• Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

Gradall fuel issue. Loosing prime??

Steve Nichols

Active Member
Joined
Jan 1, 2020
Messages
28
Location
Fresno Ca
Hello all. I am working on an old gradall with a John Deere power tech 4.5 ser#PE4045H468706.
Original complaint was it was run out of fuel.
I am able to get it bleed and have it running strong but after it sits for a couple hours it looses prime and I have to bleed it again.
In the course of working on it all the supply lines have new seals.
Is there a check valve somewhere in the system I need to look at?
I really have no idea where to go from here. Any suggestions?
Thank you for reading.
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,865
Location
WI
Any rubber suction hoses? those crack and leak air and then you're screwed, the lift pump won't suck air very well. The lift pump is the most important check valve that I know of, but it could leak back before the lift pump with a suction hose leak. How's the fuel tank? any chicken skin, rust, water? is there a screen in the tank?
 

Steve Nichols

Active Member
Joined
Jan 1, 2020
Messages
28
Location
Fresno Ca
Good morning Delmar.
The rubber suction hose from tank to prime pump is brand new.
Tank appears to be clean, no water / rust. Not sure what chicken skin?
I suppose it could be the prime pump.
I assume the lift pump is what I'm referring to as the priming pump? The hand pump right before the water separater?
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,865
Location
WI
Yes, is this lift/priming pump mounted on the side of the engine, on the camshaft?

Chicken skin is wrinkled varnish that forms in bio diesel.

You could try pumping the priming pump before starting, without bleeding it. I don't know how to test the pump without "throwing parts at it".
 

mg2361

Senior Member
Joined
Jul 5, 2016
Messages
5,057
Location
Pennsylvania
Occupation
Equipment Mechanic
If you have a water separator filter with a glass bowl, check to make sure the o-ring is between the filter and the bowl. I have seen this mistake made numerous times by customers who changed their filter and not moved the o-ring over creating hard start complaints due to air incursion.
 

Txhayseed

Senior Member
Joined
Dec 23, 2019
Messages
610
Location
Texas
Where your Is your filter head. Pre or post fuel pump ? Get a pair of hose pinch pliers. Run unit and pinch of your main fuel sunction line at what ever it feeds first. Then wait for the time frame your seeing it loose prime. Start the engine and see what happens if your able to start it and dont have to bleed the system you know its bleeding off of the supply side. Do you see any smoke after starting up ? Like maybe you got an injector thats bleeding off ?
 

Steve Nichols

Active Member
Joined
Jan 1, 2020
Messages
28
Location
Fresno Ca
As a matter of fact I do see black smoke after I get it running. Most pronounced when you aggressively reave the engine.
I did the crimp test, it would not start. The line was crimped right after the tank, before the filter, transfer pump, and water separator.
 

Txhayseed

Senior Member
Joined
Dec 23, 2019
Messages
610
Location
Texas
Black smoke when increasing the rpms quickly especially when your doing several times in a row is normal. Like mg said try the return side and see if you can isolate where exactly your loosing it.
 

Steve Nichols

Active Member
Joined
Jan 1, 2020
Messages
28
Location
Fresno Ca
Thanks for all the replies!
So, did the crimp test, both the supply and return hoses where crimped. Still no go. Scratching my head how that can be????
 

Vetech63

Senior Member
Joined
Aug 10, 2016
Messages
6,362
Location
Oklahoma
Thanks for all the replies!
So, did the crimp test, both the supply and return hoses where crimped. Still no go. Scratching my head how that can be????
This is beginning to sound like a different problem. Are you positive that it is losing prime? What exactly are you doing when you attempt to restart this engine after it sits for awhile?
 

Steve Nichols

Active Member
Joined
Jan 1, 2020
Messages
28
Location
Fresno Ca
I bleed it at the injectors. Grasping at straws here but.......
I never have bleed the fuel pump where the return line is connected to the fuel pump due to limited access. I bleed it at the bleed screw on the filter/separator. Then bleed the injectors. Do you think I could have a pocket of air trapped in the injection pump? I'm going to get the seals for those two lines (supply & return) where they connect to the pump and try bleeding it. I'm replacing the seals because when I cracked the other fuel lines (at the fuel filter/separator) the seals crumbled and came apart.
 

Vetech63

Senior Member
Joined
Aug 10, 2016
Messages
6,362
Location
Oklahoma
Its doubtful you have an air trap if your engine runs after you bleed the fuel system. Replaced your lines seals then see what happens.
 
Top