David Brown 990

For those that are following my problems with my 990, I just drained all the engine oil out. I had over 10 quarts of oil (actually a 15W-40/fuel oil combination) in the pan. Almost exactly 2 months ago I drained the previous oil out and put 7 quarts of new stuff in there. I somehow got over 3 quarts of fuel in the engine oil. That is with about 25 to 30 hours of use in that 2 month span.

I plan to wait awhile before I put oil back in the tractor to see what I get when I pull the plug. This happened to my Oliver 1755 and eventually I just had pure fuel oil coming out, had a leak on the outside of the shaft tube in the injection pump.

When I first had this problem, I replaced the lift pump. I still had fuel getting in the oil so I sent the injection pump in to replace the front seals. And since the new injection pump didn't work I put the old one on. From what I could tell the new front seals didn't keep fuel where it belongs.


The other day I took the manifold heater off and set it in a can for a day while it was still hooked up to the little black fuel line. I basically had nothing after 24 hours, although I could blow air through that heater which means it is shot from what I am told.

Can I take my lift pump off and put it in a pan or can for a day or two to see if it is leaking? If it leaks would it leak worse if the tractor is running?

How do I find out where the problem is??

Thanks.

You could by-pass the lift pump by installing an electric fuel pump. can you tell if the front seal is leaking? What is wrong with the injection pump you had "fixed" that it is not working? Injection Service gets spendy fast

AJ do you have any ideas about this?

If the lift pump diaphragm or seal is leaking it's probably going to be worse under running conditions. You can try taking it off and leaving the lines hitched up moving the manual primer lever and see if it's leaking. You may see it from that, or not. The lift pump is the easiest thing to check I think.

That is a good idea. I was planning to do that here in the future but didn't think of moving the primer lever.

Thanks.

I had this same kind of problem with my Oliver 1755, and I took the injection pump gear off and eventually discovered the leak on the outside of the pump shaft tube. (I can't remember the official name of that tube)

I thought about doing this with the 990, hopefully if there is a leak in the front I will see it.

I sent the pump in when I rebuilt the tractor to get looked at since the tractor had not been running for a couple years. They rebuilt the pump for about $550. I had fuel getting in the oil and someone suggested it had to be the lift pump. I got a new one and that did not stop the fuel getting in the oil. So I was told to send my pump back in and have them replace the front seals. The guy told me they can last for 2 day or 10 years or whatever. So there is a chance that they are shot again. It seemed like the oil level went up pretty quickly after I had those seals replaced on the pump.

Anyway, I'm going to look more at the lift pump and if that seems OK I'm going to take the gear off the injection pump and see if any fuel is leaking out the front.

It has to be one or the other. And to leak 3 quarts in 25 or 30 hours of tractor use to me is a bad leak.

Thanks.

Honestly, I don't know squat about the pumps, but if the shop is giving you a $550.00 bill and it leaks...I think I'd either find another shop or do the "crazy screaming customer" act if they aren't going to fix it right.

Is it a CAV DPA or a CAV DPS pump ?. Remember trouble with DPS shaft seals on new pumps , Installing new seals overcome problem. The DPA pumps are very reliable and not known for this problem although it can happen. They can operate without lift pump, this is fitted to pump air out in case you run your tank empty.
Another thing to check is the fuel pressure in the pump housing.

Thanks for the response. I have a DPA pump. It has been rebuilt and sent in again later. I hope I don't have to send it in again. If I do, it is not going to the same place it went for the rebuild and the front seal replacement.

Thanks.