Ford 640 - Slow Fuel

pobox1589

New User
I posted last week about my Ford 640 that was shutting down after a few minutes; at first I thought it was a bad coil, but after checking the spark, I realized it wasn't that. Seems the issue is the fuel going too slow from the valve into the sediment bulb. Once it shuts down, I look at the sediment bulb and can see the fuel dripping in with about 1/16 of an inch gap between the top of the fuel in the bulb and top of the bulb. I've tried that with the fuel valve in both the regular and reserve setting. So, it sounds like it's a clogged fuel line or fuel valve. Cleaned out the bulb and screen and it'll still do that.

What I wanted to do (let me know if there's something smarter) is shut the fuel off, remove the line, and clean it out. Was going to use mineral spirits or denatured alcohol with pipe cleaners or a boresnake or something. Is that the best way to clean it? If that doesn't solve the problem, I can drain the tank and clean out the valve, but I'd really rather not have to do it.

Thanks for all the help, everyone, I appreciate it.
 

I doubt if a line plug is your problem, unless the rubber portion of the line has collapsed. In that case, cleaning it won't help either.

It's more likely to be crud in the tanks plugging the outlet strainer . . . or valve, if the strainer is gone.
 
If that's what it sounds like, I may just drain the tank and do it all at once. Any special tricks to cleaning out the fuel system?
 
Quick test.

remove line from carb. open gas tank lid, open fuel valve, have your blow gun ready and shoot a few blasts of air. Have a glass jar or other fuel rated basin ready, see if you suddenly get real good flow from the line.

If yes, it's likely the strainer had stuff plugged around it, or as said, the strainer is missing and stuff was setting int he holes in the tap.
 
Make sure the correct bolt is used to hold the sediment bowl assembly to the carb. The holes in the banjo bolt on mine didn't align with the holes in the sediment bowl housing and caused the fuel flow to be reduced. It would start and run great at low idle, but would sputter and die if put under a load. I bet I took my carburetor apart 20 times looking for a blocked jet with no luck till I accidently found the problem with the bolt. Now it runs correctly.
 
I had a fuel dribble outta my 640 a while back so I removed tank and then shutoff valve and took mine apart to drill out and also replace the oring in there cuz it was leaking also. I ended drilling mine out to 9/64 which was as big as I dare go. New oring and I was good to go..see my pics...got some good ones

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I did go to a lot of trouble to get good fuel flow but it was worth it
 
As many times as I've taken that sediment bulb off and cleaned it, I forgot to check the alignment of that hole. I'll check that today.
 
It started doing it after running for 2-3 hours at 540 PTO RPMs, so I wouldn't be surprised if it got a little off kilter.
 
Tried adjusting that to see if it adjusted the flow, but even when I got it flowing as much as it could (tightened down as much as possible) it still didn't flow enough to keep the bulb full. I'll try blowing out the line today or tomorrow.
 

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