puff of white smoke

[matuva]

We just finished repairing a 1995 truck.

We put in a long bloc, start ... and found it has to be resurfaced: Even though she does start and run fine, except she blows in coolant surge tank and harden the upper rad hose...
So, we took another short bloc, transplant heads, IP and all goodies from the previous engine and put the all thing back in the truck.

Truck did start fine, I cleared all codes and we do the IP timing almost easy, setting it at -1.41 TDC Offset.

The truck start and run fine, pushes fine too. The only which makes us a bit confused is that, at each start, cold or hot after it sat a little while, the truck starts fine but does some hiccups, exhausting puffs of white smoke smelling unburnt fuel.
After 1/2 a minute, she runs fine and no more white smoke... :???:

No codes

Any idea?

 

[NVW]

How are the injectors?

 

[matuva]

That's what we're wondering. Doing injector balance with GMTD Scantech show that may be injector 4 & 8 should be worn.

We though about them, but it seems they were working fine on the previous engine.

 

[NVW]

I thought injectors because it was the same warm or cold, that would rule out glows. Compression I assume is good.

 

[matuva]

We didn't check compression, I too assume it is good but can't sware...

 

[Burning oil]

Timming?

 

[matuva]

we tried different timing, from -.75 to -1.88, and finally let sit at -1.41.

Still the same

 

[WarWagon]

Engine is warm, GP's are not an issue. Air in the fuel system is the issue. Likely a sticking/leaking injector allowing air into the lines. Have them pop tested after the clear return line air test. Air clears up after the IP is able to purge it out.

Air entering the system from a air leak in the fuel line will also cause this hence the air test.

Optical filter harness also comes to mind.