Oil Pressure gauge

fogcity · 04-01-2003, 06:59 PM

Hello - Yet another question regarding my new to me '84 Carrera:
What's the best way to figure out why the oil pressure gauge doesn't work. The needle is stuck at the top and apparently never worked (at least for the 7 years the previous owner had it). The temp gauge rarely gets above half way (for what it's worth)

Thanks,
-Dylan

masraum · 04-01-2003, 07:16 PM

10 to 1 it's the sender. When my pressure sender went bad it pegged to the top. The sender is easy to replace, but can be frustrating. The secret is the tool to R&R the thing. On your '84 it'll be the same as my '88. You need a really bent 27mm open end wrench, but a 1 1/16 Craftsman crows foot fits perfectly

27mm is 1.063"
1 1/16 is 1.0625"

Since the tools have a little tolerance to them mine fit perfectly.

marcesq · marcesq's Garage

Pull the lead from the sender and see if the needle comes down. If it does test the wire from the guage to the sender for continuity. If the wire is good, sender is probably bad.

Hope the idiot light is functioning.

Good luck.

marcesq · marcesq's Garage

Steve just reminded me of something, you have to support the block that the sender screws into with a wrench, as you apply torque to the sender nut. I seem to remember a story or a picture of the block breaking off a chunk of the casing where it threads into the case because it was not supported.

CrossT · 04-01-2003, 07:31 PM

Yeah, as Marc says, check the sender connector. Mine [also] pegged at the top one day. I pulled the connector and saw it was with 'operating' with one strand of the wire remaining. I cut the wire and redid the connection within the sender and all is well now.

todd
=-=-=-=-=-
86 cpe

Early_S_Man · 08:21 PM

Dylan,

You can test the gauge and wire by pulling the wire off the sender and touch or jumper the wire to a convenient ground. If gauge and wire are OK, the gauge will read zero when grounded. You can do a further functional test by substituting a 1000 Ohm or 5000 Ohm potentiometer for the sender and sweep the range of the pot.

If the tests are not productive at getting the gauge off the high peg ... the wire may be fractured internally at the connector.

fogcity · 04-01-2003, 08:19 PM

That all sounds easy enough; thanks. One thing, though - what book(repair manual) do I need to tell me which is the sender, amoung other things? Which is the best one (for shade-tree mechanics)?
Thanks,
Dylan

marcesq · marcesq's Garage

Dylan:

I have pretty good pictures of the sender under the modifications section of the conversion home page.

old_skul · 04-01-2003, 09:22 PM

This is the sender. You'll also need the sealing ring.

I just bought one myself. My oil pressure gauge has been pegged for two years solid. It'll be weird to have it work again.

The best books are Wayne's 101 Projects for the Porsche 911 book, the Bentley manual for the Carrera (better than what a lot of people say IMHO), the Haynes manual (generally useless), and the Factory manuals, if you can afford 'em.

fogcity · 04-01-2003, 09:44 PM

Marc and Mark - thank you

Adelgigs · 04-01-2003, 11:44 PM

Guys,
Mine gauge the opposite problem - the needle doesn't get off the bottom. Every now and again it springs to life (with perfect pressure reading) for no apparent reason. I've pulled the wire off the sender with no change in status.

Any ideas ?

Thanks, Simon
www.adelgigs.com/911sc.htm

john walker's workshop · 04-02-2003, 07:24 AM

the sender is connected to the lower block pretty damn tight. i've seen cases broken, and thru fittings bent by trying to loosen it with a crowfoot. you might get lucky sometimes, but generally you have to remove the block and sender as a unit, and clamp the block in a vise. this means removing the A/C bracket, which, on a carrera, requires muffler removal too.