Monday, March 12, 2007

March is Already Better Than February

February was a month that could have been done without here in the Northeast. It was cold, dark, and depressing. The only thing that made it bearable was the two weekends of work at the yacht club. It was nice to help out, and great to see all the people that I hadn't seen since Fall.

But yesterday, Sunday, the 11th, it was beautiful - in the 50's and sunny and just right for easing into the whole start of the boating season.

Since Inertia is currently for sale, I didn't do many of the projects that I wanted to if I were going to keep her. But one that really needed doing was replacing the fuel injectors.

What made me think it was needed? Well, for one, the engine ran rough at idle and wasn't capable of going over about 2200 rpm at full throttle, even unloaded (just so you know, it's not advised to run the engine at full speed unloaded so if you're going to try this, make it quick). There was no smoke to speak of, but it ran rough. Nothing had changed so there was no reason to think the fuel pump or filters were contributing to this problem. The engine did start ok. Also, the engine has approximately 2200 hours on it (almost 20 years of 100 hours per year).

The least expensive thing to do other than changing fuel filters (done already) is to rebuild or replace the injectors. The cost of rebuilding is about $45.00 each, and if you insist in purchasing them from the Westerbeke/Universal dealership expect to pay $185 each for new ones.

Universal diesel engines since about 1977 are all Kubota. The hard part is figuring out which model as Universal kindly ground off all Kubota part numbers and stamped their own. Not terribly helpful. I found that my 25XMP is really a Kubota D-950 and could order parts that way from the distributor. Brand new injectors from Kubota are $59.00 each. So rebuilding is hardly worth it. Make sure you also purchase new copper gaskets for the injectors, too. They're $.70 each from Kubota. $10.00 each from Westerbeke/Universal.

Based on all that, I decided that it wouldn't hurt to replace them and it very possibly could help!

The first nice day (yesterday) was perfect for the job. Diesels are intrinsically simple engines - the most complicated part is the high pressure fuel pump with the injectors coming in second. They are pretty forgiving about fuel with the one exception of dirt and air entrained in it. You can even have some water in the fuel!

That said, first I had to disconnect the three small lines from the pump to the injectors and remove the return fuel rail. Easier said than done. I've found that the way to do this is to remove the front connections first, then the second and finally the third - each give room for the next.

A word about these fuel lines. They're steel and the compression fittings are moderately delicate - you don't need too much force to make a good seal so you don't need too much to undo them. Don't force them. If they seem to be stuck, take a minute and make sure you're turning them in the right direction. It also helps to have what are called 'gas line' wrenches that look like box-end wrenches with a slot cut in the box to go around a gas line (like on cars). Fortunately they work on diesel fuel lines, too!

Other fittings may try to loosen, too. the line is connected to a check valve at the high pressure fuel pump, so hold that fitting to make sure it doesn't turn as you're loosening the fuel line fitting. When you've got the fittings off, cover the open holes with tape or a clean rag to keep debris from falling in. Move the fuel lines out of the way - I loosened the two brackets that hold them neatly in order to do that and then rotated them away from both the pump and injectors.

You'll have to undo the nuts that hold the return fuel rail to the injectors and disconnect that hoses to the rail. If your rail isn't solid, then just disconnect the hoses. Remove the rail. Since these are the old injectors, don't worry about dirt too much.

The injectors come out just like a sparkplug, but with a bigger wrench. They, too, are not cranked down tight. If they're stuck, a couple of light taps on the wrench handle with a hammer will break the seal. I do that because I'm not interested in banging my knuckles hard on the cable brackets and intake manifold. If you have the right size deep well socket, then you're way ahead of the game.

Remove the injectors one at a time and make sure the copper seating gasket is also removed! You should have a clean hole into the cylinder from that point. Make sure the seating surface at the bottom is clean and the threads are also clean. The new injectors come with plastic caps - remove the bottom one and leave the top one on until you're ready to re-attach the fuel lines. Drop the copper gasket into the injector hole and make sure it's flat at the bottom. Then screw in the injector. It should go in pretty easily, like a sparkplug.

When all three are done, remove the plastic caps, replace the return fuel rail and the nuts that hold it in place. There is an aluminum gasket under the rail - make sure it's on and you've put the rail on correctly. It should be smooth on top and grooved underneath. Tighten the nuts that hold the rail on - they should be snug, so don't force them. Remember, everything on the fuel system is snug, not tight. I'd be really surprised if you'd put more than 10 or 15 foot-pounds on any of the fittings. Reconnect the return and bleed lines.

Now, you can replace the fuel lines. Make sure before you do that the check valves on the fuel pump are snug, then replace the fuel lines on the injectors. These compression fittings are delicate - don't force them. They seal with very little pressure, and if you over torque them you will be purchasing new ones. Once again, snug is the key. I'd say 10 foot-pounds or less. Don't force them. I can't stress this enough. If it leaks when you're starting the engine, tighten them a little more. It's better to do that then to have them ruined.

Finally, when all is back together, turn the ignition on so the electric fuel pump runs and purge the system. Then you can start the engine - it will crank over a little longer than normal because the fuel lines from the high pressure pump to the injectors will have to fill. If there are no leaks, the engine will start within about 20 seconds or so. If it doesn't, check for leaks. Leaks in the high pressure lines will prevent the injector from providing fuel to the cylinder.

If the engine starts and runs roughly, wait a minute (unless it's really rough) for all the injector lines to fill. Remember, a diesel uses very little fuel - the line consists of minutes of fuel in volume. If it smooths out, you're good. While it's running, check for leaks. You may see some smoke - especially if you've gotten fuel on the engine head (I'd be surprised if you didn't). It will clear. Make sure there are no leaks around the high pressure pump or the injectors - it will be obvious.

If you see a leak, stop the engine and tighten the thing that's leaking. Try again. If you've tightened it more than once, you've probably ruined the fitting. That's bad, and you'll have to take that section apart and evaluate the problem.

That's really all there is to it. It took me an hour and a half to do the job, and that's because it took me an hour to get all the fuel lines out of the way. The injectors pictured here are the old ones - expect to see some carbon on the end, but you should see the little pin that comes through and there shouldn't be a huge build up of carbon on it.

Injectors are pretty forgiving, but they do wear out. If you've noticed a decided loss of power or heavy smoking from your diesel, this might be a way to get it back and stop the smoking. It's cheaper than a rebuild!

When I was done, the engine idled smoothly, started easily, and was once again able to go to its max rpm! I'm a happy guy!

It's getting warm, and I can't wait to see you on the water!


Jasson Johnson said...

Thanks for sharing the nice post on Kubota engines.

Zoran said...

Thank you for this well-written post! I gave me the right information - and needed encouragement - to DIY that job successfully ... Zoran