rear gas tank issue

[zsimonds2]

I put a new LMC rear mount gas tank in the fall. I keep having issues with the fuel going back into the tank, so it takes a long time to get it to fire after it sits for a month. Does that mean the original fuel pump has gone bad? Or do I just need an inline check valve? And where would I find one of those?

[waco]

After a month the fuel in the carb has evaporated, so the fuel bowl needs to be filled before it will start. My cure has been to supply the fuel bowl by putting fuel into the bowl through the vent for the fuel bowl. Another option is to install an inline electric pump just after the fuel tank & use it to prime the carb. Last but not least Im sure, go out an start every 2 weeks.
I hope this was helpful.
Andy

[zsimonds2]

I've tried that and spent 20 mins of pouring fuel in the carb. and still couldn;t get it to fire back up. It seemed like it wasn't getting enough fuel pressure. Thanks for your reply!

[BigMike]

Ya, mine does that too if I don't start it for a month. I never let it go that long anymore, 2 weeks max before starting it for a few minutes. Same thing would happen with a behind the seat tank, difference is the original tank had about 5+ feet less fuel line to travel through to get to the carb.

Like waco said, if it bugs you either start it more frequently or replace the manual pump for an electric one. With an electric pump (and after a month of not starting it) just turn the key on for a few seconds to let the fuel get to the carb & it should fire right up.

[custom10nut]

If there's this issue with a tank relocation, how did the factory do it with the Suburbans and Blazers? Were the Fuel pumps different? The reason for asking is that I m going to be doing this with mine and want to make sure it works.

[waco]

It's not so much a fuel pump issue as it is an evaporation issue. To the best of my knowledge, the stock fuel pump is a pusher not a suction pump.

When the fuel in the float bowl goes down thru evaporation, the float drops & pulls the needle off the seat allowing air back down the fuel line thus allowing the fuel in the line to also evaporate out through the fuel bowl vent.

I'll add this for the OP, with this being a new install, you did use new flex lines on the install & not reuse old line correct. I just ad this because used fuel line does crack & allows air into the line (ask me how I know).

Andy

[In The Ten Ring]

Originally Posted by waco

It's not so much a fuel pump issue as it is an evaporation issue. To the best of my knowledge, the stock fuel pump is a pusher not a suction pump.

When the fuel in the float bowl goes down thru evaporation, the float drops & pulls the needle off the seat allowing air back down the fuel line thus allowing the fuel in the line to also evaporate out through the fuel bowl vent.

I'll add this for the OP, with this being a new install, you did use new flex lines on the install & not reuse old line correct. I just ad this because used fuel line does crack & allows air into the line (ask me how I know).

Andy

Original fuel lines may be rusty also.....ask me how I know!

[BigMike]

No, it's not the tank. It's the fact that he waits too long and the fuel evaporates in the carb, so the fuel basically has to pump from the tank all over again to fill the void and get fuel into the cylinders. If you drive on a regular basis it's a non issue. I had a Brothers tank in mine before switching to a Boyd's aluminum one and the only time it was an issue is when I was out on hip replacement and I didn't start it for a month. If I go 2 weeks (not often) without starting she still fires right up. I LOVE my Boyd's tank, but the Brothers tank was great too.

EDIT: Could have worded it better but I'm tired...lol

Originally Posted by custom10nut

If there's this issue with a tank relocation, how did the factory do it with the Suburbans and Blazers? Were the Fuel pumps different? The reason for asking is that I m going to be doing this with mine and want to make sure it works.

[special-K]

Fuel evaporates out of a carb that fast? I never knew that. It's pretty well sealed in there and it's not out in the direct sun. I always figured it was leak-down/system depressurized. If you are pouring gas in the carb for 20 minutes to get it to start there must be some other issue. Sounds to me like a weak fuel pump. My truck will sit longer than that and of course it takes extra cranking to fire up, but once it gets the gas it fires right up. If I poured gas in the carb I am sure it would fire right up first time. Does the choke work properly? It's still chilly some here, I assume the same is true for Nebraska. One thing about the original gas tank is you have gravity on your side.
Could it be normal carburetor behavior vs fuel injection that most people are accustomed to these days? If the trucks never needed an electric fuel pump when they were made, I don't see why they should need one now.

[Andy4639]

Mechanical fuel pump has to pull the gas from rear of truck.

Most times I have found the diaphragm in the pump has gone bad. This in return makes the pump less efficient in pumping also.
When this happens the gas returns to the tank. Then if the tank is on the same level as the pump it takes a little longer to get to the motor because it has no head pressure like from the old location in the cab. In the cab tank once the gas is flowing then the head pressure will keep it full to the pump with out much work.
20 minutes of pouring fuel into the carb is not a evaporation problem.

[cdowns]

if you use nonethanol gas it will b less prone to evaporation

[Tiger Joe]

I agree, weak fuel pump

[custom10nut]

Would a mechanical High Volume/Pressure pump work, to alleviate some of the problem? The post about the Ethanol is correct. If the fuel sits for more than about a month it does seperate, causing the hesitation and other problems. I put Sta-bil in mine for the winter months, as I don't use the truck much in the cold season.

[67 chevelle]

Originally Posted by special-K

Fuel evaporates out of a carb that fast? I never knew that. It's pretty well sealed in there and it's not out in the direct sun. I always figured it was leak-down/system depressurized. If you are pouring gas in the carb for 20 minutes to get it to start there must be some other issue. Sounds to me like a weak fuel pump. My truck will sit longer than that and of course it takes extra cranking to fire up, but once it gets the gas it fires right up. If I poured gas in the carb I am sure it would fire right up first time. Does the choke work properly? It's still chilly some here, I assume the same is true for Nebraska. One thing about the original gas tank is you have gravity on your side.
Could it be normal carburetor behavior vs fuel injection that most people are accustomed to these days? If the trucks never needed an electric fuel pump when they were made, I don't see why they should need one now.

agree , and if you have a quadrajet carb , they are famous for the 2 plugs at the bottom , cracking leaking fuel into the engine , drying the carb out , that would be my first suspect