742B Project won't start

[EngineerFarmer]

I have a 742B Bobcat that I bought not running and have fixed up. It has the 4G32 mitsubishi engine in it. It had a hole in the oil cooler and a blown head gasket. I rebuilt the engine and have it all back together now, but I can't get it to start. It has spark, fuel and compression. I have double checked the timing using the marks on the cam gear and crank gear. I have built many engines in the past and this all was pretty clear. The #1 piston is at TDC with the cam at 12 o'clock and the distributor rotor pointed at #1 on the cap. That being said the timing mark on the belt sheave does not line up with the scale on the front cover. I have heard this on another forum as well with a machine that was running. I have checked with a timing light and I believe I have it in a range where the engine should start. I replaced the carburator that was on the engine with a brand new one because the venturi was halfway corroded off. The engine is getting fuel as the spark plugs are wet after cranking for a while. Compression on all for cylinders is around 150psi. I even removed the valve cover and rechecked the valve lash. Plugs, wires, cap, rotor, points(set to .018), condenser and coil are all new. Two things I am considering now are: 1.) The engine seems to crank slow after about one revolution as if it building pressure in the pump. I plan to check that both piston pumps are not on stroke next time I am at the machine, but I'm pretty sure they aren't. 2.) I broke the porcelin around the ballest resistor while attaching the wires. The resistor itself seems to be ok though and I am getting spark. from what i understand the resistor is bypassed while cranking the engine anyways. I may try bypassing the resistor all together Anybody out there have experience with these machines?? Any help would be greatly appreciated

 

[OldMachinist]

I just looked at both the Mitsubishi factory manual and the Bobcat 742B service manual and neither one says anything about positioning the #1 piston at TDC. They both say to line up the mark on the crankshaft pulley with the mark on the front cover then line up the mark on the camshaft pulley with the mark on the upper cover. Install the belt and double check that all the marks are lined up. Then do the belt tightening procedure.

 

[frogfarmer]

As far as the timing I would have to have hands on to verify but it sounds like you know what you are doing. Are you sure the fuel is not water? I have seen machines that wouldnt start because the tank had a fair amount of water at the bottom where the pickup intake is. As for the resistor it is bypassed on start because of the large voltage drop of the starter draw and the ignition would be weak to the point of failure. The resistor is used while running to save wear and tear on the points. The points can actually weld themselves together if given full voltage for long periods of time.

 

[EngineerFarmer]

As far as the timing I would have to have hands on to verify but it sounds like you know what you are doing. Are you sure the fuel is not water? I have seen machines that wouldnt start because the tank had a fair amount of water at the bottom where the pickup intake is. As for the resistor it is bypassed on start because of the large voltage drop of the starter draw and the ignition would be weak to the point of failure. The resistor is used while running to save wear and tear on the points. The points can actually weld themselves together if given full voltage for long periods of time.

Just figured it out. Turns out it was simply that the aux. Flow was turned on and that was causing the pump to build pressure. Turned it off and the engine fired right up. Timing marks under the belt are set as my service manual shows. The mark on the v belt sheave is point at roughly 3 o,clock. If I reindex it back 90° degrees with its 4 mounting bolts it is still 15° off of true TDC Thanks for taking the time to look into this guys

 

[EngineerFarmer]

Just figured it out. Turns out it was simply that the aux. Flow was turned on and that was causing the pump to build pressure. Turned it off and the engine fired right up. Timing marks under the belt are set as my service manual shows. The mark on the v belt sheave is point at roughly 3 o,clock. If I reindex it back 90° degrees with its 4 mounting bolts it is still 15° off of true TDC Thanks for taking the time to look into this guys

Well guys I have some more questions for you. I had it running and drove it around, checked the hydraulics, dialed in the timing. Had shut off And started it a few times and it started really well. Then I went to idle it down so I could play with the carb and it decided to die and now will not restart.. I still have spark on all plugs and wires. Compression is 140-150psi on all cylinders. I bought a new carb for this machine that from what I can tell is an exact match to the factory carb. It has the same barrel size and jets. The number on the old carb was SA54 4XC4 and the new one is SA7027 4Y09. Does anyone know what these numbers mean? I haven't been able to find much on sole mikuni carbs and the service manual is not very helpful. Does anyone know what settings to start with? When I pull the plugs out they are wet with fuel like it is flooded. It won't even fire with either.. how is that possible when there is spark and compression.. this thing has me frustrated

 

[EngineerFarmer]

Well guys I have some more questions for you. I had it running and drove it around, checked the hydraulics, dialed in the timing. Had shut off And started it a few times and it started really well. Then I went to idle it down so I could play with the carb and it decided to die and now will not restart.. I still have spark on all plugs and wires. Compression is 140-150psi on all cylinders. I bought a new carb for this machine that from what I can tell is an exact match to the factory carb. It has the same barrel size and jets. The number on the old carb was SA54 4XC4 and the new one is SA7027 4Y09. Does anyone know what these numbers mean? I haven't been able to find much on sole mikuni carbs and the service manual is not very helpful. Does anyone know what settings to start with? When I pull the plugs out they are wet with fuel like it is flooded. It won't even fire with either.. how is that possible when there is spark and compression.. this thing has me frustrated

Also the inline fuel solenoid is not on the machine right now. What effect would this have?

 

[frogfarmer]

Also the inline fuel solenoid is not on the machine right now. What effect would this have?

Inline fuel solenoid? It may have been a solenoid but may have been a pump. The gas motors in these rigs were bad for vapor lock when they were hot or the outside temps were very high but doesn't sound like that is your case. Verify it wasn't a fuel pump that you removed.