Fuel Pump Blues?

pastorjeep

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I need some help. The ole girl left me on the side of the road yesterday. Just died when I switched tanks going down the road. So I pull over and switch back to the other and crank...and crank! Check the fss, good. Check the shrader and no fuel. No problem, spare pump in the tool box. Swap, and nothing! I check both pumps manually and they pump fine, just a few pushes on the arm and fuel sprays. Can the fuel pump eccentric on the cam dislodge? They are huge so I don't believe it can flatten. Any help would be appreciated because I need my work truck tomorrow.
 

laserjock

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I would guess blockage in the selector valve. As a quick thing you can try blowing back through the lines and see what happens. If you've never done the shower heads or you didn't get them cleaned out I could see that happen.
 

pastorjeep

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Took the FSV off laying on the side of the road
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and checked operation and cleanliness. Switched as designed (good to know) and was clean and clear. Took the pump off and clamped it to the bumper and put the line in a jar of diesel and just three pushes of the arm had a geyser or fuel out of the other side?
 

icanfixall

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well if you have fuel you need to look elswhere for the problem. Run a jumper wire from any battery positive directly to the top of the injection pump fuel shutoff valve. See if it starts. If it does you may need to replace or adjust the ignition switch because it may not be sending power to the pump.
 

pastorjeep

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Thank, got power to the FSS. I am trying to put things together in my mind right now. I took the bed off last week and cleaned the tanks and installed new shower heads from LMC. Replaced the filter Friday, then Sat. I was purposely running the rear tank dry to see how accurate the gauge is. As the truck stumbled with the gauge all the way in the red (yay can now use all the fuel) and then switched tanks. About thirty seconds later the truck died. So I checked FSS, then the shrader and no fuel at the filter head. So I swapped pumps and no fuel. Filled rea tank back up and still no fuel from either tank Pulled FSV and cleaned and checked for operation. While pump was off i checked while clamped to bumper by manually pumping with line run into jar of fuel. Worked fine. Installed back on truck and no fuel!!!!!!!!!! A little stumped, but I know I am just missing something obvious. So in the am I am pulling fuel lines and blowing compressed air and hooking my transfer pump to the main fuel line to see if it will pull fuel. But the sticking point for me is that when I mounted the pump back on the engine and crank I get no fuel even with a line run into the jar of fuel? Just seems llike the engine is not engaging the pump arm?
 

DaveBen

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Rule Number 2 - NEVER run out of fuel in a diesel truck. I had a Kenworth, many years ago, and it took me and a roadside mechanic 2 hours to get my truck going again, after running out of fuel.
 

icanfixall

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Any chance the mechanical lift pump arm is on top of the cam lobe??? To me this is what your issues sound like to me. Yes... the cam lobe can wear down but this is not the usual issues. These mechanical lift pumps will work either on top or on the bottom of the cam lobe but on top they seldom work for very long.You could purchase an inexpensive electric lift pump and temp it into the fuel system just to see if the mechanical arm is the problem.
 

pastorjeep

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Gary, that is what I am thinking. I have tried two different pumps, but both have the straight arm. So I could be getting it over. I have been going completely through the fuel system last two weeks so I could have disturbed something somewhere ;) It is frustrating my attempts to diagnose at this point.
 

pastorjeep

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Ok guys, got it resolved. It was the mechanical lift pump. That makes the third pump in two years! The problem is the other two pumps work fine manually. The pump I just took off was put on Aug. 22, 2016! So this is my hypothesis: the cam lobe is worn enough that once the pump gets a little loose from breaking in, the cam can't push it far enough to fully pump. The wear mark on the pump arm is very small and light. The other pump I replaced 18mo ago looks like new still and works fine manually, same symptoms when it was replaced.
 

raydav

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I was purposely running the rear tank dry to see how accurate the gauge is. As the truck stumbled with the gauge all the way in the red (yay can now use all the fuel) and then switched tanks. About thirty seconds later the truck died.

Sounds like you gulped air. When one thing happens and an anomaly follows, the first place to look is at the first thing. As the man said, don't run out of fuel.

I switched from a gas 460 to a 7.3 IDI in 2005. In the early days I got air in the injection pump three times, and each time required serious effort to get it to run again. The third time I spent six hours in a rest stop until someone came along with a can of carb cleaner.

I now have a cab operated priming valve at the inlet to the injection pump. And I not afraid to spray.

The vehicle is an E350, it always had an electric supply (lift) pump. I had three tanks before the 7.3, each had a pump, and as one tank was nearing empty I would turn on the pump to another tank and run the first dry; the carb would separate out the air. I now have one pump from a primary tank and a second pump and valve to transfer fuel from the other two tanks. I can now run the other two dry without putting air in the injection pump.

And, I have a three way switch so I can power the supply pump from an oil pressure switch, the battery, or not at all. The engine starts before the oil pressure switch closes, and if I forget and leave the selector switch off the engine runs just fine, the injection pump seems to have no trouble pulling fuel from the tank.
 

pastorjeep

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Your gonna love this! The new pump lasted 100 miles ;) The cam is definitely word and will not pump fuel. So I ordered a pump for the 6.5 diesel to install. The one on my 92 K2500 lasted years and over a hundred thousand miles. So I will just plumb it in and used it for a while. I buy 3/4 of them for the price of a facet.
 

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