Yanmar RPM issue

[Jim Cate]

Have you verified the tacho's accuracy? That being agley could cause apparent low revs even when all was well.

But I'd have thought the mecho would have checked that out...

Good luck with an interesting problem.

Jim

[Toccata]

Checked the tacho twice (with separate instruments) unfortunately it is reading correctly.

[Toccata]

Just reading a few posts on removing the injector pump. It sounds seriously ugly. Lots of bits to remove before the pump can be withdrawn, and at least one impossible nut to loosen.
Of interest to anyone following this, there are several steps (involving special tools) to lock the crankshaft and lock the pump into position so there is no possibility of losing the timing relationships between the pump drive gears. (before the pump mounting nuts are undone)
After the rebuild.
The final check involves removing an inspection plug (on the injection pump), mounting a dial gauge on the injection pump and checking for max stroke travel. The pump housing can be rotated a few degrees to precisely time the pump stroke.
The engine will run without this step being carried out, but it's best practise to "get it right"

[Toccata]

The penultimate (I hope) post
Fuel pump removed and sent for testing
The Internal Fuel Regulator is faulty, allowing %30 less fuel flow than it's supposed to.
The consequence of this has been damage to the fuel pump as it relies on fuel for lubrication, and the cause of the low rpm. $3500 (Aus) repair. New pump $7000.
The Cold Start Device (wax based timing adjustment device) is being removed too.
I will post (hopefully) my last post on this issue when the pump is reinstalled and once again I can reach 3200rpm on my 4JH4-TE

[Compass790]

Originally Posted by Toccata

The penultimate (I hope) post
Fuel pump removed and sent for testing
The Internal Fuel Regulator is faulty, allowing %30 less fuel flow than it's supposed to.
The consequence of this has been damage to the fuel pump as it relies on fuel for lubrication, and the cause of the low rpm. $3500 (Aus) repair. New pump $7000.
The Cold Start Device (wax based timing adjustment device) is being removed too.
I will post (hopefully) my last post on this issue when the pump is reinstalled and once again I can reach 3200rpm on my 4JH4-TE

Ouch! If you haven't already sprung for the pump repair it may well be cheaper to buy a new one frm the USA if you know anyone there.
I've found USA yanmar price to be 1/2 NZ price & I think they pull out the big reamer in Aus too as both are Power Equipment.