Cat 248b only starts on high throttle. Have replaced battery, alternatir, fuel pump, pickup, injectors rebuilt… no change. Thoughts?
Sounds like the fuel control rack in the injection pump is sticking or worn. It may also be worn plungers in the fuel injection pump. I am assuming when you say you replaced the fuel pump you mean the fuel transfer pump.
Can you start with a Serial Number so everyone knows what you have. SCL-something maybe.? My other thought would be that you should have started asking questions long before you loaded the parts cannon. You say that you need to floor the throttle to get the engine to start. When it is running how does it idle if you let your foot off the throttle.?
As soon as it starts, you can throttle it down and it idles normally
When they idle pefectly, the injectors are doing their job. If it won't start leaning towards what Mobiltech said about injection pump rack. Could some linkage be causing a problem, worth a 2 second check. These are just straight mechanical injectors from the ones I worked on. Simon C
With this being a B model it’s a fair age. I wonder if it’s simply tired. Does the engine take a while to fire even with the throttle at maximum.? Is it burning any oil.? Does it smoke appreciably at any point.? What about doing a compression test.?
No smoke, doesn’t burn oil, does take a few cranks to fire and slowly chug to life but once running it seems normal. It’s as if it’s a cold winter start but it’s not cold here.
How many total hours on the machine.? By your description of how it fires up I would still suggest a compression test, even if only to rule out the possibility of internal engine wear being the root cause. At least it would be a relatively cheap step considering all the money you have thrown at it so far per your OP.
It might be a long shot but are your glow plugs working and have you tried using them when starting the engine? Typically best to activate the glow plugs for 10 seconds prior to attempting to start. I have a 2006 242B that will not cold start at +70 F or -30 F. I have been unable to successfully troubleshoot the issue but it will start immediately (at low throttle) after applying the glow plugs. Once it has been started and runs for a few minutes, it will restart easily without using the glow plugs. It might be a fuel delivery issue in my case but I don't want to go to the expense of replacing / rebuilding injectors or injection pump when I can get it to start easily by using the glow plugs. Note to Nige - Based on some of your previous posts, I thought you were an anti diesel compression testing kind of guy. Nice to see you that you have drunk the kool-aid
Au contraire mon brave........... My issue is/was not with compression testing per se, but with compression testing when there was no specification to test against. This was the case for pretty much all this type of product with the exception of the Kubota-manufactured engines in the later model machines. Obviously if a compression test reveals one cylinder way off from the other three then you have found your smoking gun, but generally in a worn engine you're not going to find one cylinder "low", it's going to be all four of them. but how does one know how "low" they really are without a specification to compare the results against.? The compression test numbers for engines installed in B Series machines were only released at the back end of last year, coming up on 20 years after the machines were actually built. The numbers call for an average over several tests of 2940 kPa (427 psi) new with a wear limit of 2650 kPa (384 psi) when cranking at 300 RPM.