Bobcat 763 runs and then smokes and dies

[buddyroo]

My Bobcat 763 with a Kubota engine starts and then runs for ten or 15 minutes. Then it starts to sputter and smoke and then dies and is difficult to start. We have changed the fuel filter and that didn't make any difference.

Any suggestions on what to try next would be appreciated.

 

[brdgbldr]

Sounds like fuel starvation.

Start by checking all of your fuel lines for cracks.

Also, the fuel pickup tube in the tank has a habit of cracking and/or breaking off.

 

[buddyroo]

Sounds like fuel starvation.

Start by checking all of your fuel lines for cracks.

Also, the fuel pickup tube in the tank has a habit of cracking and/or breaking off.

Thank you for the quick response. I will get that checked out.

 

[laurencen]

when it dies is the fuel priming bulb collapsed? if you try to pump it does it feel like its pumping, for sure its starving fuel

 

[brdgbldr]

Thank you for the quick response. I will get that checked out.

Yes, it could also be a plugged fuel line as "laurencen" is suggesting with the collapsed priming bulb.

 

[Topcat1952]

I now feel so obligated to assist on this platform because of a gentleman who has reached out and given me some very valuable advice... So, hear goes....Black smoke often means too rich or too much fuel... White smoke means a leaner condition and if runs then dies and a poor restart probably means 1. starving for fuel, running out of fuel and the third would be not able to maintain fuel...
1. Starving for fuel would be a lack of fuel to injectors, by plug filters or injector pump
2. Running out of fuel would probably a fuel pump issue.... A fuel pump pressure test will ID this issue (also watch for bubbles)
3. Running out of fuel, does not always no fuel in the tank, If the fuel pump checks well look for a leak on the suction side.. Ues a vacuum gage in line coming from the tank, pull enough vacuum just enough to have fuel in the vacuum chamber, and stop...If much a leak vacuum will drop fairly quickly, but a small slow drop would indicate a low leak, causing air into the system and eventually running poorly to stop... A lot of white smoke....Most likely a pinhole in the suction line from the tank to pump....Best check of that is full tank fuel and restart...
All this and the most problem of sucking leaks are primer pumps....lol, I had to cover other things.... If you wish to check the primer pump... start the engine and use a heavy oil and LOW fuel mix and spry on the pump while running ( THIS COULD BE CONSIDERED DANGEROUS) listen to the engine speed, it will start to get better or if no leak no chance...Always find cuase of the starting condition before replacing parts....

 

[Tazza]

Smoke is a very good indicator of what's going on. Black smoke is too much fuel, not enough air, or too much load. White smoke is generally not enough compression to ignite the fuel charge.

You're saying you have black smoke as it bogs and dies, this is not starving for fuel, if it's starving for fuel, you wouldn't get smoke, as there is no fuel being burnt to smoke.

It almost sounds like your engine is being loaded down, causing this issue. Could you have issues with the pump somehow?

We had an engine in the workshop that had a similar issue, it would run, then bog down, smoke and stop, let it cool and it would do the same thing. Turned out to be the main bearings, it would run fine till it got warm, then the bearings would grab, then load the engine down. The symptoms made sense, but it still had good oil pressure.

 

[buddyroo]

After a few months of frustration we have finally gotten the Bobcat fixed.
Problem #1: The fuel takeup was all screwed up and jerry rigged. Fixed. This didn't solve the problem but it helped a little bit.
The bulb that you squeeze was hard as a rock. When I looked at the machine I realized that changing the fuel pump was a simple job. So, we changed the fuel pump and the bulb at the same time. No idea which of the two caused the issue but this fixed it.

Thanks to all who assisted us in this endeavor. The assistance provided by you people is greatly appreciated.

 

[oiu789]

Thanks for letting us know what you found and what fixed it! I would have had you check that the tank vent was working. Let it run until it dies and then crack the fuel fill cap and listen to see if air is sucked in. Very easy to check. Just saying this for future people with a similar symptoms.