D2 Fuel Delivery Problem


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Rusty Driver
Rusty Driver

Posts: 113

Joined: Mon Jun 24, 2013 10:13 am

Post Fri Jun 24, 2016 8:45 am

D2 Fuel Delivery Problem

We are having a low fuel supply problem, but seemingly only after long runs. In-line filter installed between pump and carb shows 3/4 full before starting motor, then goes to approx 1/2 full after a short run, then to almost no fuel after a long run. List of parts replaced late 2014 - new side mount steel tank, new parker flexible fuel line, fuel pump rebuild. Filters have always been really clean, but still replaced periodically. Should we suspect the fuel pump diaphragm is to blame? We will try a temporary fuel line from tank to pump tonight to rule out the line as the problem.
Thanks,
-Snowman.

Golden Jubilee
Golden Jubilee

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Location: Canada's left Coast

Post Fri Jun 24, 2016 9:02 am

Re: D2 Fuel Delivery Problem

Does this fuel tank require a ventilated filler cap? Try removing the filler cap immediately after a drive and listen for the sound of air entering the tank.
There are examples of fuel tanks being crushed by atmospheric pressure on You Tube.
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Golden Jubilee
Golden Jubilee

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Location: Bothell, Washington

Post Fri Jun 24, 2016 10:39 am

Re: D2 Fuel Delivery Problem

^^was going to suggest same thing, I had a un-vented cap on my truck back in the 70s, couldn't figure out my fuel issue till one time opened the cap and Whoosh sound,,,hmmmm
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Golden Jubilee
Golden Jubilee

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Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Fri Jun 24, 2016 8:41 pm

Re: D2 Fuel Delivery Problem

Well, was a vented cap the fix?
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Rusty Driver
Rusty Driver

Posts: 113

Joined: Mon Jun 24, 2013 10:13 am

Post Sat Jun 25, 2016 1:54 pm

Re: D2 Fuel Delivery Problem

The cap is/was a vented cap. Put a new Stant vented cap on just to eliminate it as a problem. No change, still pumps slower the longer the truck is run. Many other chores today, maybe tinker some more tonight when the temperature cools off.
Thanks,
-Snowman.

Golden Jubilee
Golden Jubilee

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Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sat Jun 25, 2016 2:20 pm

Re: D2 Fuel Delivery Problem

On the off-chance the vented cap is not operating properly, I have used a paperclip folded over the top edge of the filler pipe. This allows a little air into the tank when the wire clip holds the cap just off the filler neck.
The Father of a friend stopped by here with his L110. He was having fueling problems not unlike this situation. I used my "snake inspection camera to have a look inside the tank. Someone had pushed a shop cloth into the tank. The cloth would slosh around and eventually get caught on the pickup tube. The cloth did allow a little fuel to pass through while causing a major restriction. I made up a copper fishing wire and hooked the rag. Problem solved.
The proposed idea of using a bypass hose is a good one. It is possible that an original steel fuel line could have internal corrosion that may restrict fuel flow. Does the original fuel line have any kinks or perforations? The original pickup tubes are often rusted through, this will allow air into the fuel line.
I like electric fuel pumps.
I put a 6.9 Diesel into our R120. The cam activated diaphram fuel pump design was not reliable. Getting fuel to the Stanadyne http://usdieselparts.com/i-13466051-6-9 ... -pump.html after losing the prime took too much engine cranking and may have been tough on the batteries. I installed a HOLLEY fuel pump for an almost instant prime. In time the Holley pump became the only pump.
https://www.holley.com/products/fuel_sy ... s/12-802-1
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Pile of Parts
Pile of Parts

Posts: 32

Joined: Mon Dec 03, 2012 10:44 pm

Post Sat Jun 25, 2016 2:52 pm

Re: D2 Fuel Delivery Problem

Hello;
I grew up riding in a 39 D2 contractors truck that dad bought new. I remember when riding in it when it would vaper lock and they would have to chock it to get it to keep running. If it stopped they had to blow in the gas to get
it started again. Dad rerouted the gas line from the fuel pump to the carburetor away from the exhaust manifold, and that took care of the problem.
Don

Golden Jubilee
Golden Jubilee

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Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sun Jun 26, 2016 11:25 am

Re: D2 Fuel Delivery Problem

Google AIRTEX fuel delivery systems. This company gives a good description of fuel vapor lock. They offer some ideas for a fix.
Modern fuel, with alcohol will vaporize and cause the lock in low pressure old carburetor systems.
An under hood fuel cooler will transfer heat both ways. I like a residual pressure check valve with a fuel return line. A fuel return line is installed, the return line must go to the bottom of the tank like the pick up tube. If the fuel return is not submerged there will be a bunch of other problems including fuel line evacuation after shut down.
The most destructive situation happens when the ethanol combines with the moisture in the air above the fuel, in the tank, and forms a corrosive that will destroy the fuel tank from the inside.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Golden Jubilee
Golden Jubilee

Posts: 8938

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sun Jun 26, 2016 11:41 am

Re: D2 Fuel Delivery Problem

There is a possibility that the mechanical fuel pump diaphragm has been compromised by fuel containing ethanol. Ethanol and moisture in combination are a corrosive.

http://www.airtexproducts.com/news-what ... -fuel.aspx
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Rusty Driver
Rusty Driver

Posts: 113

Joined: Mon Jun 24, 2013 10:13 am

Post Sun Jun 26, 2016 1:59 pm

Re: D2 Fuel Delivery Problem

O.K. so we have by passed the tank and flexible fuel line. Have a 2 gallon can with 1/4" hose hooked direct to fuel pump. If the can is on the fender (above the fuel pump) it works like it should. If I move the can to a chair that is approx same level as the fuel pump the flow will soon decrease and barely show fuel in the in-line filter.
-Snowman.
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