Recently purchased a Ford l9000. Went to see the truck on a cold day and it had been sitting for some time supposedly. Started great with just a quick puff of smoke and cleared right out like they should. Has paperwork on full rebuild (owner bought complete long block from cat, and injection pump, he put it together) didn't take long for us to realize if you rev the engine it will conk out when it returns to idle. If you catch it just before idle and give it some fuel it will return to idle with no issue. Owner was shocked and said it's never done that (later found out that was a lie) Assumed simple fix maybe filters or air leak. Got it home now and spun on filters and checked for air leaks. Checked afrc diaphragm and o rings. Nothing simple has come up. Hunts a little if you listen to it at idle. I will be pulling apart the governor next to check and see it there is anything missing or any visible issues. Any one ever run into this? Can't help feeling like I'm over looking something. Thank you in advance and thank you for reading.

May be simple timing delay on the pump [installed a tooth off] Is the idle set too low?

Thanks for responding, I did adjust the idle up a bit to see if it would stop the problem, but it did not, same results after you rev it up. It could absolutely be a timing issue (considering who put it together) any way I can check that?

Theres a timing hole on the flywheel housing where you remove a plug and install a pin to set the timing, you can advance it slightly and it will start a little better.

Hi Westgate,
there is a dashpot (damper) adjustment in the rear face of the governor housing to adjust the response of the governor to prevent stalling--screw too far in or fluttering--fast rpm oscilations--screw too far out.
The daspot bolt/screw is shown at the Attachment Picture Section D-D.
I would first try opening the dashpot screw about 1 1/2 to 2 turns turns out and run the unit to flush it thru with fresh oil then carry out the intial adjustment  which is done with the engine at operating temperature----turn the screw in to seat it gently and back out 1/2 +/- 1/4 of a turn--cold weather may require the extra 1/4 of a turn out for stability to stop the stalling issue.

I do not have a 3406 manual but the scan below from a same setup used in the 3306 New Scroll Injection Pump of the day show give you an idea where and what the dashpot unit looks like.
The dashpot assembly from memory has about a 7/16" socket hex head bolt with a screw recessed into the center of the head of the bolt.

Also the orifice in the dashpot could be clogged by crud and may not flush thru.
Maybe screw the complete assembly out of the Gov. Hsg. so you can check for crud clogging the orifice--remove the little screw on the bench and similarly inspect.
If OK re-assemble and re-install--initial adjustment of the screw is all the way in gently to close the dashpot unit and back out 1/2 +/- 1/4 of a turn. With the engine at operating temperature adjust minutely to stop stalling or fluttering.
Hope this helps.
Cheers,
Eddie B.

Eddie B. , thanks for your response. I should have mentioned in my original post that we have adjusted cleaned and tried every setting for the dash pot. I do have a 3406 book, which lead us to believe that was our problem. After reading your message I did try again. Pulled it, cleaned and reset, trying every setting (manual calls for 1-1 1/2 turns out 2.5 max) first trying a half like you suggested. No matter the setting the engine has no change what so ever. Took the whole adjuster out while running, no change either. Any ideas where I should go from here? Thanks,
Roger W

Hi Roger,
I have a feeling from memory that the dash-pot oil comes via a catch trough in the Gov. Hsg. this catches splash oil for its supply so maybe remove the little dash-pot adjuster screw and blow air back into the hole to see if the supply drillings and/or the trough are clogged.

It would appear from your first post above that this is either a recon. or a new injection pump assembly that may or may not have had the old Gov. fitted to it so the following may not apply :-
Flat spots worn onto the toes of the governor weights and divots worn into the Gov. thrust bearing race is another possibility--they cause the Gov. weights to be sluggish and notchy in operation especially at low rpm's or crud/metal flakes from an old engine failure in the bore of the actual dash-pot piston/cylinder assembly causing stickiness or notchy operation of the Gov.

If the rear gov. hsg. is removed you need to be extra careful to ensure the Gov. weights are correctly engaged to the Gov. thrust bearing assembly or else a renegade one will destroy the Gov. and housing.
In early days of the New Scroll (NS) pumps there was a tin shield that was fitted to stop the destruction by renegade Gov. weights but in later times Cat seemed to stop fitting this in my opinion vital safety part for when the untrained work on these N.S. Governors.

Cheers,
Eddie B.

Thanks Eddie, I’ll try blowing air and see if clears. I was told it was a replacement injection pump from cat. I did see the receipt for it but if it has the old governor mounted to it I really couldn’t say. I will check tomorrow with compressed air. Does seem a bit odd that there was no oil what so ever coming out of the housing when I pulled the dash pot out

Hey Eddie, no luck. Blew air in the pump and had no affect. I suppose I’ll be pulling the governor apart today and see if I find any issues. Thank for the help, I’ll keep you posted - Roger W