gas can directly to the pump to rule that portion of the system out. It could be debris lodged in the switching valve.

 

[Bextreme04]

Start simple. Make sure you have gas in BOTH tanks. The valve may or may not be switching between tanks correctly and the sending units in each tank may not let you pull the same amount out of each. Like Jimmy said, you can run a line from right before the valve to a fuel tank and see if the pump will pull with nothing in the way. If it does pump fine from before the valve, start tracking back from the valve to each tank. You should be able to pull the line to each tank from the switching valve and try to pull fuel directly from each tank. If that works, and the pump pulls directly from a fuel jug before the valve, your valve is bad.

 

[85 SQ]

I warranted the fuel pump just in case . I put the new one on and test ran from a gas can no issues the pump is working well . When I bought the truck seller said the passenger tank leaked so I've never used it the original selector switch is gone and has been wired up to a toggle . I just never mess with it . I did double check that it hadn't gotten flipped . Tomorrows plan is to bypass the selector valve and check out the line that runs up to the fuel pump

 

[Havasublue]

There are 2 bolts down by the fuel pump in the front of the engine...
If they are too long...
Bracket was removed...
You will bind up the fuel pump drive shaft...
Maybe flatten the cam love that drives the fuel pump. I have seen this happen...!
You have to be careful when changing/removing brackets that bolt to the motor...!

 

[Bextreme04]

I warranted the fuel pump just in case . I put the new one on and test ran from a gas can no issues the pump is working well . When I bought the truck seller said the passenger tank leaked so I've never used it the original selector switch is gone and has been wired up to a toggle . I just never mess with it . I did double check that it hadn't gotten flipped . Tomorrows plan is to bypass the selector valve and check out the line that runs up to the fuel pump

That could be it, the valve is notorious for failing. If you are only using one tank anyways, I would bypass direct to the tank you know has fuel and see what happens. The valve can fail to a position BETWEEN the two tank positions and draw from neither tank. If you are going to unhook the hoses to the valve anyways to bypass it, you should look into the valve and have someone flip the switch to see if it is moving properly and going completely to the correct side when selected. It could even be switching correctly and have some junk blocking the ports. Just go slow and check one thing at a time. You should be able to troubleshoot all the way to an actual failure point without having to buy anything. Throwing parts at it rarely makes financial sense, although i'm guilty of frustrated parts swapping myself too.

 

[85 SQ]

That could be it, the valve is notorious for failing. If you are only using one tank anyways, I would bypass direct to the tank you know has fuel and see what happens. The valve can fail to a position BETWEEN the two tank positions and draw from neither tank. If you are going to unhook the hoses to the valve anyways to bypass it, you should look into the valve and have someone flip the switch to see if it is moving properly and going completely to the correct side when selected. It could even be switching correctly and have some junk blocking the ports. Just go slow and check one thing at a time. You should be able to troubleshoot all the way to an actual failure point without having to buy anything. Throwing parts at it rarely makes financial sense, although i'm guilty of frustrated parts swapping myself too.

I have completely bypassed all three lines coming from the drivers tank to the valve it still wont pull from the tank I'm about at my wits end I'm going to drop the tank later and check out the lines sending unit etc

 

[85 SQ]

I have completely bypassed all three lines coming from the drivers tank to the valve it still wont pull from the tank I'm about at my wits end I'm going to drop the tank later and check out the lines sending unit etc

Finally figured out the problem main line from the sending unit was either kinked or collapsed on itself at the sending unit . The 3/8 line was brand new bulk off the shelf at oreilys . It seems way to soft for fuel line though the 5/16 and 1/4 line I have is way more rigid and takes way more bend before kinking or collapsing on itself . Thanks for the input

 

[75gmck25]

I have switched to using SAE J30R9 or J30R7 fuel injection hose for all my rubber fuel lines, since it is designed to hold up to modern fuel with ethanol. It’s expensive at the parts store, so I bought it in longer sections (25 feet?) from an online supplier. It seems to have a similar bend radius as regular fuel hose, but I didn’t compare it directly.

Bruce