# Diesel fuel in the oil.



## Virgil (Apr 1, 2018)

I have a 71 Ford 4000 tractor that is getting diesel in the oil. I have rebuilt the CAV pump twice thinking one of the seals may have been pinched or something but didn't see anything wrong. I also replaced all the injectors recently too. I'm thinking it's gotta be something simple but can't seem to figure it out. If anyone has any suggestions it would be greatly appreciated. 

Virgil


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## RC Wells (Dec 26, 2008)

If you have the transfer pump that looks a conventional fuel pump, the diaphragms eventually crack and dump diesel into the crankcase.


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## marc_hanna (Apr 10, 2017)

Also, how is the engine running? Is it a little rough? Check the compression because you might me getting fuel past the rings. 

How much fuel is in the oil? Over the course of 100hrs it’s very normal to get 1 - 2% fuel dilution in the oil 


Sent from my iPhone using Tractor Forum


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## Virgil (Apr 1, 2018)

Thanks for the replays. This tractor does not have a conventional transfer pump, it has a CAV pump. As far as how much oil that's getting into the crankcase, the oil/diesel rises on the dipstick about an 1" every 4-5 hours running. The motor seems to run fine, it's not blowing any white or blue smoke. It doesn't even blow black smoke, maybe a little when it first starts but very minimal.


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## marc_hanna (Apr 10, 2017)

That's a lot! I think you need to start be checking the compression, because the first an most obvious source is fuel getting past worn-out or damaged rings. That will rule out a significant variable right off the bat. Others with more experience will likely have more/better suggestions.


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## Fedup (Feb 25, 2014)

I doubt compression (or lack thereof) is your problem. Even if it were, the associated hard starting and blowby would be hard to ignore. To have that much unburned fuel passing through cylinders and getting past rings would certainly involve an unmistakable miss and more than a little loss of power. 
Since evidently that is not the case, my bet is the pump. You stated you "rebuilt" it twice. What does that mean? Most of us don't have what's required to "rebuild" injection pumps, and leave that for those equipped and qualified to do so. Maybe a bit more detail on the pump repairs thus far might offer some clues.


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## RC Wells (Dec 26, 2008)

Verify the injector and pump return lines are clear of obstructions and fuel is being returned to the tank. If that line gets plugged, fuel builds up in the CAV pump drive end and forces diesel past the pump drive hub seal. Although an inch of oil level increase from diesel contamination in 5 hours is considerably more than I would expect from that source unless an internal pump seal is compromised.


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## thepumpguysc (Jan 25, 2015)

Only 3 places for fuel to get in the oil..
1>lift pump.. but seeing its gravity fed, that's out.
2> front seal on injection pump.
3> injectors.. but as the others have stated, THAT MUCH will be accompanied by lots of smoke & very hard start & a definite MISS..
What are you TORQUING the drive hub screw to?? {how much}
Are you changing the oring behind the weight cage?
Is the drive hub scored or gouged?? there will be a pronounced ring/groove around it.
Whats the end play measurement between the hub & housing??


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## thepumpguysc (Jan 25, 2015)

Your gonna have to remove the pump.. SO.. pressure test it before any repairs are made to it..
Use about 3psi IN THE RETURN hole..
IF yours has the return on the SIDE COVER.. DONT USE THAT.. it has a 1 way check valve in it..
Remove the banjo bolt on the top cover & use THAT hole to pressure test it..
You HAVE TO REMOVE the banjo bolt because it has a TINY orifice in it & you wont be able to get enough air pressure thru it.. so take it out..
IF your return is at the front, on the main housing.. just use that hole to p.test the front seal..
Spray some soapy water on the seal & watch for bubbles..
Good luck & lemme know if you need more help. TPG


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## Virgil (Apr 1, 2018)

Thanks pump guy. I actually was wondering about my drive hub. It has a grove wore into it and had me kind of suspicious of it. I'm assuming someone sells new drive hubs, any ideas who? Also what is the recommended torque suppose to be on the Allen bolt that holds it on. I have never been able to find the torque specs on that bolt in the manual.


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## thepumpguysc (Jan 25, 2015)

I probably have a hub..
the torque on the Allen screw is >>350 inlbs 3x with Blue locktite on the screw.
That means> tighten, loosen, tighten, loosen, tighten..
Don't look at me.. that's what the book says & that's what they teach in factory training class.. & it works.. my pumps don't leak.
Do you have a pair of calipers?? if so, measure the groove in the hub.. there should be no more than .004" dif. between the groove & the reg. metal..
in other words, the groove cant be more than .004" deep.
The end play on the hub to the housing is .010" MAX, measured w/ a feeler gauge.. between the hub & the housing.
Once you get your hub torqued down, grab the hub & pull/push it in-out & measure the play..
If its OVER .010" its either the weight retainer or the housing that's at fault..
IF the hub is grooved, the fault is either dirty fuel or dirty engine oil..
You DO HAVE 2 washers on the hub screw, right?? 1 flat & 1 spring..
Good luck & lemme know if you need a hub.. TPG


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## Virgil (Apr 1, 2018)

Thanks pump guy again. I will take that pump off this coming Sunday due to working outta town the rest of the week. I have calipers and feeler gauges to check that hub and yes the bolt in front has the two washers on it. I'll get back to ya Sunday and let you know the results. Thanks again.


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