Various 911 tech tips
If you have a tech tip to submit, please send me e-mail and I'll add it here. Most of these were taken from the PorscheList mailing list.


[battery cutoff]
[break pads]
[cyl head temp sensor]
[engine removal]
[ignition cutoff]
[oil consumption]
[start failure]
[temp gauge]
[tranny (915)]
[windshield replacement]

Windshield replacement

Re: Michael Sherman's query on windshield replacement.

I replaced the windshield on my '87 Carrera in April. I had originally intended just to replace the seal because the old seal leaked badly. After looking into prices for new windshields I decided to go the whole way and have a nice, pit free screen through which to view the road ahead. I obtained four quotes from four different glass shops. The most expensive was $1200. I went with the lowest quote--$403 installed for a factory windshield. This was through Harding Glass in Omaha, NE. Don't know if they're a national chain. They claimed to have installed several 911 windshields for a local used Euro car dealer, which I verified with that dealer. I dropped off the car and four hours later had it back. It's German Sigla glass w/ integral antenna and tint strip. Cost broke down as follows: glass-$389.42; labor-$25.00; urethane kit-$13.91. The new seal was $55.00 from Stoddard. Unfortunately, my insurance didn't cover it, but it wasn't nearly as expensive as I thought it would be. BTW, the glass guys said that this is not something you'd want to try at home. They claim it's a real bear to get the new seal/glass back in the car w/out cracking it and takes 2 to 3 people to do.

Dave Andersen

Oil consumption

1. What should my engine oil consumption be?

Answer: a good rule of thumb is between 1-1/2 and 2 quarts (1.5 to 1.9 liters) every 600 miles (965 Km).

This varies with age and condition of engine. If consumption is greater, we recommend a full leak-down test.

2. In what range of oil pressure should my 911 run?

Answer: with a warmed-up engine running 175-200 degrees farenheit (79-93 degrees Celsius); pressure should be between 80-105 lbs (5.5 to 7.25 atmospheres) at 5000 rpm.

Thanks to Terry Morris
from the Automotion web site

Note: The 84-87 911 Carrera technical specifications handbook (factory publication) notes that the oil consumption should be approx. 1.5 litres for every 1000 km (1.59 quarts every 621 miles).

Battery cutoff switch

Call Pegasus racing @ 18006886946 for a battery cutoff switch with little rubber cap. You can place the switch in an unobtrusive spot and remove the key when parking the car. With the little rubber cap on it it looks very unlike a switch. Cost is about $50 with alternator protection.

Summit Racing @ 18002303030 has a battery disconnect at the battery for $15. Remove the knob and you have no battery. However, you might want to go with the one from Performance products 18004233173 because it will maintain your radio and clock when you remove the knob. Cost $20.

You can also install a small hidden cutoff switch somewhere in the car.

Revs and shifting

It sounds like a couple of our compatriots have dissimilar opinions, but my philosophy about engines (and things mechanical in general) is to avoid thrashing them whenever possible. An engine will unavoidably be subjected to higher working stresses when driven harder or spun up higher, so why do this unless you have need? If you're racing, or autox'ing or whatever, fine, and the 911 engine is certainly designed to be able to withstand more of this than the average engine, but in normal daily driving, It seems foolish to pound the snot out of it and redline it on every shift 'because it likes it'. Rebuild a 911 engine and see what a famous dent it puts in your pocket book and you get a different outlook on things... Don't get me wrong, I certainly go for the occasional excursion up past 5K, but not as a matter of course, and my 80 3.0 is perfectly happy pulling between 2K and 3K. I think you're really only into the 'lugging' scenario you describe when you ask the engine to pull hard below 2K; you can feel it vibrating and protesting, like when those bad drivers you know are too lazy to shift into first as they roll through stop signs. When I'm cruising along, I often ask myself if I really need the revs I'm pulling for passing or something, or could I just as easily go up a gear. As for the technical aspect of skipping 4th gear, there should be nothing wrong with this; the synchronizer's task is to mate speed between the gear teeth to allow them to mesh without clashing, and it has no idea what gear you've just been in. Run cooler, run longer...

Ian 80 SC Targa

Ignition cutoff switch

Pelican Parts has a technical article on installing a switch that will disable the coil. Might be worth a look:

Hope this helps,

Robert Herbert 1977 911S WideBody Coupe 1985 308 GTSi/QV

Carrera won't start

Here's a few of other useful 84-89 carrera tidbits that others sent me while going through my recent diagnosis.

