Wont start, questions about priming

[JohnMcCarthy]

Hello,
I have a F700 with P7100 12valve. Truck has been sitting for a couple of years and I am trying to prime the fuel system and get this running again after having the tanks cleaned and replacing the LP. I also replaced the filters. This was an old service truck and the tanks had an inch of sludge on the bottom and the screen in the prefilter was caked up with the stuff. Vehicle just stopped running one day.

I have pumped the bulb on the LP and am able to fill the fuel filter, get fuel to drain out of the OFV when cracked, get fuel to "leak" out the injector caps when I crack them. Then I can crank the engine for 30 seconds and I see the pressure build to about 15 psi on my FP gauge, but the engine will not start.

I have a question, when you crack the injectors (1/2 turn), should the fuel "shoot" out? I can only get it to just dribble out. Leads me to believe that the P7100 isn't doing its job?

Also, I am wondering if the fuel I have in the tank has lost its volatility? It looks OK, but it has been sitting in there for a 1-2 years.

 

[Ozymandias]

Does the fuel shut off solenoid work properly?

Yes you should get quite a shot off fuel from the cracked injecgor line.

 

[JohnMcCarthy]

Does the fuel shut off solenoid work properly?

Yes you should get quite a shot off fuel from the cracked injecgor line.

I am using a tie wrap to hold the shut off arm up for now. That is another question that I have though, it seems like there is no resistance when I move the arm from off to on (down to up). Is that what the rest of you see when you have had occasion to move it? Really seems like you should be able to feel something when moving the lever.

 

[GAmes]

The lever attaches to an arm that is attached to the fuel shut off rod. Moving it would offer little resistance. The arm has a clamp with a woodruff key. The key has been known to shear. If you look at the top P7100 you will see a short round rod that sticks up. It is the other end of the shut off rod so if you actuate the arm the rod should rotate. In the picture the screwdriver is resting on the end of the rod.

As for loosening the injector nuts, no you won't see high pressure fuel spurting out if they are barely loosened. My procedure to bleed air from the injector lines is to loosen all six and crank the engine with a helper watching for fuel. When the first one spits fuel tighten it. I shouldn't take long if the filter is full of fuel and you have pumped the manual primer until hearing the OFV squeal. Crank again until another one spits fuel, then tighten it. The engine usually starts running and spitting fuel from the other four on the next crank.

This is about Dodge trucks but the system should be very close to what you have. Written by a TDR member long ago. I suggest you take special interest in the procedure to verify OFV operation and also air leakage prior to the lift pump.

https://www.cumminsforum.com/threads/joe-gs-fuel-system-writeup.58777/

 

[HCannon]

If the return line going back to the tank is blocked it will not run. The return does not build much pressure. It would be easy to check.