Foton FT254 over-revving then no start

[FotonOwner]

I'm with Rich. Time to pop the valve cover.:thumbsup:
I'd look for bent (stuck) valve stems since the valves probably floated during the overspeed.


It doesn't even take that long to float the valves and do major damage.
Hopefully you dodged a bullet.

Guys,

Thanks for the suggestions
yes
first it over sped
then I shut it down in a couple of seconds - it appeared to be running well (but fast) until I shut it down.
Then when attempting to re-start it seems to crank too fast like no compression and refused to start.

I pulled the cover off and checked that the manual decompression shaft was not stuck. (I was a little surprised to see the coupling device was not attached at either end, but I guess that is normal)
Didn't notice anything else out of place, but never having looked there before, could have missed something.

Anything specific I should be looking for?

I checked the manual under troubleshooting and it suggests governor or injector, but offers no advice on what to look for.

 

[Rich Waugh]

To check for bent valves or busted camshaft you pull the valve cover and crank the engine or turn it over slowly while watching the valve action of the rocker arm assembly. Keeping in mind the firing order of your particular engine you watch to see that each valve is opened in the correct sequence and lifts and falls an appropriate amount. That gives you a quick visual idea if anything is grossly wrong. A bent valve stem will go down and stick there, not closing again properly. A busted cam would result in some or none of the valve train functioning at all.

In some cas3es you can hear irregularities in the valves that will alert you to problems. If everything still is the same and you haven't noticed anything really dramatically out of the ordinary, I'd probably pull the rocker arm assembly, re-torque the head bolts to spec and then re-assemble the rocker arm assembly and set the valve lash to spec. If you run into problems trying to set the valve lash you may discover that you have cam or valve problems. If not, you've just completed something that should be done after the first fifty hours of use anyway.

Rich

 

[greg_g]

Before you took off the valve cover, did you start the engine again to see if the "high revs" happened again. Because if you can't reproduce the symptom, you're now chasing ghosts.

But as long as the valve cover is off, the decompression rockshaft should rotate slightly by hand. If it doesn't it's got one or more valves stuck partially open. I don't however, understand why "the coupling device was not attached at either end". Typically the radiator end of the decompression rockshaft doesn't connect horizontally to anything. But the fuel tank end connects inside to a pivot point that goes through the valve cover. Outside is a spring-loaded lever, to which the wire from the stop cable attaches.

Anyway. On the valve train itself, the rockshaft shouldn't rotate like the decompression shaft did. But all the valve stems should be centered in the little cups at the end of each rocker arm. Look also for bent/broken stems, or any that are not aligned properly.

If a visual inspection doesn't reveal anything obvious, you're going to have to bite the bullet and try to reproduce the symptoms. Verify first that your throttle linkage is at idle. Have an old towel handy. With the valve cover still off, there will be a little oil tossed around. But that's necessary so you can check for visual cues in the working valve train. If there is no over-rev condition, this might be much ado about nothing. If it reoccurs - and you can't see anything obviously wrong in the valve train - this might end up being an injection pump issue.

But you have to prioritize. It's much less confusing if you work on one problem at a time. Especially when they're as clearly unrelated as are PTO operation and engine revs.

//greg//

 

[FotonOwner]

"Before you took off the valve cover, did you start the engine again to see if the "high revs" happened again. "

I have tried cranking a few times, it wont start at all, wont even cough, it seems to be cranking too fast; although, it is just a subjective thing.


" I don't however, understand why "the coupling device was not attached at either end". Typically ... the fuel tank end connects inside to a pivot point that goes through the valve cover. Outside is a spring-loaded lever, to which the wire from the stop cable attaches."

Yes the coupling device just dropped out when I took the cover off. I inspected it to see if there was a hole in it that could be used to attach it to the lever or decompression shaft but didn't see any. I popped it into the housing in the cover and aligned it so it would mate with the shaft and re-installed.


" If a visual inspection doesn't reveal anything obvious, you're going to have to bite the bullet and try to reproduce the symptoms. Verify first that your throttle linkage is at idle."

The linkage looks fine.

" Have an old towel handy. With the valve cover still off, there will be a little oil tossed around. But that's necessary so you can check for visual cues in the working valve train. If there is no over-rev condition, this might be much ado about nothing. If it reoccurs - and you can't see anything obviously wrong in the valve train - this might end up being an injection pump issue."

Yes I can live with no PTO clutch but not with a dead engine. I will do a physical check of the valves as you have outlined and see how things look, as you say it may be normal and just an injector problem.

 

[FotonOwner]

Thanks Rich,
I will start on that.

 

[Bob Rooks]

=FotonOwner;2198738I will do a physical check of the valves as you have outlined and see how things look, as you say it may be normal and just an injector problem.

If it seems to be cranking faster than normal it's not a fuel issue. Are you getting any smoke at all from the exhaust when you attempt to start it? If so, what color?

 

[FotonOwner]

If it seems to be cranking faster than normal it's not a fuel issue. Are you getting any smoke at all from the exhaust when you attempt to start it? If so, what color?

Bob,
Didn't notice any smoke and the exhaust is right in front of me.

I rotated the engine and checked that the valves operated okay. Didn't see any sticking. All the push-rods were in place with some (0.5 mm or so) clearance when released.
The decompression shaft could be turned by hand and the rocker shaft was good.
I re-checked the coupling for pin holes but found nothing.

 

[greg_g]

I re-checked the coupling for pin holes but found nothing.

I misinterpreted your wording again, thought you were talking about the rockshaft itself. Anyway, you're still gonna have to spin the engine and watch the valve train for anything unusual. Watch too that the nubs on the decompression rockshaft don't make contact with any moving parts. Given that the coupling disconnected itself, the shaft could have inadvertently rotated down into the "decompress" position.

Not that it's likely related to your other problems, but that's an awful dry looking head. I would have expected more visual evidence of engine oil. Or did you wipe things up for the photo shoot?

//greg//

 

[Smalljobs]

"tried topping up the fuel and bleeding off any air"

Are you sure fuel is present at the injectors?

Is there any chance the turning over faster is simply due to a warmer temperature?

 

[FotonOwner]

I misinterpreted your wording again, thought you were talking about the rockshaft itself. Anyway, you're still gonna have to spin the engine and watch the valve train for anything unusual. Watch too that the nubs on the decompression rockshaft don't make contact with any moving parts. Given that the coupling disconnected itself, the shaft could have inadvertently rotated down into the "decompress" position.

Not that it's likely related to your other problems, but that's an awful dry looking head. I would have expected more visual evidence of engine oil. Or did you wipe things up for the photo shoot?

//greg//

Okay will try cranking the engine and see how things look. The photo may not show the oil clearly but there seemed to be a lot there.
I rotated the decompression shaft but I am sure it was in the up position when I took the cover off.