Ford 6640 Fuel Priming Problem

JFR · Feb 22, 2012

This is a 1992 model with a cab and MFD. It has a gas tank in front of the radiator and one under the drivers side of the cab. What i have done so far is shut the needle valve going into the top of the sediment bowl; disassembled and cleaned the sediment bowl and reassembled; i have removed and replaced the fuel/water separator filter and filled with fuel and reassembled; so far so good right? Well the shop manual then proceeds to explain how to bleed the system once the above has been completed. The very first step is to open the needle valve and loosen the bleed screw on top of the sediment bowl housing. This is where the problem is: NO FRICKIN' FUEL. Ok, so i think alright this needle valve might be clogged up. So i remove the fuel line going to it to see if there's fuel. And there is not.

My question is how do i get fuel to the sediment bowl to proceed with the bleeding procedure?

When i turn the key on i do not hear a fuel pump run. I looked for a fuel pump fuse or relay and did not see a slot for one.

Any advice, of course, is greatly appreciated.

slowzuki · Feb 22, 2012

To start with, the 40 series needs that top tank filled to the very brim to prime after changing filters. I don't think it has a lift pump.

JFR · Feb 22, 2012

I'm off to the fuel depot. Thank you and i'll let you know what happens.

Harry in Ky · Feb 22, 2012

Most 40 series tractors came with a hand primer pump, built into the top of the fuel filter base near the bleed screw you mentioned. It's a diaphram pump, actuated with the palm of your hand. Does your tractor not have it? The TS series, which came next had an electric pump mounted in basically the same place, probably due to the fact the hand pumps were prone to fail when they had some age. As long as things are working normally, the hand pump is non functional as the supply pump built into the injection pump is capable of pulling fuel from the lower tank as long as no air leaks develop. Once you open the system for service, it's a different story. It does help to have the fuel fairly high in the front tank, as even if the hand pump funtions, fuel has to be drawn by vacuum from the lower tank through the water separator which is mounted up high on the engine. If you don't get all the air leaks sealed in the seperator unit, it can be dificult if not impossible to pull fuel through it if your fuel is only in the lower tank

RickB · Feb 22, 2012

They are among the most miserable tractors to prime ever built, right up there with an IH 806. Without question fill the front tank above the level of the water separator. If you disassembled the water separator without replacing the seals, replace them. Other advise given is spot on. Very, very late 40 series tractors had electric lift pumps from the factory; I have seen only one firsthand.

slowzuki · Feb 22, 2012

Yup, the neighbours 7740 has the hand prime pump. Mostly useless unless everything is full. We used to be warned not to run it out of fuel. Its got over 10,000 hours on it now.

whodat526 · Feb 22, 2012

RickB said:
Very, very late 40 series tractors had electric lift pumps from the factory; I have seen only one firsthand.

i have seen a bunch of them also

JFR · Feb 23, 2012

UPDATE:

Slowzuki, you were spot on. Filling the front, UPPER, tank to the brim was all that was needed to bring fuel to the needle valve and to subsequently fill the sediment bowl and remaining fuel lines.

Harry in KY, yes this model has a primer bulb affixed to the fuel filter housing. It's use apparently is only to pressurize the lines once everything is purged of air.

Rick B., no electrical or mechanical fuel pump on this model. Once primed the injector pump does all the work.

All in all once I had something to work with (FUEL) the rest of the bleeding process was fairly easy. Albeit messy. I just let the fuel flow out of the bleed screw atop the separator until there were no more bubbles. Then i bled the screw that's on the front of the fuel filter housing until it was a steady stream. After which i depressed the primer pump 5 or 6 times until i felt resistance. Lastly, i started her up and witnessed three short sputters before she evened out to operating normally.

Hey, thanks a lot for the quick responses yesterday. I really appreciate it.