Fuel flow problem

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Model T Ford Forum: Forum 2015: Fuel flow problem
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Benedict, Hunboldt, TN on Sunday, April 05, 2015 - 05:37 pm:

I have been batting a thousand with answers to solving problems that I've had with my 26 coupe so I'm going to hit you with another one.

Let's start with what I have... I have a clean gas tank with fresh fuel which is filtered by a glass sediment bowl in place of the original bowl. I wanted to see the fuel flow.

My problem is...After driving my car for about 10 miles, it starts to loose power especially on hills but also noticeably on the flat.

I then check my fuel bowl and its down about 1/16" from being full. If I loosen the fuel line nut at the carb and let gas escape, the bowl will refill it's self and the car will run fine again for a time. When ever I remove the bowl and open the shutoff, fuel runs freely. When I replace the bowl and tighten it up, open the shut off, the fuel does not fill the bowl until I loosen up the bowl to allow the air to escape.

Question...Where does the air escape to in order for the bowl to fill when system is tight? My vent hole on the gas tank filler cap is open.

Any suggestions????? Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Sunday, April 05, 2015 - 07:00 pm:

Bob

Air has to escape either up thru the tank or be forced down into the carb and then out thru the vent hole.

Is your carb vent open and free ??


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rick Goelz-Knoxville,TN on Sunday, April 05, 2015 - 07:03 pm:

Bob, if you bought one of the new shiny gas caps they are not vented, you will need to drill a hole in it.

Rick


Top of pagePrevious messageNext messageBottom of page Link to this message  By brass car guy on Sunday, April 05, 2015 - 09:58 pm:

Some flow thru filters are designed for pump delivery. These filters are designed to work under pressure and will restrict flow from a gravity system such as the model t. Back in the day we had the same issues with VW bugs before they added a mechanical fuel filter. Using the wrong filter caused the car to run out of fuel while being driven. Changed to the gravity flow fuel filter problem solved.

just sayin,

brasscarguy


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Sunday, April 05, 2015 - 10:07 pm:

" filtered by a glass sediment bowl in place of the original bowl"
I too would suggest the gas cap also pull the fuel line off the carb and check the flow there. Do you have a loop in the line or anywhere that the fuel line sits higher then the outlet from the filter, if so you could be getting an air pocket in the line. You can still have flow even if the bowl appears not to be full.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Don Lyon, PDX, OR. on Monday, April 06, 2015 - 02:22 am:

Make sure you have a vented gas cap--very small hole is enough, Don.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Monday, April 06, 2015 - 07:43 am:

Yep. My money is on the tank not being vented. Air has to replace the fuel as it is used, or else you form a vacuum in the tank. Just like Coke in a soda straw with your finger plugging the top.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Monday, April 06, 2015 - 08:45 am:

I thought he said "My vent hole on the gas tank filler cap is open".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Benedict, Hunboldt, TN on Monday, April 06, 2015 - 08:55 am:

The gas cap vent is open, I even tried running with the gas cap unscrewed halfway. I'm going to pull the carb today and check how clean it is or isn't. My car had set for 6 years before I purchased it last August and I just pulled and reconditioned the tank, lots of sediment. The carb is new but could have blocked vent hole. As suggested, it appears I'm running out of gas probably from the float bowl. I'll let you know. Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Benedict, Hunboldt, TN on Monday, April 06, 2015 - 09:04 am:

Is there a gas additive that will offset the Ethenol gumming problems recommended from experience? Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By G.R.Cheshire on Monday, April 06, 2015 - 09:28 am:

Bob you didn't specify what type of carb. you are running. If it is one of the original carbs for a model T (Holley / Kingston / Wizard etc) then check the carb vent hole, if however you are running one of the "modern" lawnmower carbs the vendors sell they require a fuel pump. If you are running an original carb then what Brass Car Guy said is probably correct Just because it is a glass filter don't mean it will let fuel flow by gravity.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Benedict, Hunboldt, TN on Monday, April 06, 2015 - 10:06 am:

I am running a new Holley NH carb. When I remove the gas line from the carb, the gas flows at full force. Still believe the problem is in the carb vent as suggested above.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Georgetown TX on Monday, April 06, 2015 - 10:23 am:

If it is one of the new reproduction NH carbs it has a Grose Jet in it that is causing the problem. Here's how to fix it:

http://www.mtfca.com/discus/messages/411944/469501.html


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Monday, April 06, 2015 - 12:19 pm:

Oops. Sorry.:-(


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, April 06, 2015 - 01:40 pm:

I've found the new rubber tipped valve needles sticking in a couple of NH carbs. I replaced them with the original Ford type.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Benedict, Hunboldt, TN on Monday, April 06, 2015 - 06:23 pm:

The needle and seat is like the original 2 piece but with a black end on the needle. When I set the float and turn the carb upright, the float falls but the needle stays in place. Just a tap on the housing and the needle will fall. Is this delay in falling possibly my problem. I would think that gas weight on the needle would release it. I think I'm going to order a stainless needle and new seat. Any comments? Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Tillstrom 30 miles N of Memphis TN on Monday, April 06, 2015 - 08:36 pm:

Hi Bob. Gary T here. I used one of those glass sediment bowls on a T I used to have. If the tank is empty, remove that bowl and see if there is a fine screen at the inlet. If there is, remove the screen and flush some liquid through the tank to get any immediate trash out and put it back together without that screen. Now the trash will drop out in the glass bowl.


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