Difficult to start Bobcat 743

[DBCoop]

Hello to everyone as this is my first post! I own a 1990 743 with 2400 hours that I am having problems getting started.I have replaced the fuel filter (it appears to be sealed) and have replaced the rubber hand pump.About 5 years ago I replaced the pickup tube in the fuel tank and the hoses and hose clamps seem to be tight.Before I try to start I check the rubber hand pump and it is not firm,somewhere I am loosing pressure. When I engage the starter there is white exhaust and it takes a fair amount of time of priming the hand pump before the engine trys to fire.With work being as slow as it is I would like to try and get it going myself.Any imput would be appreciated! Thanks in advance Doug

 

[Fishfiles]

Sounds like I would start with fuel , I would take a gallon jug of diesel , remove the hose going into the hand prmer bulb on the tank side and install another hose , put that hose into the jug of fuel and prime the fuel system then try to start machine , this will eliminate the pickup tube which could very well be bad as the soft clear tube doesn't last very long sometimes , I think that different fuels will shorten it's life --------another approach is to hit the motor with some starting fluid and see if it will pop , I perefer to have someone spinning the motor while I give it a short blast or use a remote starter , this will tell you if it is indeed a fuel delivery issue --------another issue to look is to try ad pump the bulb with the out end dissconected and see whats coming out , sometimes I have seen the check valve in the end of the bulb get clogged up with trash ---------so work is slow where you are at , where is that ?

 

[DBCoop]

Sounds like I would start with fuel , I would take a gallon jug of diesel , remove the hose going into the hand prmer bulb on the tank side and install another hose , put that hose into the jug of fuel and prime the fuel system then try to start machine , this will eliminate the pickup tube which could very well be bad as the soft clear tube doesn't last very long sometimes , I think that different fuels will shorten it's life --------another approach is to hit the motor with some starting fluid and see if it will pop , I perefer to have someone spinning the motor while I give it a short blast or use a remote starter , this will tell you if it is indeed a fuel delivery issue --------another issue to look is to try ad pump the bulb with the out end dissconected and see whats coming out , sometimes I have seen the check valve in the end of the bulb get clogged up with trash ---------so work is slow where you are at , where is that ?

Thank you for the reply Fishfiles! I will give that a try. I live in Southern Oregon------ a beautiful place to live ------ just not a lot of construction right now.

 

[Tazza]

Thank you for the reply Fishfiles! I will give that a try. I live in Southern Oregon------ a beautiful place to live ------ just not a lot of construction right now.

You mention white smoke, thats a sign of fuel delivery.
Have you had your glow plugs out to check them? I'd even ensure they are operating with a test light or multi-meter. Without glowing the engine will start but it will puff white smoke for a while before it fires.
As Fishfiles said, there is a one way valve in the fuel tank that helps prevent fuel leaking back, but if you entire system is leak free that shouldn't matter as no air can get in.
I persoanlly would start with the plugs, pull them and use a heavy cable and battery to ensure they glow rite to the tip. Ensure you have power going to the glow plug rail too.

 

[Fishfiles]

You mention white smoke, thats a sign of fuel delivery.
Have you had your glow plugs out to check them? I'd even ensure they are operating with a test light or multi-meter. Without glowing the engine will start but it will puff white smoke for a while before it fires.
As Fishfiles said, there is a one way valve in the fuel tank that helps prevent fuel leaking back, but if you entire system is leak free that shouldn't matter as no air can get in.
I persoanlly would start with the plugs, pull them and use a heavy cable and battery to ensure they glow rite to the tip. Ensure you have power going to the glow plug rail too.

I didn't mention the check thats in the screen in the tank as that would have been eliminated by trying to start off of a can of fuel , I was referring to the check ball in the inlet side of the primer bulb

 

[DBCoop]

You mention white smoke, thats a sign of fuel delivery.
Have you had your glow plugs out to check them? I'd even ensure they are operating with a test light or multi-meter. Without glowing the engine will start but it will puff white smoke for a while before it fires.
As Fishfiles said, there is a one way valve in the fuel tank that helps prevent fuel leaking back, but if you entire system is leak free that shouldn't matter as no air can get in.
I persoanlly would start with the plugs, pull them and use a heavy cable and battery to ensure they glow rite to the tip. Ensure you have power going to the glow plug rail too.

I bought the machine new and the glow plugs have never been checked.I will test them for sure!I will read some of the previous posts regarding the plugs.With your suggestion and Fishfiles fuel system test,I am pointed in the right direction.It may be a week or two before I can work on it as I am now busy at work.I will let you guys know and thanks again.