Truck died

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JimmyC
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Joined: Tue Feb 18, 2014 4:59 pm
Location: Lafayette, LA and Highlands, NC
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Truck died

Post by JimmyC »

My truck quit yesterday going up a hill and I am looking for pointers. Ignition seems good but not getting fuel to carbs. Upon inspection there is no suction on the intake of the fuel pump while cranking. I took the pump apart and it seemed ok except there was some corrosion under the top cover that holds a diaphragm that apparently opens a discharge valve. I am thinking either there is a fault in the pump That I cannot find or there is something wrong with the pump drive. One strange thing: you cannot blow through the pump. Blockage seems to be on discharge side as you can blow through the intake when it is apart. Seems like you should be able to, but the double discharge valves has me confused. I think I am going to pull it again tomorrow and examine the discharge valves a little better. Any suggestions?
Jim Chance
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All my post fully incorporate the Dunning-Kruger effect
JimmyC
Posts: 217
Joined: Tue Feb 18, 2014 4:59 pm
Location: Lafayette, LA and Highlands, NC
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Re: Truck died

Post by JimmyC »

Truck is back on the road. It was the fuel pump, though I am not 100% sure what about the fuel pump. I put a “good used” one on from my buddy’s pile and eventually got it running. Learned a bit in the process. First is the pump is not so great at primming itself when cranking. My suggestion to anyone changing a fuel pump is to pull the inlet fitting on the top of the carbs and pour some gas into the screened bowl vents. That will get it going long enough to let the pump prime. The second is the clarification about setting the pump height. The manual is confusing at least to me. Looks like the cam has about 3mm of stroke on the pump lobe. You want to check/set the pump height when it is at the bottom where you want about 1 or 1.5 mm interference. The manual says to set the engine with cam down, set pump in place and measure the gap between the mating surfaces. I found measuring the gap hard. Instead measure how high the tapper is sticking up with a machinist ruler then measure how far down the rocker arm is from the flame. The measurement down to rocker arm needs to be 1 to 1.5 mm les than the measured tap pet hieght
Jim Chance
710M

All my post fully incorporate the Dunning-Kruger effect
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pcolette
United States of America
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Joined: Sun Dec 10, 2006 7:38 pm
Location: Southwest Wisconsin

Re: Truck died

Post by pcolette »

Another possible issue to consider with the fuel delivery is that if the fuel line from the tank to the pump is old, dry and cracked, air will leak in as the pump is trying to prime itself. Sometimes just replacing the rubber fuel lines can make a considerable difference.

Glad you're back on the road!
Paul C.
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ChickenPinz
United States of America
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Re: Truck died

Post by ChickenPinz »

Great point, pcolette!

Also, I'd imagine the pump is sensitive to things that prevent the valves from seating, so if you get a piece of something in the top diaphragm/valve section it could prevent pump operation.

Pumps are relatively cheap in the grand scheme of Pinz parts, so a new one sounds like a wise move.
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Texas710
United States of America
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Joined: Thu Jan 22, 2015 4:00 pm
Location: San Antonio, TX

Re: Truck died

Post by Texas710 »

When you get a new pump, change out all the hoses. It's cheap, easy to do, and you can upgrade to an ethanol friendly hose. Sometimes just messing around in there will knock lose gunk in the lines, which then can clog pumps, carbs, all sort of things.

I recently switched over to an electrical pump and have been very happy with the results. That said, I ran the original manual pump for years without issue.
JimmyC
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Joined: Tue Feb 18, 2014 4:59 pm
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Re: Truck died

Post by JimmyC »

A follow up: Ran out of gas and once again really had to struggle to get fuel pump primed. Thing does not like to pump air! Did the trick of filling the bowls through the vents and that worked. Also stuck the filter on the suction side in a cut off pop bottle filled with gas. When I cranked it (running on bowl fuel) it first blew air out of the filter, then sucked a little gas in. Once the pump got a little gas in it it drained my pop bottle in no time. I am going to put a new pump in. I think the valves in the one given to me are leaky.
Jim Chance
710M

All my post fully incorporate the Dunning-Kruger effect
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