What could cause my HPOP reservior to be empty?

Truck has been sitting for 3 weeks, oil drained out of pan for a week. Was going to suck oil out of reservior before refilling with fresh T6 synthetic. Nothing but residual came out. I verified that the fluid extractor works. Wasn't anything in there to suck out.
I thought that it would hold a reserve for the HPOP and not just drain back into the block. Was I wrong about that?

 

I dealt with this 2+ years ago. In my case, the rez would drain down to the point it couldn't actuate the injectors - from one day to the next. I would top off (about 1 qt +/-) the rez and all was good. I changed out the LPOP and haven't had the prob since. In retrospect, I would characterize my prob as a weak LPOP that couldn't keep the rez full, and less about it draining out.

Your description indicates the rez drains down almost completely, as though it is leaking out when it sits. There is a check valve as part of the reservoir. I do not have direct experience with this part of the system. It has been discussed a few times here, however.

 

https://www.ford-trucks.com/forums/1...reservoir.html

Id start here, and see what sparks a thought. 🤷🏻

 

@kd5zll thanks for the link, was a good read.

I don't think it's the LPOP, I think it's a leak. Bad/weak LPOP wouldn't be filling the reservior and/or keeping up with the demand of the HPOP. Truck was running without a problem, a deal LPOP isn't going to do that. Fluid isn't going to drain out due to a weak LPOP, might not be full, but there would be something in there. The reservior was empty, the straw for the fluid extractor only had residual on it, not covered in oil like it should have been.


The truck was running fine three weeks ago when I drove it to my parents house and into the shop to start working on it. Only notable problem it had priot to that was a "cold start" issue that I mentioned in another thread a few months ago. I'm starting to suspect that I may have figured out what is causing my hard start after sitting for a few says. Starting after a day or two was never a problem, after 4 or 5 was a different story. If the HPOP reservior was leaking down and there wasn't a supply of oil for the injectors, then the truck would be difficult to start until it got oil back in there.

I finished reassembling the truck after posting this thread. As one would expect from an empty HPOP reservior, it took a bit of cranking to get the truck to start up. (Note to self, next time refill the reservior before trying.) Once it did, it ran fine. Proceeded to drive it 30 miles back to my house, including a short stop to dump old oil, without an issue. I romped on it a bit and no problems. Will say that fixing the boost leak I had feels like it made a difference.

Right now I'm leaning towards it being either the check ball not seating or an HPOP seal as talked about in that other thread. Either would be valid possibilities. The valley was damp when I inspected it, but so was everything else and all signs pointed to it being a CCV leak. CCV was defintely leaking, but that doesn't mean that HPOP seal isn't as well. On the other hand if it is the check ball it won;t be visible externally, but will still eak down. Will look into that further at a later time. Truck is running and I need to spend a little time on other projects.

Still appreciate the input and any additional y'all care to give.

 

I’m at the same point with my bus. Except mine died while I was driving.

anyway, I filled the hpop and let it sit over the weekend. This should be a good indicator of the reservoir leaking back down. (Bad check ball) I will report back In my thread later today.

you might want to do the same thing one night and check the reservoir level the next morning?