Not having any problems with cold starts.

[RED-Z06 2,379]

It still confuses me how i never have any long crank times in my rear mounted tank horses, i know many on here have had ongoing issues with long crank times and have installed electric pumps and primer bulbs inline to try to combat the problem.  My 416-H is by no means low hours, and the 312-8 gets worked hard pushing dirt unapologetically a few times a year.  So, both have been sitting outside under covers since like 2nd week of February because i had 2 deere in the shop getting stuff worked on...and i haven't needed to use them...so this morning i figured id see how they started after sitting 3 or 4 weeks.  Stock pulse fuel pumps on both..and the 312-8 needs a battery and a starter.

 

So both started normally, its not cold here..but even over new years when it was in the high teens, they both started up fine.

 

We know, that fuel doesn't drain back out of the carbs on engines because the inlet is above the fuel level..fuel can drain back past the pump, and a longer crank time could be noted, if the carb was empty.  Even if i run out of gas and choke them dry..I only get a crank time of 5 to 7 seconds to refill the carb, which is normal.

 

Im trying to figure out what variable is in play to cause some people to have to crank excessively..while others fire instantly.  Is the fuel evaporating out the bowl vent for some?  Chokes not closing tightly? Compression low?

 

 

 

 

 

 

[Handy Don 13,046]

2 minutes ago, RED-Z06 said:

Im trying to figure out what variable is in play to cause some people to have to crank excessively..while others fire instantly.  Is the fuel evaporating out the bowl vent for some?  Chokes not closing tightly? Compression low?

 

Spotted one possibility right away (and thanks for the video). You start with the throttle at or near idle.

In my mind that would substantially increase the pressure difference between the atmosphere and the intake manifold and help the carb deliver more fuel quicker. I’m gonna try that (I usually put the throttle at or near full to start).

[RED-Z06 2,379]

7 minutes ago, Handy Don said:

Spotted one possibility right away (and thanks for the video). You start with the throttle at or near idle.

In my mind that would substantially increase the pressure difference between the atmosphere and the intake manifold and help the carb deliver more fuel quicker. I’m gonna try that (I usually put the throttle at or near full to start).

Ive aways found Onans start best at hard idle, i started doing it because with the throttle open and choke shut it would immediately flood the cylinders.  My Linamar OL18 (newer p218g) i can actually start without choke for 2 or 3 days after running it just moving the throttle down to idle.

[wallfish 17,175]

1 hour ago, RED-Z06 said:

Im trying to figure out what variable is in play to cause some people to have to crank excessively..while others fire instantly.  Is the fuel evaporating out the bowl vent for some?  Chokes not closing tightly? Compression low?

My guess, fuel is evaporating (or slow leaking) and the fuel isn't draining from the carb bowl through the line but draining back down the fuel line itself. Air inside a pulse or manual fuel pump will make it slow to pump.

My 520HC does not have a belt tensioner to release the belt from the trans. It's a snowblower machine so most often it needs to be started in the cold which adds quite a bit of resistance for those easy starts at idle. This tractor always starts much easier and faster in the warm months when moving it or something.

[clueless 3,070]

So what 312-8 engine do you have with a stock pulse pump?

[RED-Z06 2,379]

18 minutes ago, clueless said:

So what 312-8 engine do you have with a stock pulse pump?

Its the mechanical pulse pump driven off the cam, might call it just a mechanical pump or a diaphragm pump, its not driven off crankcase pressure like the Onan and virtually all modern engines.

 

I call it a pulse pump because the fuel pulses out, i guess if you go by how its driven...it would be pulse on the onan and mechanical on the kohler.

Edited March 9, 2023 by RED-Z06

[RED-Z06 2,379]

The carb in my Command 27hp on the Simplicity has a bowl leak, its the o-ring to the fuel solenoid...its not like actively dripping, but if it sits a week, it has to refill the bowl...it takes about 10 seconds to start...so that would make sense if someone has a bowl leak on an onan, it has to completely refill the carb.

[kpinnc 13,075]

With my tractors, sitting for about a week isn't really an issue. Two weeks? The primer bulb works wonders. Two machines currently have the bulbs installed- a Magnum 10 and an Onan P220. 

 

Both will start without the bulb, but can take a few seconds or sometimes more than one start attempt. With the bulb pumped up, both start on the second revolution. It just works.