DP70 Low Oil Pressure / Flow

[Thomas Piccione]

We're having a bit of a perplexing issue with 1 of our 2 Norelco's. For whatever reason, the oil pump does not seem to be producing sufficient oil pressure, and as such, there's a very minimal to non-existent amount oil coming out of the intermittent and the top 2 oil spouts inside the projector head. That alone isn't terribly confusing, but we've been having a hell of a time trying to fix it. We are really not keen on blowing up an intermittent, so we are not running this machine for any significant amount of time until we can sort the issue out.

In an effort to resolve the issue, we have:

• Changed the oil. What was in there wasn't too old or dirty, but not perfectly fresh either.
• Removed and cleaned the oil filter. The screen and magnet were both clean. The screen is in good condition.
• Removed and cleaned the oil pump. There was a small amount of darkened oil inside the internal tube running from the impellers to the filter housing, but it was not clogging anything. We took the bottom plate off and the impellers looked good.
• After reinstalling the pump and running the projector, we still had low oil pressure & flow. We had a spare oil pump from our parts machine, which we installed and had the same issue.
• We also had a spare oil line / distribution tree in our parts machine and installed that, which was not any better.

What's particularly confusing is that when first starting after filling the oil, oil flow is quite good and seems to match our other machine, but after just a little bit of running it falls off quite hard and the flow out of the spout above the oil pump goes from steady stream to intermittent drip. This sounds like it's running low on oil, but this is absolutely not the case, we are actually a little overfilled at the moment.

So, having replaced every component in the oil distribution system and being left with the exact same issue, we're a little stumped. I have a couple theories that don't make much sense at all, so I would really like to hear from someone who has more experience on these machines.

My theories that make minimal sense:

1. I suppose it's possible that both our oil pumps are bad, which would really be unfortunate. However, visually they both look good, and do pump oil without an output line connected. Additionally, the pump from the parts machine worked fine when it was last used several years ago. All the plugs on the pumps are tight, so it's not like the oil is leaking out the side somewhere.
2. Is there something wrong with our oil somehow? It's several years old but has been stored in a sealed container and works fine in our other projector.

[John Eickhof]

a couple suggestions...first, i have seen this in different machines that the oil pick-up is out of adjustment or set too high and when started the pump operates well then the oil level drops below the pick up and the flow lessens, even though at idle the oil is at the level line, also there could be a defect in the pick up tube and it is drawing in air causing loss of good suction to pick up the oil? did you prime or 'burp' the pump with oil after having the assy apart? the pump can have a partial air lock, pour oil in from the top of the feed tube into the pump before use and rotate machine by hand to expell any air...lastly, make sure there is no debris in the sump where the oil is piucked up like a flake of metal or paint etc that may be pulled into the pick up and lessen the amount of oil...good luck!

[Thomas Piccione]

a couple suggestions...first, i have seen this in different machines that the oil pick-up is out of adjustment or set too high and when started the pump operates well then the oil level drops below the pick up and the flow lessens, even though at idle the oil is at the level line, also there could be a defect in the pick up tube and it is drawing in air causing loss of good suction to pick up the oil? did you prime or 'burp' the pump with oil after having the assy apart? the pump can have a partial air lock, pour oil in from the top of the feed tube into the pump before use and rotate machine by hand to expell any air...lastly, make sure there is no debris in the sump where the oil is piucked up like a flake of metal or paint etc that may be pulled into the pick up and lessen the amount of oil...good luck!

On the DP70, the bottom of the pump and its gears are submerged in the oil directly, so no pickup tube to worry about thankfully. I also had the thought that it might be oil level, so we added a bit more and at this point the whole pump is submerged, so it's definitely not sucking air. We completely cleaned the area where the oil sits when we swapped the oil, so it should not have ingested any particulate.

I think you're right about about a trapped air bubble, though we did try to prime and burp the pump several times. I think we will try a different technique next time around to do our best to completely fill the thing with oil. We tried just pouring in from the top but that really didn't work so well.

Thanks for the suggestions!

[Mark Gulbrandsen]

This is beyond bizzare. During my career I worked, on or rebuilt over 50 DP-70, never had this happen! I have to wonder if the parts in your spare projector are also messed up. Did you try blowing air through the main oil feed line? It could have some crud in it. Could the input point on the intermittent have some hardened sludge or gear pieces stuck in there? And by sludge I mean if these projectors sat for any long periods, regular petroleum based oil can dry up and become a clog. In theory the filter should keep any gear particles out, but who knows how well the oil filter was maintained over the years... that round filter screen is also very fine... Beyond this stuff, let us know what you find when figure it out...

[Thomas Piccione]

This is beyond bizzare. During my career I worked, on or rebuilt over 50 DP-70, never had this happen! I have to wonder if the parts in your spare projector are also messed up. Did you try blowing air through the main oil feed line? It could have some crud in it. Could the input point on the intermittent have some hardened sludge or gear pieces stuck in there? And by sludge I mean if these projectors sat for any long periods, regular petroleum based oil can dry up and become a clog. In theory the filter should keep any gear particles out, but who knows how well the oil filter was maintained over the years... that round filter screen is also very fine... Beyond this stuff, let us know what you find when figure it out...

Yes, we were able to blow air through the oil feed line and feel it come out all of the spouts. We checked the inlet of the intermittent that connects to the oil line, and it was perfectly clean in there. We did clean out a small amount of sludge from inside the pump when we had it apart, but nothing massive and nowhere near enough to clog it.

I think our next step is to try and manually prime the pump and fill it with oil before we install it. Hopefully we can eliminate any air bubbles before we actually spin the pump.

I'll update the thread once we *hopefully* figure out this silliness.

[Mark Gulbrandsen]

Nah, I never had to prime a pump in any make of projector, so I doubt it's that... I would substitute the pump in from the good machine first. Its sure easy enough to do...

[Thomas Piccione]

Managed to sort it out! There must have been an air bubble trapped *somewhere* in the pump. I used a syringe to force an amount of oil in the top of the pump, and hand cranked the pump backwards to pull the oil through. I also took the line off and filled it with oil using the syringe to further confirm the oil line was clear. Last I ran the pump at low speed (around 2 frames per second on the VFD display) and held a finger on the output to confirm pressure and try and force any bubbles out. Put the line back on and everything got oil, and lots of it, just like our 2nd projector.

[John Eickhof]

thats good news! i have seen air-lock in oil pumps on simplex and brenkert machines too, even an occasional cinemeccanica! i was told years ago by Howard Straight to always prime the pump before install, it was more critical with rock and roll projectors as the pump had to be redesigned so it would pump in both directions! brenkerts had a habit of the rubber connector hose would break down internally and cause a check valve action so oil would not flow kinda like brake hoses on automobiles can have happen! anyway, glad ya got it solved, glad i could be helpful.

[Pete Naples]

I had this exact issue with No2 of a pair I service.

By laying parts out on the bench, side by side, I notived that for some reason the gauze filter on the No2 machine was either 180º flipped compared with No1 or sitting in a different alignment on the magnet. Whichever it was, I made it look axactly like No1's filter, and the normal gushing of oil was restored.