bobcat 773 down on power/fuel related

[James Clark]

When I get home from work today around 430 central time I’ll check thx

 

[James Clark]

I ran the machine last night but only for 15 min never got up to full temp cause we had snow and ice falling from the sky. winter just wont leave.
so if its a little warmer tonight i"ll try again

 

[James Clark]

Well for the first time in a week the temp came up enough yesterday to get the machine back out and see what would happen. After it was fully warm it did run better for say 30 min, then it went to bogging down and stalling then dying so I got out and loosened the fuel cap and seen no results. the fuel pressure was staying above 6-1/2 psig through the hole test. So I"m still at a loss as to whats going on. There doesn't appear to be a lot of smoke really at any point, and certainly no black visible smoke as it really is running very clean. When it does die it does seem to be worse when try to put machine under load I.E. moving ect rather than just setting still but even then it still struggles mightily. Once again I'm just not a expert on injectors and or pumps

Thanks again guys for any suggestions

 

[thepumpguysc]

This is a serious head scratcher ..
Just to catch everyone up.. u bypassed the fuel tank & ran out of a jar.. A gallon jug like an old oil jug probably woulda been better.. but nevertheless..
& it died..
Then u hooked up an electric pump & it died..
Are u doing all these tests w the AIR CLEANER REMOVED.?
That would be my 1st thought..
Is there any kind of an electric solenoid to shut the fuel system off.? If yes, either remove it or straight wire it off the battery if possible.. if it’s a 3 wire sol.. don’t straight wire it.!!
With an electric fuel pump and a good fuel supply (gal. jug)
And w the air cleaner removed and a shutdown sol. removed..
It autta run fine.. Try all those things all at once & see what it does..
Can u post a pic of the fuel system, including the injectors.??

 

[James Clark]

I haven’t ran the machine with the air filter out at any point but I’ll try that
Also I have tied the fuel stop in the open position and it didn’t help

 

[James Clark]

I haven’t ran the machine with the air filter out at any point but I’ll try that
Also I have tied the fuel stop in the open position and it didn’t help

 

[thepumpguysc]

Can u send a pic..??
It sure would be helpful..
I’ve had fellas swear up & down they “adjusted” the sol. correctly & their so adamant about it they wanna fight.!! & when they show up the dam thing isn’t pulled or pushed enough & when I “fix it”
they’re just amazed how well it runs..
So a pic sure would relieve any doubt & we/I can move on..
If a pm would be easier (phone #)
we can do that..
Just snap a pic w your phone & hit send.. lemme know.

 

[ThreeCW]

I understand that your fuel pressure gauge is installed downstream of the fuel shut off solenoid and just before the high pressure injection pump ... is this correct?

You said your "fuel pressure was staying above 6-1/2 psig through the whole test". Was the pressure fluctuating any during the test? How about just prior to shutting down ... did the pressure change then.

If the fuel pressure was rock solid, than any component upstream of the pressure gauge should be working fine ... eliminating any blockage in the fuel delivery system and also eliminating the fuel shut off solenoid I would
deduce. That being said, I think it would still be good to check out the fuel shut off solenoid ... despite what your pressure gauge says.

More brain storming - we know you show pressure coming from your new electric pump. Just for shxts and giggles, I would disconnect the fuel supply line going into the injection pump and measure the rate of fuel delivery. Use a cup of a know volume and measure the time to fill or partially fill it to determine the fuel pump rate. It would be worth doing when the engine is cold and again after it has failed after warming up. If you have a good fuel delivery rate both cold and warm, then that eliminates a lot of guessing.

And some more brain storming - How about sensors ... like I mentioned earlier, perhaps a faulty sensor (oil pressure, air sensor, others?) that is killing the engine when it warms up. Does anyone have a wiring diagram for this machine to see how the sensors work? I assume the sensor would kill the engine using the fuel shut off solenoid ... but that is just a guess, not based on any personal experience.

 

[James Clark]

Clark, post: 883136, member: 86515"]I haven’t ran the machine with the air filter out at any point but I’ll try that
Also I have tied the fuel stop in the open position and it didn’t help

 

[James Clark]

Here’s a photo of when the machine was running,

 

[James Clark]

This pick was of the unit before the electric fuel pump was installed thus the pressure is only in the 3-1/2 psi range rather than the 6+ psig I have now after the eclectic pump was installed
If I could figure out how to send video I would

 

[James Clark]

Here’s some more pic.s
These pics show the machine after it has run say 5 min it also shows how clean the engine is running

I believe the 3 picks are after it been running maybe 10 min

 

[James Clark]

Here are the rest of the pics

 

[James Clark]

The pic with no pressure is where I opened the bypass bleeder and just to see if the pressure was true and it relived it all by doing so

 

[thepumpguysc]

I was going to suggest that, until I saw the last pic.. lol
I have 1 on my bench right now..
.. & always get confused for some dumb reason on which way to shut off the bleeder..??
Its definately a supply problem.. The pressure need to be as hi as 10psi to feed that pump..
The test spec for that pump says 6-8 psi inlet fuel pressure at full load..{constant pressure}
So either the electric pump isnt strong enough or your mechanical supply pump is bad..

 

[James Clark]

Meaning injector pump?

 

[thepumpguysc]

Please re-read my post slowly..

 

[James Clark]

Gotcha so I may need to get a elec. pump with just a little more heart in it.

 

[thepumpguysc]

Yes Sir.. U have 1 thats a 1-3 psi.. u NEED a 10psi..
MOST of them dont hit that target range & theyre 10-12.. If u can find 1 thats 7-10 that would be good..
IF your just diagnosing.. u can certainly use a 10-12.. most of'm are on the lower side anyway.. so a 10-12 will prob. put out 8-10.. which is perfectly fine..
The thing I find is, people have a Holley pump hooked up that blasts 30psi & wonder why they're getting fuel in the oil.. lol
Have fun at work..

 

[James Clark]

Just so you know the pump I bought is much like you said
I got a 7-10psi and it’s putting out about 7 or 7-1/2 psi
So I’ve been looking at 10-12psi pumps