Boost Leak Test = 0psi But No Leaks???

[Spoolin96DSM]

Ok so my car was starting to spit/pop when going into boost, so I brought it in for a boost leak test and to check the spark plugs. Now we have boost leak tested the car before with no problems. However, this time when we tested it, the boost gauge did not read more than 0psi...Now we checked all couplings, pipes, BOV, boost controller, Intake manifold, throttle body, and exhaust manifold and such for cracks, holes, etc. and it they all rendered to be in perfect condition. Now when the air is pushed into the turbo you can hear/feel it coming out the exhaust.

We fixed the gaps on the plugs which proved to be the problem of the popping/spitting. So the car runs fine now and boosts to 23psi fine now, but when the boost leak tester was hooked up it wouldn't build any boost. I'm just curious as to why? And this seems like a problem to me and was just wondering what it might be. Thanks.

 

[Sam@RRE]

where do you have the guage tapped into? before the FPR solenoid or after?

 

[nfernotalon]

Mine did the exact same thing, although I cant help you very much on this one because I bought a new front mount and piping and it fixed the problem, i didnt get the front mount because of the leak but it was the problem.

It has to be the piping,intercooler, or a coupler.

 

[romeen]

Valve overlap. When you shut the car down before the test it just happened to stop where intake and exhaust valves were both open. Air went in the combustion chamber and right back out through the exhaust valves. Sounds like everything is fine.

If you want to be certain you can repeat the boost leak test with the motor spun to 30* ATDC and it should hold boost fine. Usually this is not necessary as more often than not the valves will not be overlapping when the motor is shut down.

Sputtering when getting into boost (motor under load) is pretty classic for a misfire most commonly caused by excessive plug gap.

 

[crimsondragon]

+1 on valve overlap. Use this for your BLT next time.

1. Disable your mbc.

2. Turn your motor to 30* ATDC to avoid valve overlap.

3. Start your test at the TB elbow and focus on area behind the TB first.

4. Spray soapy water at TB gasket, BISS, TB shaft on both sides, IM gasket, injector insulators, brake booster, afpr and all vacuum lines/connections.

5. Open your oil cap and listen for leaks. (PCV, valve seals/guide, rings)

5. Listen to your tailpipe for leaks. (EGR, valve overlap, jumped timing, bent/unseated valves)

6. Once all leaks are fixed, move the tester back to the turbo inlet.

7. Spray down the compressor cover (known leak), BOV return/flange (DO NOT TAP YOUR BOV LINE FOR YOUR MBC!!!), IC end tank/fins and all connections. Re- test.

8. Note that you will leak air into the crankcase through the turbo seal but do not panic, this is normal during a static pressure test as long as there are no shaft play.

The desired test result from the begining of the LICP (bypassing turbo) is around 20psi (on boost gauge) with the compressor set at 30psi, while taking no less than 30 seconds to bleed down to 0.

As a reference, my last test on my 500 mile new engine, I was able to pressurize the system to 25psi, bled down to about 16psi (my 1G bov) in about 30seconds, then took about 3 mins to 6psi and just kinda lingered there for a while. It's not easy to do but the point is it's possible. My next goal is 30psi After motor break in and Dodge modding my BOV. A boost leak test is one of most pita but important regular maintenace task, the key is patience and endurance