Anyone have a pic of the inside top of a 6.2 injection pump?

[Humpty]

When the solenoid is active it causes the timing to advance, all this has nothing to do with the check valve in the fitting and only effects emmisions, Stanadyne IPs before emission controls did not have the cold advance feature and none of the off road (tractor) IPs have this feature.
But if the pressure rises to the same as the charge pump (completely blocked return) then the plungers will not be able to take in any fuel and the engine will die, the differential in pressure between the charge pump and the housing is what forces fuel into the plungers.
The check valve ensures that the proper pressure is maintained in the housing so you should replace that fitting, although I have run several IPs with that ball removed over the years with no obvious detriment although another job of that check valve is to ensure the fuel does not bleed back to the tank causing a fuel starvation upon startup.
Here is an explanation of the Stanadyne cold advance system.
View attachment 942462

What I can tell you is my check valve was, when removed, normally closed. The solenoid needle pressed into the check valve to open or close it. Maybe the needle kept it normally pushed open and when activated it closed it? Either way, the check valve is wide open on my IP now.

 

[Humpty]

The cold advance solenoid does not "open" the return check valve.

Unless i’m missing something.. and I very well could be.. the only thing the “Cold Advance Solenoid” physically does is open and close the check valve.

I may have the manner of operation backwards.. but at least on my truck.. that cold advance solenoid is only capable of opening and closing the check valve in the fuel return.

Got my brand new $35 Cold Advance Solenoid delivered today. Not that it was ultimately my issue, but the old one was for sure broken at the hot lead insulator.

 

[Milcommoguy]

Unless i’m missing something.. and I very well could be.. the only thing the “Cold Advance Solenoid” physically does is open and close the check valve.

I may have the manner of operation backwards.. but at least on my truck.. that cold advance solenoid is only capable of opening and closing the check valve in the fuel return.

Got my brand new $35 Cold Advance Solenoid delivered today. Not that it was ultimately my issue, but the old one was for sure broken at the hot lead insulator.

"Unless i’m missing something.. and I very well could be.. the only thing the “Cold Advance Solenoid” physically does is open and close the check valve."

On the surface...there's more to it than that. While to many ?? it looks to be a check valve... BUT it is a regulator (5 to 15 psi) with the solenoid acting as an override. Very important little deal. Drilling it out just removed housing pressure to near zero, so that the transfer pump pressure behind the power advance piston can easily advance the cam ring for easier cold starts. So that pressure circuit...not electrical, will not feather the advance servo for normal operations at speed. Likely run a bit crappy thur the power band.

The Big guy says "Drill Baby Drill" Not this time, CAMO












'

 

[Humpty]

"Unless i’m missing something.. and I very well could be.. the only thing the “Cold Advance Solenoid” physically does is open and close the check valve."

On the surface...there's more to it than that. While to many ?? it looks to be a check valve... BUT it is a regulator (5 to 15 psi) with the solenoid acting as an override. Very important little deal. Drilling it out just removed housing pressure to near zero, so that the transfer pump pressure behind the power advance piston can easily advance the cam ring for easier cold starts. So that pressure circuit...not electrical, will not feather the advance servo for normal operations at speed. Likely run a bit crappy thur the power band.

The Big guy says "Drill Baby Drill" Not this time, CAMO

I'd read in a few places that a stuck closed return valve would cause the pump to starve for fuel, so I drilled it out really just to eliminate a stuck or faulty check valve as the source of my issues. My new solenoid arrived today and I fully intended to replace the valve with a new one once the new solenoid arrived.. good to know that it opens/closes also with pressure and not just the solenoid.

 

[Humpty]

Update: The pump guy wants me to stick a piece of clear hose on the fuel return with a loop and between the filter and the input of the injection pump. He says the surging is a result of air and looking for bubbles after it sat overnight would suggest where the air is coming from. He also told me the valve I drilled out was like a $100 part.. so that may have been a tactical error. lol Although, Insee ‘em on fleabay for about $30

 

[Milcommoguy]

Update: The pump guy wants me to stick a piece of clear hose on the fuel return with a loop and between the filter and the input of the injection pump. He says the surging is a result of air and looking for bubbles after it sat overnight would suggest where the air is coming from. He also told me the valve I drilled out was like a $100 part.. so that may have been a tactical error. lol Although, Insee ‘em on fleabay for about $30

Listen to the pump guy. Clear hose and looking for bubbles could be an indicator of air in the housing. The housing operates completely full (at pressure) from the bottom to the top of the housing regulator little ball thingy. (The 100 dollar part on sale now at amazon LOL) Pumps being hydraulic gadgets don't like air or bubbles to compress... so there is a vent wire to catch them and pop them allowing them float up to the upper housing and burp out the return line.

Where the pump guy is going... and what has been stated, seals leaking (do you have a puddle under it IP, right side?) or stuck / worn parts.

It's not just a pump... But a very sophisticated device... the heart of the HumV. After all the CPR, get it replace.

Throwing money at the HumV, CAMO

 

[Humpty]

Listen to the pump guy. Clear hose and looking for bubbles could be an indicator of air in the housing. The housing operates completely full (at pressure) from the bottom to the top of the housing regulator little ball thingy. (The 100 dollar part on sale now at amazon LOL) Pumps being hydraulic gadgets don't like air or bubbles to compress... so there is a vent wire to catch them and pop them allowing them float up to the upper housing and burp out the return line.

Where the pump guy is going... and what has been stated, seals leaking (do you have a puddle under it IP, right side?) or stuck / worn part.

It's not just a pump... But a very sophisticated device... the heart of the HumV. After all the CPR, get it replace.

Throwing money at the HumV, CAMO

Put a clear hose between the filter and the IP, and a clear hose put of the fuel return line. That fuel return line hose looks like a bubbler in an old Whirlitzer jukebox. The supply line has 0 bubbles at idle but if I gun the pedal some bigger bubbles pass through.

I put a clamp on the fuel return line just in case it was maybe sucking air but still bubbles like hell.

 

[Humpty]

UPDATE: May be sorted out?

After conferring with “Pump Jesus” Dennis Erickson I hooked up a clear line from the fuel filter to the injection pump.. I had been getting sufficient fuel pressure but what I didn’t know was I was also getting quite a bit of *air*.

After replacing the “juicy spots” on the fuel line and still getting air I ran the truck with a fuel can right at the lift pump.. no more air.

So ran a whole new line from the lift pump to the fuel tank. I pulled the check valve and blew and sucked on both ends and couldn’t get it to pass air either way.. so I just removed it all together.

No more air in the line between the filter and the injection pump. Engine running smooth again.

I’m still getting a bit of “fizz” bubbles out of the front of the IP at the fuel return.. i’ve left the clear hose on both the in and out of the pump to monitor things. My new fuel return/cold advance solenoid has arrived and I’ll replace that along with the replacement fuel return check valve when it arrives.

Fires right up no problem in sub 30 degree weather with the drilled out fuel return check valve, and it seems dramatically peppier.

I acquired a motorcycle lift and plan on lowering the tank enough to cut in a top access panel in the not too distant future.. maybe take a peek in the tank and see how that looks once I burn through some of this full tank of fuel.