Check before starting an engine after rebuild

[IsaakOker]

Ok, so for those of you following along, I’ve had to rebuild a Yanmar 4jh2-te & and trying to get it started after sitting for years.

Anything I shouldn’t of should do before testing it?

I’ve primed the fuel till the injectors & have tried starting it but after 10-15 seconds and it about to start, quite some smoke comes out the mixing elbow.( suppose this is normal) but I just want to make sure I don’t over crank it without it starting…

I just fitted the impeller and no, the water supply isn’t on yet but I have it ready in case it starts.(also lubed the impeller veeeery thoroughly with silicone grease so I don’t damage it with the dry start).

Ideas and suggestions welcome! Bear in mind that I’m trying to do a quick 1min test before putting it in engine compartment do I don’t have the wiring harness on yet!

[Striker]

Keep the air filter off and have a block of wood ready to cover the intake in case the engine redlines on start up.

[markxengineerin]

When I first started mine, I cranked until I had oil pressure, before allowing any fuel flow. I recall it taking a lot of cranking, was glad I took that step.

After allowing fuel to flow, it started right away, I had bled all the air out using the vent on the fuel filter housing.

[IsaakOker]

To choke it?

I currently have the fuel coming from a bottle so I was thinking I could always just starve it…

Anyways, just checked my valve clearance and readjusted but it still won’t start so I think I’ll take the injectors out tomorrow and will give them a clean as that’s the only part I didn’t do 😅😴

[IsaakOker]

Hmm ok, I haven’t got any oil pressure dial conected…maybe I’ll have to wire it up although I wanted to test it before putting it in the compartment…

[markxengineerin]

Yes, I did not want it to fire before there was oil everywhere it should be, and it also helps to find leaks before it's really running, if there are any. I would run the real fuel system myself, as there's more chance for air to be in there with a temporary system. That's my guess as to what your problem is.

[markxengineerin]

https://www.youtube.com/watch?v=TKexFbQQcGQ

recent Utube with starting an engine which hasn't run a while- air in fuel system ; )

[IsaakOker]

Ok, I’ll watch the video later on but from what I can see, I have the return and the supply of diesel in the same container so I can see fuel returning when I push the butterfly pump handle so I suppose I’ve gotten all the air out…

[markxengineerin]

How do you plan to clean the injectors? I've done that on other diesel injectors by taking the nozzles off and using an ultrasonic cleaner, but it's something to be careful with if you haven't done it before. I've never done it for yanmar, just replaced mine with new and kept the old ones for backup.

[IsaakOker]

Ok, so a little update.

I decided not to pull the injectors just yet as I noticed only 1 & 4 had fuel sitting at the top and 2 & 3 are completely dry.

So, any ideas why this could be? Is the fuel injection pump a possibility? I wouldn’t have thought it’s bleeding air as the other two injectors get their dose of fuel so I suppose it’s something else.

Would be great to hear opinions and where to look 🙂

[IsaakOker]

Ok so when I loosen the injector pump nuts(where the high pressure pie connects, air bleeds and fuel comes out but when y retighten again no fuel pushing through so I’m going to take those apart and see if the plunger is blocked or stuck…

[Mickeyrouse]

I re-built my engine last summer. To put it mildly,it was, well, tight. So much so the starter (new) wouldn’t turn it over. I removed the glowplugs to relieve compression and eventually was able to rock it back and forth. After some time of that I used the starter to crank, still without glow plugs. After some time , checking to make sure the starter wasn’t getting too hot, I started cranking adding 1st, 2nd, and so on glow plugs. In my case I opened the raw water feed, so I left the mixing elbow unattached. It took a couple hours, but the engine finally fired up. I re-connected the mixing elbow and commenced break-in. It now has about 100 hrs SMOH and running fine, normal oil pressure, just slightly cooler than before the re-build.
However, it sounds like you’re padt where this would be meaningful for you. It also sounds like your injectors could stand a little attention. Things can sure gum up in a engine sitting that long.

[skipperpete]

Originally Posted by IsaakOker

Ok so when I loosen the injector pump nuts(where the high pressure pie connects, air bleeds and fuel comes out but when y retighten again no fuel pushing through so I’m going to take those apart and see if the plunger is blocked or stuck…

The only way to get fuel out of the 4 high pressure outlets on your inline injector pump is to spin the engine over with the starter motor, priming with the manual pump can only be done up to the plunger side of the delivery valves, but not past them. It takes a lot of pressure to lift em off their seats. IF there is fuel coming out at low pressure it means those valves are stuck open or damaged. No high pressure delivery probably( as you suggest) means a plunger is stuck, probably at full fuel and if this is the case, you’ve been very lucky it didnt start because to stop the engine the plungers need to be rotated to the no fuel position by the shutdown mechanism and this is impossible if a plunger is stuck. The easiest way to verify whether a plunger is stuck at the top of its stroke is to take the side plate off the injector pump (5or 6 screws) and manually rotate the engine to view the cam follower movement.
Be prepared to take action if your engine has an overspeed caused by the stuck plunger and rack, blocking off the air intake with suitably sized bit of 10mm plywood should stop it

[IsaakOker]

Ok, great!

I’ve just tried removing the side plate but the three bottom screws are slightly seized in so the Philips head is now round so I’ll think of some way to get them loose tomorrow as I’ve released the top three with a pair of vices…

Once open, I should see the springs move and the plunger too I suppose?

Also, should I not remove the delivery valve holder to be able to take the plunger out and check it?

What course of action would you take once the side plate is off?

And yes, as I said earlier, the fuel comes out of the high pressure fitting at the injection pump when I release just a bit the size 17 pipe thread(delivery valve holder) but when cranking it doesn’t even dribble…

Number 4(crank side) seems to work just fine and number 1 had to also work because the injector has a little puddle of fuel sitting on the top when I took it off but now at the injection pump it also doesn’t release any fuel 🤔

Anyways, I’ll update you all tomorrow as I’m in the US East Coast and it’s late here…

[skipperpete]

Yes, those screws are always tight and yes you will be able to see whats going on, the springs of the stuck plungers will remain compressed. Yes, if you release the delivery valve holder it will allow low pressure fuel to leak past the oring ....but you can’t get the plunger and barrel ( or either) out the top. In extreme circumstances ( like if this happened at say, Chagos) its possible to use a copper drift to tap the top of the plunger, sometimes they snap back down to the cam, sometimes not. Mostly its time to take off the pump and find a fuel injection tech to overhaul it. Be really careful and clean if you decide to remove the delivery valve holders... pay careful attention to the order of the parts as they come out..... and don’t forget the plywood if you free em up and try for a start!
Good luck, PeteJ.