Need Help With Pulse Pump Output

[Walleye Guy 23]

This is a long shot, but would anyone be willing to make a short video of a pulse pump pumping fuel into a small jar so I can see how much output can be expected?

 

Or maybe tell me a pumping rate (quarts/minute, etc)?

 

We have an NOS pulse pump on our Wheel Horse 753 but can't get the engine to run.  It does run fine...and sounds healthy...when the carb is fed from a gravity tank we had leftover from an old Craftsman push mower.

 

We cranked the engine over with the pulse pump discharge fuel line going into a jar and there is barely a dribble coming out.

 

We took apart the pump and the diaphragm gaskets all are soft and in good shape, but yet when we hook up the Craftsman mower tank and gravity feed it then she fires right up and runs strong.

 

I have verified that the oil dipstick is screwed in tight. 

 

I also removed the spark plug and put my finger on the plug hole when cranking the starter and from what I can tell the "pulse" I feel on my finger feels strong.

 

Thanks in advance!

[rmaynard 16,633]

What you feel is not the pulse that powers the pump. Pulse (or vacuum) is created in the crankcase as the piston goes up and down. If the diaphragm is good, then the one-way valve disks may be stuck or dirty. It does not take much pressure. All you are doing is filling the bowl of the carburetor. I'd love to show you how one of mine pumps, but I am not able to do that today. When you took the pump apart, I hope you didn't lose the tiny springs that sit over or under the little disks. There are several types of one way valves, ones that are just sitting free with springs, and ones that are enclosed in a cage. Putting it back together you have to make sure that the disks and springs are in the correct position so that you have the one-way action going in the right direction.

[953 nut 62,561]

I don't have a to take a video of but can tell you the pump has two check valves in it that allow fuel to be pumped out and not run back toward the tank. If one or both of these valves are leaking by the pump won't work well. Here is a company that can provide the parts to repair your pump.  

https://www.then-now-auto.com/kohler-fuel-pumps-2/

          Bob @rmaynard types faster than I do.

[Handy Don 14,858]

What engine are we discussing?

When you re-assembled the pump, did you leave slack in the diaphragm? If you tightened it flat between the two pump halves, you made it impossible for the crankcase pressure change to deflect the diaphragm enough to pump adequate fuel. 

A steady trickle is all that’s needed to fuel most engines.

Many older engines have a crankcase breathing system as well as the pulse fuel pump. The breather contains a reed valve which, if installed incorrectly, defeats the crankcase pulse action. Have you hand this out and reassembled?

 

[Walleye Guy 23]

rmaynard: Good point on the pulse, I didn't think about that.  I double checked with my dad (the tractor is at his house and we live two hours apart) and yes he was careful to reassemble the pump exactly as it was.  He is a retired mechanic and has rebuilt many carburetors in his lifetime so the pump should be in the same condition as it was when we purchased it.  

 

953 nut: Thanks for the link to the rebuild kit.  I wish I would have known about that before we purchased this one because we searched high and low for a NOS pump since the shop told us that pump was an obsolete P/N.  

 

Handy Don: The tractor is a 753 and the engine is a 7 hp Kohler (engine SN = 652365, engine spec number = 28626E, engine model number = K161S).  We removed the spark plug, unhooked the pump discharge line and put it into a jar and then spun the engine with the starter.  With the original pump we got zero fuel in the jar.  With the NOS pump it was just a tiny drip....drip...drip.  We did take apart the breather to check the reed valve and it was working properly so we reinstalled it.  That too should be installed the same as it was originally.

[Handy Don 14,858]

3 minutes ago, Walleye Guy said:

He is a retired mechanic and has rebuilt many carburetors in his lifetime so the pump should be in the same condition as it was when we purchased it. 

 

3 minutes ago, Walleye Guy said:

That too should be installed the same as it was originally.

No dig on your dad, but many a mechanic thinks that diaphragm should be taut. Also, it is dead easy to reverse the reed valve without a conscious check--BTDT.

 

6 minutes ago, Walleye Guy said:

spun the engine with the starter

Not fast enough. Better to hook up the alternate fuel supply and test the flow with the engine running. 

