640 starving for fuel after getting hot

wfd2 · Aug 21, 2014

Bought my 640 and didn't use much for work until now. After the engine is hot (after using 15-30 mins bush hogging) the engine starts to starve for fuel. When the issue is happening, if I pull out the choke 1/2" or so the engine will settle down, which leads me to believe it's gas related. *Because of this I did not check ignition coil.*

What I did so far...after I looked on the YT website...

1. I jumped ignition switch for fun... No difference.
2. I checked gas cap- venting tank- no difference.
3. Checked fuel line for heat...My fuel line was rerouted by someone else. At that time, the sediment bowl was replace, along with a newly rebuilt carb. I can put my hand on the fuel line and it's not warm at all.
4. I very recently replaced shut off valve. Checked screen - ok clean.
5. I removed fuel line at carb. Nice, steady stream of fuel coming from tank.
6. I noticed sediment bowl was tilted almost at 45 degrees. Upon further inspection found gunk in bowl. Cleaned bowl.
7. Had an issue where fuel wasn't being shut off in carb. Removed carb, thoroughly cleaned and found spring in float was pinched. Repaired spring- seemed ok... cleaned carb while it was off of tractor.

But I'm thinking that sediment bowl at 45 isn't good. I took a picture and posted. So I started looking at pictures here on site and found that fuel line used to run between head and exhaust manifold. Someone reran in an attempt to stop fuel from boiling? And they put the wrong sediment bowl on tractor because clearly it doesn't fit between generator and carb.

So.. I bought the right one (taller and skinny). I'll need to make sure my bolt will fit properly (I saw pics here about bolt stem hole is supposed to be seen in square opening in the top of the sediment bowl.)

But before I removed the current bowl... does anyone have any information if the bowl is at 45 degrees will it still work?

And if you think the sediment bowl at 45 will not affect the operation or cause the tractor to starve for fuel, do you have any other ideas on what to check?

Thanks in advance for your help,
wfd2

old · Aug 21, 2014

45 degree can make things not work like they should since the sediment bowl work on the principal that particles are heavier then fuel so they fall to the bottom and at an angle they fall to the side

john in la · Aug 22, 2014

When the issue is happening, if I pull out the choke 1/2" or so the engine will settle down, which leads me to believe it's gas related

That thinking could be wrong. Pulling the chock makes the gas/air mixture rich and this will compensate for a weak spark.

I removed fuel line at carb. Nice, steady stream of fuel coming from tank.

Did you do this while the fuel starve problem was supposedly happening. If so tell me again why you think you have a fuel starving problem.

does anyone have any information if the bowl is at 45 degrees will it still work

Will it cause a fuel starve problem if the bowl is clean. NO you could mount upside down and fuel will still flow; it just will not filter the fuel.

You have one of two problems I can see from your statements.
You have a ignition problem
OR
You have junk in the tank. As the tractor runs over time this pulls the junk to the fuel line clogging the screen in the tank. Letting fuel run at the carb will sometimes show good flow but still have this problem cause it is running for two short a time or to fast for the junk to settle on the screen in tank.

Texas! · Aug 22, 2014

It sounds like you have a spark problem to me.

wfd2 · Aug 23, 2014

(quoted from post at 12:07:51 08/22/14) When the issue is happening, if I pull out the choke 1/2" or so the engine will settle down, which leads me to believe it's gas related

That thinking could be wrong. Pulling the chock makes the gas/air mixture rich and this will compensate for a weak spark.

I removed fuel line at carb. Nice, steady stream of fuel coming from tank.

Did you do this while the fuel starve problem was supposedly happening. If so tell me again why you think you have a fuel starving problem.

does anyone have any information if the bowl is at 45 degrees will it still work

Will it cause a fuel starve problem if the bowl is clean. NO you could mount upside down and fuel will still flow; it just will not filter the fuel.

You have one of two problems I can see from your statements.
You have a ignition problem
OR
You have junk in the tank. As the tractor runs over time this pulls the junk to the fuel line clogging the screen in the tank. Letting fuel run at the carb will sometimes show good flow but still have this problem cause it is running for two short a time or to fast for the junk to settle on the screen in tank.

I had a few hours of time yesterday to work on the tractor.

Here is more information:

John was right-- the coil looked to be bad. It was leaking a light oil and even if this wasn't the culprit, it looked to be pretty old (from when Standard still made coils in USA- now they are made in China). I replaced it with a new USA coil and checked spark-- hot blue spark 1/2" away from block when cranking and 1.5 ohms.

I also replaced the distributor cap and rotor. They looked pretty old as well.

Plugs looked fine to running a bit hot. No cracks in them and they looked new besides the color. Checked gap to ensure .025-.028. They are Champion H10Cs.

