B&S 28Q777 crankcase vacuum line sucking oil up to fuel pump

[warreng5995]

Ok, a bit of an update.
I looked at the vacuum line today and about 1.5 to 2 inches of it was filled with oil (see first photo attached). ILENGINE & Born2Mow both of you said oil in the line may be normal. So I figured ok, lets not drain the line and leave the oil there and try to start it and see what happens. With the choke on, cranked it over and it fired right up.

So, I figured I might as well as pull the dipstick and see how much pressure it was pushing. Pulled the dipstick, and a light spray of oil did come out until I put my hand and paper towel over it. I could feel some air but didn't seem more than what I thought would be normal. After holding the paper towel over it for 5 or 10 seconds, I removed it and replaced the dip stick. There was some oil spray on the towel, but not soaked or anything. Oil level has stayed at the full mark this whole time.

Just for a comparison, I went out back to my other mower with B&S (16.5hp) and did the same thing. it actually sprayed more oil into my paper towel than this one did. But I am pretty sure it doesn't have a oil pump (but is "splash lube" only - I could be wrong about this though) as it doesn't have an oil filter like this engine does.

Back to this Vanguard, I ran the engine and let it come up to full temp, I watched the head and some other points with a infrared "laser" thermometer to see if I could find any abnormal hot spots. The hottest point on the head was near the spark plug, with temps around 280 to 300 f. The hottest spot I could find on the muffler was 680F at one point. Most of the muffler was around 450 to 500 f. Oil filter stayed between 122 and 130 f, as did the crankcase next to the filter. Valve cover got up to about 135 f. Other parts of the head and case were much cooler due to the air flow from the flywheel "cooling fan". I think the float bowl on the carb was around 110 f.
I will add there is no odd sounds or anything. It doesn't surge or etc. Runs smoothly.

Now that it was at full temp, I pulled the dipstick again and the air and oil spray seemed exactly the same as when I first started it. So no difference there.

Finally I turned off engine... let it sit for about 2 minuets or so. Tried to restart, it didn't want to, it chugged a bit, I let off the key and it chugged a few more times on its own but then picked back up to normal engine speed. So I ran it a few more minutes, and turned it off again. This time i let is sit about 5 minutes. Tried to restart, Nothing. Didn't even try to hit. Tried to restart it a few more times, letting it sit a minute or two between attempts, but never hit. Same as it did the other day.

I didn't have any more time to mess with it today, so that's all I was able to test.
But in short, it appears that the oil in the vacuum line isn't the issue, as it was that way today when I started the engine cold, and it fired right up just fine. So I guess that part is "solved" and appears to be a non-issue.

At this point, I don't think I'm getting piston blow by or bypass on the head gasket. As cold and hot both seemed to be the same with my mediocre "dip stick test".
I can't do a proper compression test on this engine, because it has the compression release on the cam shaft so it is easier to start. Which this compression release "lobe" doesn't move out of the way until the engine is running and the centrifugal force moves it. So from what I can see and understand, due to this compression release the compression PSI will never show correctly when just cranking the engine over. If anyone can confirm or refute this, please feel free to post such.

With that said, I did check my service manual StarTech and it listed 220 in-lbs as you said the old versions did. So when I have the time to pull the covers, intake/carb and etc. I may up the torque on the head to 250 in-lbs as per your suggestion.

So in the end with what little I was able to "test" today.... Why does the engine start cold just fine and seems to run "normally" and smoothly... but once hot when you shut it down for a few min, it won't restart?? Could this still be an issue with compression? Vapor lock in carb, but only after the engine cools?? Or...??? ?

Thanks All

 

[StarTech]

Question. When it doesn't restart, does it spin normally while cranking?

 

[warreng5995]

Question. When it doesn't restart, does it spin normally while cranking?

Yep, no hard turn over or anything. It just cranks and cranks, but doesn't even try to hit.
When cold, it starts and runs fine... until you turn it off for 5 min.
Before I re-adjusted the valves it had a very noticeable amount of power loss under load, but after the last adjustment power is improved (although its still less than it should be).

