12.7 questions

I just read through this entire thread. Two things:
If the batteries were moved from one side to the other and the wires are cobbled up, I would concentrate on getting the harness properly repaired. Doing so will probablyprevent many future headaches.
I am at a loss as to why using air to push fuel won’t pressurize the fuel system. With air injected into a fuel tank via the vent hose on that tank, the air should push the entire tank of fuel through the system.
If that doesn’t work because of the type of fuel pump Detroit uses, then surely spinning the engine over and turning the fuel pump should push fuel through and remove any air lock.
Without a check valve I could see not being able to pressurize the system.
If I understood it correctly, the op dissembled the check valve when he removed it. That is easy to do when you don’t know what you are taking apart. He needs to be 100% CORRECT at reassembling and reinstalling it. Otherwise it won’t work as intended.

 

I just spent 20 minutes typing, hit reply and now it doesn’t show.

The op needs to properly redo the harness from the batteries to the ecm because it had been hacked earlier. (Along with any other butcher jobs.)
He needs to be 100% CORRECT on reassembling and reinstalling the check valve.
Myself, I don’t understand why putting air into the fuel tank via the vent whiling spinning the engine won’t prime the fuel system.

 

I don’t believe it. Retype post. Hit send. Both posts pop up. Oh well.

 

Its all about pressure. If you put say 5 PSI air pressure into the tank you will have equal pressure through out the whole fuel system. Nothing can flow.

Liquids and gasses can only move from areas of high pressure to areas of low pressure. Only way pressurizing the tank will work is if you disconnect the return line from the tank so that it won't be under the same pressure as the supply line.

 

Oh and be prepared for a fuel bath if you pull the return line and pressurize the tank.

 

Now I follow their point on pressurizing the system. Here is the rub.
On a two tank system most commonly used on a highway truck (which I hope it is in this situation) the fuel will return to the other tank providing the vent on it is not obstructed. Or pull the return line off past the check valve.
Basically just push fuel from one tank through the entire system and engine over into the other tank.

 

The fuel will take the path of least resistance. Why would the fuel go through the whole engine when it can just go splitter valves and back to the other tank.

The only way it will work is if you isolated the second tank and removed the return from pressure as stated by Amodelcat.

 

Another thing to check (better still is to replace it) is the fuel supply line to the head from the secondary filter.

I have a fuel pressure gauge plumbed between the back of the head and the check valve. This way I know for sure the head has a good supply of fuel.

Hold the fire in the cab lecture. No reason to have a pressurized fuel line in the cab.

 

How is the fuel going to get into the return line from the pressurized tank to get to the splitter and back over to the other tank? It can’t unless the return has a tube to the bottom of the tank. The fuel would need to “jump” up to the return fitting at the top of the tank.