D7F Fuel getting into the oil

[Hillmaniac1993]

Hello all, we have a 1970's model D7F with a D333 engine. It has the scroll type injection pump. We recently rebuilt the engine and had the injection rebuilt at the same time. We got the dozer running, we ran it for about an hr, checked the oil and noticed that the level on the dipstick has risen one inch on the dipstick. You can tell that it's diesel fuel. So we pulled the transfer pump and had it rebuilt, put it back on, changed the oil and tried it again. Ran the machine for an hr, shut it down and checked oil....same thing, oil level had rose another inch on the dipstick with only 1 hr of run time. We were told that not having a return line can cause pressure to build in the injection pump, and therefore make it leak into the oil lubricated section on the injection pump. BUT there is not a return line from what we can tell on this injection pump, there was only the fuel supply line. I will post a pic of the injection pump. Does anybody have any experience with this? Any advice would be greatly appreciated! We hate to pull the injection pump if we're not sure that's the problem...

 

[Old Magnet]

Any transfer pump or injection pump leakage should travel internally to the tell tale drain line off the bottom of the accessory drive housing. If that drain is plugged leakage can build up and enter the front timing gear housing.

 

[Hillmaniac1993]

Where would that be on this pump? Here is some better pictures. We have the transfer pump off currently

 

[Mquinista]

Not very familiar with cat pumps,(to secret too find info about) but almost all inline pumps i have seen either leak into oil through Lift Pumps, or main gallery wrong assembly, or cracked assy. Anyways one inch of oil rise in 1 hour is really too much. Since u had the pump rebuilt the shop should that did it , should have done the check list... at least we do in our shop specially for those 2 particulars.
good luck.

 

[Hillmaniac1993]

 

[Old Magnet]

The drain I'm referring to is not on the pump, it comes off the bottom of accessory drive housing right up against the back of the timing gear housing. 1/4" line.

 

[Hillmaniac1993]

Can you tell where the drain is from this picture? And how does the pump keep from being overpressurized if there is no return line? Even if it has some kind of bypass, where would it go? That transfer pump runs constantly so it has to just keep pumping in fuel

 

[Old Magnet]

The drain line is #22 in the parts diagram
The compact scroll pump does not need a recirculation line. The transfer pump has a pressure relief/recirculation valve built in.
I see a 45 degree elbow and what looks like a pressure sensor mounted the bottom of the accessory housing? What's that about? Could be drain line that has been repurposed?

 

[Hillmaniac1993]

Ahhh I gotcha! So does that drain go to the atmosphere?

 

[epirbalex]

Ahhh I gotcha! So does that drain go to the atmosphere?

The amount of diesel you are losing it will show in every puddle in the district

 

[Old Magnet]

Yes, it's there to drain any leakage and give a visable sign that there is a leakage problem.

 

[Hillmaniac1993]

Ok sounds good. I am going to go back and look tomorrow to see if that's where that drain should be. Thanks for all the info guys!

 

[56wrench]

And whats all that blue crap between the accessory drive and the timing cover? Gaskets are easy to make

 

[Hillmaniac1993]

One more quick question, what is the little T-handled valve on top for? It is circled in red in the first pic that I posted. Is it for the hand primer pump?

 

[jezow2010]

One more quick question, what is the little T-handled valve on top for? It is circled in red in the first pic that I posted. Is it for the hand primer pump?

that is your air bleed. loosen it up and while you pump the hand pump or roll it over fuel or air if its not bled will come out.

Did you get it? I tore one of these down and spent quite a bit of time on it for a 977

 

[Old Magnet]

My understanding is that is the bleed valve and the drain route is through internal passage to the accessory housing and out the same drain line we've been talking about.

 

[jezow2010]

That is correct. I fought a massive fuel leak from that line for a while. Every time you would turn the machine over or start it up it would pour fuel from that line. Took it all apart, rebuilt the transfer pump, everything I could only to realize they were connected and that my bleed screw was bent so it wouldn’t tighten down all the way

 

[Old Magnet]

OK, thanks. That system is a bit of a head scratcher????

 

[Hillmaniac1993]

Yes, I think we have figured out what we did wrong thanks to you guys. When we first got this scroll pump rebuilt, we had installed that 'sensor' in that drain hole that Old Magnet had pointed out, because the book didn't give any detail at all on what that open port was for, and that 'sensor' was laying with the pump when we were putting it back together, (lesson learned, I need to do more research before plugging up random holes) And I guess we had that bleed valve open, which was causing it to build pressure and pushing fuel into the oil (so we think) since the drain hole was plugged off. So.....we have now removed the 'sensor', and installed a piece of drain tubing, and we have closed off the bleed valve. We are going to change the oil tomorrow and run it for a while to re-check for fuel in the oil, but hopefully this was our problem. Thanks again guys! I'll try to give an update tomorrow night on how it goes.

 

[LCA078]

When you say "re-check" for fuel in oil, you mean send an oil sample out for analysis, right? You didn't mention if you're doing regular oil samples so wanted to emphasize it. Just because the oil level stays the same on the dipstick doesn't mean much when trying to determine if the oil is contaminated with 3-6% or whatever fuel Cat says is the max contamination rate.

I don't know the exact oil capacity of your motor but if it holds 8-10 gallons of oil, that means it will take 1-2 quarts of fuel leakage to barely get to that dilution rate. I doubt running it for an hour or two then checking the dipstick level probably will be a definitive answer on whether or not your dropping 1-2 quarts of fuel into your oil every hour or two of running. And even if the level stays the same, you have no idea how much oil you're consuming (burning or dropping or pushing into another area) and the fuel is just keeping the oil level constant but continually diluting it. And that's especially true when you're doing a standard oil change when your running for 50x or so longer.

I bought a bag of bulk oil sample bottles from my local Cat a while back and it was $95 bucks for a half dozen or more kits that were pre-paid shipping and pre-labeled for shipping. I get the results online a week or so after mailing it in. This will keep your engine in much better condition than eye-balling a dipstick or using the paper-towel wicking test...both of which can only detect fuel contamination much higher than the max dilution. After you get the fuel pump straightened out, maybe send a few samples out after 1-2, 5, and maybe 25 hours if your dipstick level is constant just to ensure your repair (and other stuff) is good.