I have a problem with a Komatsu pc300LC6. It is slow to start. The cranking power is fine and when I try to start it it cranks with no smoke at all from exhaust for 5 to 10 seconds. Then it will start to smoke and fire within another 5 to 10 seconds. I changed the fuel filter and have checked for any leaks along the fuel rail and injectors and have found nothing. I am not very familiar with the fuel system on these. So I gues my big question is can anyone tell me why it would loose prime quickly? or should I be looking at the preheater or something else entirely. One more note, once it is started, it runs great. If you shut it off after it is warmed up, it is the same problem. It is still slow starting. So I figured that it is losing prime quickly, or I am looking in the wrong place entirely. Any suggestions would be greatly appreciated. Thanks
Sounds like a computer problem or something like that.
Not a lot of computing on dash 6s. Pull the banjo fitting on the fuel feed line. Should be a inline filter in that that plugs with all your tank junk before the first filter. See if your governer motor linkage is set right for your low idle spec, could be not moving the pump lever out of the no fuel stage.
Check check and double check all connections from tank to injection pump. Sounds to me that air is being introduced to fuel Lines.
How many hours on this machine. when you check the fuel filter is it half empty
That machine probably has the Cummins clone which should have an in line fuel strainer. I have seen many machines where that strainer has been replaced with a gas filter from Napa. If that is the case go get the strainer from the Komatsu dealer and see if that makes a difference. A photo of the engine might tell us more about what you have.
Yes, it should have an inline strainer right by the primer pump. I use the Napa ones w/o issue but they are direct replacement for the KOM part, definitely worth checking though. We had an issue with our 300-6 where the fuel s/o solenoid was getting weak and not pulling the lever on the pump all the way causing a hard start.
Thank you for all of the ideas. I will get a picture of the engine today and post. I will be working on it again this morning sometime and will let you know what I find. Thanks again
The fuel filter is full. 4000 hours. ish. It acts like it is getting air to me as well, but just not familiar with the system. I will get those pictures up as soon as I can.
The Napa filter is a paper filter. The Komatsu replacement is a brass strainer that can be cleaned. I have heard of the solenoid issue but not personally seen it happen. It's good to check it out.
did not get time to take pictures yet, but pulled all banjo fittings and found no strainer; however I did find that several of the crush washers are completely bad. All rubber about gone and a couple of the fittings had some sign of leakage, small, but there and those had the worst washer degradation. I have ordered new ones and they should be here today. I will install them and see what happens. I will post results. and if I get time Pictures. Thanks again for all the responses.
I'd put money on it being the shut off solenoid. We had the same thing on our pc300-6 and our early Case IH Magnums tractors. They all have 8.3L Cummins with Boucsh injection pumps in them. To test it use baling wire to hold the solenoid in the run position and start the engine, or have someone watch it when you turn the engine over. The solenoid doesn't energize until the engine starts to turn over, so it won't throw the with just the turn of the key to the run position.
Sorry, I had another problem develop and have not been able to get back on here. I replaced all of the crush washers on every banjo fitting and still no improvement. I checked the shut off solenoid and it is working. I was really thinking that that was it. The problem became worse today and it would not even start at all, so while I had someone crank it, I pumped the manual lift pump and it started. I think that the lift pump is bleeding back. I may be wrong, but will find out when the new lift pump arrives tomorrow or Wednesday. Thanks for all the help. You have all aided in other repairs that needed to be made that I would have missed otherwise.
Well...That did it. It was the lift pump. It has always been a slow starter, but it just got to the point that you had to crank for 20 seconds or more,or it would not start unless you manually primed it while cranking. replaced the lift pump today and now it starts in about 4 seconds.