Need some help diagnosing a motor with low power. 2004 Fuso FG649

[aschafer14]

So I just purchased this FG649 with the 4D34T and am trying to figure out a low power issue. I know these aren't built for speed but sit feels really sluggish. There is a significant amount of blowby, the oil cap bounces right off with the oil cap test. I hooked up a boost gage and I'm maxing out at 11psi under full load. I did a compression test and leak down test and both seem fine (see results below).

I pulled the injectors and the pop off pressure is low so I'm wondering what some new injectors might do.

I also borescoped the cylinders and everything looked good except for #1 where there was some wear on the cylinder wall and some strange discoloration around one of the valves on cylinder #4.

I tested the pop off valve and it releases at 22-25psi and the wastegate actuator starts to open at about 15psi and fully open at 20psi.

I plan on sending some oil out to get tested but other than that I'm running out of ideas. Any help would be much appreciated. Has anyone replaced injectors and noticed a big improvement?

	#1	#2	#3	#4
Compression Single Burst (psi)	140	125	140	140
Compression Constant Cranking (psi) Spec 370psi, minimum 285psi	342	345	345	350
Leak Down % Lost @80psi	8	9	4	8
Injector Pop Off Pressure (psi) Spec 3130psi	2900	2900	2950	2700

 

[SkiFreak]

Maybe @Ausie-Iron will chime in on this one, as he is pretty familiar with this model.
If not, maybe you can send him a PM.

​

 

[aschafer14]

I sent him a PM but no response yet. I'll probably be ordering injectors on Monday just to see if it makes any difference. I hate throwing parts at it but not sure what else to do.

 

[aschafer14]

Well I got the new injectors and unfortunately didn't make much difference. I'm thinking I need to figure out why I'm not getting boost over 10psi. Does anyone else have a FG649 with a boost gage? What are your typical reading under full load.