John Deere 990 performance

machineryman · Aug 9, 2016

Gave the 990 a run out today with the add on electric fuel pump. Tractor never ran so good with performance on governor and engine. That pump gave even pressure to my injectors and performance was up at least 25%. I'd never messed with the factory pump just installed the small electric pulsating pump. Advising so others might want to consider. It ran as a totally different tractor...

leon · Aug 10, 2016

Now that seems really strange. Mind you I'm not even hinting nor implying that what you've experienced and are saying isn't true, but it's hard for me to accept that Deere and Yanmar, the manufacturer of the 990, would have put on the market a tractor that didn't even run right. As I recall, the 990 is basically an up-powered version of the 970 and it's lineage dates back many, many years to the 950. I'm wondering in the little auxiliary fuel pump you added isn't really compensation for something else that has gone wrong in your tractor's fuel system. I'm wondering if the real problem isn't the fuel transfer pump that's part of the main injection pump itself. Up to tractor SN 590000 that transfer pump carried number AM876343 and after SN 590000, part number AM881833.

Mike M · Aug 10, 2016

BINGO !

machineryman · Aug 10, 2016

Okay, I did some more investigation as before and after 59001 you will see the electric pump that I added...they added another component or canister plus the filter...my set up has these return features on the filter. But anyway John Deere knew they had a rear fuel transfer problem....I think my pump on injector works or the tractor would not have run but it was not delivering adequate fuel....I upgraded similar to the 59001 set up....they did change the pump as mentioned, and don't know reason other than marketing thought I'd readvise....best Chuck

machineryman · Aug 10, 2016

Okay more research...I see the problem with John Deere design. They never had problems till they came up with the rear mounted tank some 8' from the fuel filter/injector pump. Looks like they constantly tried to redesign. They even added extra tank fuel outlets in an upgrade. Changed injector pumps "then finally" just added the electric pump like I just added. They never had any problems with the later 4000 series as they put the fuel tank directly over the engine. I have a 4400 and never had any issues as a matter of fact they just used the same filter body of the older 990. Engineers just outsmarted them self with a brain **** and then had to come back to basic what will work...I'm sure they re-engineered the electrical harness on the later model 990 as customers would not have liked the add on wires. But what I'm advising is what will work well and I think it might improved others...the little pump is standard low pressure and is used on a lot of equipment now.

leon · Aug 10, 2016

Yes, in the parts book I do see the little electric fuel transfer pump AM876266 was added at SN above 590000.

leon · Aug 11, 2016

Again, kinda strange and some things that don't add up. According to the on-line parts book for the 990, there's no change in the rear light and wiring harness with advancing serial numbers. Same for fuel tank - the same tank, and thus must be tank location, throughout 990 production. Now it's a different story when it comes to fuel filter and fuel lines - a change at 290000 and another change at 590000. Just curious, what's your serial number and how long since you changed the fuel filter? Until adding the electric fuel pump did the tractor run crappy it's whole life? Did you own this 990 from the time it was new?

John Deere 990 performance

machineryman

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leon

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Mike M

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leon

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