JLeake

Well I was running lean so suspected a vacuum leak. Sure enough the hose clamp on the MAF sensor was loose. Fixed that. Better, but still lean. So I fabricated an adapter and pressurized the intake to 15 psi. I've got a leak somewhere under the intake manifold, but I can't pinpoint it. I reached my hand deep under there, and the leak appears to be in the general vicinity of the base of the oil filler tube. Any ideas what it could be? I really don't feel like pulling the intake...but if I do can I leave the injectors and fuel rail intact? TIA for any help...I want to get the a/f right before I chip the car.

Danno

Yeah, you can leave the fuel-rail & injectors intact. Remove the four bolts holding the fuel-rail to the manifold. Then pull up on the rail, taking the injectors with it (might need to unravel ignition wires). Then strap it out of the way to the cruise-control actuator.

Rob

[quote] and the leak appears to be in the general vicinity of the base of the oil filler tube. <hr></blockquote>

Remember, when you pressurize your intake you are pressurizing some things that are not meant to see pressure, like your oil pan/crankcase and air-oil separator. You might be getting air from the oil filler cap o-ring, air-oil separator o-rings (by the block) the air oil separator cap o-ring (the cap is pressed/snapped onto the body of the air-oil separator and has a o-ring seal, this may leak under pressure but not under the normal vacuum), the air-oil separator elbow at the top, the thermo-switch connectors or thermo-switch potting to name a few. Since I don't like to pressure the crankcase and associated equipment, I disconnect the large hose that comes from the top of the air-oil separator and ties into the j-boot (it has about a 1/2 metal end on it) and plug the j-boot with something appropriate before applying pressure.

Good luck,
Rob

Peckster

How do you relieve fuel pressure from the system? Last time I removed the rail I pulled the fuse for the fuel sender (I think that was it) and ran the car until it stalled, but there was still lots of pressure left in the system. What is the fuel sender, anyway? The pump?

JLeake

This may sound like a stupid question, but what is the J boot? I just bought the 951 so am still learning about it.

Perry 951

[quote] You might be getting air from the oil filler cap o-ring, air-oil separator o-rings (by the block) the air oil separator cap o-ring (the cap is pressed/snapped onto the body of the air-oil separator and has a o-ring seal, this may leak under pressure but not under the normal vacuum), the air-oil separator elbow at the top, the thermo-switch connectors or thermo-switch potting to name a few. <hr></blockquote>

Ahh... most likely you will not add much pressure to the crankcase unless your rings are shot. Also, you should be using about 10psi to find the leak. Since I run 18+ psi boost, tell me how that 10psi is going to hurt anything. And to further debunk your analasys, during normal operation, your crankcase has pressure in it.

Alpine951

The J boot is the rubber boot that goes from the stock air flow meter to the turbocharger. Is is curved in the shape of a J.

Rob

[quote]Originally posted by perry951:
<strong>

Ahh... most likely you will not add much pressure to the crankcase unless your rings are shot. Also, you should be using about 10psi to find the leak. Since I run 18+ psi boost, tell me how that 10psi is going to hurt anything. And to further debunk your analasys, during normal operation, your crankcase has pressure in it.</strong><hr></blockquote>

If you pressurize your intake with the typical method of replacing the AFM with something to pressurize your intake, you are now pressurizing the j-boot. The j-boot does not normally see any pressure since it is on the inlet of the turbo. There is a large diameter hose that goes from the j-boot to the air/oil separator. Since the air oil separator is essentially just a large empty container that is tied into your crancase, you have now just pressurized you crankase with whatever value you are testing with. The line that goes from your air/oil separator to the J-boot is there to (normally) provide your typical positive crancase ventilation (PVC). In your typical car, a PCV valve functions as a check valve allowing only pressure to escape the crankcase (our cars don't have a PCV valve). Other, (Race cars typically) just vent the crancase to the atmosphere to releave any pressure. So if your crankcase see's any pressure normally, it would be relativaly small. Can the crancase handle 10-12 psi? Sure, I just personally don't like subjecting it (and the seals) to it.

Later,
Rob

JLeake

Ahh I see. That makes much sense. I'll have to try it again this weekend. Thanks for the words of wisdom. BTW the only reason I'm using 15 psi is that my pressure regulator doesn't do it's job very well below that.