No-start Diagnosis (84-89 Carrera)

1. Remove a spark plug wire and insert a test plug into the wire, place it next to the engine, have someone crank the engine and look for a spark (or remove one of the plugs and do the same). I didn't have a second person to crank the ignition, so I clamped vice grips on my key, ran a wire from the end of the vice grips through the door handle (with the door open). This allowed me to pull the wire and crank the ignition while standing at the back of the car looking at the spark. Crude, but it works. You could, of course, get a remote starting tool to achieve the same, and there are also special long coil wires available that allow you to see the spark while sitting in the driver's seat (just a long wire from the coil that has a spark plug socket on the end).

2. Remove the air cleaner cover and air filter, and spray some fuel into the intake. You will have to hold open the little "door" inside there with something. If it starts briefy then dies you probably have a fuel problem.

3. You can jumper a hot wire to the fuel pump and listen to it whir to prove that it's working. Run a short wire from the fuel pump fuse (#6) to an adjascent fuse (#5 or 7) at the bottom of the fuse terminal, the pump should whir. BTW my car didn't have the fuse info on the fuse cover (I think the old one broke), so Jim Bauman gave me his info from his '86 (#21 is closest to the front of the car):

        1. window winder, seat heater, sun roof
        2. booster fan, seat adjusters
        3. headlamp washers, electric cabriolet top
        4. clock, radio, interior lights
        5. locking system
        6. fuel pump
        7. brake light, cruise control
        8. electric mirror, heating control
        9. fresh air blower, cig lighter, rear window defrost
        10. wipers
        11. rear blinkers, back up light
        12. front left blinker
        13. front right blinker
        14. left high beam
        15. right high beam
        16. left dim
        17. right dim
        18. parking left
        19. parking right
        20. fog lamp switch, rear fog lamps
        21. foglights

4. If the fuel pump whirs (when jumpered), try starting the car this way (this overrides the DME control of the fuel pump). If it runs, it probably indicates some kind of DME problem (the DME is not sending power to the fuel pump). If still doesn't run, it's probably not a DME problem. Thanks to Jim Bauman for sharing this tip.

5. If it is a DME problem, replace the DME relay, which sends power to the fuel pump. This is another one of those parts that is known to be flaky. The relay is under the driver's seat next to the DME computer. It's highly recommended to carry a spare DME relay anyways (a $40 part), so go ahead and get an extra just in case.

6. If the relay doesn't fix it, it could be the DME computer itself, faulty sensors (flysheel speed and position), or faulty grounds. Try disconnecting the DME computer and cleaning the contacts.

7. Check all ground connections (brown wires) for corrosion. Disconnect them, clean them, and replace. Check especially the ground points in the engine tin. There's on on the manifold pipes, and another on the left side of the engine tin behind the fuel filter. There is apparently another one on the bottom of the car coming from the flywheel area.

8. Check all fuses for corrosion. Remove each fuse and replace. All DME-related fuses are up front, but there are three fuses under the plastic cover at the left rear side of the engine compartment.

9. If you have one available, swap in a known working DME computer from a 911 friend. Be careful that you have the right production year and part number because there are differences in the pin mappings.

10. If you need a new DME computer, parts heaven will trade your old one for a rebuilt unit for $650. You can find them at I have also heard of a source in Stanton CA, rebuilt DMEs for $550 with one year warranty (714-995-0081). Also, C&R Automotive Center in Los Angeles, CA sells rebuilt DMEs for $350 (not sure about warranties), you can reach them at 310-538-8605 or 310-538-8233.

11. If the DME is okay, you can listen to the injectors with a stethoscope, if they click, then power is getting to the injectors.

12. At this point you probably want to have a shop check the fuel pressure and flow rate in the system. This requires special tools. In my intermittent problem, this test unveiled a faulty fuel pressure regulator ($75 part).

13. Finally, Chuck H sent me some detailed info on the DME system. I didn't get this far (thankfully), but if you want to get down to the nitty gritty, here's the DME connections. Note that NTC stands for Negative Temp Coefficeint sender (meaning as temp goes up, resistance goes down).

