Cautionary LD28 Tale

[TorreyWP]

Since purchasing my 1985 27FC, I had always wondered why after warming up, it s smoked like crazy and left a slick of unburned fuel behind the boat. The engine in question a Nissan LD28 6 cylinder NA diesel. This is a rather modern diesel that features a Bosch style Kiki injection system that is very precise and efficient when tuned correctly. Luckily, mine has an extensive documented service history and was well cared for so far at 2200 hours. At hull speed the smoke seemed to go away but at idle, it was like an old 2 stroke outboard. I knew something was not right but the damn thing always started, never left me stranded and sounded like it was running normally. I recently found the problem and thought posting my findings here might help others;

Things I did in attempt to cure the smoking:

- Scoured internet for resources, the Nissan diesel forum site is awesome! http://nissandiesel.dyndns.org
- Got the service manual. There is a copy in the library section of AOG.
- Confirmed all fluids were clean and up to level. It had never used or leaked any fluid in the nearly 300 hours I have put on it
- Removed and cleaned fuel tank to ensure clean fuel was all that was inside. It was very scummy.
- Had injector nozzles sent out to be tested and rebuilt as necessary. This was not cheap (about $85 per nozzle) but they all tested bad and had signs of having water/fouled fuel going through them
- Checked and cleaned air filter.
- Checked for blow by by removing oil cap on valve cover while the engine is running. This can be an indication of a head casket issue. Nothing abnormal.
- Timed engine per service manual specification; This one is tricky, Ill explain.

FSM LD28 Timing.jpg

The manual shows how to make sure the engine is on number one cylinder TDC on the compression stroke, then removing the belt and lining up two marks one on the crank (hard to see, get a paint pen) and the correct mark on the injection pump pulley. This procedure is basically identical to lining up cam sprockets on a OHC gas engine. The crank pulley turns twice for every single revolution of the injection pump, 2:1. Knowing all this, I timed the engine once per the manual, put it all back together, no change. Then I thought, Ill get it all lined up and instead of lining the two marks up, Ill go one cog in one direction and one cog in the other and see if it makes any difference. Sort of like turning a distributor to get the timing right...in one direction it barely ran and in the other it rapped hard like it was over advanced.

Ughh, frustration setting in. At this point I assumed that the injection pump itself must be over fueling. It can happen, there are parts inside them that wear out and over time they need to be calibrated by a shop that has special equipment (read: expensive!!). Not wanting the boat down for an extended time I found a guy in Maine parting one out and I bought his injection pump, took it to my diesel shop and had them confirm it was calibrated properly. 350$ later I had a known good injection pump in my hands.

Last week I went to install this pump. Removing all the parts I had apart in all my attempts to time the engine properly. To remove the pump, the injection pump pulley has to be removed and the nuts holding the pump to the engine loosened (mine were rusty and stuck). Figured I would fight the pulley first. Using a 2 jaw puller, I broke free the nut holding the pulley on and popped the pulley off the tapered shaft. This took hours and was a fight. I noted the location of the key and was perplexed when I noticed that the pulley was installed in the wrong key way.

LD28 Pulley.jpg

Note one mark labeled "AB" and one blank

FSM Pulley mark.jpg

The FSM shows one labeled "B" and one blank showing the blank spot not used!

When I removed the pulley, I noted its location before removing, it had been installed on the blank key way. This is way off and would have caused fuel to be injected at the wrong time. In fact, I can't even believe it was able to run this way.

Decision time, just install the pulley back to the correct "AB" mark and time the belt properly? or go ahead with hours more work and install the spare calibrated pump? I chose to install the pulley correctly and see what happened.

It started right up, sounded 100% better and did not smoke at all!

I have also noted it runs cooler, leaves no fuel slick behind the boat, requires almost no use of the glow plugs to fire at any time. Over all it sounds much happier. The bottom line here is I was so close to this when doing the timing belt procedure and I never confirmed that pulley was in the right spot. Our boats have a lot of years under their belts and lots of owners ahead of us who may or may not have tinkered somewhere without proper knowledge.

I hope this can help someone else.

[hetek]

Great find!

I bet you found your "Ah ha!" Moment when you saw the two key ways.

Servicing the injectors, cleaning the fuel tank and having a spare injector pump now aren't exactly bad things either, although probably not what you would have wanted to go through.

[kerrye]

Pretty amazing find and surprising that a gear that crucial has multiple keyways. Is there a way to determine proper installation without removing the pulley? I know from my experience with Mercedes 80's diesel cars that an IP can be way out of time by being installed incorrectly but it will still run. My recollection is that a Mercedes pump that many degrees off will not allow the engine to reach full rpm's even though it runs.

[WillieC]

What a story! Good work and thanks for sharing. A wiser person has noted that sharing is caring. Very impressive.

[Beta Don]

The two key slots look like they're a long way apart, but the fact is they shift the pump timing by probably less than half a tooth on the belt. Not certain why they have the two choices, but I would guess maybe it has something to do with using the engine in a fixed RPM application like on a GenSet? If you don't need the variable speed for a boat or car, maybe optimum injector timing for a constant 1800 or 2400 RPM is a little different?

I put many, many miles on an old Datsun 240Z, (two different engines) which also has a 6 cylinder OHC engine made by Nissan. The 2.4 liter Z motor has a chain driven overhead camshaft and the chain is by necessity quite long. To make adjustments for the chain wear (wear a thousandth or two off every link of a chain with a hundred links and you have a measurable difference in length and therefore cam timing) and the head gasket thickness *or* the possibility that the head has been surfaced, both of which also affect cam timing, Nissan offered 3 different positions for the camshaft sprocket to adjust for such things. That sprocket didn't mount using a keyway like the LD28, but it had a pin in the camshaft with three different holes in the sprocket you could use to correct the cam timing depending on chain wear, headgasket thickness or how much your head has been decked when you had it rebuilt at the machine shop

If you've ever torn down an old American V8 and seen the sloppy cam chain (and that's a very short chain by comparison) and compared it to a new one when you reassembled everything, you can well understand why they gave adjustments for a cam chain over 3 feet long

I wonder what a shop manual for the Nissan diesel has to say about the two choices for the injector pump sprocket - How and why you choose one over the other

Don

[Hobbit]

Just doing some research and found your post. Thanks for the detail. Your pictures are invaluable.

I have the same boat and engine and spent some time getting intimate with water pumps and alternator this year. If you did all of this while the engine was still installed you have earned my deep respect.

My next project is the timing belt. Your description makes my task look easy by comparison.

Hobbit
1987 A27 FC I think hull #216
Nissan LD28
Hood Canal, Washington State