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I have a Bobcat 643 that the fuel hose inside the tank

I have a Bobcat...

I have a Bobcat 643 that the fuel hose inside the tank deteriorated and fell off. I have replaced the hose and primed with the ball pump but it still won’t start. I don’t think it is getting the fuel still. Is there a place to bleed any air out?

Mechanic's Assistant: What is the complete model and serial number of your machine?

Customer:(###) ###-####m-14003

Mechanic's Assistant: Anything else you want the construction mechanic to know before I connect you?

Not that I know of. It was running fine and then it stopped

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Answered in 12 hours by:
7/24/2018
Mechanic: Fieldtech59, Shop manager replied 4 years ago
Fieldtech59
Fieldtech59, Shop manager
Category: Construction and Road Equipment
Satisfied Customers: 202
Experience: Construction equipment repair technician since 1986, JLG certified, Shop manager since 2006.
Verified

Greetings. Deteriorated fuel pick up tube dropped in tank is a pretty common Bobcat problem, I've done piles of them. Did you replace that tube with Bobcat supplied parts including the strainer screen that goes on the end of the tube?

I assume you didn't take that CAV fuel filter apart when it quit, I hate those filters. If you did, did you verify the seals made up correctly, if that sediment bowl and the filter cartridge doesn't seat proper then it will suck air.

If I recall correctly the 643 had a three cylinder Kubota diesel with a Mikuni lift pump along with the primer bulb. First thing to do, on the side of the injection pump, just below where the injection lines connect, you should have a valve that has a small thumbwheel knob on it. That knob is used to open the restrictor valve during priming. For running it should be screwed in CW until it seats. When priming the fuel system using the primer bulb you grip the thumbwheel knob and turn it CCW until it stops, but don't jam it into the stop. Once you've done that, work that primer bulb. It may take a number of bulb squeezes since it has to draw fuel up the pickup tube and through the filter and lines. Once you get sufficient fuel that has flowed through the pump and out of that valve you close the valve by turning knob CW until it seats. Crank engine. If it doesn't start, repeat process. If it still doesn't start after several attempts you may have to crack the injection lines where they connect to the injectors. Can't really crack them at the pump, they're too close together. And I typically connect a remote starter button to the starter if I have to do this, too big a PITA to climb in cab, crank engine, stop, check fuel lines. Naa, I want to be right there at the engine when it's cranking.

One other thing, and you prolly already know this, those engines, once they get some age on them, they won't start worth a flip unless you use glow plugs, even in the hot summertime. Make sure your glow plugs are working.

Let me know what you find or if you need further assistance.

Oh, and just to be sure, make sure that inline fuel shutoff valve at the lower right side of the tank isn't closed.

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Customer reply replied 4 years ago
Thank you for your response! I did not replace the strainer screen because there wasn’t one when I took the old hose out. I have since found a parts list and will install one. I also did not take the fuel filter apart. I inherited this machine and I don’t think it had a lot of preventative maintenance. It is currently stuck out in the yard and I would like to get it into the garage so that I can work on it easier. I did find the primer ball but I didn’t realize that there was a restrictor valve that could be opened. I will have to locate this and try it but I won’t get back to this project until Saturday. Thanks again for your help.
Mechanic: Fieldtech59, Shop manager replied 4 years ago

It's been years since I've worked on the 43 series Bobcat. And if the 643 is anything like the 743 (likely is) that CAV fuel filter is in a bit of a PITA location to service. If it were a spin on filter it wouldn't be so bad, but the CAV filter is a cartridge held to the filter housing via a glass or plastic sediment/water bowl, it comes apart in pieces. It has a rubber lathe cut ring that seals it top and bottom with a 1/4" bolt through the center that secures the pieces together. If it's like the 743, the easiest way to access it is remove the coolant recovery tank (if it's still there), it simply pops out of the bracket that mounts it to the machine, gives you better access to the filter.