        1  coil ground (1)
        2  micro switch (throttle, idle)
                closure to ground at idle position

        3  micro switch (throttle, wot + throttle valve) test connection b
                closure to ground at wot

        4  t54, starter active
                +12 volts while cranking engine

        5  gnd
        6  gnd, air flow sensor, ntc I
        7  air flow sensor +
        8  speed sensor +
                0.6 to 1.6 kohms between pins 8 and 27

        9  air flow sensor -
        10 plug for exhaust data (ground)
        11 t54, speedo
        12 test connection a
        13 ntc II
                1.4 to 3.6kohms at 70oF
        160 to 210ohms at 212oF

        14 t55, injector control signal
        15 t55, injector control signal
        16 gnd 
        17 gnd
        18 +12v
        19 gnd
        20 control signal, dme relay
        21 t54, goes to speedo
        22 air flow sensor, ntc I +
        23 .75ohm connection to pins 5, 25, 26, 8 & 27
        24 oxygen sensor
        25 ref mark sensor +
                0.6 to 1.6 kohms between pins 25 and 26
        26 ref mark sensor -
        27 speed sensor -
        28 altitude sensor
        29 a/c compressor clutch 'on'
        33 idle speed positioner +
        34 idle speed positioner -
        35 +12v

        pinout, looking at the DME connector, NOT the DME...

           | 35                            19 |
        +--+ - - - - - - - - - - - - - - - - -+--+
        | 18                                   1 |

Doug (87 Carrera Targa)

Shifting on a 915 tranny

Just finished getting my newly rebuilt transmission into the the correct condition....namely it shifts smoothly up/down, without any histrionics of any sort. Now, a few confessions are in order....before the advice at the end. Please humour this slightly demented Canuck.....

The original transmission was rebuilt by the PO and was the only component not restored in a complete rebuild of my car which spanned 12 years. The PO, in his wisdom, rebuilt the transmission and forgot a shim on the mainshaft....things eventually hammered against each other enough that another shim shattered....result was like a hand grenade went off inside the transmission. Ended up getting a new core transmission with 7:31 (off of a '74), added a Quaife limited slip (that Kremer 3,2 pumps out the ol' ponies) and all was well....sort of.

The C.O. reassembled the transmission/engine, put it in the car, had intermittent shifting problem (not going into first/reverse without grinding slightly) spite of umpteen linkage adjustments/clutch adjustments and significant taking of the Lord's Name in vain. Took the engine/transmission out, found out that the idiot who put it together the previous time had forgotten a lock washer on one of the retaining was jammed in there, caused a small misalignment between engine and transmission, which in turn caused the pilot bearing to spin the input shaft slightly even with the clutch disengaged. Problem fixed, with appropriate sobbing, hair pulling, gnashing of teeth etc, engine replaced and all was supposed to be well in Porscheland. NOT TRUE!!

The first gear/reverse grinding had gone, but things were still not smooth...not perfect, not the buttery smooth up/downshifts we all dream of. Again the C.O. was blamed, needed his head/arm/coordination examined. Linkage was appropriately played with, clutch clearance was checked, rechecked, rerechecked etc. No avail.

Finally in desperation the C.O. consulted the manual. Carefully went through all of the setup from the beginning.....and wonder of wonders. The wretched thing shifts like a dream, no grinding, no baulking, no fuss, no mess, no bother.

So for those who have trouble with type 915 transmissions and shifting, based on a broad statistical sample of 1....I conclude the following which is of no validity nor supportability. Given that the synchro's are in good shape and they are adjusted right....the suckers are not hard to shift at all. Yes they baulk on forced shifts....but that is what they are supposed to do. If you shift smoothly and crisply there are no need to run it through other gears at stop lights etc. The key is proper shift linkage adjustment.

So for those who are having problems, here is the "trick"

1. Check the bushings in your shift linkage. This includes the 2 at the coupler between the rear seats, the one under the housing which is in the hoop retained by the 2 smaller bolts on the shift housing and the cup at the bottom of the shift rod. Make sure they are in good shape, they are cheap and easy to replace.

2. Make sure that if you have a later housing, that the longitudinal pivot pin is nicely snug, not too loose. You can tell if you have this housing as it will have a lock nut on the front (visible when you peel back the rubber boot around the shift lever. Consider upgrading to the later (post '78) housing and factory short shift kit if you haven't already.

3. Make sure your clutch is adjusted right. It should engage about 1/4 to 1/3 up from the floor board (IMHO) and have about 20mm of free play, measured by pulling the clutch pedal there is a spring which is pressing it towards the floor board, hence the bit of tension.

