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
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
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 http://www.partsheaven.com. 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
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
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
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
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 -
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)...in 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 studs....it 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
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 problems...no need to run it through
other gears at stop lights etc. The key is proper shift linkage
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
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 back...as 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
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.
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
well....my fervent suggestion is that you START OVER at b. ....I have
never had any luck fiddling with the linkage.
Drive and be happy.
'75 911S with Kremer 3.2
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
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
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.