View Full Version : Vanguard eating plugs and running rich
04-08-2008, 02:30 PM
23 hp briggs vanguard
on a simplicity ZTR, engine replaced
Belongs to a friend I'm trying to helpout...
Last year we replaced a coil that was misfiring about half the time and it ran great till now.
The other day it started acting up, popping and sputtering and black smoke running rich.
Changed the plugs, and it ran smooth as long as it was sitting still, seemed like it was flooding when we tried to mow with it. But then started misfiring again. Removed and checked the new plugs and they were firing through the side of the porcelain.
Changed the plugs and removed the kill harness from both coils. The diodes ohm out alright, but is it possible they're not working at times, and the rapid/double firing is ruining the plugs?
It runs fair with the air filter removed, but turns rich with it installed. The filter was new last year, and looks good. I know about the 2 different air filters for the briggs and the kohler, already been through that.
Also, there are 2 vent tubes on the carb, are these supposed to be open, or connected to something or plugged or what? One was plugged and one was open, but when I removed the plug it ran better, ie stopped flooding.
Been through the carb and it's CLEAN!
Is it possible to generate enough centrifical force on the carb when turning to cause fuel issues? It seems to sputter quite a bit when spinning hard. The air intake is to the back of the mower, and the whole engine sits behind the drive wheels. But it did run great last year...
Anybody got any other ideas? Is this particular carb a "bad" one?
A local shop said they changed them mid year.
Would bad diodes fry the plugs in 30 minutes like an old 2 stroke?
Thanks for your help.
04-08-2008, 07:32 PM
First, You created a vacuum leak by removing the plug which let the carb pull more air in turn leaned the engine out. Re-plug this port, The other one is the float bowl vent. It must be left open, I believe your problem is a bad (non-seating) float needle valve. Also, When you took the carb a part did you remove the main jets ? If so, Did you put them back in the exact port they came out of ? They are different to #1 and #2 cylinders.
This engine only has one carb listed for it by model/type and code numbers, If you were to purchase a new carb @ $185.35 you would get the same exact carb but one that works.
04-08-2008, 09:22 PM
I'm guessing the lower vent would be for the float bowl....
I did not remove the main jets. Inspected and flushed them (they were actually quite clean already) and blew a little compressed air through them.
But there's no fuel leaking out when it's sitting, and it will flow thru the fuel pump cause I had to turn the valve off when I disconnected the fuel line from the carb.
And what about the plugs screwing up every 30-60 minutes of operation? I put another kill harness on it today (not a new one, from a engine ran without oil) and 20 minutes later it was popping and sputtering again. I ran it a good hour or more yesterday with the harness removed (and no air filter) and it ran perfect. put on a clean air filter and another harness, and it screwed up again in 20 minutes. I pulled the plugs, and one of them is spittin sparks through the insulator again, a brand new set of NGK's!!
04-09-2008, 10:45 AM
If they did change the carb wouldn't there also be a change in the type or code numbers??
04-09-2008, 12:30 PM
I read the symptoms you explained and made a suggestion "I believe" as to what I thought your problem may be with my 31 yrs. experience under a roof (yeah I read your bio).
What causes any engine to run rich ? Too much fuel.....What regulates the amount of fuel entering a carb ? Float and needle valve assembly.....Why do plugs turn sooty black ? Too much fuel.....What does soot cause spark plugs to do ? Miss-fire.....
The main jets in a fixed jet carb are sized to run with the air filter in place, If a engine runs rich with a old filter then a new air filter is installed and the engine still runs rich I'm sure the the ports in the main jet(s) didn't wear larger all of a sudden to let too much fuel flow through them.
Can a float valve seal gravity pressure and not fuel PUMP pressure (while running) ? You betcha.....
As for a different carb, I've already explained but will go deeper.
Look up carb part number, Go to part pricing, No price but gives a superseded part number, Look that part number up then there's a price.
It has nothing to do with changing model or type numbers, There is no different carb for your engine than what's on it.
Now, There are different carbs on newer engines as with the car market. Things change all the time and if there is a change that will work on previous models it would be listed, Other wise it will not work.
I made a suggestion, If you can't sort the problem out then maybe do as your sig. line states.....:)
04-09-2008, 09:22 PM
GEEeeeees man, chill... I was just askin.....
I DON'T know it all, that's why I'm posting questions.
I haven't seen everything, but I have been mechanicing since before I could get a drivers license.
I appreciate your "suggestions" and was returning comments. I wasn't saying anybody was wrong, or right.
If we were talking face to face and you made suggestions that probably wouldn't be the end of the subject.
I can see from your numerous comments on this board that you have experties and lots of specific info.
If an automobile makes a change mid year the vin usually reflects it. So I figured doing a parts search with these numbers would only return these parts. If the setup of the engine was altered there would be different numbers to reflect the change.
If I enter a parts store and request a fuel filter for my Dodge truck, they have to know if the 6th number in the vin is K, L, or 6.
It's not an argument dude, It's question and answer.
Have a nice day.
04-09-2008, 10:30 PM
OK, Sorry dude.....I took a chill pill. Was havin a bad day and should not have posted at lunch time.....
I don't know if I'm right or wrong with your problem, As you posted in another thread "without me seeing it" but I know that's something I would check into.
What I was speaking of about changes in the car market is by year, A ECU for a 2008 may have changed from a 2007 but that wouldn't change the vin number. You are most likely asked for a vin number because you got a ex burger flipper helping you that doesn't know engine sizes by liter etc, I don't recall ever being asked a vin for parts....
But, The last 10 years I've been looking my own parts up on-line because I got tired of having to wait for the burger flipper to figure out what I needed and 24 mile trips with wrong parts.
Back to your engine, Something else came to mind. If you haven't checked valve clearance it's a possibility they could be a little loose and not opening fully.
Keep us posted as to what you find, Maybe this Ole dog can learn a new trick.
04-12-2008, 12:12 PM
I did consider the valve clearance, but haven"t got back to it yet.
I bypassed the fuel pump to see if it would make a difference, but haven't got another good set of plugs yet.
I cleaned 2 sets it had screwed up to see if they would do right, but they're still shorting through the tip insulators.
I removed the kill harness, even though I had changed it and got the same results. It ran the best the longest when I took it off and tried it out before getting another one. I don't see how it could matter if the harness is good, but that's what happened.
I'll let you know if I run across anything else.
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