Fuel Pump Primer Bulb.

Help Support SkidSteer Forum:

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
Hi everyone. My 1998 773 Bobcat skid steer has been hard to start for the last couple of winters I'm wondering if the problem I'm having would be caused by my primer bulb. It's hard like a rock. It used to start no problem in the winter but the last couple of winters it cranks and cranks for a long time before finally starting. I plug it in, I have a battery heater also, I added fuel conditioner, I also added a Lucas fuel treatment. I'm thinking that maybe the fuel primer bulb is bad. The plastic or rubber that forms it seems to be aged to the point of making it very stiff. Could it be that it is also loosing it's prime and therefore making the engine hard to start? Any feedback from anyone would be greatly appreciated.
 

foton

Well-known member
Joined
Mar 1, 2018
Messages
1,278
you can replace that bulb, it can not hurt if the rubber is that hard, but have you looked at your glow plugs and there I believe there is a lift pump on the injector pump that might have issues of course a restricted fuel filter could be a problem. have fun
 
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
you can replace that bulb, it can not hurt if the rubber is that hard, but have you looked at your glow plugs and there I believe there is a lift pump on the injector pump that might have issues of course a restricted fuel filter could be a problem. have fun
Thanks.
 
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
you can replace that bulb, it can not hurt if the rubber is that hard, but have you looked at your glow plugs and there I believe there is a lift pump on the injector pump that might have issues of course a restricted fuel filter could be a problem. have fun
How can I tell if the glow plugs are working? Would some kind of electrical tester work for this procedure?
 
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
you can replace that bulb, it can not hurt if the rubber is that hard, but have you looked at your glow plugs and there I believe there is a lift pump on the injector pump that might have issues of course a restricted fuel filter could be a problem. have fun
I do have a service manual and I see that all this is explained in it so thanks again, I'll see what I can find out with the help of my manual.
 

reaperman

Well-known member
Joined
Dec 18, 2011
Messages
598
I do have a service manual and I see that all this is explained in it so thanks again, I'll see what I can find out with the help of my manual.
You could pull the glow plugs and watch them when you turn the key. They should be bright orange, or even the fuse that controls them could be blown
 

reaperman

Well-known member
Joined
Dec 18, 2011
Messages
598
You could pull the glow plugs and watch them when you turn the key. They should be bright orange, or even the fuse that controls them could be blown
My mistake, the glow plugs are fed from a relay not a fuse. Relay #10 in fact. You can swap the relay for one that you know is working, like for the headlights.
 

ajwgator

Well-known member
Joined
Oct 12, 2005
Messages
58
How can I tell if the glow plugs are working? Would some kind of electrical tester work for this procedure?
You can test them without pulling them out. Disconnect wire from the top and use an ohm meter to test for continuity. A good glow plug will have very low resistance. A bad one will read open. Place your positive lead to the post the wire connects and your black lead to the body of the glow plug (wrench flats).

Concerning loosing prime in fuel system, check your fuel line going into & inside your fuel tank. They seem to dry rot at the top area inside the tank. Same with your fuel bulb, being hard it could have cracks in it too.
 
Last edited:
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
You can test them without pulling them out. Disconnect wire from the top and use an ohm meter to test for continuity. A good glow plug will have very low resistance. A bad one will read open. Place your positive lead to the post the wire connects and your black lead to the body of the glow plug (wrench flats).

Concerning loosing prime in fuel system, check your fuel line going into & inside your fuel tank. They seem to dry rot at the top area inside the tank. Same with your fuel bulb, being hard it could have cracks in it too.
Would one faulty glow plug be the culprit. I don't think one out of 4 glow plugs would cause such a fuss, but I don't know. I do have a faulty glow plug. Does anyone think this is the problem or maybe I'm not getting any voltage going to the glow plugs? Is there a way to confirm this without pulling the glow plugs? Feedback on this would be appreciated. I did swipe the relay and it is good. Member of this group ( foton ) mentioned that it could also be a lift pump on the injector pump that might have issues. Feedback on this would also be appreciated.
 

ajwgator

Well-known member
Joined
Oct 12, 2005
Messages
58
Would one faulty glow plug be the culprit. I don't think one out of 4 glow plugs would cause such a fuss, but I don't know. I do have a faulty glow plug. Does anyone think this is the problem or maybe I'm not getting any voltage going to the glow plugs? Is there a way to confirm this without pulling the glow plugs? Feedback on this would be appreciated. I did swipe the relay and it is good. Member of this group ( foton ) mentioned that it could also be a lift pump on the injector pump that might have issues. Feedback on this would also be appreciated.
Take a volt meter set to measure 20vdc, connect the positive lead to the top of a glow plug, negative lead to ground, energize your glow plug circuit and read the voltage that is on the meter. It should be close to your battery voltage while energizing the circuit. I'm like you I don't think one bad glow plug would cause the problem. How old are your glow plugs? They my be weak or close to failing and not getting hot enough. They do wear out but still heat some.

Have you checked the fuel line inside your fuel tank? On my 843 the fuel line was cracked inside the tank and it would suck air once the fuel got below the cracked hose. It also had a really clogged up fuel pick screen on the end of that hose. I put a primer bulb on mine machine thinking it needed assistance but once I fixed all the fuel hose problems in the tank the primer bulb stays tight and doesn't seem to be needed anymore. The fuel pick up screen is also a check valve that prevents fuel from draining back into the tank so the lines are always full.

