2006BLKMegacab

I have a 3116 mechanical engine(98z serial # prefix) in an IT28G wheel loader, we bought it 3+ years ago with 15,250 hrs and it has 18,500 hours on it now. From the time we bought the loader it had a cold start issue, it would lose fuel pressure over several hours and we would have to manually prime the fuel system to get sufficient pressure for it to start easily and it would smoke for a few seconds upon startup but only when cold, we were told by finning to start with the little stuff and work our way through the diagnostic process in chasing the fuel prssure bleed issue. We changed the check valves on either side of the fuel pump, didn't fix it, changed the fuel pressure regulator valve post engine, still no change, changed the fuel pressure relief valve pre engine as a last resort and still no change. This is where the diagnostic part gets odd in my mind, sitting in a heated shop if I plug the loader in for 3 hours prior to initial startup each morning we DO NOT have to prime the fuel system, it starts like it was running 5 minutes ago. CAT says its injectors, cups and o rings and also wants to rebuild the valve train while they have it apart, at 1500/ hole plus core for injectors I would like to avoid that, as good as it starts when warm and doesnt smoke when working it I'm not convinced that injectors are needed, the cups and o rings would be my next step as well as bench testing the injectors.

thoughts???

Sorry its really long winded but its as short as I can make my diagnosis of the ole girl

1-5-3-6-2-4

Injector cups really suck to do on those engines. and if you don't do it exactly right. its a 100% waste of time and money. because you'll be starting again from scratch.

2006BLKMegacab

So would you reccomend the bench test injectors and change the o-rings while I'm in there or bite the bullet and have finning do the whole 9 yards?

pind

have you already removed the injectors?

2006BLKMegacab

nope, we're still using the loader on a daily basis so I was hoping to have a good idea how to proceed before I started

k.si.

May I ask, why the injector cups? Why is it only in the colder temps would the injector cups be a problem?

2006BLKMegacab

I was told that the injector cups were possibly part of the problem by Finning when i first started to diagnose what was going on, thats pretty much it......

1-5-3-6-2-4

are you getting fuel in the coolant? inspect the surge tank, smell for diesel? it'll float to the top. you might not see it but youll smell it.

NoSparkplugs

At 18,500hrs I think its just tired and due for a rebuild. I can't remember what style injection system is on those 3116s but I do know that injector cups are a pain. It could be at colder temps the cups are allowing fuel to bleed off into the cooling system and once its warm, they expand a bit and seal off thus holding pressure. Proper tooling is a MUST have to swap the cups out too.

Watch when installing the injectors too, we had one where the o-ring was nicked on installation and we couldn't find out why it was losing prime. Put dye in the fuel filter and voila! #6 had orange liquid (under the UV light and goggles) pouring out.

I did a few volvo wiggle wagons (D9B engines if I recall correctly) and getting the old cups out can be real fun... Even with the factory tooling. But you knew when they failed because the lovely clear water separator bowl had green diesel in it haha

2006BLKMegacab

So far no fuel in the coolant.

It is Cats Mechanical unit injection system and I dont know too much about it so any work that got done to it would be done by someone smarter than me haha

at this time i'm not ruling out that its just time for a rebuild either, just trying to avoid doing it if there is another solution

Hvytrkmech

I thought the 3116 had heui injection?

pind

Early 3116 had MUI, later ones had HEUI. Both, as you know, are nothing more than a pain in the butt.

The heui ones are actually easier to work on. Sad state of affairs.

2006BLKMegacab

Update: after a few tanks of fuel with what has been probably unhealthy levels of sea foam and lucas injector cleaners (seperate tanks not at the same time) it is starting better without priming the system, it still likes to be plugged in for 2 hours so it doesnt smoke like a chimney, its holding fuel pressure good enough that I've all but eliminated injector or cup issues.

I'm going to send in an oil sample when I change it next to see if there is any fuel dilution I need to worry about and re evaluate what to do with it then.