Running off a temporary gas tank
 

We're in the process of trying to get an old engine running. As it's set of 12+ years, I've removed the rubber hose between the tank and the hard line, and have added a temporary hose that's around 5 feet long.

The plan is to run this hose to a temporary fuel tank while working on the engine.

Here's where I'm lacking knowledge. I know the hard line runs to a mechanical fuel pump that feeds fuel to the carb. I'm guess that since it's pushing fuel to the carb, it "should" be pulling fuel from the tank but am not sure.

I guess what I'm asking is: Is the pump gravity fed? Meaning I need to rig up the temp tank to be higher than the pump. Or will the pump suck the gas out of the temp tank meaning I can just sit it on the ground?

We were going to test by pulling the fuel line running into the carb to see if gas was coming out, but couldn't get the line off and have to mess with that later (as I need to replace the fuel filter anyways).

thanks

Re: Running off a temporary gas tank
 

Not sure how much suction * would be left in an old mechanical fuel pump. They were built pretty much bomb-proof, though. Just to be safe, elevate the temp tank to the same level as the bottom on the In-Cab tank.
[The stock behind-the-seat tank does add a little gravity to the feed, especially when full.]
The stock mech fuel pump will pull gas from the frame-level, aft-of-axle tank in the Blazer, no problem. When I had a 454 in a K/10 Suburban I went to an electric Holley Red fuel pump, but that was a long pull to a hungry engine.

* Academic at this point, but you could put a pressure gauge on the fuel line to find out.

Re: Running off a temporary gas tank
 

Thanks. A follow-up based on your response....

Do I need to rig up a tank where the hose can be run out the bottom so that gas is flowing down the line to the pump?

As it stands, I'm justing a regular 2-gallon gas tank and have the hose run down into the tank. With this method, even if I elevated the tank, the pump would still have to pull the fuel up and out of the tank.

If all else fails, I can check for fuel when I remove the line to replace the fuel filter and adjust my method accordingly.

thanks

Re: Running off a temporary gas tank
 

In that case, I wouldn't worry about it. It's a pickup truck, not a NASA mission.

Re: Running off a temporary gas tank
 

Ha! Not trying to overthink things, just planning for all possibilities. As the truck is an hour away and once there I'm not real close to a parts store, I prefer to plan ahead and take whatever I need with me (even if it's extra things I may not need right then.)

I've seen a lot of pics where people have replace the hard line running from the pump to the carb with a flex line and inline filter. Kinda like that idea. Need to research how to go about that.

Re: Running off a temporary gas tank
 

Itll suck it it right out of the gas can with the can sitting on the floor. I do this all the time. If you have any doubts you can put a clear filter between the pump and carb to see the fuel flowing

Re: Running off a temporary gas tank
 

Thanks! I was hoping this was the case.

I certainly want to add a flexible line with inline filter to replace the hard line between the pump and carb. Now I just have to figure out how to go about it.

Re: Running off a temporary gas tank
 

It is best to keep the hard lines and only use the rubber/flex-able hose only where needed.

Re: Running off a temporary gas tank
 

Is there a particular reason for this?

To be clear, I was only talking about between the pump and carb. I saw a lot of pictures where it had been replaced with braided line so figured that was a "normal" modification.

thanks

Re: Running off a temporary gas tank
 

I have an old school 5 gallon tank in my bed. I ran the original fuel line to it. It works but I got to keep it at an angle to keep the fuel on the line side. It's a temporary tank, but I've used it for almost 5 years to take trips around the block.

As for a gas can, that will work also just sitting on the ground. A nice way to keep my battery from dieing while trying to get fuel up to the carb is to use an electric fuel pump to prime the mechanical pump

Re: Running off a temporary gas tank
 

People don't normally run a rubber line from pump to carb because the gas will eat the rubber. And when not running the engine, the hose will dry out and crack causing fuel leaks. If it's just temporary, you can run a rubber line from pump to carb, but if you plan on it being permanent, don't do it. It's more of a safety precaution not to run rubber from pump to carb.

Re: Running off a temporary gas tank
 

On my shinny chrome motor, I run a braided line with a clear glass fuel filter. I don't have any problems with the braided line.

