742 carb soleniod

[part-time skid steerer]

I have had a bobcat 742 with the ford gas engine for 10 years or so. recently I have been struggling with the machine starting fine cold, running strong for 5 mins then shutting off like it ran out of gas. If I let it sit and cool down for a while it will start back up and do the same thing again. it doesn't matter if I'm running it at low idle or full throttle. I thought it was an overheating issue but have replaced all the cooling system components and temp sensor and the engine temp is only in the 120s when it shuts down. after reading lots of threads I am going to look at the fuel delivery. I have an electric fuel pump that bypasses the mechanical pump. I checked the filter sock, in-line fuel filter, and replaced the fuel line that was brittle and starting to crack. I read something about a carb solenoid and a modification that people have done because of ethanol gas damaging the carb.

Does anyone have any advice on what I can do to the carb to help my situation?

 

[craigb93]

The solenoid at the carburetor is installed part for potential roll-over protection and part for anti-dieseling.. If you use ethanol content fuel it going to be prone to stick. My machine sits for weeks at the time and had the problem. Using ethanol-free fuel will go a long way toward solving the problem but not eliminating it. I chose to remove the solenoid. Even with an electric pump, which I have, the intermittent sticking and thus no start was a nuisance. Dieseling was never a problem as the ethanol-free is 89 or 90 octane in my area. There have been NO issues in the 6-8 years w/o the solenoid. There is a second solenoid up closer to the gas tank but I have not had any trouble with it. Probably because of the relatively cooler location. -Dick

 

[part-time skid steerer]

The solenoid at the carburetor is installed part for potential roll-over protection and part for anti-dieseling.. If you use ethanol content fuel it going to be prone to stick. My machine sits for weeks at the time and had the problem. Using ethanol-free fuel will go a long way toward solving the problem but not eliminating it. I chose to remove the solenoid. Even with an electric pump, which I have, the intermittent sticking and thus no start was a nuisance. Dieseling was never a problem as the ethanol-free is 89 or 90 octane in my area. There have been NO issues in the 6-8 years w/o the solenoid. There is a second solenoid up closer to the gas tank but I have not had any trouble with it. Probably because of the relatively cooler location. -Dick

Thanks for the reply...if I remove the solenoid do I just unhook the wire and plug the hole?

 

[craigb93]

Physically remove the solenoid. Get a new brass fitting that matches the thread in the carb bowl on one end and a barbed male hose on the other. New fuel line and clamps to finish it.

 

[part-time skid steerer]

Thanks

 

[part-time skid steerer]

Well I got rid of the carb solenoid, cleaned the carb and am still having the same problem. 5 mins of run time and then shuts off, every time. My next guess is the ignition system. Anyone have any thoughts...coil? points? condenser?

 

[part-time skid steerer]

I still have spark after it dies so....I don't know what's shutting it down. I tried spraying a hose in near the hydraulic pump while it's running and it ran for 20+ mins. Not sure why but this leads me to suspect a temperature issue with the pump or ??? Can anyone offer me some thoughts on what could be causing my shutdowns. Is there a hydraulic sensor that could stall out my engine?

 

[brdgbldr]

Are you sure it isn't your electric fuel pump?
It could also be an intermittent electrical short that powers your fuel pump. Electrical shorts can be effected by heat.

 

[part-time skid steerer]

Are you sure it isn't your electric fuel pump?
It could also be an intermittent electrical short that powers your fuel pump. Electrical shorts can be effected by heat.

The fuel pump still makes noise but maybe isn't pumping...I will check this tomorrow.

 

[spitzair]

Check and see if something is blocking your fuel supply. Not unheard of that someone dropped a rag in the fuel tank that would move and cover up the suction port… also check the electric fuel shutoff solenoid between the tank and the fuel pump, they are known to go bad as well. If it's as consistent as you say that would be my prime suspect. Not sure if it's in the same place on the 742 but on the 732 it's on the right side of the engine compartment sort of behind the blower housing. They have been removed on both my machines…

 

[part-time skid steerer]

Thanks for the advice. I removed the carb solenoid and last night I bypassed the in-line electronic fuel shutoff. I thought for sure it was going to be the problem, but it still shut off after 6 mins. I have a new hydraulic temp sensor that i plan to install but I wasn't sure how this would shutoff the engine? It seems like if I mist the right side near the blower housing and the hydraulic pump with cold water it solves the problem so I'm leaning towards hydraulics over heating but am confused at how it shuts down the engine. Is there another way fuel can be cutoff from the engine?

 

[Dave1234]

You might try loosening the fuel cap. If it is failing to vent, eventually the vacuum in the fuel tank could starve the fuel pump and carb. 6 minutes seems a little fast for that, but its an easy test.

 

[part-time skid steerer]

I thought of this too and tried to run with no cap on. The last test this morning only ran for 2 mins...after it killed I had good spark on all 4 wires and it ran on starting fluid so its definetly fuel related. The fuel pump was pretty warm, so I am going to replace it (it was an amazon puchase over 4 years ago) and I am also wondering if the fuel shutoff valve on the front of the filter might be restricting the flow to the pump.

 

[brdgbldr]

Did you look at the fuel pickup tube inside the tank?
There are two issues that can happen with it:
1: The tubes crack and/or break off.

If broken off he engine will normally not start since the fuel level is below the broken off tube.

If cracked, it will suck air into the system once the fuel is below the crack but may still get intermittent fuel.

2: The screen filter/check valve at the end of the fuel pickup tube is getting clogged with debris.

It's pretty easy to remove and check or you can kind of see it with a good flashlight from the fuel tank fill opening.

You can also try to siphon fuel from the bottom of the tank to see how dirty the fuel is.

 

[craigb93]

Pretty easy to check both the fuel pick-up and electric pump with a small temporary gas can for a tank.Place it under the air cleaner so the pump has to work up hill.

 

[foton]

If you can get the portable tank up high enough above the carb .( 1 foot or more should do it) it should be able to gravity feed if need be.