Gas tank rope and power loss

   / Gas tank rope and power loss #1  

MountainBuck

Silver Member
Joined
Aug 7, 2016
Messages
159
Location
TN
Tractor
Ventrac 4500P; Kubota RTV-X1100C
My Ventrac 4500P is having some momentary power issues again. This is even after I have replaced the fuel filter.

With several other postings here, I decided to take the leap and see if anything was in the gas tank.

I took off the fuel filter panel and released the gas line at the fuel filter and let gravity drain it into an available gas can. This was surprisingly slow. I removed the gas cap and with an explosion proof light, I watched the gasoline drain from the tank. (Yes, I would also watch my disk defragment back in the day.)

As the gasoline got low enough that I could actually see the bottom, I saw what appeared to be a white fuzzy rope laying in the bottom of the tank. At first I wondered if it was some kind of sealant.

Finally when the gas was all drained out, the "rope" was actually now a line of fine sediment.

My hands are too big to fit into the tank, so I used a non-lint rag in a flexible pickup stick approach to wiping this out. It mostly looked like fine rust on my white rag. I can't explain why it looked white before it was completely drained.

I probably got 7 - 10 good "dirty" wipes out of the tank before I called it good.

I decided to consider the drained gas "contaminated" and disposed of it at our local recycling facility which took contaminated gas.

Then I took apart the Ventrac gas cap which was a bit of a challenge. I used a screw driver and pried the inside section out. This exposed the inside ratchet mechanism and the small white ring of filter material. This all looked clean so I used a vice to press the two halves back together.

I took out the spark plugs and the gap is supposed to be .030 according to the engine manual shipped with the tractor, however in the engine service manual it states .028 - .031. Mine were both at .032, so I closed them down to .028 and re-installed. I installed these plugs earlier this year, so they are new-ish.

With fresh gasoline, I'm still having a momentary power loss occasionally. It happens quickly so I can only vaguely describe it. Last time it happened, I had the throttle at about 2800 rpm and lightly raking gravel downhill (not much of a task) and the rpms momentarily dip to like 1500, but then bounce back up to the 2800. In 15 minutes, this might have happened about 3 or 4 times.

This hasn't happened on a "cold" engine, only when it has warmed up. It doesn't really sound like a misfire. Sounds more like a hesitation.

I'm thinking maybe the air horn needs cleaning?

Any ideas?
 
   / Gas tank rope and power loss #2  
sounds like what happens when air gets into a diesel engine fuel system
 
   / Gas tank rope and power loss #3  
Is it carbureted of fuel injected? If it’s carb, I’d check the float, needle, and seat. You’ve already checked the tank, fuel lines, filter, etc. that’s the next thing in the line, other than maybe a fuel pump. Is your fuel pump electric or mechanical or vacuum?

If you eliminate all fuel problems, you then have to start looking at spark. Maybe your coil(s) is(are) opening up. I had a chainsaw that had a cracked coil. Through process of elimination, I finally took the coil off and it had a crack in it that would open up at temperature. Would run fine for about 5 minutes, then lose power.

Good luck.
 
   / Gas tank rope and power loss #4  
y hands are too big to fit into the tank, so I used a non-lint rag in a flexible pickup stick approach to wiping this out. It mostly looked like fine rust on my white rag. I can't explain why it looked white before it was completely drained.
I wonder what the jet exhaust would look like if you had used a vacuum to get it up.
 
   / Gas tank rope and power loss #5  
Is it carbureted of fuel injected? If it’s carb, I’d check the float, needle, and seat. You’ve already checked the tank, fuel lines, filter, etc. that’s the next thing in the line, other than maybe a fuel pump. Is your fuel pump electric or mechanical or vacuum?

If you eliminate all fuel problems, you then have to start looking at spark. Maybe your coil(s) is(are) opening up. I had a chainsaw that had a cracked coil. Through process of elimination, I finally took the coil off and it had a crack in it that would open up at temperature. Would run fine for about 5 minutes, then lose power.

Good luck.

The P has the fuel injected Kawasaki.

Did you also replace your fuel filter after cleaning the crud out of the tank?
 
   / Gas tank rope and power loss
  • Thread Starter
#6  
Found and fixed the problem.

This morning I decided to do a "leak check" on both of the cylinders with a leak check gauge. If you are not familiar, that is where the piston is moved to Top Dead Center while air pressure is injected into the spark plug hole with the leak check gauge. I got a 20% leak rate in both cylinders, which is considered "good."

Then I did a compression test. Both cylinders only pumped up to 70 psi. What? That is terrible! It should be much closer to 120 psi.

So I felt that I could rule out valve leak, head gasket leak and rings because of the leak check.

I decided that it would be either cylinder wall scoring or valves out of adjustment.

With only 300 hours on it, I was hoping for the valves being out of adjustment.

I took off the valve covers and moved the piston to TDC and found ZERO gap between the rocker and the valve. The spec calls for .006 inch gap. I still cannot believe there was no gap. So I got out the feeler gauge and went at it.

BTW, that adjustment is more ART that SCIENCE. I'm not going to go into all of the sage I had to burn to get it correct, but I will SUGGEST a pro tip of leaving the feeler gauge in the gap while tightening it down. I don't like that approach because putting pressure on the gauge isn't good for the gauge, but it was the only way I could get the gap to stay put when tightening it down.

Did it work? Yes, I repeated the compression test and BINGO - 120 PSI in both cylinders.

Fired it up and WOW - It was like a completely different engine! It sounded strong and I had power galore. Hesitation was gone. I tried to run it through some tasks and the engine rpms didn't bog down like it would before.

In hindsight, I did find that checking the valve gap is not in the Ventrac manual, but it is in the engine manual at 300 hours. The manual also says the dealer needs to adjust it - probably because how finicky it is.

I'm also surprised that before I adjusted the valves, that the engine could even RUN with compression of only 70 psi.
 
   / Gas tank rope and power loss #7  
Glad you found it. (y)

I haven’t had to adjust valves in decades. Our Kohler has hydraulic lifters. I’m thinking the last time I adjusted valves was a solid lifter 396 Chevy. Yikes! That was 40 years ago.
 
   / Gas tank rope and power loss #8  
Congrats on finding and fixing the problem. Glad to hear it is running better for you now. I just finished lapping and adjusting the valves on a Briggs Vtwin so can relate to the tediousness of the procedure.
 
   / Gas tank rope and power loss #9  
Excellent find. Odd for such a quality engiine to be out that much so soon.

In the event you run into a potentially clogged fuel outlet again, remove the line from the entry of the fuel filter and blow back into the tank with air blast to clear the line. As slow as your fuel drained, you may wish to do that anyway next time the tank is low and dirty fuel can be drawn out. There is a kitchen strainer basket insert that fits our fuel tank openings very well. Gas station gas can be cruddy, especially just after a tanker off-loads.

prs
 
 
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