My Tractor Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
177 Posts
Discussion Starter #1
1988 316 with Onan p218. Hours unknown, but probably 1000+

I have about 1.5 acres I cut weekly, takes about 1.5 hours. the last 2 times I've cut, it wants to die at full throttle (with PTO on), after just about an hour. it runs flawlessly before that. The stumbling usually occurs after starting from a stopped position, PTO on. When it starts to stumble, I switch the PTO off, and throttle down to half throttle, and it catches its breath and runs fine.

I checked for obvious issues 2 weeks ago, and found that the air cleaner was pretty fouled. So I changed it with a new one. I cut this week, and the same thing happened after about 1 hour.

I have fuel filters before and after the fuel pump. I can clearly see fuel flowing through each filter. I have not changed either filter yet, but they are only about 1 year old. The flow after the pump does have some air bubbles in it, if that means anything. I have read some things about vapor locks due to fuel filters, but I've had both filters in the line for 3 years with no problems.

Sounds like it's not getting enough fuel. I replaced the fuel pump with a brand new Onan unit about 3 years ago. I also rebuilt the carb at the same time.

What is strange is, why does it only show problems after an hour of cutting? Some of that cutting is up and down hills, with a lot of start/stops.

Any advice on what to try is appreciated.
 

·
Super Moderator
Joined
·
33,653 Posts
Sounds like coil may be going, heres what you need to test

onan coils deliver 3.9 - 4.7 ohms on the primary windings (measured on the terminals) and 12,600 - 14,400 ohms on the secondary windings (where spark plug wires go). This is with coil at room temperature.
 

·
Registered
Joined
·
177 Posts
Discussion Starter #5

·
Registered
Joined
·
177 Posts
Discussion Starter #6
Sounds like coil may be going, heres what you need to test

onan coils deliver 3.9 - 4.7 ohms on the primary windings (measured on the terminals) and 12,600 - 14,400 ohms on the secondary windings (where spark plug wires go). This is with coil at room temperature.
I got 3.3 on the primary, and 17,560 on the secondary.
 

·
Premium Member
Joined
·
2,224 Posts
seaweed
the specs that you were given are for the point style ign.
your engine is electronic ign.
the electronic ign specs are 2.90 to 3.60 for the primary.
the secondary is 14,500 to 19,800.

you coil specs slide in right where i like to see them.
the thing i would check is the ign. module.
there used to be a link to a online service manual here.
poss one of the members or mods can tell where it is now.
thank you. boomer ( the used onan engine parts guy )
 

·
Registered
Joined
·
177 Posts
Discussion Starter #9
Ok, so it's not the coil. I'll check into the iginition module. When I got the tractor, I replaced the IM with another unit. Have no idea how old it is. thanks for the help guys.
 

·
Registered
Joined
·
9 Posts
Hi Seaweed

Sounds like a similar problem to what was going on with my 316

I was at my wits end and tried all of the fuel related maintenance.

If there is an obstruction it's possible it could cause your symptoms.

I did all of the simple fuel supply and ignition things - purge lines, empty gas tank, replace fuel and air filter, clean carburetor as able from removing the top half, replace spark plugs and ignition wires, verify good contact at distributor wire connections, fully charge the battery.

All this over a period of multiple removals of tins and top half of carb.

I was getting pretty frustrated. I had it purring like a kitten. BUT only at low idle or maybe 1/3 throttle. If I tried to go to WOT....it would just suck wind and die. Not always right after I put it back together, a few times it seemed as though it was fixed, but short lived.

So many posts about surging at idle and I have this thing humming but can't open the throttle without a stall :dunno: I could ease it up to better than 1/2 if it was sitting still, but anything toward wide open and it would cut out within a few seconds.

After having the carb top off 4 or 5 times and pulling the idle needle each time, I know it clogged again after the first time, maybe even up to three times. I used a piece of 28g wire I stripped from a CAT5 ethernet cable to poke through the holes.

Anyway......

I ended it all yesterday.......the problem that is :congrats:


I disconnected and removed the fuel line from the filter to the carb inlet. I pulled the carb top once more, pulled the idle needle rechecked for clean. Pulled the float as I was going to check the float level.

I poured a little seafoam into the gas inlet orifice below where the float needle goes. It seemed to just stay there. I blew it out with some compressed air and it seem like it stop up completely.

I put my little wire though the hole and a little more seafoam and now it drained quickly. BANG, there is the smoking gun. For me anyway.

I put the air on the inlet in both directions several times to be sure there wasn't any remaining sediment and blew some seafoam through.

I put it all back together and ran it for a while at WOT cutting my already cut lawn ( I have a 185 Hydro as a back up).

I want to thank all of the posters on this forum. Even before the currently described problem (as in last time it ran sort of good) I had a surging problem that I would just choke to smooth out. It would not idle down without stalling (so I would keep it at 1/2 or better) and it just plain wasn't the tractor it should be.

I went through all the simple maintenance and trouble shooting using the guidance and suggestions of many posts on this forum.

Now this thing runs like a bear. Throttle at any position is very smooth. Plenty of power. I set my air gap on the electric clutch at .012 while I was in there. I know it's tighter than spec, but I finally can switch it off and on even after 30 min of mowing.

SO.........before you go crazy...I suggest you get into the top half of the carb again and do all the things you may have already done...again. It worked for me and I am freakin' thrilled. :fing32:
 

·
Registered
Joined
·
177 Posts
Discussion Starter #11
Mostly, thanks a lot for that story. I feel like the issue is fuel-delivery related, and I plan to get into the carb and fuel lines to check for blockage. That's got to be it, I just need to find where it is. I know for sure that my fuel tank has crap in it, as evidenced by the first time I changed the pre-fuel pump filter... looked like someone was cutting wood inside the fuel tank. Maybe something got into the carb since my air filter was a mess... i hope so... that's an easy fix.

still has me wondering why it runs fine, idle to WOT, for just about an hour before the issue starts. a dirty carb should affect performance from the time you turn the key, shouldn't it?
 

·
Registered
Joined
·
9 Posts
You might thinks so, but when there are loose particles that are big enough to block or partially block orifices the symptoms can be intermittent.

Maybe you have a heat related electrical problem. Your symptoms certainly allow that possibility.

But all the fuel line and carb cleaning and recleaning are pretty simple and cheap and should be rechecked.
 

·
Registered
Joined
·
177 Posts
Discussion Starter #13
I changed both of my fuel filters today. the one before the fuel pump was pretty jammed, with lots of fine sediment in the bottom of it. I didn't realize just how bad it was clogged. Shame on me. But I just changed it last year! So needless to say, after mowing season, I need to remove the fuel tank and clean it out.

ran it at WOT for about 35 minutes with PTO on... smooth and no stumbling. Fuel was flowng much smoother through the filters (duh!).

So I hope that closes this chapter.
 
1 - 13 of 13 Posts
Top