My unit is still hard to start when cold but it is being caused by low compression when the engine is cold. Once it gets up to operating temperature it starts up fine.
 
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
Take a volt meter set to measure 20vdc, connect the positive lead to the top of a glow plug, negative lead to ground, energize your glow plug circuit and read the voltage that is on the meter. It should be close to your battery voltage while energizing the circuit. I'm like you I don't think one bad glow plug would cause the problem. How old are your glow plugs? They my be weak or close to failing and not getting hot enough. They do wear out but still heat some.

Have you checked the fuel line inside your fuel tank? On my 843 the fuel line was cracked inside the tank and it would suck air once the fuel got below the cracked hose. It also had a really clogged up fuel pick screen on the end of that hose. I put a primer bulb on mine machine thinking it needed assistance but once I fixed all the fuel hose problems in the tank the primer bulb stays tight and doesn't seem to be needed anymore. The fuel pick up screen is also a check valve that prevents fuel from draining back into the tank so the lines are always full.

My unit is still hard to start when cold but it is being caused by low compression when the engine is cold. Once it gets up to operating temperature it starts up fine.
Thanks
 
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
Take a volt meter set to measure 20vdc, connect the positive lead to the top of a glow plug, negative lead to ground, energize your glow plug circuit and read the voltage that is on the meter. It should be close to your battery voltage while energizing the circuit. I'm like you I don't think one bad glow plug would cause the problem. How old are your glow plugs? They my be weak or close to failing and not getting hot enough. They do wear out but still heat some.

Have you checked the fuel line inside your fuel tank? On my 843 the fuel line was cracked inside the tank and it would suck air once the fuel got below the cracked hose. It also had a really clogged up fuel pick screen on the end of that hose. I put a primer bulb on mine machine thinking it needed assistance but once I fixed all the fuel hose problems in the tank the primer bulb stays tight and doesn't seem to be needed anymore. The fuel pick up screen is also a check valve that prevents fuel from draining back into the tank so the lines are always full.

My unit is still hard to start when cold but it is being caused by low compression when the engine is cold. Once it gets up to operating temperature it starts up fine.
I did order new glow plugs and should be getting them sometimes in early December. I hear the old ones could be brittle and break off inside while trying to remove them. I wonder if I run the engine for a bit, would it help to prevent this to happen?
 

foton

Well-known member
Joined
Mar 1, 2018
Messages
1,278
I would take a spary lube and soak it down around the glow plugs the night before glow plug disassembly. brand is your choice, i am not get into that on who thinks what is best nightmare.
 

billyb

Active member
Joined
Oct 13, 2022
Messages
38
I did order new glow plugs and should be getting them sometimes in early December. I hear the old ones could be brittle and break off inside while trying to remove them. I wonder if I run the engine for a bit, would it help to prevent this to happen?
I would agree with checking the fuel line and screen/check valve in the tank. Common problem!
Also have seen where outside below zero and machine parked a while, water in tank froze and blocked suction line. I am thinking if your block heater is working you shouldn't need glow plugs for it to start.
 
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
Did you get the issue fixed. If so what was the fix?
I am working on the problem. The glow plugs don't seem to be working. I swiped the relay with another one and this didn't help. Yesterday I checked the glow plugs with an ohm's meter and detected one bad glow plug. I have new ones on order. Foton advised me to take a spray lube and soak it down around the glow plugs the night before glow plug disassembly witch I will do. I'm wondering if after the harness is disconnected from the glow plugs but still connected to the relay and battery, could I check with a voltage meter to make sure that I am getting proper voltage there?
 
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
I would agree with checking the fuel line and screen/check valve in the tank. Common problem!
Also have seen where outside below zero and machine parked a while, water in tank froze and blocked suction line. I am thinking if your block heater is working you shouldn't need glow plugs for it to start.
Thanks for your feedback. How hard is it to check the fuel line. I do have the service manual but if you're familiar with this, is this a simple task?
 

ajwgator

Well-known member
Joined
Oct 12, 2005
Messages
58
Thanks for your feedback. How hard is it to check the fuel line. I do have the service manual but if you're familiar with this, is this a simple task?
Raise the roll over cage, then there should be two metal plates screwed on top of the fuel tank. One for the fuel gage float/sender and the other one for the fuel line. Mine has four screws holding it on with a 90 degree fitting in the middle of the plate. Remove the 4 screws and life the plate off. That will bring up the fuel line & screen/check valve. Pretty simple really but I don't think the manuals cover it much.

You can check the voltage on your glow plug circuit wire before or after removing the glow plugs. If you have less than battery voltage at the wire that attaches to the glow plug then check it before (going in) and after (coming out) of the relay.
 
Last edited:
OP
OP
little_fellow

little_fellow

Well-known member
Joined
Oct 6, 2009
Messages
205
Raise the roll over cage, then there should be two metal plates screwed on top of the fuel tank. One for the fuel gage float/sender and the other one for the fuel line. Mine has four screws holding it on with a 90 degree fitting in the middle of the plate. Remove the 4 screws and life the plate off. That will bring up the fuel line & screen/check valve. Pretty simple really but I don't think the manuals cover it much.

You can check the voltage on your glow plug circuit wire before or after removing the glow plugs. If you have less than battery voltage at the wire that attaches to the glow plug then check it before (going in) and after (coming out) of the relay.
Good stuff. Thanks.
 

Latest posts

Top