bnao

I have had problems with my 79 Turbo cutting off all of a sudden and then suddenly starting up. It runs fine in between. I posted a thread a few years ago about this and people talked of an Overboost switch and relay going bad. After 2 years in storage, it started right up but continues to have this problem. I am finally trying to get it running for this year. I have read threads talking about a yellow overboost relay. I have a 79 930Turbo and I see no yellow relay in the engine compartment. The service manual mentions an Air Flow Sensor/Charging Pressure Relay and when I look in the engine bay, it is Reddish in color. Is this what they are referring to but for the 79 Turbo? There is also a Charge Pressure Safety switch located on the Pop-off Valve housing. Is this the Overboost switch they are referring to. How do I test them.

Lastly, I have had a leak from an oil line that appears to go into the top of the turbo between the two turbine housings and appears to go to the front of the engine. I thought it went to the oil pressure switch housing in front. Can this be changed without pulling the engine. I don't like the fact that it is running down the line onto the top of the turbo. Hope to finally enjoy the car this year. Thanks for any advice.

Brian

Mark Houghton

You are correct in identifying the charge pressure safety switch and the relay. Diferent colors/designs for different years. The pressure switch can be tested by removing it and applying air pressure up to 1.4bar (I believe that's where it's supposted to open), thus interfering with the ground connection from the attached wire. Put an ohm meter on it and look for continuity. It should be normally closed.

Testing the relay....no known way. Pull the cover off and look any obvious carbon tracks or breaks in the circuit board pathways or poor/corroded solder joints. Clean, resolder if needed, and hope for the best. I did all of that and gave up with purchasing a new.

Your leaking oil line to the turbo sounds like what mine used to do. Mine wasn't real bad, but enough to **** me off. I just gooped some sort of oil and gas resistant glue around the crimp joint and it stopped leaking. Replacing it looks like a bugger (I looked at it when I last had my engine out and decided it looked like too much work for something that wasn't leaking anymore). You could "probably" do it with the engine in, but either way a bunch of stuff has to come off. Maybe someone else has some experience they can share.

x98boardwell

Brian,

First, I have an 87-930 and my overboost switch is yellow. If you provide your email I can send a picture for you... but for some reason I remember the 78 930's did not have this same relay. You may want to do a search either here or on pelicanparts in the turbo forum to try and see what your year switch looks like.

Regarding your leak, there should be a fitting shortly before the top of the turbo. I'm telling you this because the line your referring to is in two pieces. The first is the long one that runs under the intake and over to the front of the motor as you described above and ties into the case underneath the oil temperature switch. The other line is the short one that makes an "S" shape just before it attaches to the top of the turbo. If you look in the engine compartment you will see where these two meet up.

My thought is that your seal between that line and the turbo is going bad. You can purchase the top and the bottom seal for under $6 from Pelican Parts. This is most common leak and I have not heard of the other hard line leaking before. You can also get this line for around $100 but it is very difficult to install/remove without the engine out or the intake off. You may want to check the seals first.

Lastly, there should also be another small overboost switch with one wire attached to it that shuts off the fuel pumps if you reach too much boost. This may be going bad. If you ground that wire you will bypass the switch. I would only do this temporarily but at least it will help to see if that is your problem.

Best of luck,
Bryan

Mark Houghton

If it helps, here's a thread I started awhile back to help with identifying the relays in the engine compartment.
http://forums.pelicanparts.com/showthread.php?t=470389

The picture is typical of mid to late 80's 930's. Note the yellow relay. Your relay isn't the same color, but I'm thinking it should be in the same location. Also, it may have a wire leading from it to ground - whereas the later models didn't have that wire. Hope this helps.

JFairman

That turbo oil feed line could be leaking from where the rubber hose is crimped into the metal line or from the rubber hose if it's cracked and dry rotted, or where the rubber part of the hose is attached to the short metal S line just above the turbo with a compression fitting. Might just need the compression fitting tightened.
Other stuff will need to be removed to get to it.

Either of the small gaskets on the top and bottom of the turbo could be leaking too.

