Driver side tank not working.

[Jcoronado09]

I have a 87 350 5.7l with a 700r4 with dual tanks. Currently running on passenger tank. I can hear my fuel selector valve flip back and forth when I switch from Rh to Lh. I have noticed that when I start on the Rh I can hear the pump. When I flip to the Lh, the truck uses the fuel in the line and shuts off. Turn the key off and forward to start I do not hear the Lh pump. When I bought the truck I was told it has new tanks and new pumps. Lifted the bed and check the grounds and they look solid. Not sure what els to do from this point need help. Thanks in advance.

 

[SirRobyn0]

I have a 87 350 5.7l with a 700r4 with dual tanks. Currently running on passenger tank. I can hear my fuel selector valve flip back and forth when I switch from Rh to Lh. I have noticed that when I start on the Rh I can hear the pump. When I flip to the Lh, the truck uses the fuel in the line and shuts off. Turn the key off and forward to start I do not hear the Lh pump. When I bought the truck I was told it has new tanks and new pumps. Lifted the bed and check the grounds and they look solid. Not sure what els to do from this point need help. Thanks in advance.

Ok I know a fair bit about the fuel switching systems on these trucks but I have some problems with what you have said and need a clarification.

You posted this in the Carb fuel system section, but you mention that you can hear the fuel pump run. Well unless an electric pump has been added in the carbureted trucks came with a mechanical pump on the block and you should not be able to hear that at all.

Unless someone has added the second tank and used an older style valve it is hard, but not impossible for the tank to not change over and the gauge to change. The old one wire valves were known for that but I don't know the exact year they stopped with those but early 80's I'd guess.

If this was my truck assuming it's a carbed system, I'd disconnect the lines at the valve from the tanks and blow a little air back to see if they are clear. You need to be super careful doing this be cause there is some risk if static electric charge casing a fire, more so if you use a lot of pressure. Regulating your air pressure down to less than 10 psi or blowing back carefully with your mouth would be best.

In an ideal world you'd pull the tanks and see what kind of shape they are in. There is a screen / sock on the bottom of the pick up tubes both carbed and FI systems have these, but if the tanks are rusty of the truck sat long enough for the fuel to turn to varnish then those socks are plugged and fuel is never getting though it no matter how good the valve is.

So in the real world I try the air trick first, then replace the valve. If it's still not working right I'd drop the tanks and inspect.

Good luck.

 

[SirRobyn0]

Yes, I'm aware that this post is 11 days old and the OP has only made this one post and might be gone. It's a risk I took answering this thread, if he doesn't make use of it maybe someone that knows how to search the forums will when they land on the 100's tank switching posts.....

 

[Jcoronado09]

No I'm still here and fiddling with this issue. New member and unfamiliar with where to post. Yes the truck is carbed, as for hearing the fuel pump(only on the right side) it's the sending unit priming the fuel line just before I start the truck. Can not hear the same sound when the switch to LH side.Tanks are new, sending units are supposedly new. Fuel hose lines look new besides the metal the lines that go across the frame. I have searched many duel tank, switch, valve switch, and gas gauge threads. To which I have taken all the info and have applied. I know I'm not having power issues as to which I can flip the switch and hear my valve go from RH to LH. I just ordered a multi meter to check voltage.

 

[WP29P4A]

Did your truck begin its life as TBI? Or has it always had a carb?

 

[SirRobyn0]

No I'm still here and fiddling with this issue. New member and unfamiliar with where to post. Yes the truck is carbed, as for hearing the fuel pump(only on the right side) it's the sending unit priming the fuel line just before I start the truck. Can not hear the same sound when the switch to LH side.Tanks are new, sending units are supposedly new. Fuel hose lines look new besides the metal the lines that go across the frame. I have searched many duel tank, switch, valve switch, and gas gauge threads. To which I have taken all the info and have applied. I know I'm not having power issues as to which I can flip the switch and hear my valve go from RH to LH. I just ordered a multi meter to check voltage.

Did your truck begin its life as TBI? Or has it always had a carb?

Yea, no factory configuration had any kind of electric pump on a carb. It should only have one wire to the sending unit for the gauge. I've given you my best troublehooting info. Let us know what you find.

