4JH2E teardown report- 8000 hours

[Nineteen]

Hi
If you are going to 'spill time' an inline pump, you really need to remove the delivery check valve from the #1 cylinder pump fitting. It is the only way to keep the process both accurate and repeatable in my experience.
Cheers
Tom

[markxengineerin]

I went ahead and removed the valve and re-checked the timing. I was too "advanced" using the original (delivery valve still present) method. There is still something of a gray area with this procedure, as there are a few degrees of range between "fuel clearly streaming out" and "fuel totally blocked". I chose to use "fuel totally blocked" as my cutoff point, and am now within 1.5 degrees of the mark on the flywheel. This method results in a lot of spilled diesel, glad it's done now.

[skipperpete]

Nice work. There are a few tricks to doing tidy spill timing, customers and EPA don’t like engineers who drop litres of fuel oil in the bilges so we use a swan neck pipe on the delivery valve holder with a funnel below it that drains into a bottle. Also as you get better at spill timing there is a lot less overflow to worry about ( unless the pump timing is really lost and multiple attempts made) often less than a tablespoon full depending on the engine/pump type. Use a short piece of wire to locate the valve spring and button for reassembly.

[markxengineerin]

Yes, I can imagine spilling less if I needed to do it again. Like everything else, as soon as I'm good at it, the job is done ; ). Thanks for the tips

[markxengineerin]

Final notes here

[skipperpete]

Originally Posted by markxengineerin

Final notes here

Very well done and documented, sorry to hear that your first machinist turned out to be less than satisfactory but happy to hear that you finally found a good one. Have you had it running yet?

[markxengineerin]

Thanks, yes, it has run about 50 hours so far and all is well. About the original machine shop- I did not dig deeply enough into their google reviews or ask enough questions about their equipment- lesson learned there. Nasco Machine is a great choice for anyone local.

[kenbo]

Mark,

Great write-up.

Going back to the HX. You identified one of the two most significant issues with the JH series of engines, the aluminum HX core. What I've found that helps retard the corrosion of the end cap/core corrosion is not to assemble those parts dry. I slather every bit of metal with Tefgel, the bolts, the bronze end caps, and core facings. It helps a lot but it's no magic bullet.

The other issue is the choice of coolant and frequency of change. I've used with good success Shell Rotella ELC with distilled water and drain and refill every year. Yanmar heavily relies on coolant to prevent corrosion.

I've never figured out a place to add an anode. the only physical place is the bronze end cap and there's not enough depth for a pencil zinc of any size. I thought about brazing a cast bronze tee onto the end cap where the raw water enters the end cap from the oil cooler and fitting a pencil zinc on the bull of the tee. Never did it though.

A saturated solution of very hot, super-saturated citric acid will clean the tube stack better than muriatic with no/little loss of aluminum.

Yanmar JH series are fairly tolerant of high exhaust back pressure but you may want to measure yours. The reason is that a high-revving, 4-cylinder engine with a 2" wet exhaust is borderline. The bronze box mixing elbow that Yanmar designed for the JH series is a 3" wet exhaust. Few manufacturers use that mixing elbow because it raises the price of the engine and exhaust system considerably. Instead, they use a modified GM series cast iron mixing elbow at much reduced cost.