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nylyon

Is the gas draining back to the tank?

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nylyon

I know I remember seeing quite a number of posts on this, but I am completely brain dead this morning.  Went to start up the 414-8 today and it didn't want to go.  This happened during the summer as well, and I suspect that the gas is draining back into the tank.  After a lot of cranking and help from a shot of brake cleaner in the carb, it fired right up, runs perfectly and will restart easily.

 

What stops the gas from draining back into the tank and does this sound like a reasonable diagnosis?  

 

When I park it later today, I am planning on turning off the tank petcock to see if that helps.  

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AMC RULES

Link to eBay allowed since a direct answer to question.  (nylyon)

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stevasaurus

Just had a discussion with RacinBob on this subject.  One thing you could try, until you put on an electric fuel pump, is jack up the rear end or back it up a ramp to try to keep the gas from draining back.  Bob, said it did help, but did not cure it.  If you can get the tank above the carb or fuel pump it should help.  :)

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slammer302

There is check valve's in the fuel pump small rubber discs with a spring. Maybe something has gotten stuck under one of them and not letting it close

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squonk
On 10/15/2017 at 12:12 PM, AMC RULES said:

Thanks for the link Craig. I have the same issue with Elvis. :banana-wrench:

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Lee1977

I just close the tank petcock on my 312-8. Sometimes it isn't fired up for two or three months.

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Jerry77

Well, I'm not sure, but it seems to me that this cheap gasoline that we get nowadays, boils out of the carb  after the engine shuts off for a time. then the fuel pump has to work very hard to get the gas up to the engine from it's tank which is well below the pump...to fill the carb so the engine will start..I really don't think that it drains back to the tank...I had all these same problems as you all until I put an electric pump on...I let it run for 5 or 6 seconds before going to the start position and it starts every time - not so with my vacuum pump..I figure that it is filling the bowl back up..just my :twocents-02cents:

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Ed Kennell

These fuel pumps actually  have two check valves and most of them do not seal tight enough to keep the fuel from leaking back to the tank.

This was not a problem when the tanks were above the fuel pump, but when they were put under the seat, the fuel drains back and the pump looses its prime.

It takes a lot of cranking to purge the pump of air and to reprime itself.

If you keep the tank over half full, the pump should be covered and not loose its prime.

Another solution, if you don't want to add an electric pump, is to  add a marine primer bulb.

 

https://www.amazon.com/Ninth-City-Rubber-Transfer-Gasoline-Accessories/dp/B0148G078G/ref=sr_1_16/146-9118746-0112145?ie=UTF8&qid=1508107203&sr=8-16&keywords=fuel+primer+bulb

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rmaynard

Invest in a couple 1/4" check valves. They go inline between the tank and the pump. 

check.jpeg.21a482aeae8c13ce2b52365e56da31de.jpeg

 

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953 nut
7 hours ago, stevasaurus said:

If you can get the tank above the carb or fuel pump it should help.

Not too sure I would do that. If the needle valve in the carb leaked by over time you could end up with gas in the oil pan, pump OK.

I have gone to electric pumps on anything that doesn't have the older type pump with a built in primer lever.

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oldredrider

Just recently, I have gone to the electric fuel pumps. Unbelievable how much it improves starting times. Makes it so much easier on the battery and starter.

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JimmyJam

 

When you convert to a electric fuel pump, What kind do you guys prefer?

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JPWH

@953 nutI saw in a previous post that you recommended them so I bought the same ones for my custom. Now I have to figure where to mount it. Will it perform well in any location or is it critical where to place it.

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oldredrider

FWIW, I mount mine on the frame in front of the hood stand. Lower than the tank and tucked out of the way. Also gives room to install a filter and convenient for servicing, if needed. Central to wiring as well.

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953 nut

Mounted mine low on the frame near the front axle, sort of a protected area and close to the carburetor. I ran a fused wire from the ignition coil to power it.