The strainer screen on the pickup tube serves three purposes, 1) it's a screen to prevent large debris entering the fuel line and clogging it, 2) it has a check ball inside it to prevent fuel back flow into the tank out of the fuel line, and 3) it provides a weight to keep the flexible pickup tube at the bottom of the tank. Kind of a necessary item.

I'm attaching a pic of a 543 injection pump, pretty much the same engine as in the 643, with a red arrow pointing to the bleeder valve on the injection pump. Turn the knurled know CCW to open the bleeder valve, pump the primer bulb to purge air from the injection pump, then close the bleeder valve by turning the knob CW until it stops. Just don't jam it against the stops, it's easy to strip out that brass knob on the stem.

Again, if too much air got in the injection pump and it died you may have to crack open injection lines at the injectors because the pistons inside the injection pump won't pump air and as I recall those injection line nuts at the injectors are not easy to get to because the intake is smack in the way, but seems I recall I've done them before, prolly with some choice swear words included.

Fieldtech59
Fieldtech59, Shop manager
Category: Construction and Road Equipment
Satisfied Customers: 202
Experience: Construction equipment repair technician since 1986, JLG certified, Shop manager since 2006.
Verified
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Customer reply replied 4 years ago
I will be trying this out tomorrow as the machine is at my summer cottage. I will let you know how I make out thanks.
Mechanic: Fieldtech59, Shop manager replied 4 years ago

I hope everything goes well. BTW, if I recall, which gets way back in the cobwebs inside my head, I think most of the 43 series Bobcat machines used a cable operated manual shutdown as opposed to electric solenoid shutdown on later models. If this is correct, make sure that shutdown is in run position or you won't get fuel out of the injection pump, common simple thing that sometimes get overlooked.

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Mechanic: Fieldtech59, Shop manager replied 4 years ago

Yes, that's the fuel bleed valve. What that valve does is it's a spring loaded check valve. As the fuel lift pump (seen in bottom of pic) pumps fuel into the injection pump, the spring loaded check valve creates a bit of back pressure in the injection pump. Once a certain amount of pressure is achieved it pops open and dumps excess into the fuel return lines at the injectors to return to tank. When you change filters and such, you open the bleed valve, this allows you to pump fuel through the injection pump, it negates the spring loaded check valve for the moment. Once you've purged the air from the injection pump, you close the bleed valve, then pump the primer bulb until it gets hard, or at least somewhat firm.

In your case, since the fuel line broke off inside the tank, it may take a few minutes to get good fuel flow through the new fuel line. What I would consider doing is take the fuel supply line loose from the lift pump, drop the loose supply hose into a clean coffee can or fuel can, then pump the primer bulb until you get good fuel flow from the line. Hook it back up to the lift pump and do the bleed valve procedure.

Also, it appears in the pic that you have the shutdown lever in the run position, I can see the manual cable that operates the shut down.

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Customer reply replied 4 years ago
You are very observant and very helpful! Thank you for all of your help, it is running great and now I will get the correct parts. It appears to be a screw on fuel filter and I want to change it. You said something about a glass bowl but I don’t see one. Is it possible that it is just a screw on filter?
Mechanic: Fieldtech59, Shop manager replied 4 years ago

Someone may have previously changed it to a spin on filter, which is good, originally it came from Bobcat with a two piece CAV filter which was a filter cartridge with a glass bowl at the bottom of it. I'd way prefer a spin on filter. The old CAV filter had a 1/4" hex head bolt running through it to hold the filter and the bowl attached to the filter housing, the hex head to loosen and remove the filter was on top and in the center of the filter housing, 7/16" hex head.

Good to hear you got it running!

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Customer reply replied 4 years ago
Thank you so much! You are the best and I will be sure to give you a great review! Thanks again for the help and have a great day!
Mechanic: Fieldtech59, Shop manager replied 4 years ago

Thank you for the kind words. I've been working on machines for over 30 years and I still love it when we get a customers machine up and running again. Cheers!

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