P218G Onan Hard start

[Toasty 52]

I have a 1988 518-H.  When I first got it, it would not run at all.  Past owner decided to mess around with the electrical and got it all wrong, and the key had snapped on the flywheel.  During trying to figure out what is all wrong, I have installed a new coil, plugs, and carb.

 

It has always had a hard time starting even when I got it to start working.  Found the only way to get it to start the easiest is to keep the throttle at it lowest setting, and have the choke off.  Once it starts to run I have to slowly move up the throttle and choke at the same time till I get it about half way throttle.  Then I remove the choke and raise the throttle to the desired amount.

 

Any help getting this issue resolved would be highly appreciated.

Thanks!

[oldlineman 1,513]

probably needs a good carb cleaning. Bob

[Handy Don 13,743]

I agree. By far, the likeliest issue is a clogged carb not doing the job.

Thorough cleaning--ultrasonic bath if you have access, or else lots of carb cleaner, on the stripped down carb. There are a lot of passageways in that one. 

Also, confirm that the Welch plug is in place (search this forum to see posts about it).

You'll need a carb overhaul kit and (be sure to use the model/serial number from your engine when ordering) and new gaskets for putting the cleaned carb back on the engine--Onanparts.com is one good source. Members have had mixed results from kits on the Bay or Jungle sites--some have been fine and some worthless.

 

You'll want to read this manual from our manuals archive carefully. It isn't hard for someone with basic mechanical skills, but there are some useful tips and tricks in there. If there is something you don't understand, c'mon back and ask! 

 

The next likeliest possibility (ignore if you've already dealt with these!) is a constrained fuel supply. Look for pinched fuel line, clogged fuel strainer at the fuel tank, or clogged inline fuel filter. If you have a transparent filter or fuel line, can you see fuel flowing once its running?

 

You didn't mention if starting with the air cleaner off is easier. If it is, replace BOTH the foam and cartridge in there--these have a remarkable effect on airflow.

[peter lena 9,194]

@Toasty agree with others above on the carb cleaning routine , more than likely also have a filthy fuel tank and degraded fuel lines . knowing I would have to do a total on the fuel system , done this first , get a gallon jug or 3-5 gal gas can, I can of seafoam  and fresh gas , with stabil in it , separate line to tractor fuel pump, start it up and run it at a fast idle , also have an aerosol carb cleaner handy , to spray in while running .  done this on 3 engines now , and it really helped clean out the crud , also heated up the engine for a hot oil change . engine started and ran well , with fresh fuel and increased cleaners.  later I  went after the filthy gas  tank , put a new valve in it , 2 new filters and all new clear gas line .  the separate gas can running helped verify engine operation . one way or the other , you are going to have to do this , found it made things easier .  just my own experience, pete 

[lynnmor 7,733]

If it acted exactly the same way with the old and new carb, maybe we can rule out the carb, but it sure sounds like you need to clean it out.

[cleat 7,192]

I worked a 416 that acted like that until it would not start at all.

 

Coil had failed.

 

New coil and it started right up just like all my 520's.

 

The hard starting must have been due to weak spark.