No Turbo Boost Pressure
 

Turbo is working ,winning when engine rpm is increased but no pressure.I pluged the line that comes out of intake to swichover valve, put gauge on output of turbo that feeds wastegate input but very little pressure maybe 1 psi. If the egr valve was leaking some how could this be my trouble. Thanks

Stuck wastegate will do that.............................

When I blow through line that goes to wastegate air comes out bottom side of waste gate is this normal ?

The line going to the wastegate diaphram should hold pressure....but not the end going to the inlet turbine housing......or the diaphram is ruptured if it isn't..............anke certain the hose isn't ruptured or split..........But that will not cause it to not build boost....that actually stops it making boost at a certain level determined by the spring pressure.

It lifts the wastgate open efectively bypassing the exhaust turbine.

It sounds like that wastgate is not closing or its seat has craked or broken.

The spring tension should keep it closed where it does not vent into the exhaust if there was no pressure on the wastegate at all is this correct? If the egr valve was leaking somehow would this leak boost pressure. Thanks for the help.

Just to satisfy my curiosity, can you kindly explain exactly how you setup your boost gauge and whether you took the vehicle for a drive at high rpm's under load when checking the boost pressure.

It would be beneficial if you setup the boost gauge to tee into the line from the manifold to the overboost protection valve. You can run the gauge into the vehicle and monitor it while moving.

Exactly the wastegate spring holds the wastegate close therefore forcing all the exhaust to go through the turbine making bosst by spinning the turbo....the pressure line to the wastegate works to oppose that sping pressure............I.E. the sping might exert 12 lbs of pressure to hold it closed....when the boost excedes 12 psi it opens the wastegate droppping boost to 12 psi.

My understanding is the EGR rarely leaks but it might.......

How did you determine this? At idle or with a guage rigged into car on highway?

I rigged it up with the car in park and increased rpm to about 2000 I expected at least a 5 psi or so increase in pressure but I get just a very little deflection of the pressure gauge. I would have thought with everthing pluged it would be very high if everthing was working right and I would just remove pressure gauge from turbo nipple that feeds wastegate if pressure got out of hand over 15 psi.

Put a "T" fitting there and take it for a drive.......at 2,000 you aren't going to see much......and you really need to goose it good to see any boost in driveway.

What you have just described is inconclusive............they way you checked it.

You must take it for a drive and the rpm's must be above 3000 and you must be under maximum load. Then you can determine what full boost pressure actually will be.

The best way is to T into the manifold line from the back of the manifold to the overboost protection valve. If you get decent pressure here (above 8 psi) then reconnect the gauge and T it into the line from the overboost protection valve to the ALDA. Make sure you get the same reading, otherwise the valve needs a good cleaning.

Also, if the line from the banjo bolt (back of the manifold) had not been cleaned in awhile, you may not get any boost pressure, even if the turbo and wastegate is working properly.

Thanks for the help, One other question can you apply postive pressure to line that comes out of intake to switchover valve and plug nipple that feeds wastegate to see if the leak might be in the egr valve.

If the engine runs fine at idle, it is very unlikely that the EGR valve is stuck open. They normally fail in the closed position due to heavy carbon. The diaphragm fails and they cannot open.

I'd not worry about the EGR valve right now.

Brian, I was under the impression that the line comming out the back of the intake to the switchover valve was a safety device to vent the intake when the pressure switch on top of the intake closed due to more that 15 psi of pressure atcuating the switchover to atmosphere is this not right and I pluged this line to bypass the lines completly to eliminate any possible leaks in hoses.

You are exactly right.

But, follow the line that goes from the switchover valve over to the ALDA (on the top of the injection pump). This is what gives the engine more fuel when the turbo produces boost. Without this line, you have the boost but no fuel for it, so the vehicle doesn't go anywhere. You must leave this line intact, and it must be clean.
I'd like you to check this line for boost pressure, both before and after the switchover valve.

Removing and cleaning the banjo bolt on the back of the manifold would be a good idea in any case.

Brian , if I plug the line that goes to wastgate and put a pressure gauge on the line that feeds the switchover valve and rev engine up should I not get some pressure indication on the pressure gauge in park.