Replaced the wire to + side of coil back to wiring harness. It was all taped up and had a crack in the insulation.

Started tractor and seems to run really good. Went to cut grass for test.

Problem came back after about 20-30 mins of running.

Engine bogging down like it's starving for fuel. Pull out choke and it settles down a bit. Throttling down causing pops and backfires. Engine dieseling when ignition switch is turning off.

I let it cool for about 20 minutes... started up fine, ran again for about 15 minutes and problem returned.

I did notice air bubbles in the sediment tank when problem was present.

Gas cap seems to be vented.. it's loose fitting. But... that's when I have the hood open for inspection. I noticed that the top of the cap is rubbing on the hood. Maybe the hood is pressing down on the cap and causing a venting problem when the hood is closed? That's the next thing I'm checking later today.

What else could be causing air bubbles in the sediment bowl? Remember, my sediment bowl is mounted at a 45 degree angle because the previous owner re-routed the metal fuel line away from the exhaust manifold. I checked the fuel line when the engine is sputtering.... it's cool to the touch all the way from the tank to the sediment bowl. And there is a constant downwards slope from the fuel tank to the sediment bowl.

wfd2 · Aug 23, 2014

Here is a pic of how the sediment bowl is mounted.

wfd2 · Aug 23, 2014

I also forgot to mention...

There is some slop in the distributor rotor. The old rotor had it.. and so does the new one.
What I mean by slop is I can turn the rotor by hand from 4-5 o'clock before it stops. It's not solid on the distributor. I checked for slop in the distributor shaft by trying to turn it left, right up and down and there is zero play, so it's in how the rotor attaches to the shaft. But, like I said both rotors exhibit the same slop.

Kurt-NEPA · Aug 23, 2014

Just a thought about the rotor slop. Is the spring clip in place on the distributor shaft? If it is missing you would have the rotor slop you are talking about, might be causing some of the ignition problems.

wfd2 · Aug 24, 2014

Thanks Kurt! After looking a parts list for the
distributor, the clip was missing. To make a fast
repair, I went to the local New Holland dealer and
they had one. (It was $7!). I think these clips
should be supplied with the new rotor!

wfd2 · Aug 24, 2014

(quoted from post at 03:58:19 08/22/14) Bought my 640 and didn't use much for work until now. After the engine is hot (after using 15-30 mins bush hogging) the engine starts to starve for fuel. When the issue is happening, if I pull out the choke 1/2" or so the engine will settle down, which leads me to believe it's gas related. *Because of this I did not check ignition coil.*

What I did so far...after I looked on the YT website...

1. I jumped ignition switch for fun... No difference.
2. I checked gas cap- venting tank- no difference.
3. Checked fuel line for heat...My fuel line was rerouted by someone else. At that time, the sediment bowl was replace, along with a newly rebuilt carb. I can put my hand on the fuel line and it's not warm at all.
4. I very recently replaced shut off valve. Checked screen - ok clean.
5. I removed fuel line at carb. Nice, steady stream of fuel coming from tank.
6. I noticed sediment bowl was tilted almost at 45 degrees. Upon further inspection found gunk in bowl. Cleaned bowl.
7. Had an issue where fuel wasn't being shut off in carb. Removed carb, thoroughly cleaned and found spring in float was pinched. Repaired spring- seemed ok... cleaned carb while it was off of tractor.

But I'm thinking that sediment bowl at 45 isn't good. I took a picture and posted. So I started looking at pictures here on site and found that fuel line used to run between head and exhaust manifold. Someone reran in an attempt to stop fuel from boiling? And they put the wrong sediment bowl on tractor because clearly it doesn't fit between generator and carb.

So.. I bought the right one (taller and skinny). I'll need to make sure my bolt will fit properly (I saw pics here about bolt stem hole is supposed to be seen in square opening in the top of the sediment bowl.)

But before I removed the current bowl... does anyone have any information if the bowl is at 45 degrees will it still work?

And if you think the sediment bowl at 45 will not affect the operation or cause the tractor to starve for fuel, do you have any other ideas on what to check?

Thanks in advance for your help,
wfd2

I finally found the issue with my 641 and it runs fine now. I had a bad ignition switch wire between the terminal block and the ignition switch. When I tested the ignition switch early on in the troubleshooting process, I jumped it at the switch's terminals. The broken wire was upstream from the switch, so this made no difference. Only after I checked the switch again and by dumb luck wiggled the wires when she was sputtering, did it immediately clear up the problem.

Thanks to all who took the time to help me!

640 starving for fuel after getting hot

wfd2

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old

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john in la

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Texas!

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wfd2

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wfd2

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wfd2

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Kurt-NEPA

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wfd2

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