I am not a diesel mechanic but I try to capture what I learn as I work through different issues. I read everything I can find about the early L-Series Tractors. I understand the L175, L210, L225, L225DT, and L260 are essentially the same tractor except for differing engine size. Also the L225/L225DT has a 3 cyl engine and the 225DT has 4 wheel drive components. If you know other wise, let me know. I think the 1969-70 L200 is somewhat like these but didn't have headlights.

Sunday, February 26, 2006

Hard Starting

Volumes have been written about starting diesels – especially when it’s cold.
Bottom line – The fuel air mix has to get sufficiently hot to spontaneously ignite. Fuel and ENOUGH Compression are all you need. But the devil is in the details.

Rule number 1: If the engine doesn’t rotate fast enough, it won’t start. Even a new engine won't start if it the starter won't crank it fast enough.

Start with a kick-ass battery. Diesel compression goes to 450 PSI. In a small cylinder that has 10 square inches of piston surface, that means 4500 lbs of pressure at Top Dead Center. I had winter starting problems that all went away when I replaced a 5 year old 575 CCA battery with a brand new 850CCA battery. Make sure the terminals and cable lugs are clean and tight on both ends of the main power cables. You want 4 gauge cables to prevent too much voltage drop.

Starter – A new OEM starter is hard or impossible to find. Here is a place that rebuilds them. The original starter had a .9KW draw. Thats 75 Amps. There's new starters out there that draw 210 Amps.

I’m not sure if it's a good thing, but my tractor has a Nippon Denso manufactured John Deere starter. It’s part number RE51447. Denso Part 028000-8401. I think the OEM starter has a 9 tooth pinion but the pages about the JD starter here and here say it is 10 or 11 tooth pinion. I have not removed it to count the teeth.
There are now some gear reduction starters that translate higher motor speeds into more torque. If I need to replace my starter, I’m going for the “high torque gear reduction unit”.

OK – Good battery, clean terminals and connections, dash lights power up when the key is turned on, glow plugs heat as designed. When you crank it, you should see at least 400 RPM on the tachometer and 400 RPMs will be enough if compression and fuel are working.

White exhaust when you crank is unburned fuel, it's getting fuel but not enough heat to fire. It's usually insufficient compression or not cranking fast enough. It means the compression is good enough to vaporize the fuel, but not enough to combust it. If you are seeing white exhaust, don't crank more than 10 seconds. You need some more heat in the cylinders. If you want to put the time into it, use a blow dryer or heat lamp to heat the oil bath filter. It’s slow but it will dump serious heat into the process. Heat in a diesel is like a spark to a gas engine.

If you crank and there’s no combustion and no unburned fuel, you have a delivery problem. Check your fuel tank, bleed your fuel system at the filter and at the injection pump. Make sure the kill handle is pushed in and the kill actuator at the injection pump has released back to the “run” position.

If loosening the bleeding screw at the injection pump allows the free flow of fuel, it’s either the wrong fuel, bad fuel injection pump (insufficient pressure), timing injection cam is completely out of whack or injectors are completely clogged. If you’re at this point it means you probably want to see a pro. If you still don't get vaporized fuel, you can back out the injectors and confirm that no fuel is atomized, but without a fuel pressure tester and other gadgets, you won't be able to diagnose the problem.

Theoretically, you aren't supposed to need glow plugs unless it's cold but I use them all the time on the first start of the day. If it won't start, heat up the oil bath air cleaner with a heat lamp or a blow dryer.

If it isn't starting even when cranking at 400 RPM, you can try the compression release to try and coax a higher cranking speed, but I've seen only limited success with the compression release.

If you are cranking fast enough and getting fuel, and have applied heat and it still won't start, you can try a very small amount of starting ether in the intake. This is not recommended by most diesel manufacturers for several reasons. Use ether at your own risk. I take no responsibility for damage you do to your engine. But it pretty reliable if you have an urgent requirement to get the motor started. Use very little.


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