Bobcat 763 hard starting when cold

[jparr763]

I have a used 763 (low flow) that is a b*tch to start when cold (50f or lower). It is a fuel issue, that much I am sure of. It starts by not wanting to turn over at all. Then I go around back, pump the fuel bulb (with pliers because it is so stiff), operate the drain plug on the filter, and the air release on the filter. Honestly, I'm not sure which of those things works, but the next time I try to start it, it sounds like it wants to start.
Often enough, I can start it for a few seconds, then it dies.
After trying these things fairly randomly for a few minutes, it will finally start.
I do use the glow plugs, for 10 slow seconds, but that doesn't seem to help. I checked to make sure they were working by pulling them out, grounding them, and watching them glow when triggered. So I know that power is getting to them, and that they are getting hot.

Any suggestions?

/ Once I get it started, it runs fine the rest of the day.

 

[MGW]

Hi jparr,

You say "It starts by not wanting to turn over at all". You've got me confused when you say you think it's a fuel issue. If it doesn't want to crank over it's a battery/starter issue, unless I'm misinterpreting what you said. Could you clarify this for everyone here?

Thanks
Marv

 

[jparr763]

Sorry for the confusion. It tries to turn over, and the battery is doing its job. It just sounds like it doesn't have any fuel.

 

[willie59]

If you're operating primer bulb with pliers because it's so stiff, you already have sufficient fuel pressure in line going to injection pump. If you are in fact purging air from fuel system by opening bleed screw on filter base then you need to first replace your fuel lines to prevent ingress of air on suction side of fuel lines, and if it's a 763 that has the b-i-itch CAV fuel filter tucked in behind coolant recovery tank, you must make certain that seal is good where sediment bowl meets filter, where filter meets filter housing, and o-ring is good on filter securing screw.

Aside from this, the older 763, C and F series, used a Kubota that had pre-combustion chamber heads, requires good glow plugs, which you have established work proper, but require good injector spray pattern as well to start. You may consider pulling your injectors and have them tested and rebuilt if required.

 

[jparr763]

I'm interested by the injector spray you mentioned. Does that get used just to start it? Would it matter that it is only this way when I first try to start it during the day. After it has been started and running for a bit, then it starts fine. I would have thought a bad injector would be bad all day (or at least on every start).
Also, the CAV fueld filter... is that a 2nd filter? The main fuel filter is easy to get to (thank god), and is front and center when you open the engine compartment. Is there a second one?
I'm about to go start the beast. I'm considering making an audio recording of the starting to see if that helps with diagnoses.

 

[willie59]

From what you're describing your machine only has the single fuel filter, no issue there.

As for the injectors, I'm only saying that if you have confirmed your fuel delivery system, hoses, lift pump, etc., is in proper order, you may consider having your fuel injectors tested. Pre-combustion chamber engines have to have good atomized fuel from the injectors and good glow plugs to start up cold. Injector nozzles that don't atomize fuel properly make them difficult to start cold. Once running and warmed up, they can behave normally. Not like injector that is bad affecting engine running operation.

 

[crewchief888]

I have a used 763 (low flow) that is a b*tch to start when cold (50f or lower). It is a fuel issue, that much I am sure of. It starts by not wanting to turn over at all. Then I go around back, pump the fuel bulb (with pliers because it is so stiff), operate the drain plug on the filter, and the air release on the filter. Honestly, I'm not sure which of those things works, but the next time I try to start it, it sounds like it wants to start.
Often enough, I can start it for a few seconds, then it dies.
After trying these things fairly randomly for a few minutes, it will finally start.
I do use the glow plugs, for 10 slow seconds, but that doesn't seem to help. I checked to make sure they were working by pulling them out, grounding them, and watching them glow when triggered. So I know that power is getting to them, and that they are getting hot.

Any suggestions?

/ Once I get it started, it runs fine the rest of the day.

when you try to start it, is the fuel shutoff solenoid pulling over?
if it is......
you could also have a bad glow plug relay, removing and testing the glow plugs is ok, but are they actually working when you activate them ?
if they are...
sounds like fuel is draining back to the tank. the primer bulb could be part of the problem, you may also have a suction hose in the tank cracked, check valve leaking/missing or missing clamps.
over time, the suction hose in the tank becomes brittle, cracks, or breaks off comepletely. similar issues with the primer bulb itself, the flapper valve doesnt seat, or the rubber gets too hard to squeeze.
i'd start at the suction hose in the tank.
raise the cab, the fuel pickup is at the top, front of the tank just about under the drive hoses


:drinkup

 

[jparr763]

I finally solved the problem. It was air in the fuel line, nothing more.

I had a pro come out and poke around a bit. He noticed that the fuel hoses were all relatively new, but the hose clamps weren’t fully tightened.
After he tightened all the clamps, we noticed a leak from the fuel injectors. I ordered a new set of o-rings from Bobcat and replaced the old, stiff ones ($16).
Now the Bobcat starts like a champ. All the starting problems are gone. Completely. Yay.

One thing I learned: To get the air out of the line, I used to open the top of the fuel filter and squeeze the fuel pump bulb until gas came out. It would usually only take a bit of a squeeze. My friend showed me that you have to keep squeezing hard, and wait for it to stop sputtering. It makes a mess, but there is still fuel in the filter (at least in my case), and it all had to come out.