The Diesel Stop banner
1 - 10 of 10 Posts

·
Registered
Joined
·
783 Posts
Discussion Starter · #1 ·
I have a `96 HPOP on the bench. I removed all the plugs and fittings, and I did not find a check ball in it anywhere.

Is it possible for the check ball to be lodged inside somewhere? Seems to me it should be right there ready to fall out.

If it was left out by the last mechanic, could that be a reason for the hard start? My gut says absolutely.

Any thoughts?
 

·
Registered
Joined
·
1,847 Posts
My gut says the same thing. I've never had one apart, but it seems to me that there should be SOMETHING there to stop unwanted drain back.
 

·
Premium Member
Joined
·
8,138 Posts
I have a `96 HPOP on the bench. I removed all the plugs and fittings, and I did not find a check ball in it anywhere.

Is it possible for the check ball to be lodged inside somewhere? Seems to me it should be right there ready to fall out.

If it was left out by the last mechanic, could that be a reason for the hard start? My gut says absolutely.

Any thoughts?
Left out by the last mechanic ? He would not be a mechanic then would he ? Keep looking , maybe one will appear :)

Then , try putting the pump back together again ( & have it work) :) I showed you the oil path . At start up the HPOP gets unfiltered oil from the C Case . Once the res has sufficient oil the LPOP takes over . The oil in the res is then filtered through the edge filter . Its location depends on the year of the truck .
 

·
Registered
Joined
·
10,925 Posts
In 96 starting with serial number 201681, the HPOP did not have an integral check valve in the body. There would have been the "check valves" (not really balls per se, but springs and spool I guess) beneath the hose fittings. Some folks remove those and don't have problems with drainback, but I imagine they were there on purpose. Cheers!
 

·
Premium Member
Joined
·
8,138 Posts
My gut says the same thing. I've never had one apart, but it seems to me that there should be SOMETHING there to stop unwanted drain back.
There is , it is in the block & rarely fails .Even if it did , the stand pipe in the res will help keep it full .
 

·
Premium Member
Joined
·
8,138 Posts
In 96 starting with serial number 201681, the HPOP did not have an integral check valve in the body. There would have been the "check valves" (not really balls per se, but springs and spool I guess) beneath the hose fittings. Some folks remove those and don't have problems with drainback, but I imagine they were there on purpose. Cheers!
Interesting info . Never heard of that one , Check valves in the hoses . So , what was the reason they were removed if they were there in the first place ?What changed ? They all have stand pipes in the res ..
 

·
Registered
Joined
·
783 Posts
Discussion Starter · #7 ·
In 96 starting with serial number 201681, the HPOP did not have an integral check valve in the body. There would have been the "check valves" (not really balls per se, but springs and spool I guess) beneath the hose fittings. Some folks remove those and don't have problems with drainback, but I imagine they were there on purpose. Cheers!
Thanks for the info. I'll check the serial number when I get back on that project.

I do have the check valves at the discharge manifold. And yes, they are a spring attached to a flat plate, about 5/16" diameter. There are two of them and they are under the fitting that the oil line connects to.
 

·
Registered
Joined
·
783 Posts
Discussion Starter · #8 ·
So , what was the reason they were removed if they were there in the first place ?
Some remove the check valves so-as to increase oil volume.

Joey at Terminator leaves them out of the pumps he rebuilds - unless (like me), you demand he reinstall them.

It's a piston pump. My guess is they (check valves) help reduce pressure dips (pulsation) in the oil system. They could also provide some benefit in troubleshooting.
 

·
Registered
Joined
·
10,925 Posts
The standpipe didn't get put into the reservoir until serial #187100 (sometime in the 95 engines). Cheers!
 

·
Premium Member
Joined
·
8,138 Posts
The standpipe didn't get put into the reservoir until serial #187100 (sometime in the 95 engines). Cheers!
There are 2 that I can see .Got any pics of the 95 oil path ?
 
1 - 10 of 10 Posts
Top