[Walleye Guy 23]

No worries Don, I understand...everyone makes mistakes.  Even the most experienced ones.  

 

Your points are all valid and makes sense but still...the engine did not start with the NOS fuel pump when it was installed out of the box.  It wasn't until later when the engine wouldn't start that he disassembled it.

[ri702bill 10,232]

By chance, does you 753 have the fuel pump with the manual activation lever found on the 702?

If so, use that. They were discontinued around 1963, my 854 did not have one (but does now!). Handy to prime a tractor that has been sitting for a while...

 

[ri702bill 10,232]

3 hours ago, Handy Don said:

When you re-assembled the pump, did you leave slack in the diaphragm? If you tightened it flat between the two pump halves, you made it impossible for the crankcase pressure change to deflect the diaphragm enough to pump adequate fuel. 

A valid and often overlooked tidbit that makes the difference between "done" and "Have to do over".

[Walleye Guy 23]

Unfortunately no, it does not have that type of pump.  The cam has a lobe for a mechanical pump but by the Kohler spec number this engine was originally equipped with a pulse pump.

[Walleye Guy 23]

19 minutes ago, ri702bill said:

A valid and often overlooked tidbit that makes the difference between "done" and "Have to do over".

That's good information, and I appreciate you sharing it.  We can certainly disassemble it again to verify there is slack but again, the tractor did not run when this pump was installed new-out-of-the-box.

 

Would a new pump need to be primed for some reason?  Maybe we should have dunked it into a coffee can of fuel first?  Seems crude and unnecessary but the engine won't run with this pump.

[pfrederi 19,074]

My solution for recalcitrant mechanical or pulse pumps...and no risk of gas getting into the crankcase.

 

 

[Walleye Guy 23]

Is that an electric fuel pump?  I can't quite read the label because the picture is a little blurry.

[Handy Don 14,858]

41 minutes ago, Walleye Guy said:

... the tractor did not run when this pump was installed new-out-of-the-box.

 

Would a new pump need to be primed for some reason?  Maybe we should have dunked it into a coffee can of fuel first?  Seems crude and unnecessary but the engine won't run with this pump.

No, priming shouldn’t be an issue since the tank is nearly level with the carb. When I park my K181 for more than a month, I shut off the fuel cock and run the carb dry. After its vacation, it always cranks for about five seconds and then goes. 

I'm gonna throw out one more thing...

The body of the pump with the input and output connections is symmetric to accommodate right-hand and left-hand fuel feed carburetors. The orientation of the check valves inside determines the proper fuel flow. If your NOS pump was for an engine that “went the other way", it would be trying to take fuel from the carb and put it in the tank. Not a tasty test, but you should be able to blow through the pump in the proper fuel flow direction but not in the reverse. DO NOT use compressed air, it’ll break the one-way valves. 

After this, ya gotta start checking the fuel plumbing upstream from the pump for clogs and fuel restrictions. 

[Handy Don 14,858]

3 minutes ago, Walleye Guy said:

Is that an electric fuel pump?  I can't quite read the label because the picture is a little blurry.

Facit Posi-flow. 12v. 1-2psi .

[Walleye Guy 23]

Don, that's an interesting observation about the pump being symmetrical.  I'll ask him to remove it and try blowing through it as you described.  Duly noted on not using compressed air.

 

Facit pump: very cool idea.  I wouldn't think he'd be opposed to this but we're still hoping to get this pulse pump working.

 

He is also supposed to disconnect the fuel inlet line to see if fuel is coming out.  If not, then remove the glass bowl fuel filter (it's a new element) and reinstall the bowl to see if fuel then will drain out of the line.  This should tell him if the element is defective.

Edited 1 hour ago by Walleye Guy

[Handy Don 14,858]

12 minutes ago, Walleye Guy said:

he glass bowl fuel filter (it's a new element) and reinstall the bowl to see if fuel then will drain out of the line.  This should tell him if the element is defective.

The glass bowl “filters” used only a mesh screen and relied on any sediment to settle in the bottom of the bowl. A too-restrictive filter could definitely impede fuel flow. Not a good place for “more is better."

Edited 1 hour ago by Handy Don