Kubota L4150 slow to start

[double hunter]

New to me Kubota L4150 slow to start on initial startup, I warm the glow plugs until the indicator on the dash gets hot to the feel, it never does glow like I have seen on other tractors, it usually takes 3 or 4 prolonged attempts to get tractor started.. after initial start up it cranks and runs good, tractor has 2590 hrs and does not smoke, it has a hot battery in it, I just repalced the fuel filter and air filters, I checked the glow plugs and I think they are good, this tractor set up since last summer until I acquired it a couple weeks ago, looks like this tractor has a secondary fuel pump on it, could this be bad, any help or advice on what to check will be appreciated

 

[al b]

How long is prolong? I have a l345dt that when it is 40* I hold the glow plugs for 60 seconds. Bellow that I plug in the heater. Have you checked the glowplugs on the bench? May be a bad connection or a bad wire.

 

[double hunter]

Kind of a update, working my road this afternoon after the monsoon went thru last night and this thing doesn't want to crank hot or cold, was working mu neighbors drive and he is a diesel mech and said I was having fuel problems, I've already changed the fuel filter, I am going to change the fuel pump out tomorrow if I don;t have to order it, after that may be injector pump.