T770 Fuel Starvation

[Brian M.]

Hello and thank you in advance.

I ran my 2021 T770 out of fuel, then cranked some more. Not a proud moment.

I have followed the procedure for bleeding air from fuel filter (on phone with Bobcat tech), and for priming. Still won't start.

When I try to start, I continue to get code M0309 low voltage (after about 3-4 seconds of cranking) and I am told the injectors won't work when this happens. (Battery tested, full charge - replaced battery anyway and still same code... also used a booster battery and booster cable just in case - still same code)

Is there a way to bleed air from the system, from the fuel filter to the injectors?

Is the low voltage affecting fuel during start?

Bobcat techs in my area are nonexistent or are busy for months.

Please help!

 

[reaperman]

I know if the system has low voltage for whatever reason, low battery, bad alternator, etc, the computer will shut down the machine. This seems to be your case. The newer fuel system has automatic priming of the filter, I still like the old school way. But I believe the 770 still has a primer bulb that runs alongside of the filter. It seems like your on the right track with bleeding the system. Perhaps a little assistance with the battery will help.

 

[Brian M.]

I know if the system has low voltage for whatever reason, low battery, bad alternator, etc, the computer will shut down the machine. This seems to be your case. The newer fuel system has automatic priming of the filter, I still like the old school way. But I believe the 770 still has a primer bulb that runs alongside of the filter. It seems like your on the right track with bleeding the system. Perhaps a little assistance with the battery will help.

Thank you so much for the speedy reply - There's no primer bulb after 2020 models. Mine is a 2021 - AT6327810 is my serial no. Bobcat tech confirmed no bulb on my model/serial no.

I've bled the fuel filter twice, dropped about 1.5 - 2 gal diesel in the process. The process for my model is 3 full turns on the fuel filter screw, then turn on machine (but not turn over) so fuel pump is activated.

I replaced the battery and I boosted each start with my F450 running with 2ga booster cables.

Battery is good (full charge), alternator is good, starter is good, fuel filter is good, fuel pump is good, air filters good. Just no ignition and possibly no injectors (due to lack of voltage).

Is there a way to bleed air out of the fuel lines from the filter to the injectors? Is there a fuse I should check?

Codes I've had so far:
M3304
M0309
H3948

Bobcat tech said all were low-voltage-related

THANK YOU!

 

[brdgbldr]

You may need to remove the fuel lines at the injectors in order to get all the air out.

 

[Brian M.]

Actually I am beginning to think the injectors won't operate anyway due to low voltage situation. Any ideas?

 

[brdgbldr]

Actually I am beginning to think the injectors won't operate anyway due to low voltage situation. Any ideas?

I assume you cleaned the battery terminals when you replaced the battery. If not do it.

Clean all of your grounding points and tighten them down. This is the cause of low voltage in 90% of the cases.

 

[Phil314]

You may need to remove the fuel lines at the injectors in order to get all the air out.

That engine is the Doosan common rail. The injectors are self bleeding. You do not need to crack the lines.
In fact that is extremely dangerous as they can run at 26000psi.
Have you ever seen a waterjet cut metal. Not a good idea.

Sounds like it won't start because of the low voltage. In that case, the computer will not fire the injectors at all.
You need to find and fix the voltage problem.

 

[foton]

I agree, think about it you took a working charging system from what you jumped from and it still read low. It almost has to be a bad connection and since you changed out the battery it should not be that, do you have a battery load tester? you could move it around the battery circuit and see where the resistance fault is possibly. and yes the grounds are overlooked often but that is the other side of the circuit, it has to be good.

 

[Brian M.]

Update:

Bobcat Tech came out yesterday.

Fuel system was not the problem.
Voltage was not the problem.

Removed drive belt, and it started right up.

Hydraulic pressure charging on start - bobtach driver is stuck on. Calling for hydraulic power on startup.

He also found the main wire harness for the cab was being crushed due to a missed zip tie during factory assembly not sure yet if that's an issue.

Towing to shop today.

Also if you have a newer T770, check and add oil to the drive motors Every 50 hrs. Mine were bone dry at 208 hrs. He opened it up and nothing came out. Supposed to be 17oz. of oil. My buddy has a T770 that needs new drive motors, his went out at 400hrs. Same issue, one year newer. (Mines a 2021, his is a 2022). Seems like assembly issues during the pandemic bullshit.

Thank you all for the help and advice.

 

[foton]

that is so strange that this issue did not show up till you ran out of fuel, that is some wierd timing going on. totally unrelated stuff.

 

[Brian M.]

Agreeeed.

Warranty work

 

[reaperman]

Id make sure they changed out the wiring harness. It would be a big job but it could sure raise hell down the line. Nothing worse than chasing electrical issues.

 

[Brian M.]

Finally got some help at the Bobcat shop. Hydraulic pump failure. Pump replaced (finally), picking up Monday... woooohooo!
Maybe I should ask them to extend my warranty 3 months since it was in the shop sitting for that long?