Help diagnosing engine problem please.

[SARG]

I have a Husqvarna 2354GXLS tractor with a Briggs 23 hp Vanguard engine. It has under 200 hours on it and I've not had any engine issues until today.

After mowing heavy grass for about two hours I was headed back to the garage and the engine started to stumble and misfire. It will idle OK but as soon as you put any load on the motor it stumbles. I went through the normal checks and the air filter and fuel filter were like new .... I changed both maybe a month ago.

I did find that "both" spark plugs had a very heavy soot deposit. These plugs have less than five hours on them. I installed two more new plugs and the engine stumbles under load just as before. I did check to be sure the choke was totally off.

Now I'm scratching my head. If it was a valve problem then only one cylinder would be fouled. It was 85 degrees today so I'm considering it might be heat related and something on the ignition system is croaking.

Anyone give me some ideas ?

 

[alchemysa]

Heres a problem I found on my B&S 18hp engine recently. The symptoms were similar. I discovered the choke had stuck in the closed position. It did not return to the fully open position when the lever was pulled back. (Mine has a single throttle/choke lever). The thing to note is that the choke (on mine) is not directly connected to the cable. It is spring loaded and only returns to the fully open position if it can move freely of its own accord. (Just because you have pulled the choke lever does not mean the choke has opened).

So, it might be worth checking that your choke is opening and closing correctly.

 

[sam5570]

sounds like the fuel pump is bad. it's mounted on the side of the engine has 3 hoses connected to it. I have a BS vanguard on my washer and had kind'a same problem. they around $32 for new one.

 

[Midniteoyl]

Def sounds like a fuel/carb problem.. Double check all the linkages and look at the governor for correct operation.. Even though you changed the air filter, pull it and clean it. Is there an enrichment adjustment on the carb?


However, even though it seems like a carb issue, check the coil too...

 

[SARG]

Thanks for the responses.
The choke is a manual one and works fine.
I seem to be getting excess fuel when the engine is put under load so suspecting the fuel pump is hard for me to understand. Yesterday I disassembled the carb and cleaned it. It really was not dirty at all but thought I might get lucky.
After several hours I got it all back together with no change. From idle if you rev it up.... it stumbles and blows the black smoke. The same if you turn on the PTO from the high RPM.
The fact that it just started out of the blue makes me suspect something electrical even though the "rich fuel" condition is obvious. Time to study a service manual for awhile.

 

[pacerron]

See if the gas cap has a little vent hole in the center of it. If it does, be sure it is clean. A paper clip or small wire will clean it. Don't puncture the rubber vent under it, just clean the hole. The Briggs on John Deere lawn tractors has the same problem and people have spent tons of money and time before they discover the hole is clogged.
Give it a try, it's free.
Ron

 

[sam5570]

sounds like the fuel pump is bad. it's mounted on the side of the engine has 3 hoses connected to it. I have a BS vanguard on my washer and had kind'a same problem. they around $32 for new one.

sorry I didn't explain better. the fuel pump has a regulator or preasure valve and if the diahapram goes bad in pump will still pump but will not stop the fuel once the preasure builds. hope this helps

 

[SARG]

sam5570 ....... Thankyou for your inputs. I suspect you have solved my issue. After reading your post it made me think it had to be caused by what you described.

AND... there are two components that would do the same thing. I think that it is either the fuel solenoid or the pump. I tore it down again today and bench tested the solenoid. It does nothing when 12 volts is applied and I've ordered a replacement.

I hope it is the culprit because they cost $59. It will be here tomorrow or Monday and I'll post the results.

 

[sox3]

The solenoid just stops the fuel on shut down to stop backfires. Clip the tip off the bad one and install to see if it runs ok, don't need to hook up wire.

 

[SARG]

Today I received the new fuel solenoid and I just got done installing it. The tractor now runs as good as it ever did so the bad solenoid did indeed cause all by problems.

The "expert" at Vanguard B&S had told me it would not fix my problem and I've sent him an email to clarify my solution just so he's aware for future inquiries.