Re: Running off a temporary gas tank
 

I'm talking about braided steel fuel line. Not plain rubber line.

Apologies if I'm misunderstanding.

Re: Running off a temporary gas tank
 

Ok. Good.

That's what I was talking about, sorry if I didn't explain well.

Is this something you buy off the shelf? I'm assuming you have to get various pieces and build it yourself?

Re: Running off a temporary gas tank
 

I went to autozone and bought 2 of there longest braided line they had on the shelf. Used one piece from the pump to the filter, then cut the second one down a little and used it from the filter to the carb

Re: Running off a temporary gas tank
 

Thanks!

Is this something I need to be doing at this stage in the restore? Nope! LOL

Just looked like something fun to do that I can do here at home (since the truck is an hour away) and can then install it when I get a chance to go work on it.

Re: Running off a temporary gas tank
 

A follow-up, as I know squat about this stuff....

Any special fittings I need to use to work w/ my engine? Or are these things a one-size-fits all kind of thing?

thanks again

Re: Running off a temporary gas tank
 

You can get the braided line that is Teflon lined or rubber lined. The issue is with the ethanol in the fuel, it will eat up the "rubber" lines in time. Probably the Teflon also, but it should/would take longer.

When you were first mentioning the rubber lines I thought that you were talking about the complete fuel line all of the way from the tank.

Re: Running off a temporary gas tank
 

No worries. I'll keep the ethanol issue in mind.

Just looking to replace what I can, when I can. I need to get a long of built-up gunk off the engine, which mean removing a lot of pieces that are in the way. Figure while I'm pulling things off, I'll replace/upgrade them as I go while I'm at it.

Everything is theoretical at this point....just going where the wind takes me right now.

Thanks again for the advice.

Re: Running off a temporary gas tank
 

I've had my braided line for almost 12 years on 3 different motors in the same truck. I have yet to have any problems with the fuel eating the rubber. Although tcrist is correct as I've stated also, the fuel will eat the rubber, dry it out, and cause cracks. But like I said, I've had mine for almost 12 years.

As for pieces needed, all you need is the braided line. There are different sizes, but you can tell them that it's for a fuel line and the parts people will get you the right size.

Re: Running off a temporary gas tank
 

Thanks. I was looking at the glass filters, but my research shows that a lot of people say that's a bad idea. Any opinions on that or going with a different type of filter housing?

Re: Running off a temporary gas tank
 

My glass fuel filter never gave me problems for 12 yrs until a couple weekends ago the rubber sealing cracked and dumped fuel all over the motor. IMO, the glass filters are more for show. On a vehicle that's driven and worked on, the glass can get hot and do weird things such as create leaks. On my other vehicles that aren't modified, I use the clear plastic filters.

Re: Running off a temporary gas tank
 

The pump has to pull the gas up out of the top of the tank but I don't know how much actual pull it has since once gas gets past the high point it becomes a siphon effect. You should be fine pulling fuel from anywhere you could set the tank on the truck.

Don't get rid of your hard line. If you want a inline filter cut out a section and add the filter with the 2 supplied pieces of rubber hose. I use the metal filters.

I wouldn't be worried about ethanol drying out your rubber lines. It's been required that most rubber fuel line be resistant to it since they first put it in the fuel system. Sometime in the 80s I think. It will attract water and that can rust steel parts though. Make sure you get high quality fuel hose that says it is resistant.


http://www.gates.com/oreilly/tech_ti...patibility.pdf

Re: Running off a temporary gas tank
 

I used to run ethanol fuel (E85) back when it was cheap ($1.67 a gallon) and yes it ages rubber hoses quickly, after 3 years they looked 20 years old! steel hard line should outlast your truck- unless you have rust issues, rubber will have to be replaced as you would with radiator hoses. The main drawback to steel is it soaks up heat which leads to vapor lock. One "best of both worlds fix" I've seen done is to cover the hard line with rubber hose (slit lenght wise) to insulate

Re: Running off a temporary gas tank
 

I've heard of that idea as well, but never tried it. Vapor lock can defiantly be caused depending on where you route your line. If your steel line is ran near something that gets hot, you can put the rubber hose in just area to act as a heat shield