Small Engine Problems? Ask an Engine Mechanic for Answers ASAP
Hello, welcome to Just Answers. My name is Tim, and I would like to help you with your question
What engine do you have in this machine?
21 hp vanguard
model and code
ok no problem. a few other questions and then I should be able to help you diagnose your problem
do you have an electric meter or access to one, and know how to read one?
yes and yes
now on the coils, did you replace the ignition coils chasing the charging problem?
alright. unfortunately on this engine the ignition coils do not have anything to do with the charging.
there should be a square box mounted on the side of the engine
ok no problem this thing will all brand new when I get done
yep there is
3 wires red and 2 yellow
there is usually two yellow wires going to the box, and a connector there.
rectifier/regulator 797375 part number
on the vanguard it is usually this part that goes bad on the charging. you can do two checks to verify if it is this or the stator under the flywheel
ok which one first
first disconnect the red wire, you want to check the side going to the machine for voltage with the key turned on. you should get battery voltage at this wire
this will make sure the charging circuit is intact
if that is ok, you next want to check the two
wires for the yellow connector. this one is sometimes tricky to get a good read on with the meter.
you want to check these two wires with a/c, not d/c, with the engine running
at full rpm you should see around 20 volts or more. more is ok, much less or zero is bad
ok but why would it show a negative on the amp meter
the negative from the meter is because it takes voltage to run the fuel shut off solenoid, and also even more voltage with the pto engaged. if the engine is producing no voltage, the meter will see it as a negative draw on the system
if you have good voltage from the two yellow wires, (put one meter probe on one wire, and one on the other, not the engine ground), then your problem is the regulator
if you have low or no voltage from the two wires, then the stator is bad, and you could still have a bad regulator but not able to check it without a good source voltage from the stator.
(if you have good voltage from the two yellow wires, (put one meter probe on one wire, and one on the other, not the engine ground), then your problem is the regulator) explain that one more time please
touch both sides of the of the plug ?
on the check for a/c voltage from the two yellow wires, you are checking the ones coming from the engine, and the way to check them is with the meter on both wires. so the red on one of the yellow wires, and the black on the other yellow.
yes. you are checking for voltage using only those two wires and not the engine ground
just want to make sure i explain it correctly
yes me too lol
It is almost always the regulator, but if you dont check you can wind up with a new regulator and still not have the problem fixed
on the coils again, you mentioned a concern about the diodes, are the still there just not plugged in?
what about the alternator ?
yep they are cut not attached
sorry, the stator i mentioned earlier is another term for the alternator. same thing
so there is one then
yes. that is what the two yellow wires are from
ok got it
what about the 2 wires off the coils for the shut off
and the black wires from the ignition coils should be the kill wires. most models do have diodes in there, and if it is supposed to have diodes and they are not there, most of the time it will only run on one side.
with the wires hooked up direct i mean
it wont even start with them hooked like that to the connector
ok, you can check with your meter and make sure those wires are not grounded with the key on. if that is the case, then a new wiring harness piece with diodes should take care of it.
the new coils didnt have diodes installed on them so it goes from the coils to a little tab at the side of the engine and with them hooked up it wont start at all
I tried that and it back fires at me
the diodes should be in the wiring
not on mine
not on the coils its just 2 straight pieces of wire
something like this here..
keeps the coils from cross talking
if that looks like what you tried, then i would check the wires for ground when off of the coils, and the key turned on, and then off
ok that came off the old ones but not on the new ones
most of the engines i see from briggs have something like that on them.
yes there was one of those but am I suppose to use the old one ?
I figured it was more like a fuse and needed to be replaced
ah, yes you re-use that. it is considered a part of the wiring harness.
the coils try and ground each other out if the diodes are not in place. that explains the problem there.
ok but not the charging part ?
that doesnt have anything to do with that right ?
correct. the ignition coils and the charging are two seperate systems
can you just come here and fix it
if it ends up being the regulator as i suspect, then its a pretty easy fix :)
I hope so Im tired of spending money on this thing
I guess I will have to figure this out tomorrow and let you know where
I end up
ok sounds fine. I will check back in tomorrow afternoon.
ok cool thanks for your help with this
you are welcome. let me know what you find, and I will help you as best I can