1986 GMC Astro rebuild...questions

If I remember right the pump to jack the cab up on the fishbowl was about like other cabovers , if it didn't raise the cab all the way up you dropped the cab then you filled it up while the cab was down , and jacked it back up and they all had I lock as I remember

 

Got rusty stuff? Phosphoric acid is your friend.

Klean-Strip 1 gal. Phosphoric Prep and Etch-GKPA30220 - The Home Depot

 

If I remember correctly, the two-strokers have a supply and return galley on each head. Then under the valve covers, there are two metal lines that go from the galleys to each injector—supply and return.

I’m pretty sure the fuel pump is driven off the blower... but it’s been a VERY long time since I’ve worked on one and my memory is like Swiss cheese.

 

When I get home, I’ll go through my stuff. Somewhere I have a service manual for the 6-71’s but a lot of it is applicable to the other motors.

 

Is it feasible that the two fuel filters that are placed under the cab just in front of the driver side tank could have "vent" that could be opened and then pressurize the tank to blow the air out before the filters? Forgive me...I've dealt with cars for years and this diesel thing tends to overwhelm my thinking (worse as I'm aging lol)...

 

Basically, you fill the filters full of fuel, crack the nut on the return line and then crank it until you get fuel coming out. Then tighten it back up and crank until it fires.

The rail in the head has to be full of fuel before the engine will start. Don’t be tempted to run the motor on ether to prime it. The injectors are lubed by the fuel and running the engine on ether can cause them to sieze.

 

Yea that ether is a curse and a blessing. Just a dab shot will do ya.

Those old air breathing desiel engines were a joy to me, air start not so much but one of the regular COE engines that had it was pretty reliable. Usually the cylinders began to fire one and then added more until all 6 was trying to fire to life just before the air ran out. I don't recall using ether in that particular rig even down to -30. (Engine block heater)

Ive fed many mack R models with ether... ugh. PFFTH. shot, jump in cab, crank. Those old air intakes were handy though. The big gallon cans I guess. Fill em with ether. There be enough to have a go really good at starting.

 

Dig Dig Dig we have a winner.
The fuel pump is not positive displacement meaning if it has air it will not prime itself. The inline pump like Retired said is a good program.
Air can be used to purge the entire system and no more than 5 PSI is needed. Disconnect the return line from the tank and cap the tank fitting. When you have steady fuel from the return line, don't be in a hurry, reconnect everything and start it. If you get fuel to the pump it should pick it up. Or If you do not open anything else in the fuel system when you drain the tanks vacuum will likely hold fuel in the system and you will have no problem. If it has an air bubble a wiff of ether will often get past that. As mentioned not a good idea to run on the stuff and high RPM can go really wrong really fast with these engines.

 

Do you remember ether balls? No not a joke.