Sometimes the white plastic overboost sensor gets oversensitive with age and starts shutting off the fuel pumps around .9 bar
Thats what mine was doing so I got a new one and that never happens anymore.
Origonal new ones are special order from Germany and are around $60 new but you can get an adjustable hobbs switch for around half that.
http://www.alliedelec.com/Search/Pro...PN=76062-15-01

Mark Houghton

Just for kicks, I've had great luck with these nifty little fully adjustable dual function pressure switches (normally open and/or normally closed), and handle up to 15 or 100 psi, depending on the part number. They work great, and for the $18 price tag you can't beat them. The only drawback is that you have to plumb a pressure line to them. For the boost pressure switch, simply screw a nipple in place of the stock switch, attach a piece of vacuum hose, and route it to the switch. I use one in conjunction with a solenoid for my boost controller.
http://www.poweraire.com/pressure-sw...-c-29_214.html

bnao

Thanks for all the info. The following are a picture of the oil line. I think it is leaking at the crimp. Can this be crimped? The other picture is the relay that I believe is for the overboost. Any thoughts to why they switched to the yellow one? I believe the yellow one costs a lot more. Also, you may note that the wiring harness plug is held on by a cable tie. In my haste and ignorance, I cracked the housing to the side attached to the aluminum base. Any suggestions on how to replace the housing without mucking up all the wire locations. Again, thanks to all for your advice.

JFairman

If it's leaking at the crimp the hose has shrunk and dryrotted over the years from time and heat cycles..
You can either replace the whole oil line which is expensive or remove the crimped steel piece on each end and replace the rubber hose section and either have it recrimped at a hydraulic hose place or put a good hose clamp or two on each end.

Cut a slit in the crimp lengthwise very carefully without going too deep. Just cut through enough where you can see the cut is just going into the black rubber hose under the steel you are cutting away with the death wheel because there are barbs on the steel line inside the hose and you don't want to cut into those.

When you get to the end of the crimp you can't get at the last part to cut it. Stop there and stick a flat blade screwdriver into the slotted cut you made in the rest of the crimp and twist it. The last little part of the steel crimp you couldn't get to with the cut off wheel will break apart.
Now peel off the remains of the mangled steel crimp with needle nose pliers or whatever and you can pull the leaky hose off the barbed steel line.

Get a new hose and put it all back together with the best wide stainless steel hose clamps you can get. You can use 2 of them next to each other if you can only find narow ones.
You can even buy small T-bolt clamps that would be better and more reliable than wormgear hoseclamps.
Thats what I would do to save money on that line by fixing it myself.

You can buy better quality high temp/pressure oil line than Porsche used 30 years ago nowadays.

Mark Houghton

Yep, that's exactlly where mine used to leak from - and believe it or not I was able to goop enough sealer around to to stop. JFairman, good idea and instruction on how to fix without replacing the entire expensive line. I may just have to do that.

Mark Houghton

You have what looks like a standard fuel pump relay in place of the normal overboost relay. In the earlier cars that is a shortcut work-around to get the engine to run if/when the normal relay fails. Unfortuantely it won't work in my'87 (BTDT). I don't know why they changed relays over the years, probably somebody's idea of new and improved. If it's working for you, then you might just as well leave it alone. That's a $14 relay....replace it if it's suspect.

Did you recently crack the wiring plug....and could that be the cause of your car shutting down unexpectedly? Ignition instead of fuel related? Also, looking at your picutures it appears that at one time something shorted out and arced through the hole where the red wire goes into the aluminum housing. It may not be a bad idea to pull the housing, look beneath it for any signs of toasted wires, etc. I'll be doing the same thing here shortly, as I continue to look for a phantom that's shutting my pumps down (a new OB relay did not fix it). Thought I had it fixed, but just last night while checking control pressures the damn thing shut down a couple of times. I "think" I have a bad wire at the OB sensor.

bnao

It is very possible that the problem is in the harness. I have a new one but I am trying to figure a method of color coding them so they do not get mixed up/rearranged when I replace it. I was thinking of using marking pens and coloring the pins in sequence then cleaning it off afterwards. That fuse block is getting oxidized and I really should change that whole unit. I like JFairman's suggestion. Thanks.