bobcat 773 down on power/fuel related

6-8psi. It’s either a faulty/dirty filter or a weak lift pump..
I assume it’s a cam driven supply pump.?? The love might be worn down a smidge..
I would put on an electric pump & be done..
No more than 10 psi.!!!

Ok im on ebay now and going to order tonight

Thx thepumpguysc

Wait, what? Why are we talking about the pickup tube inside the tank at this point? You're not there yet, back the truck up skippy. Again, I repeat what I stated previously. Disconnect the fuel supply hose to the injection pump and fit a new hose to it. Run that hose straight to the outlet of the mechanical lift pump. Connect another new piece of hose to the inlet of the lift pump and stick that hose in a clean container of fuel. Start/run engine until it warms up. If it falters, disconnect the mechanical pump and install an electric diesel pump in its place, try again. If it still falters, the problem ain't the pickup tube inside the tank.

As to the wiring I was thinking I could wire it right in to the same harness for the fuel cut off solenoid thus when one is open the pump is on.
what do you think folks.

willie i did run it to a bottle straight to the lift pump and then straight to the injection pump and it didn't help, but what I was saying is i have a new tube and screen so I might as well install it to since I'm going into it for a electrical pump

sorry for the confusion willie

Does any one have any thoughts as to the best place to power the electric fuel pump when it arrives this week

I like this suggested method to wire a fuel pump using a relay with an oil pressure safety switch in the wiring circuit.
- With the ignition turned on and the engine not running, there would be no power to the fuel pump.
- When cranking (with no oil pressure yet), the starter circuit would activate the fuel pump relay.
- When the engine has started, the oil pressure switch will activate the fuel pump relay from the ignition switch.
- If you lost oil pressure, the fuel pump will turn off.
- If the ignition key was left on (with the engine not started), the fuel pump would be off.
A wiring diagram for this is shown below:



See some more tips for placing and wiring a fuel pump here:
http://www.how-to-build-hotrods.com/electric-fuel-pump.html

There are also other wiring options shown in this attached Holley Fuel Pumps Installation Instructions:

Thx Threecw

Well folks I got the new electric fuel pump and hooked it up after starting my machine up the fuel pressure was running between 7-7 1/2
psig, so I thought things looked pretty goodI let the machine warm up and ran 200gal. of water to my cows. Which took about 20 min of run time so I thought things were going well, then the machine did the same old thing, in that it started to bog down and it wasnt long after it died with all of the same symptoms that it has had for the last few weeks.I completely bypassed the lift pump and hooked the new elec. pump in it place.
I did note that when it started acting up that the fuel pressure was down to around 6 psig .
so now everything has been ruled out but the injectors and the main injector pump so my question now is what should i try next. I'm not sure who could preform a pop it test on the injectors of if i should replace them or what.

once again im open to any thoughts.
Thx

Sounds like there’s sumpin in the tank.?? Unless u took it out OR ran from an auxiliary tank..

James,

Sorry to hear that you are still having problems. A little brain storming here …or possibly brain farting!

As you said in your post #4, before you installed the electric fuel pump, you eliminated the fuel tank and ran from a quart bottle … but the engine still it still bogged down and died. So that should eliminate the junk in the fuel tank theory … or the bad fuel pickup theory.

You said in Post #50 your engine ran for 20 minutes successfully while you were watering cows … a question for other readers of the thread … does that 20 minutes of good running eliminate a fuel injection problem or is that still a possibility after the engine warms up?

You mention in Post #40 that with your mechanical fuel pump, the engine ran at 3.5 to 4 psi fuel pressure and the engine started stalling at 3 psi. You also mentioned that the fuel gauge was “right in front of the injection pump”. But with the electric fuel pump in Post #50, it ran at 7 – 7.5 psi and started acting up at 6 psi. I “assume” that you had your fuel pressure gauge installed in the same place. Base on those pressures, you are getting fuel delivered to your injection pump and your problem is NOT with fuel delivery.

What other sensors will shut down an engine after it warms up? Sensor after the air cleaner? Faulty oil pressure sensor … oil gets hot and shuts the engine down. Are there any other sensors that will shut down an engine (check your wiring diagram if you have one)?

This is a real mystery … but it could end up being something relatively simple. “Assuming” it is NOT the injection pump based on the 20 minutes of good running and “assuming” that fuel deliver is NOT the problem … what else will shut down an engine?

I can say the gauge is in the same location for all testing,
It doesn’t seem to me to be a cut out shutting the machine down because it will big down/pick up a few times then die or just idle so poorly no mater where the throttle is/wide open or useless down

At this point I wish I new how to do a pop it test on the injectors, or just new more about both the injector pump and injectors

Why is the pressure dropping from 7 to 6 PSI? when the engine is not under load, so not using a lot of fuel ,and not smoking to prove it's not using a lot of fuel. With the electric pump, the pressure should only drop if the engine is loaded up at full speed and blowing smoke, and even then, the engine is not using a lot of fuel compared to the fuel pump capacity.

If there's air getting sucked into the fuel, it will do this, mostly maintain the fuel pressure, but not run right. The injection pump is a very small piston pump, extremely bad at pumping air. Check the fuel return for air, use a clear vinyl hose into a jar of fuel to see bubbles.

The injectors are easy, take them to get checked, or just replace, but I don't think that's likely the issue. Thepumpguy will say the injection pump could be worn out, but I don't think we're there yet either.

As far as the fuel pressure dropping off I’ve seen the throttle wide open or at idle When it bogs down
But I will try the return line and see how it goes
The biggest thing I struggle with again is why injectors and or pump being fine when cool and struggling when warm

If there is air in the return line I will be surprised since I’ve ran the machine from a jar to the lift pump to rule out all the lines up to the lift pump

When it bogs down and stalls, will it start up right away again? Does it try to start ... cough and sputter, attempt to start but will not start? Or does it just turn over with no result? If it restarts, how does it act?

If it does not restart when warm, will it restart easily when cold (without any other intervention)? How does it act then?

It will start right back up but seems like most of the time it just runs like **** then it might catch its self and come up to rpms but when you then move it will bog again maybe even die
But after it cools off and hr or so it runs fine again till it get up to temp. And it’s never even getting close to over heating

Some brainstorming to eliminate what might have been overlooked:
Have you checked that the fuel cap vent is working?
Pulled the fuel cap after stalling to ensure no vacuum on the fuel tank?

No I haven’t done that but that’s an easy check thanks