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nylyon

So after posting the topic, I hadn't used the 414-8.  Since I am getting ready for snow (while it's warm out for a change) today's task is the plow on the 414-8.  When I parked it on Sunday, I shut off the fuel petcock.  This morning I went out, opened the petcock and it fired up like it sat for only a minute.  I like the idea of the electric fuel pump, but think that I will buy a bunch of one-way valves and put them on all the machines.

 

So the next question is where is the best place to install?  Closer to the tank (lowest spot), just before the fuel pump or between pump and carb?  

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Ed Kennell
16 hours ago, 953 nut said:

I have this type on three of mine, low cost and work well. 

Link to eBay low pressure fuel pump

I  just placed an order.      Two pumps for $16.25  +$1.00 shipping and a lifetime warranty  from  Richard.      :woohoo::ychain:

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JimmyJam
21 minutes ago, nylyon said:

I like the idea of the electric fuel pump, but think that I will buy a bunch of one-way valves and put them on all the machines.

 

So the next question is where is the best place to install?  Closer to the tank (lowest spot), just before the fuel pump or between pump and carb?  

 

I recommend just before fuel pump. I think if you place it closest to the tank, that would be the lowest spot, and gravity will make the gas naturally flow to to that point, you may be defeating the use of the check valve. Just my :twocents-02cents:

20 minutes ago, Ed Kennell said:

I  just placed an order.      Two pumps for $16.25  +$1.00 shipping and a lifetime warranty  from  Richard.      :woohoo::ychain:

 Ed let us know how they work out for you. Curious on where you run the wires to, obvious the ignition, I think ???

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Racinbob
On 10/15/2017 at 12:18 PM, stevasaurus said:

Just had a discussion with RacinBob on this subject.  One thing you could try, until you put on an electric fuel pump, is jack up the rear end or back it up a ramp to try to keep the gas from draining back.  Bob, said it did help, but did not cure it.  If you can get the tank above the carb or fuel pump it should help.  :)

 

Yes, it made a difference but I think a couple things kept it from working better. I have a Command engine and the fuel pump is on the back of the engine. On level ground the pump is at a height basically like it's sitting on top of the tank. When I backed it up the ramps it barely put the tank higher than the pump. Add to the fact that the tank wasn't full and I believe that gravity helped but didn't totally solve the issue. I have a couple of the electric pumps and have been pondering them. Just yesterday I installed a check valve (the metal style) in the line so we'll see what that does. :)

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elcamino/wheelhorse

I installed an electric fuel pump on my 416-8 and the instructions said to mount near the tank ( lower than tank ). Mounted it on the seat stand below the seat pan. No more starting issues.

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953 nut
9 hours ago, JimmyJam said:

where you run the wires to

If you have a points and coil ignition system run a fused line from the "+" side of the coil to the pump. On a Magneto or trigger ignition system you can use the accessory terminal of the ignition switch.

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Racinbob
On 10/20/2017 at 11:55 AM, Racinbob said:

 

Yes, it made a difference but I think a couple things kept it from working better. I have a Command engine and the fuel pump is on the back of the engine. On level ground the pump is at a height basically like it's sitting on top of the tank. When I backed it up the ramps it barely put the tank higher than the pump. Add to the fact that the tank wasn't full and I believe that gravity helped but didn't totally solve the issue. I have a couple of the electric pumps and have been pondering them. Just yesterday I installed a check valve (the metal style) in the line so we'll see what that does. :)

 

The verdict is in. It's been 8 days since I installed the check valve. Plenty of time to force me to crank it several seconds to get the fuel back to the pump. This time I don't think the engine made a complete revolution before it was running. :banana-wrench::banana-wrench:

Most of the fuel line is hidden so I picked a spot that was easy to get to. I don't really think it's critical where it goes, just between the tank and pump. Mine happens to be just in front of the steering tower where the line comes out from underneath. :)

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woodchuckfarmer

I think I would put a filter before the pump.  Don't want dirt in the pump.

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nylyon

Got mine today, going to put it on the 414-8 tomorrow.  Think I will do the 416-H as well since that one seems to have had this issue since new, but it would take a while for it to drain back.

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