 

[WP29P4A]

So if it still has the relay on the firewall, with the fuel pump test lead, can he just use the test lead to check both pumps? Like the manual shows?

 

[Grumpy]

Interesting how it is the Left tank that doesn't work. I would check and verify if it already qualifies for welfare, then kick it out of the basement and tell it get back to work.

 

[SirRobyn0]

So if it still has the relay on the firewall, with the fuel pump test lead, can he just use the test lead to check both pumps? Like the manual shows?

I would think so, but a TBI pump rated for way more pressure than a carb can handle. I'm starting to wonder if he actually has a TBI truck and if he isn't real familiar with the old trucks might be mistaking the throttle body for a carburetor. That pic looks like a TBI harness to me.

@Jcoronado09 I hope I have not offended you with that, we get guys with all kinds of experience levels here from pretty much experts to very green. Would it be to much trouble for you to take a picture of the passenger side of the engine block down lowish, and another one looking down the throat of the carburetor? It seems like we must either be working on a TBI system or something that someone has made changes to in one way or another at sometime. Thanks.

 

[WP29P4A]

Was TBI an option in 1987 on the 350, or did all 350's come with TBI in 87?

 

[SirRobyn0]

Was TBI an option in 1987 on the 350, or did all 350's come with TBI in 87?

It was an option but it is not just that cut and dry because of the emissions standards were different by weigh rating. For example in 1991 as the last of the crew cab 1 ton squares rolled off the assembly line the 454 was still available with a carburated fuel system. By 87 TBI may have been standard on a 1/2 ton. Let me check and see if I can find anything in my references.

So for a 1987 Chevrolet V10 with the 350 TBI, in my parts catalog I only see TBI parts listed I do not see carburetor parts listed at all.

So I think that confirms our suspicion this is a TBI truck.

So that being the case @Jcoronado09 I think if your hearing the right fuel pump kick on but not the left pump, you likely have a bad pump in the left hand tank. You could disconnect the line to the left side tank, flip the switch to that side turn the key on (may have to crank it for a couple seconds) and see if any fuel comes out of that side. If not you may want to check for power at the pump, but in all likely hood you have a failed pump in that tank. We are now running under the assumption your truck is TBI not carbureted as I initially thought.

What do you think @WP29P4A Mike?

 

[Jcoronado09]

No your all good. Here are the pictures. Just got home and going to test to see if I have fuel flowing the line and check voltage.

 

[SirRobyn0]

No your all good. Here are the pictures. Just got home and going to test to see if I have fuel flowing the line and check voltage.

Yup, that's a TBI system, if you look in the second picture you can you can see the wiring and the connectors for the fuel injectors. A TBI system is just like that 2 injectors on the throttle body. I'd test that left side pump next.

 

[WP29P4A]

It was an option but it is not just that cut and dry because of the emissions standards were different by weigh rating. For example in 1991 as the last of the crew cab 1 ton squares rolled off the assembly line the 454 was still available with a carburated fuel system. By 87 TBI may have been standard on a 1/2 ton. Let me check and see if I can find anything in my references.

So for a 1987 Chevrolet V10 with the 350 TBI, in my parts catalog I only see TBI parts listed I do not see carburetor parts listed at all.

So I think that confirms our suspicion this is a TBI truck.

So that being the case @Jcoronado09 I think if your hearing the right fuel pump kick on but not the left pump, you likely have a bad pump in the left hand tank. You could disconnect the line to the left side tank, flip the switch to that side turn the key on (may have to crank it for a couple seconds) and see if any fuel comes out of that side. If not you may want to check for power at the pump, but in all likely hood you have a failed pump in that tank. We are now running under the assumption your truck is TBI not carbureted as I initially thought.

What do you think @WP29P4A Mike?

Sorry for the late response, I actually had to put in a full days work today. I wasn't sure about it having TBI but everything he was describing sounds exactly like what we went through with my son's truck, which is TBI. I didn't think they made them with dual tanks with the pumps in the tanks, and a carb.

 

[Jcoronado09]

Finally got time to work on the truck. After dropping the tank. I tested the pump on the sending unit, it was bad. Picked up a new one from parts store. Tested before putting it in the tank and it was good. So did the switch a roo. And put everything back together. Both tanks working as they should.