Tecumseh engine 17.5hp wont start unless primed

[larrylwill]

I have a Tecumseh engine 17.5hp on a Murry Lawnmower. 2 years ago it started serging, I cleaned the carb and that fixed it for a year, then last year it got so it wouldn't start unless I primed it. Today I put on a new carb but have the same problem. I have to pour gas in the air cleaner and choke it and get it started. Once started it runs ok and will start normally as long as its hot, but as soon as it cools I have to prime it again. Does anyone know what I should check now?

 

[BoomerCTD]

If your sure the carb is ok, I would check the fuel pump and hoses going to and from it.
Mike

 

[larrylwill]

I thought the fuel pump was the diaphragm in the carb. Its all new.
Also it runs fine after starting with a prime and will continue to start as long as the engine is hot.
There is a hose from the gas tank to the filter to the air filter box which is connected to the carb. So where would a fuel pump be?

 

[SZR48207]

I have a similar issue on my mower. Usually the first start after it sits all winter requires a shot of starting fluid into the carb.

I know the carb is not the problem in mine. I have wondered if it is a compression issue given the mower's age. I'm curious what would happen if I ran some sea foam through it to relieve what is probably 10+ years of carbon buildup.

 

[boraticus]

Is the choke working? Is the choke linkage connected properly.

Not familiar with that type of engine but doesn't the carb have a float and float bowl? Don't see too many diaphragm carbs on a riding mower.

 

[larrylwill]

yes there is a float bowl and yes its working ok, and the choke closes the valve about 90%.

 

[boraticus]

If it has a float bowl then it's not a diaphragm carburetor. Pull the carb off and clean in. Sounds like the pilot (low speed) circuit isn't working.

The choke should close completely. 90% isn't good enough. Get the choke to close all the way before taking the carb apart. Try it. If it works with just the choke fix, skip the other stuff.

 

[doitmyself]

Check that the mounting connection (gasket) between the carb and cylinder is snug and air tight (could be sucking air there).

Make sure the muffler is clean (clogged = backpressure)

Air vent in the gas tank cap is working?

Check all hoses/filters for blockage, leakage, etc..

Let us know what you find. As above, is a compression test in order?

 

[morris]

if its a diafram or mechanical pump. convert it to a electric fuel pump. iam in the middle of putting a airtex (carter) e84070 elec pump on my case/onan 16 hp. you'll need one or two filters, and a holley fuel pump safety switch 12-810. from advance auto. BIG warning do not use copper or hose. the ONLY thing to use on fuel lines is steel break line tubing. and a fuel pressure regulator Mr. Gasket #9710. [email protected]

 

[Deltona_Dave]

I would remove the float bowl and look at the nut holding it in place. That is the main jet in most small engines. Run a piece of fine wire (telephone, network cable, piano wire) through the orifices on that nut/bolt. That may fix the issue.

Dave

 

[larrylwill]

ITS A NEW CARB.
"Today I put on a new carb but have the same problem."

 

[boraticus]

Are you certain that the choke is being fully engaged?

If you know the choke is working right, I'd look at the fuel pump next. If it's a vacuum driven pump, there might be a leak in the line from the engine to the pump that drives the diaphragm or the diaphragm might be defective or weak. The pump may not produce enough pressure to get fuel to the carb without the engine spinning at operating speed.

 

[Texan4Life]

I assume its OHV.. maybe check the valve clearance. If you sure its not a fuel/air delivery problem, I would just spark next. Maybe a weak spark?

 

[SOHCman]

Ill second the choke adjustment. adjust it so that it closed 100% of its range. That may give you the rich condition that your mower requires to start.

Given that it is a new carb, perhaps the adjustment got off when the instillation was done?

If its not that, I might guess some other fuel issue like vapor lock or air in the line or even a plugged up gas cap preventing fuel from flowing before the engine reaches full power/temp.

 

[Hokiefyd]

Make sure the choke is adjusted right. I just sold a Murray tractor with the same 17.5hp Tecumseh single on it. When cold, it'd surge real bad and yes, after a real dry start, I'd have to prime it with some TB cleaner spray. Cleaning the carburetor helped, but keeping the choke in proper adjustment did the most good for it.

 

[larrylwill]

The problem was I reversed the linkage and the choke was not closing full closed. Its starting now. Now for a new battery and an inner tube for a rear tire then for sale.

 

[Hokiefyd]

I sold mine on CL for 400 bucks! I had no idea that even older riding mowers were worth that. Mine was in good shape and well cared-for, but it was still 10 years old.

 

[larrylwill]

Jason: Whats CL?

 

[boraticus]

Craigs List

 

[larrylwill]

thanks