# MF40 flat spotting



## arfafergi (Mar 11, 2007)

Gday all, 

I have recently bought an old Massey Ferg MF40. It runs the 3 cyl Perkins diesel. I have replaced all fluids and filters yet I am still having a problem. The tractor will start and run fine but after about 10-15 mins of work it developes an intermittent flat spot. I can hold my foot flat to the floor and it just wont rev, then it will slowly start to climb after about 5-10 seconds. Seems to be reving to full revs when revving properly but just cant get rid of this flat spot. It is also seems unhappy at idle once this problem starts. 


Any ideas? 


Regards

Sean


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## wass (Jan 3, 2007)

*Morning!*

Almost sounds like a governor problem, wear marks and everything. Does it sound like it's making good power otherwise? Sometimes a restricted fuel system can act about the same and fight for rpm's and be lean at idle. Glad it's your problem and not mine.


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## Archdean (Jul 15, 2004)

Try this: Could be the injector pump relief valve is sticking wide open , returning fuel directly back to the tank when it does that!

If possible look at the fuel flow that is being returned to the tank when it is idling normally and then when it is running at rpm should be less, if it is returning fuel at the same idle rate when it wont rev with your asking it to (foot to the floor) Then I suspect you need your injector pump rebuilt!

Just my thought!

Dean

:cowboy:


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## arfafergi (Mar 11, 2007)

Just a follow up to this post guys after a very long time. 

After much investigation, I found I had a few leaks in the fuel system which were allowing air into the system. Once the flat spot occurs, I bleed off the injectors whilst the engine is running and it comes good. So with all leaks sealed up, she's running well.. As well as an old rusty, oil leaking, paint fading, hinge wearing old girl can be  

Thank you for your assistance gents.


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## shona13 (Aug 12, 2011)

Hi Mr arfafergi.
just a few quick points .
The three cylinder diesel is a great little engine it is economical to run and it will start without heat even on really cold weather.
check simple things first ,the fuel filters have three O rings ,one on the bottom of the filter one which fits inside the top housing this one has a blue mark on it make sure the old o ring has been removed before fitting the new one and importantly there is a smaller O ring that fits round the centre of the filter housing ,where the holding bolt comes through THIS IS THE ONE THAT WILL CAUSE AIR LOCKS in the fuel system.
next thing to do is remove the fuel line from the fuel tank ,the one with the fuel tap on it open the fuel valve fully open with say 1/2 tank of fuel it should fill say a coffee mug in 15/20 seconds,
If it only comes out slowly drain all the fuel out of the tank and remove the tap assembly there is a gauze filter in there pull it of and give it a good clean also remove the small retaining screw and screw the tap out completely and blow out with air ,wash the tank out with diesel and reassemble fill with clean fuel and bleed the system all should be well . 
As I have said the fergie is a great little workhorse.
If you need more info just post there are plenty of members only to willing to help.
REgards 
Hutch.


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