Porsche-O-Phile

I finally finished the turbocharger replacement on the 951 (whoo hoo!!!) I started it up, let it idle for a while - tightened up a few connections and finally felt it was good enough to road test. It drives well and my overvoltage problem seems fixed now courtesy of a new voltage regulator (I must say removing / installing an alternator on the n/a cars is MUCH easier than on the turbo cars!)

Problem is: still no boost. The turbo SOUNDS normal and I get a nice "whoosh" sound from it spooling, but the needle doesn't go over 1.05 bar (or thereabouts). I know I do have a couple of hoses that are less-than-perfect and I had to do some taping of some of them that were really dry / splitting for the time being, but I suspect it would take one helluva leak to reduce from 1.7 to 1 atmosphere. Any thoughts on what to check?

I also can't verify the operation of the turbo water pump - any idea how to jumper that or otherwise test it for normal operation? I NEED MY BOOST!!!

Just remembered this too: the RPMS seem to cut out at about 5,500 to 6,000, but I'll verify this (I didn't want to beat on it too badly my first time out). AFAIK the fuel vaccum lines are fine and I just resealed all the injectors / checked for leakage.

Cyrus951

It takes a little leak to lose a lot of boost.
Check your IC pipe connections, my IC to Turbo pipe used to be loose, and cause my no boost problems.

hosrom_951

And also make sure that the vacuum lines are connected right and DOUBLE/TRIPPLE check the boots for the IC pipe and TB.

Porsche-O-Phile

I'm pretty sure the IC boots are tight but I'll look at them again. There's a part of the J-boot that's torn and I suppose might be the culprit. There's a largeish air hose (about 1" O.D.) that goes from the J-boot to a metal connection on the apparatus under the intake manifold (air / oil separator?) The end at the metal connection is clamped, but the end in the J-boot is supposed to plug into a cylindrical protrusion off the J-boot that's part of it. This tore off (the J-boot is kind of old), however it has a metal "nozzle" end that I was able to jam in there. I suppose I can try siliconing it also to see if it helps with the seal. There is also another connection off the same apparatus that goes to the side of the supply intercooler pipe; this hose had split so I had to hack the split part off and tape / clamp the heck out of it for the time being. Could this do it? What the heck are all these hoses? I'll post some pictures after dinner and a well-deserved beer or five.

I suppose before anything else I should work on replacing all the rubber hoses; they're mostly all old and junky. I guess the Lindsey silicone replacements would be a good idea, eh? Could a couple of small leaks like that really affect boost that much? I think I should be getting at least SOMETHING.

NZ951

My LR hose split on two seperate instances! The walls on their hose are too weak, I think SFR do a hose which has thicker walls. What are you doing for boost control?

Porsche-O-Phile

AFAIK the car is 100% stock - the only thing that I've seen weird about it is the test pipe. Other than that, the parts seem completely out-of-the-book.

Rob

Have you checked to verify that the bypass valve is good?

Porsche-O-Phile

Yep, seems to be - I can't blow through it when it's in the closed position (i.e. no leakage) so I'm pretty sure it's okay.

Claus Groth

The turbo water pump will run when the temperature sensor plug is grounded. The connector is round and sticks up to the left of the throttle body and right in front of the #1 intake manifold tube. Pull it up and ground it in one corner of the TPS mounting bracket. No ignition key rewuired. The pump should run for 30 seconds or so. If it doesn't, first check fuse #7, then fuse #34 (I think). Report to us if it doesn't work and I can give additional troubleshooting info. Actually, report either way.

Ian Carr

if you have a tear in your j boot then air might be coming through there and not through your MAF which in turn could mean its not telling the system to give more boost? Most likly not but a small hole in the intercooler, also the vacum line off the bypass valve (although you say its intact) could be one problem... also your wastegate might be opening really early (get a 60$ boost controler from lindseyracing.com (MANUAL BOOST CONTROL REGULATOR
Code: LR-VBC-25
Price: $64.95 )????

good luck to ya man hope this helps a little

Ian

Porsche-O-Phile

Good advice; thanks for all the tips. I'll try checking all that tomorrow - along with some good heavy-duty silicone to seal up the troublesome areas that I know about. Suffice to say but it sounds like the boost problem is a relatively easy one to solve - it's got to be a leak somewhere - I simply don't know what else it could be. If it's the wastegate opening early I suppose I can do the "pull the vaccum line and carefully check it" thing.

AFA the water pump thanks also, I did check the fuse today just to make sure that was okay (it is #7 - 7.5A IIRC). I'll definitely do the grounding check and see if it runs. Maybe I just didn't run the car for long enough to get the coolant hot enough and get it to kick on.

At least I'm getting to the "troubleshooting / tuning" part of this repair and have at least a working car! It's such a relief to have everything back together!

special tool

Did you unplug the cycle valve during any of your repairs? Look under intake runner #4 and see if the 2 wires are connected to the round brown and tan solenoid. It defaults open.

Also, it is posible that you have triggered an error, which is easily readable from the diag. port with a multimeter. If there is an error, the cycle valve will stay open. There are error codes for a PARTIALLY connecetd tps and afm. Make sure your engine sensors are well connected.

Make sure there are absolutely no obstructions BEFORE the turbo, like a rag, rubber glove, chicken bone, feminine hygene product, etc.

Porsche-O-Phile

I know the connection you're talking about - two rectangular "spade type" connectors on top of a cylindrically shaped device under the intake - I was pretty sure that was the cycling valve but did not see the need to disconnect it. I'll check the contacts on it, but I think it's pretty good. I made ABSOLUTELY certain that the entire induction system was spotless before starting up (especially after last time). Oddly, I never did find the object (assuming it was an object) that caused the failure of the last turbo though. It's fender -> air filter box -> MAF sensor -> J-boot -> turbo -> turbo outlet pipe -> intercooler -> intercooler outlet pipe -> intake runner -> engine. I'm positive there's nothing blocking the induction system. I did "plug" the turbo impeller with a paper towel plug to make sure nothing got in there during installation, but I made sure to remove it. Ditto with the turbo outlet side and intake chambers. I'm pretty sure it's not a blockage, since the car runs.

Is there a way to test the cycling valve? Is there a procedure for reading the "easily readable" trouble codes from the diagnostic port that you could post or point me to - I'll check that.

Peckster

It just might be. Sounds like you need to go over all the rubber, top and bottom, where you cant see the cracks..

Porsche-O-Phile

Well. . . I know there are some problem areas with the rubber hoses and connections - the car IS fifteen years old and a lot of those hoses are quite brittle. It looks like one or two might have been recently replaced (they're a lot cleaner and more supple than the others) but what I'm asking is whether a couple of small air leaks here or there could account for losing ALL the boost or whether I should be suspicious of a bad wastegate or error in the system that controls wastegate position (i.e. something more insidious). I'm going down to do some experimenting now. . .