Turbo Boosting Gauge/Vac Leak

wcc · 07-03-2006, 11:05 AM

My '87 930 boosting gauge needle has been all over the map lately. It used to be right on .8 bar and lately it's been dropping down to .6bar and got as high as 1bar a few times. I believe that my 'Charging Pressure Sender' is going bad so I was planning on replacing it. So I was looking for it when I found this vac leak with a nipple broken off of it. It looks like it's been broken off before and someone along the way glued it back on.

First off what is the name of this part? I couldn't find it in my book.

Also, do you think this will fix my problem of my gauge being all over the place? I would think so. But what do you guys think..

Oh Haha · 07-04-2006, 05:03 AM

bumperoonie

wcc · 07-05-2006, 06:31 AM

Thanks Wayne for the bump!

How about a Post 4th of July Holiday Bump!

Anyone?

Sandman?
Craig?
Kurt?

Bueller?
Bueller?
Bueller?
Bueller?
Bueller?
Bueller?
Bueller?
Bueller?
Bueller?

sand_man · 07-05-2006, 10:22 AM

WCC - I think the stuff that powers the boost gauge is on the front of the BOV housing. It's the orangish/red looking rubber boot with a spring around it (to help seal it)...there's a sensor on it. The picture you have posted I believe is related to the air injection stuff. I have removed all the air injection switches-solenoids-hoses-pumps, etc on mine (including that thing you have pictured) and my boost gauge works fine. I'll post a picture tonight.

Best,
Jeff

sand_man · 10:31 AM

Here's an image from beepbeeps BOV housing rebuild thread. You can see the part I'm talking about...it's redish/orange.

sand_man · 07-05-2006, 10:31 AM

Of course I suppose it's possible with that open hose that you have pictured that the vaccum leak could be causing part of the problem. I'm not sure how reliable these boost gauge sending units are...

wcc · 07-05-2006, 10:33 AM

Ok, so it's probably my 'Charging Pressure Sending unit'. This makes sense cause I was still getting normal boosting with this vac disconnected. So I guess I won't worry about this vac line then. Should I just leave it hanging there, plug it, or remove it?

Here is what I was thinking it was.....
http://www.pelicanparts.com/cgi-bin/ksearch/PEL_search.cgi?command=show_part_page&please_wait=N&make=POR&model=911L&section=ELswch&page=1&bookmark=8&part_number=993-606-103-00-M100

sand_man · 07-05-2006, 10:36 AM

I'd hate for you to sink that kind of dough into a new sending unit only to find out that it's something else...maybe someone else can provide instructions on how to test it...BUMP!!!

wcc · 07-05-2006, 10:43 AM

Well I figured it's either that sending unit or my wastegate is going bad. Those are my guesses and that's all they are for now, guesses.

Sand_man - At least you shed some light on this thing for me.

If there is a way to test it, I'm all for it............

sand_man · 07-05-2006, 10:52 AM

I'll be honest with you - I'm sure someone will spank me for saying this - but I think an OEM waste gate that's never been serviced is a ticking time bomb! I have since discovered that the previous owner of my car installed a 1 BAR spring in mine...and the gate itself was in need of repair: pin holes, torn diaphram, etc! I'm now running a 46mm Tial with .8 BAR spring and couldn't be happier. I think my original engine might have lasted a little longer had the spring been left alone or had the faulty waste gate been replaced. Just food for thought. I think Supertec can rebuild the stock waste gate, but the Tials are sooo darn pretty!

wcc · 07-06-2006, 08:19 AM

Sand_man - Really? I've never heard that before. That Tial does look nice. Maybe I'll rebuild my wastegate this winter.

Plus does anyone know how to test the Pressure Sending Unit?

sand_man · 07-06-2006, 09:03 AM

Yep...I'm thinking the quickest way to "overboost" an engine (amongst other ways) is with a faulty/malfunctioning waste gate...or too heavey of a spring. The waste gate is critical for bleeding the pressure.

sand_man · 07-06-2006, 11:48 AM

WCC, do you have the factory workshop manual?

sand_man · 07-06-2006, 11:52 AM

I have the pages out of the factory workshop manual for testing this. I can send them to you via email (PDF files). PM me your email address.

JL

wcc · 07-06-2006, 12:07 PM

Sand_man - Sent you a PM.........

rooked 930 · 07-06-2006, 12:08 PM

Being newbie status, I hope I don't get flogged for suggesting this, but I had my guage (stock) doing a dance from .6 to 1 bar as well. It turned out that the pressure sensor (mounted under my Kokeln IC) depends on the grounding of the IC itself to function. I checked the bolts, found one loose, tightened it and all works OK. A ground strap has since been added instead of relying on that bolt.

Those Tials are very slick - my stock gate was rebuilt a couple of thousand miles ago and still functions ok. Is there a recommended store / fleabay to buy the Tial (in other words, the cheapest place)?

Cheers,

Rob
'79 930

wcc · 07-06-2006, 12:20 PM

Rob - That's my first inclination of being my problem. I'll look into a possible loose bolt/wire. I haven't torn into it yet because other projects are ahead of this one. But my plan as of now is check/replace the sending unit and now Sand_man has pretty much talked me into doing something with the wastegate. Either replace it or rebuild it. I haven't decided yet.

As you can see in the pic in my first post I have a vac line just sitting there. Is that a big deal to leave it unhooked? Is your's hooked up?

Where did you have your wastegate rebuilt? What did it run ya? I was going to check with that Supertec too.

sand_man · 07-06-2006, 01:09 PM

Bill...email sent!

sand_man · 07-06-2006, 01:11 PM

I got my Tial from Imagine Auto...he sells a ton of them for our cars/engines. I won't quote prices, because he offered me a deal due to all of the parts I purchased from him.

wcc · 07-07-2006, 11:22 AM

Thanks for the info Sand_man! According to that stuff you sent me I tested the Pressure Sender and it is faulty. So my next question is it ok to drive the car? I mean if I do a full boost my gauge isn't correct but am I overboosting the engine or is it still only delivering a .8bar boost even though the gauge says 1bar?

Also when I removed my intercooler I don't have two vac lines. One is capped. See pic. Is this ok/normal?