4. Follow the factory shifter adjustment procedure. It is as follows:

a) Take off the cover between the rear seats which exposes the shift coupler. Pull up the shifter boot, particularly so you can see the lower part of the shifter lever where it bends from "angled back" to more vertical.

b) Loosen the retaining bolt which pinches the shift rod on to the spline on the shift coupler. Let it be very loose.

c) WITH THE TRANSMISSION IN NEUTRAL, rotate the shift coupler clockwise when viewed towards the front of the car. You should be able to feel the coupler rub against the various shift stops as you rotate it back and forth. Rotate it to the furthest clockwise position, as seen when you are facing forward. Don't pretend you are Tarzan and turn it with huge force....lightly is all that is necessary..

d) Keep your hand on it and hold it there. Don't let it wiggle, if it does, turn it back to the furthest clockwise position.

e) Move the shift lever so that the more vertical part of the lever is vertical (ie 90 degrees to the level...sticking straight up so to speak). Move it so that it lightly touches the side of the shifter housing which is on the 1st/2nd gear side.....closest to the driver. Again, gently.

f) They should now be properly aligned.....lever closest to the driver with bottom part vertical, coupler clockwise in the neutral plane.

g) Carefully tighten the pinch bolt. Make sure it is quite tight.

h) Check things out. You must be able to engage reverse clash free (give the gear a little bit of time to stop after you stomp on the clutch), shifting should get to all the gears easily when driving.....things don't work as smoothly when stopped and lastly, there must be a little bit of rotational play when 5th gear is selected. This is checked by shifting into 5th, and feeling whether you can wiggle the shift coupler with your hand. It should just click back and forth slightly...not much, but clearly discernable play.

i) Assuming all is well, put all the covers back. If it is not fervent suggestion is that you START OVER at b. ....I have never had any luck fiddling with the linkage.

Drive and be happy.

Dennis Kalma
'75 911S with Kremer 3.2

Break pads

Scott Galaba asked for a street pad recommendation for his 1987 911. I put OEM pads on my 86 Carrera (either Textar or Jurid, I forget which) and have been very pleased with them. They are quiet, don't produce a lot of dust, and stop good enough for me, even on the track. They also cost $42.00 total for all four corners from Don McGill Porsche in Houston (mention their ad in excellence and get a 20% discount). I couldn't justify more expensive pads given the stock nature of my car and my rookie status on the track.


Al Cabrera
86 Carrera

Temp guage readings

Beau wrote "Does anyone know what the degree numbers that are equivalent to the two bars on the guage in my 84 911 are?"

I looked at my 87 911. It took my flashlight, reading glasses and a magnifying glass but here's what I saw:

       Temp (C)     Bar               Location of gauge face
       ----------   ---------------   -------------------------
        150         Wide red          Top 
        120         Narrow white      First one below the red
         90         Narrow  white     Second one below the red
         60         Wide white        Bottom

Upgrading Cylinder Head Temperature Sensor

I recently upgraded my cylinder head temperature sensor as part of an intermittent diagnosis. It turns out that the sensor was okay, but it's one of those parts that is known to be flaky on the 911 carreras (1984-1989), so I'm glad I did it now to avoid problems in the future. Also, a reputable p-mechanic recommended upgrading the sensor to avoid being stranded in the future. Following is how I upgraded the sensor with no special tools.

-- Doug (87 Carrera Targa)

Upgrading Cylinder Head Temperature Sensor (84-89 Carrera)

The cylinder head temperature sensor measures the temp from clinder head #3 and sends it to the DME computer. The original part (911.606.405.00) got its ground from the cylinder head and had a single wire going to the DME. Apparently this method of providing ground is unreliable, so the updated part provides its ground from a second wire (964.606.405.00). Interestingly, on my car (87 Carrera), there already was a second ground wire in the car (two wires running to a 2-pin connector), even though the original sensor had only one wire (1-pin connector) and didn't use the ground. This was good news, because it meant that the upgrade didn't require any new wiring.

On the left side of the engine compartment towards the back, you'll see a bracket with three wire connectors on it, the top one is for the head temp sensor. If you try disconnecting the sensor while the car is running, you'll see that it does run but very roughly (and overly rich). I have heard some differing opinions on whether a faulty sensor could cause no-start conditions, but my car it definitely will not start with the sensor unplugged. It's easy to check if you have the upgraded (964-style) part in case you're wondering. If you disconnect the sensor at the bracket in the engine tin, you'll notice that the left side (wire to DME) has two wires going to a 2-pin connector. The right side (wire to sensor) has a 1-pin connector if it's the orginal part (911.606.405.00), or a 2-pin connector it's the upgraded part (964.606.405.00). The upgraded part also has a thicker wire going to the sensor because it's really two wires (additional one for ground) under the insulation instead of the single wire on the original part.

