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While driving the motor popped back through the exhaust with a poof sound and a puff of black smoke. After that turbo will only build to 25 pounds and it has roaring noise over around the turbo area. And still pops back through the exhaust but it is random. No check engine light. The motor runs good still pulls loads fine. Changed the fuel filters on it and found silicone chunks in the top of the primary filter. But it is still doing the same thing

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Jacobs, ?  Ok, somehow i dont recall Jacobs on an ASET. Well, can you check the valve adjustment to see if its in spec and look for a sticking rocker arm,?

And the motor seems to run great as long as you keep in under 20 pounds of boost no miss or hesitation in the take off but going from 20-25 pounds of boost you hear a roaring noise coming from under the hood and it won’t go to 30 pounds it stays right at 25. 

15 minutes ago, Joey Mack said:

Jacobs, ?  Ok, somehow i dont recall Jacobs on an ASET. Well, can you check the valve adjustment to see if it’s in spec and look for a sticking rocker arm,?

Yeah I can check that this weekend if the truck doesn’t get any worse and it makes it till then

I'm wondering if there's a fuel delivery/ignition issue?  Loading up fuel in one cylinder from poor atomization in a failing nozzle, or there's a hot spot on one piston that occasionally causes an untimely detonation.  Our 1979 endt676 had a slight miss when my dad bought it, wound up being a piece of silicone stuck in the piston cooling nozzle. But that was before I was born, so just anecdotal on my part... Just throwing out dumb ideas...

1 hour ago, JoeH said:

How are your oil seals on your turbo? Do you have oily soot in your exhaust or oil in your intake pipes?

The intake pipe is clean I am going to pull the exhaust side tonight and look at the fins. I had an old mechanic tell me the same thing he thinks that with the turbo not building enough boost fuel might be accumulating in the exhaust and detonating especially it being so intermittent. I have been running the truck for 8 hours so far today and it has only happened 4 times

Especially since it is just a straight turbo no vgt or watergate the only 2 reasons it won’t build boost is either the fins are bad on the exhaust side of the turbo or it has leak somewhere. I hooked a smoke machine to it last night and didn’t see any leaks. 

What chassis is this? Probably not an RD600, but the charge air coolers on RD's do tend to crack along the seams where the core mates to the tank. But this shouldn't yield the popping sound in your exhaust, just the low boost.  My '95 RD688 went down to 21 psi max til I noticed it had cracked.

Posted (edited)
4 hours ago, JoeH said:

You'd need to pressure test it, not just smoke test.

It is cv 713 yeah I am going to figure out how to pressure test it with the smoke.  But what ever happened yesterday happened all at one time I heard the pop and after that I had the boost problem.also when it pops you get puff of black smoke out the exhaust.  But also the primary filter is only half full of fuel isn’t that supposed to completely full all the time? I also have replaced the fuel lines from the tank to the filter and the filter to the pump. 

Edited by petehall12
36 minutes ago, petehall12 said:

It is cv 713 yeah I am going to figure out how to pressure test it with the smoke.  But what ever happened yesterday happened all at one time I heard the pop and after that I had the boost problem.also when it pops you get puff of black smoke out the exhaust.  But also the primary filter is only half full of fuel isn’t that supposed to completely full all the time? I also have replaced the fuel lines from the tank to the filter and the filter to the pump. 

Measure inside of the CAC rubber boots, if it's same as my '95 RD then two 4 inch pvc pipe caps should fit in there, one on inlet, one on outlet. Mount a tire valve stem on one and pressurize it.  Should hold up to 35psi with no leaks, but if there's a leak you'll hear it quick. 

Does this turbo have a waste gate? Your waste gate could be faulty, which would explain sudden black smoke and low boost.

7 minutes ago, JoeH said:

Measure inside of the CAC rubber boots, if it's same as my '95 RD then two 4 inch pvc pipe caps should fit in there, one on inlet, one on outlet. Mount a tire valve stem on one and pressurize it.  Should hold up to 35psi with no leaks, but if there's a leak you'll hear it quick. 

Does this turbo have a waste gate? Your waste gate could be faulty, which would explain sudden black smoke and low boost.

No I don’t have a wastegate

9 hours ago, petehall12 said:

Checked the exhaust side and rechecked the inlet side of the turbo tonight the fins look good and there is no oil around it

So check all the turbo boots and charge air boots for splits . also the air compressor hoses to and from the inlet on the lower manifold and at the compressor!

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