View Full Version : weird starting behavior

Bill & Sonja
02-17-2012, 03:38 PM
Hello Newell gang, I've encountered another weird behavior.

Our Perkins / Kohler 12.5 generator is behaving strangely. Or maybe it has always acted strangely. History: Oil and filters changed regularly, new glow plugs a month ago, new starter 2 years ago, control box professionally reconditioned same time as starter. I believe it has about 3,500 hours running time.

Generally it starts like this: first crank does not start, it cuts out cranking itself after a short crank. (that is, with the switch held down it jut quits cranking) Second crank it starts right away or occasionally behaves the same as the first crank and starts on the third attempt. Each time I have held the glow plugs 15 seconds. It started the same way before the starter was replaced.

Now a couple days ago it cranked until I released the switch - and no start or fire. A number of times it cranked continuously till released and no firing. Let it sit a while and tried it and it started in its old characteristic way. Has run in its usual way for a few starts and then behaved strangely by continuously cranking again and not firing. Left sit a while and started in the usual way again.

Any thoughts on this one?

Richard and Rhonda
02-19-2012, 12:14 AM
Let me replay what I think you said. The engine turns over just fine, just doesn't fire. Does it try to fire?

In some ways, diesels are easier to diagnose than gas engines. Fuel and air are the keys. Since it runs fine when it does crank, I am thinking fuel. If it doesn't stumble when it's misbehaving, I think the fuel shutoff solenoid isn't opening. That could be a relay or a bad connection. Is there any way you can slide it out and observe the fuel solenoid while someone else hits the start switch?

02-19-2012, 01:28 AM
If this problem showed up on my coach I would start by checking the Battery Cables both positive and ground to be sure that you have good power to the Generator, you should check both ends (Battery Starter and Engine Block) since you stated that it just quit cranking.
Our Perkins will crank over until it starts. When I had a Fuel Leak it allowed Air into the Fuel System and it took longer to start but it always cranked until it started.