If you are diagnosing a no-start condition and have the original sensor, you might want to test the sensor's resistance to ground with an ohmmeter. Put the positive probe on the single pin in the connector coming from the sensor (the connector on the right which is fixed to the bracket) and the negative probe on a known good ground. If the sensor is working properly, it should read in the 1-2k ohms range. If it reads zero or infinity the sensor is probably bad. Interestingly, I can't seem to get a proper resistance reading from the new sensor, but it definitely works.

Okay, here's the procedure for upgrading the sensor without using any special tools. Jack up the car (rear) and secure it on jack stands, remove the left rear wheel. Inside the wheel well you'll see an oval-shaped grommet in the engine tin with a wire coming out, then the wire runs through another grommet up higher in the wheel well (along with two other wires). Remove the lower grommet by prying it out with a screwdriver. You'll see the head temp sensor in cyclinder head #3 inside the hole in the engine tin. Normally a special tool would be required to remove and replace the sensor (a slotted socket that fits over the wire), but it's not needed.

Instead, cut the wire off the old sensor (as close as possible to the sensor itself), then extract the old sensor with a deep socket. Thread the new sensor in by hand and tighten it with some needle nose pliers (it's a bitch to get in there but works). Now pry out the top grommet with a screwdriver (this was very difficult, I actually had to cut out my old one). Feed the new wire through the bracket inside the wheel well (you'll need to remove and replace the little bracket). You'll notice that there are two additional wires that run through the top grommet (back into the engine compartment) along with the head temp sensor wire. Fortunately, the new grommet is slotted so these extra wires slip in easy. Slip the two extra wires into the new grommet and feed the wire through the hole. Don't replace the grommet till you've installed the wire in the engine compartment.

You should be able to reach into the back of the engine compartment and grab the new sensor wire. You'll see that it runs around the manifold pipes and through a bracket in the middle of the engine. This bracket can be easily removed with a 4" socket extension and wrench to feed the new wire through. To install the new wire on the bracket at the left side of the engine compartment, you need to take apart the bracket. You'll notice that there are two little screws on the face of the bracket. Remove these screws and the bracket slides apart. It's easier to get at these screws if you uplug all three wires (be sure to label them appropriately). Slide the old plug out, the new one in, replace the cover of the bracket.

You should see two pins in the connector on the DME end (left side). The top pin is for the temp signal, and the bottom pin is for ground. You may want to check that you are in fact getting a proper ground by reading the bottom pin with an ohmmeter. You'll notice that the connector on the sensor end (right side in the bracket) now has two pins instead of the original single pin. To complete the job, don't forget to reinstall the top grommet in the wheel well. This part is difficult, so be prepared to let a few profanities fly ;-)

That's it, head temp sensor 101, for the DIY mechanic. Thanks to Darrin Sacks for explaining how to do this with no special tools.

Engine Removal

You can remove the engine with just a floor jack and some jack stands. It helps to have another jack as the engine/transmission combination can be tough to balance on just one jack. If you have never done it before, figure on it taking the better part of a day. Once you've done it once, it is fairly straightforward. Drain the oil from the tank and the engine. Disconnect the oil line from the tank to the engine. Disconnect the electric cables at the left side of the engine. Disconnect the throttle linkge and the fuel lines. Inside the car at the shift linkage inspection area in between the rear seats disconnect the shift linkage and the electrical connections. Disconnect the CV joints at the transmission and tie the half shafts up out of the way. Position the big jack at the engine/transmission joint and loosen the four bolts (two on the transmission mount and two on the engine mounts). Remove the engine mounting bolts first, and then the transmission mounting bolts and lower the unit out of the chassis. Once clear of the engine cavity, you may have to jack the chassis higher to get the engine out from under the car. Simple to write, a little harder to do; but, significantly easier than some cars to remove the engine/transmission

Headlight upgrades

You might want to add somthing about upgrading pre 87 cars headlamps. I have an 86 Targa and was quite unhappy with the factory lighting. I was able to upgrade to the Euro H4 which not only look a hell of a lot better but give off much better lighting. They were $220 for the pair from Vertex and $80 for the paintable trim rings. I had John Paterek (Paterek Bros) paint the trim rings and installed the lights myself. Very easy job.

Marc Gelefsky
86 911 Carrera Targa (50K Miles)

Michael Sherman <>