older 743 bobcat

[madmike1735]

i am a diesel mechanic, so fixing construction equipment isnt an issue normally.... i work on big diesel equipment, mostly CAT bulldozers, escavators, pavers, yukes, ETC... Ingersoll Rand, Hitachi, John Deere,... anyways, my father has an old bobcat - (Melroe) 743..... now, ive fixed bobcats, they suck to work on.... heres my question.... i need part #s and i cant find a diagram online, and our books at work dont go back far enough... for those of you still reading.... the melroe 743 that im referring to has a Kubota engine.... the problem is it wont stay running.... i diagnosed it over the phone..... the fuel filter; has the water seperator GLASS bowl on the bottom.... well, i talked my ole man through what to do over the phone.... he says the glass bowl has a big chip out of it like someone dropped it trying to change the filter.... he didnt notice this until i told him to drop the filter..... ( i told him it was a 7/16" bolt head on top, and to hold the knurled nut beneath the glass bowl) he is also a mechanic (cars-light duty trucks) he knows how to turn a wrench.... anyways, there is a gasket between the glass bowl and the filter.... i told him to hold them together with one hand, and tighten the bolt on top..... he did... then he primed the system- no visable leaks..... tried to start it, would only smoke... he suggested either- i said no way!!! not in a glow plug engine, so i said wd-40.... a quick shot... it started for 10 seconds.... looking at the engine from the rear-towards the bucket.... you have a fuel line from the tank to the primer-that goes to the filter..... from the filter it goes under the engine to the fuel cut-off switch.... cut off switch is on the injector pump obviously.... out of the cut off switch it goes to a valve.... almost like a garden hose valve???? hard to explain... main fuel feed comes out of the cutoff, goes through this shutoff which has 2 ports on the sending end.... like a Y for say.... comes in on the bottom, but goes out to 2.... one side is the main feed for the 4 injectors.... but each injector has a return..... well, the 1st injector (closest to the rear door) is where a little hose comes off the shut off valve.... now, that valve i believe is only a bleeder.... im only going by experience here, so dont give up on me yet! the main fuel line goes through the valve-but there is that tiny hose that comes off.... the hose serves no purpose.... when you prime the system, you open the valve, and thats how you bleed the air from the system right before the injectors.... now remember i diagnosed this over the phone, but i know a little bit about bobcats.... when the system is bled, it runs for about 45 seconds.... obviously its getting air, and shutting off.... this was my diagnoses, any help is appreciated.... also, i do need part #s for the glass bowl.... all i know is it is an older 743 - melroe... email me at [email protected] since i will never find this site again... thankyou in advance...

 

[Tazza]

Ok, you are on the rite track.
When priming you loosen the valve on the injector pump, the one with the main fuel line from the pump and it has a fitting to the tap off lines ot the injectors. With it open, pump the hand primer till you can't *feel* air and the bulb is nice and firm as you squeeze. you MUST close the valve on the pump ot it will start for a few seconds then shut down. The tap off line has no pressure, it flows back to the fuel tank. With the valve open you won't have enough fuel pressure.
Start with ensuring the valve is fully closed, it has caught many people, even me when i was new to Kubota engines.

 

[mrfixitpaul]

Ok, you are on the rite track.
When priming you loosen the valve on the injector pump, the one with the main fuel line from the pump and it has a fitting to the tap off lines ot the injectors. With it open, pump the hand primer till you can't *feel* air and the bulb is nice and firm as you squeeze. you MUST close the valve on the pump ot it will start for a few seconds then shut down. The tap off line has no pressure, it flows back to the fuel tank. With the valve open you won't have enough fuel pressure.
Start with ensuring the valve is fully closed, it has caught many people, even me when i was new to Kubota engines.

Ditto on the bleed valve needing to be shut. If it is bleeding out ok then still running out of fuel, you need to check the fuel pickup hose it may be cracked and once the engine starts the vibration opens the cracks and lets air in.

 

[djack]

hi madmike: are u talking about the little thumbwheel on the injection pump? they call this a jet start valve why i don`t know, it is for bleeding after it`s bled an running u r supposed to close it my experience is it will run fine open. sounds like t u have a problem with the pickup either tube or screen or crap in the shutoff valve ( right hand side o f machine by lift cyl.