I just thought about something... what if its just a coincidence?? What I mean is, what if it not restarting when hot doesn't have anything to with the rebuild itself... and instead the issue just happened to occur during the time period of this rebuild?
Most of the time I really dismiss anything as "coincidence"... but what if the coil is breaking down?? Starts fine when cold... but once the engine is hot, the coil could be overheating to the point it has weak spark when hot??? It has to have some spark or it wouldn't run at all when the engine is hot. But once you turn the engine off, and the engine cools down enough. It takes a full powered spark to restart, but if the coil is still too hot and still has a weak spark, you get a hot engine no start condition???

Does this seem plausible? Anyone have a opinion?

 

[bertsmobile1]

Spend $ 20 & get a red in line spark tester
No flashing = dud coil or kill wire shorting
Remove will wire from coil
Flashes red = short in wiring or faulty safety switch.
If it only does it when the blades are on suspect the reverse switch.

 

[ILENGINE]

The oil is colleting in your vacuum line due to the sag. The line should run downhill from the fuel pump into the fitting on the breather to prevent oil pooling in the line. I am wondering if you are not loosing spark when the engine gets hot. heat sinking the ignition module.

 

[warreng5995]

Spend $ 20 & get a red in line spark tester
No flashing = dud coil or kill wire shorting
Remove will wire from coil
Flashes red = short in wiring or faulty safety switch.
If it only does it when the blades are on suspect the reverse switch.

its not switches nor kill wire.
starts and runs when cold, continues to run when hot. After its hot, if you turn off engine for 5 minutes, it won't Re-Start.

 

[warreng5995]

The oil is colleting in your vacuum line due to the sag. The line should run downhill from the fuel pump into the fitting on the breather to prevent oil pooling in the line. I am wondering if you are not loosing spark when the engine gets hot. heat sinking the ignition module.

ok, i'll try to see if there is a way to re-run the line. the carb and choke rods are in the way.
ignition module, possible. hadn't thought about that either. its mounted on a "plate" via one of the starter bolts.

 

[ILENGINE]

ok, i'll try to see if there is a way to re-run the line. the carb and choke rods are in the way.
ignition module, possible. hadn't thought about that either. its mounted on a "plate" via one of the starter bolts.

The ignition module is what you are calling the coil. Don't confuse it with the regulator/rectifier for the charging system which could be located next to the starter.

 

[Born2Mow]

Why does the engine start cold just fine and seems to run "normally" and smoothly... but once hot when you shut it down for a few min, it won't restart?? Could this still be an issue with compression? Vapor lock in carb, but only after the engine cools?? Or...??? ?

In my experience this is due to coating of the jets.

The EPA has made all engine builders lean out their engines. This started this about 1988. They have gotten progressively leaner in stages, which is why many motorcycles now have fuel injection. If they have their way, look for electronic fuel injection on mowers in the next 10 years, or all-electric mowers mandated by law.

When everything is "perfect" your engine is running on a very minimal amount of fuel. Should anything happen to the float level or the jet size, then there won't be enough fuel to start a hot engine without using the choke.

Enter ethanol loaded fuels. When these are left in the carb for any length of time, the alcohol attracts water. The alcohol and water mixture leaves a very thin layer of (usually dark brown) "varnish" on everything.... including the inside of the jets. This makes the jet smaller on its fuel metering orifice... which in turn further leans out the fuel mixture. It's not much, but it's enough. The engine seems to run correctly, but it's really starved for fuel. Thus, the only way a hot engine will start is by using the choke.

Since the engine seems to run OK, I wouldn't open the carb. In your shoes I'd start using a "fuel stabilizer" AND carb cleaner, such as StarTron. The stabilizer will work to prevent future problems by keeping the alcohol in solution with the gasoline, and the cleaner will work to clean out any varnish that has accumulated. And it will do this while you run the engine on your regular schedule.

I implement this plan in my shop by treating the fuel in the BIG cans as soon as I bring it home from the gettin' place. In this way the StarTron works its way into my chain saw, leaf blower, weed whacker, my Exmark and both my walk-behinds. And the plan works. None of my equipment ever has carb or fuel issues.

Hope this helps.

 

[StarTech]

Fuel injection via throttle bodies is already here especially on v-twins. Briggs, Kawasaki, and Kohler all have fuel injected engines. Even Robin/Subaru even tried it on singles years ago. An example of the Robin is the EX21-EFI which they finally reverted back carburetors because they had so much problems with it.