Boost Leak Question

[ska]

SR20DET Blacktop s13: I did a boost leak test from the turbo inlet to the pipe that goes into the throttle body. I had a major leak so I fixed that. Now this is where I lack knowledge of turbo cars...I read somewhere that you're suppose to check the whole system for a boost leak, as in from the turbo inlet all the way to the engine. Correct me if im wrong? and If so, when I pressurize the whole system at 8~psi, it only holds 2psi and I can start to smell fuel. I would guess that I have a boost leak somewhere around my fuel rail or injectors? Can anybody shine some light on a fellow 240 owner :-/

note: my car does not idle on its own unless I give it some gas, could this be my problem??

[army240]

Check your injector O-Rings... and yes, this could be your problem!!!

Frank

[curbhuggerrps13]

or vacuum lines

[ska]

ok I'll check for them. could someone explain something? when doing the boost leak test how is it that the pressurized air not going out of the exhaust? I don't get it lol..

[curbhuggerrps13]

the vacuum runs from throttle body to crankcase and not exhaust...excess boost pressure is transferred to the exhaust via waste gate.. had to add that so you dont get confused

[ska]

hey guys so I did the full system leak test and it still doesnt seem to hold pressure. I checked the O-rings and it seemed fine and all vacuums are hooked up. Is there anything else I should be checking? IACV? Intake gasket? I am still confused as to how the engine is suppose to hold boost. Ok so the pressurized air goes through the throttle bottle into the intake,pcv system, through the valves(?) and into the piston and wouldn't it exit through the exhaust valve therefore not hold pressure? I dont get it still lol

edit: problem solved, had to replace the throttle plate gasket. So now it holds pressure but it doesn't seem to be my idling problem.

[s14unimog]

the vacuum runs from throttle body to crankcase and not exhaust...excess boost pressure is transferred to the exhaust via waste gate.. had to add that so you dont get confused

He's asking why it doesn't go through a cylinder and out the exhaust. I have no idea what you're trying to explain here...

hey guys so I did the full system leak test and it still doesnt seem to hold pressure. I checked the O-rings and it seemed fine and all vacuums are hooked up. Is there anything else I should be checking? IACV? Intake gasket? I am still confused as to how the engine is suppose to hold boost. Ok so the pressurized air goes through the throttle bottle into the intake,pcv system, through the valves(?) and into the piston and wouldn't it exit through the exhaust valve therefore not hold pressure? I dont get it still lol

edit: problem solved, had to replace the throttle plate gasket. So now it holds pressure but it doesn't seem to be my idling problem.


Its b/c the engine operates in cycles, where either the exhaust valve is open and the intake is closed, vis-versa, or both closed. There isn't a position where both the intake valve and exhaust valve are both open; unless the cams have overlap. When you pressure test the charge system and engine, air goes everywhere. So effectively you can have leaks in ALL of those areas. I've always had a hard time getting the intake manifold to seal with a "thermal spacer". There are smoke testers to do this more acurately but I just squirt seams, areas under investigation, with soapy water. Just start from the turbo and inspect every seam until you get to the head. It's best to do a boost leak test while the engine is warm.