The Kohler Courage 25 HP on one of my riding mowers finally gave it up. It got to the point where I was burning more oil than gas and had to mow with the wind so that I wouldn’t get all the smoke. I think it must have eaten a ring as the oil consumption reached a level where it could barely stay running. Finally it just locked up.
I picked up a replacement engine that will bolt right up with the electrical and mechanical connections just fine. The replacement is used and I got it for almost scrap price of the metal it is made from. The only concern I have is that the engine on the mower sits at about the same level as the gas tank. The engine on the mower had a vacuum line from the valve cover to a tiny fuel pump inline with the carb. The replacement engine came from a mower where the gas tank sat way up higher than the engine so there are no provisions for a fuel pump. The replacement engine is not overhead valve so there are not valve covers. There is also no vacuum port on the intake. I have seen spacers with vacuum ports that I have considered bolting between the carb and the intake but would that cause other issues?
I have also considered a tiny 12V fuel pump wired into the ignition so if the switch is on, the pump is also on. The problem is all the pumps I have found are for automotive use and likely too strong for the purpose I have. I probably only need like 1psi of boost where these start out at 5psi and more. Anyone have a suggestion?
Assuming there’s no way to gravity feed this thing the 12 volt automotive pump will probably work fine but what you could do is add a rheostat and just dial in the fuel pressure as needed.
An old dashlight dimmer switch out of a junk car would work.
I expect a 5 psi electric pump would be fine. The carb float/needle valve shouldn’t have any problem regulating a 5 psi fuel stream.
You can also find slightly lower pressure pumps (3-5 psi) on eBay.
All the electric fuel pumps that I have seen use spring pressure to force the fuel out and the electric solenoid pulls the plunger back for intake when it bottoms out.
John Deere uses an electric fuel pump on its lawn tractors so it should work on yours. The only problem is they cost about $125.
Idea 1. What if you did a kludge?, i.e. install an external gas tank somewhere high enough gravity feed would work?
Idea 2. The vacuum in the intake manifold should provide a considerable suction force. I’m wondering if there’s a way you could harness that to lift gasoline to the engine. Might require a intermediate tank though.
Idea 3. Some vehicles, often diesels, have intermediate fuel pumps, that pump gasoline at lower pressures from the back of the car to the front, then there’s another high pressure fuel pump that supplies the fuel injection system. Maybe one of those intermediate pumps might work.
I bought a very low pressure electric fuel pump for a motor scooter on Ebay, I think it was a Carter P60504. It was pretty cheap, under $40 I think. And you can buy a pressure regulator as well. There’s also a pump made by Mr. Gasket that could work. The quality is uneven at best. A higher mounted tank and gravity feed would be fine, and you can find a cheap petcock to shut off flow when the engine is off, on Ebay.
Have you googled the engine manufacturer’s website to get the engine specs including fuel pressure? Modern cars run upwards of 40psi, and you wouldn’t want to put that much pressure on a gravity feed design, or even a carburetor (carbs run low pressures).
I googled the Tecumseh site earlier this year and there was all the technical data there… even though Tecumseh has been out of business for five or six years. It’d be worth a try for you.
Both the old and new engine I plan to install are Kohler units. The old engine was almost a gravity feed design. The only reason for the tiny vacuum operated pump is that the tank sits at pretty much the same level as the engine. I have seen some spacers that fit between carbs and the intake manifold that include a vacuum port so I am looking to find one that will fit my unit and see what it does. My first search found a ton for car setups but nothing for mowers.
I know I will hardly need and pressure so need to either make the old pump work or find a very small one for my purpose.
Some of those Kohler pumps need both vacuum and pressure pulses to do the pumping. Usually, there is a block plug using the light pressure/vacuum pulses from the crankcase to actuate the pump. Some pumps have a return spring and only need either a vacuum or pressure pulse. Be sure what you need before starting modifications…
I recall reading somewhere about a guy that tapped into the dipstick tube to get the pressure pulses needed for the pump. That would be an easy fix compared to drilling into the block…
If crankcase pressure/vacuum is needed there has been a vent connection from the crankcase to the carburetor just above the throttle plate on every small 4 stroke engine I have ever seen from the 1950s till present and from 3hp B&S to 18hp Wisconsins. There is an oil baffle in the crankcase behind the vent port.
That is a good idea. I am sure this engine has a crankcase breather setup like you describe. AS you say, they ALL have one. How would be best to tap into this without messing up the breather system?
Suprised Carolyn hasnt callled the good people to task on this post,just put the little solid state fuel pump on it.Ported vacuum would be better-Kevin