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Discussion Starter · #1 ·
Hey guys, I just finished swapping a 96 12v Cummins into my 01 f350 with a zf6 and can’t get it to build boost. The following things have been done: Wicked wheel and exhaust wheel in the turbo with a new waste gate actuator. Boost elbow screwed all the way in. Governor springs afc full forward and fuel plate cut. Also pump was just rebuilt. On first start up it was hazing pretty bad so I turned the fuel screw down some. I’m dumping a little cloud of black smoke when flooring it and making only 4 to maybe tops 6 psi of boost. I have no idea what the problem could be. Also I have 30psi of fuel pressure at idle at the pump. This thing should be making like 35 or more psi right??
 

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Boost leak somewhere?
 

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Discussion Starter · #3 ·
No obvious ones. Will a small boost leak like pin hole in a boost tube from welding cause this big of a loss?
 

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Any pin hole or holes will cause low pressure
 

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Discussion Starter · #5 ·
Any advice on the best way to check? I have a vac/pressure pump. Do I pull off from turbo and plug and then pull off inlet tube and pressurize from there back to see if intercooler and boost tubes are good or should I just go ahead and pull it all apart and test one by one?
 

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Hey guys, I just finished swapping a 96 12v Cummins into my 01 f350 with a zf6 and can’t get it to build boost. The following things have been done: Wicked wheel and exhaust wheel in the turbo with a new waste gate actuator. Boost elbow screwed all the way in. Governor springs afc full forward and fuel plate cut. Also pump was just rebuilt. On first start up it was hazing pretty bad so I turned the fuel screw down some. I’m dumping a little cloud of black smoke when flooring it and making only 4 to maybe tops 6 psi of boost. I have no idea what the problem could be. Also I have 30psi of fuel pressure at idle at the pump. This thing should be making like 35 or more psi right??
DUH because its a cummins not an eco-boost, that's the problem. Sorry not helpful and couldn't resist.

You're in the right place, low boost is usually a fuel delivery issue if there aren't any boost leaks. Have you checked all your charge air connections? Plug off the wastegate just to validate the turbo will spool.
 

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Most likely a boost leak. Pin holes matter! A pin hole from a bad weld could be more than a 10psi loss. Also, check your intake manifold gasket. Put some copper gasket spray on a it and torque it down. Probably the most commonly overlooked place for a boost leak. Get a boost leak test kit from power driven diesel.
 

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My choice to find leaks is a smoke generator.
 

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Discussion Starter · #10 ·
Today I rebuilt the one cold charge tube because of a weird angle going into the intercooler. Then I pumped 30 psi of pressure into the charge pipes while still connected to the intercooler. It held pressure. So I checked the intake gaskets, it’s brand new from having the plate and horn off. I tightened up the bolts just to be safe and still not getting much boost. It’ll smoke if you gun it and you can hear the whistle of the turbo but just not building boost. I’m not sure what else to check. I’m not a fan of the boots that came with intercooler piping kit. Kinda short and Iv broken a couple of the clamps already. Any other ideas?
 

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I’m dumping a little cloud of black smoke when flooring it and making only 4 to maybe tops 6 psi of boost. I have no idea what the problem could be.
I'm going with a fuel delivery issue. Maybe FSS not going up all the way?
With a large boost leak there'd be an awful lot of smoke.
 

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Discussion Starter · #13 ·
It’s a stock turbo with a new exhaust wheel because I didn’t realize lefty tighty. It has a wicked wheel and has been clocked. I also put a new wastegate actuator on it. Ensuring it was closed tight when I adjusted it. I double checked it’s working today. Holds 30 psi fully actuated. I’m going to try to reach up with a pair of pliers and make sure I got the snap ring seated back good. I made sure the wheel didn’t rub when I put it back together but I’m still going to double check. Also FSS? It does smoke quite a bit when you floor it. Not a freight train but a good bit. I also just bought some better boots and clamps from vibrant. I’m thinking maybe it’s leaking past those cheesy boots. It was tough getting those to seal while pressure testing the system.
 

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Discussion Starter · #14 ·
The waste gate gets its pressure ready from the afc housing. I tested from there when I tested the gate was working properly.
 

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re-tighten your exhaust bolts at every connection. You will get boost leaks at the manifold too.
 

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Discussion Starter · #16 ·
Well. I made the little tester that was linked. I found a massive leak on the back of the turbo where the snap ring rides. Fixed that and now it’ll hold 25psi through the snout of the turbo until the little tester explodes off. However I’m still not making more than 10psi of boost WOT in 3rd or 4th. She’s smoking still but I adjusted it a bit to see if it was being bogged down and so far Iv found nothing. I’m losing my mind at this point. Any other ideas?
 

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Is the wastegate functioning properly?
 

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Discussion Starter · #18 ·
I thought maybe it was being held open a little so this morning I disconnected it from the actuator and wired it shut and still no change. 10 psi max. Double checked for leaks again and still none.
 

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I'm going with a fuel delivery issue.
I haven't changed my mind.

We can now all agree it'll hold boost. I'm by no means a mechanic,
but the only thing missing could be fuel.

Unless of course the internals of the spinny thing are bound up.
Which is not entirely impossible I guess.
 

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I agree with Rubberfish. So long as the inducer / exducer spin freely on the common shaft, a fuel delivery issue is the likely culprit.
 
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