From running like a raped Ape to no spark, 84 won't start

[Crude Rudy]

The other weekend the wife and I left the house to run a few errands on Sunday; Car started and ran great a usual, a 1/2 mile down the hill it just died, like someone thru the shut off switch.

So, being a good researcher of this forum, first thing I did was swap the DME with the spare one I kept on board.... nothing. Pulled and cleaned all fuses and relays too, no change.

Walked home and got the truck and tower her back and winched her up the driveway into the garage. Proceeded to read the Bentley manual and trouble shoot. I had proper fuel pressure and anyway I had recently replaced the original fuel pump just because. I had 12 Vdc at the coil so I checked for spark and sure enough, when I pulled a wire and stuck in a new plug and grounded the case to the engine, no spark. SO it's gotta be the coil right ???

Replaced the coil with a new one from Pelican and still no spark, WTF. The Bentley manual says next check is the crank position and speed sensors. Pulled the connectors and measured the resistance per the manual.

1 of the 2 has proper resistance between pin 1 and 2 of 1K ohm, the other two pins on connector 1 are open and s/b > 100 Kohms. The 2nd connector (sorry don’t recall which is speed and which is crank position) all contacts are open circuit, again WTF. Both sensors can't have gone bad at exactly the same time, could they? The wires to the sensors look fine and normal.

So I'm stuck and it looks like replacing the speed and crank position sensors is a pia without either pulling the lump or at least dropping the exhaust on the driver’s side.

Beside a rebuilt DME, or dropping the lump and replacing the sensors I don't know what else to try....

Does anyone in the South Bay PV/Torrance/Redondo have a spare DME I could swap and try (I know Wayne is close and maybe just a chance he might have a spare)

Really could use some advice from the forum so I can avoid a tow to Dutch Treat to have Rob sort it out.

Thanks ... Rich

[Joe Bob]

Is the DME relay clicking when the ignition is turned on? Or does it click repeatedly when cranking the engine? If either is happening you have a switched power issue.....

[j911brick]

Could very well still be the crank sensors. They have a strong history of failure. Its been my experience that they really can't be tested. I've seen many that tested good but didn't work in the real world.

[rusnak]

Check for a loose ground (find the dme grounds in the Bentley), or a loose starter or battery cable. Good time to clean them anyway. When the key is in "run", does the idle control valve hum? Check 12v at the coil?

[rusnak]

The sensors can be changed with the engine in, it's that grommet that is a pita.

If you have a known good sensor, plug it in and pulse the sensor against the rear fender while turning the motor over with a remote starter switch

[Crude Rudy]

Joe Bob,
I just checked, the DME relay only clicks once when the key is turned to on and does not click when cranking her

[Joe Bob]

Then your problem is down stream.....are you getting power to the coil? If not then check the connector under the triangular cover in the engine bay, driver side.

[rusnak]

I think the DME is not getting signal from the crankshaft position sensor. I think this is the lower of the two.

[livi]

..running like a raped ape..

I just keep learning so much good English phrases on PP.

[DRACO A5OG]

Originally Posted by Crude Rudy

Does anyone in the South Bay PV/Torrance/Redondo have a spare DME I could swap and try (I know Wayne is close and maybe just a chance he might have a spare)
Thanks ... Rich

Hey Rich,

I'm in SP, Western & Westmont, PM me your address & cell. You can try my DME.

From what you have wrote, it can be the Speed & Ref Sensors. No need to drop anything except the rear wheel. It;s tight but straight forward repair.

You can also buy BMW sensors, heck of allot cheaper.

Jim

[Crude Rudy]

Darco, as soon as I can figure out how to send a email I will shoot one off to you. Many thanks, my boat is in the San Pedro Marina behind Fisherman's Seafood in ports of call so I'm in SP all of the time.

I did check and had +12 Vdc at the coil but I replaced it any way, no change and the ICV was new last year also

[rick-l]

Sounds like 1 sensor is good the other bad. Open is >100k ohms

Originally Posted by Crude Rudy

1 of the 2 has proper resistance between pin 1 and 2 of 1K ohm, the other two pins on connector 1 are open and s/b > 100 Kohms. The 2nd connector (sorry don’t recall which is speed and which is crank position) all contacts are open circuit, again WTF. ... Rich

When you disconnected them did you mark them for which goes where? They are easily confused and won't work the wrong way.

[Crude Rudy]

I did make sure to keep the sensors/connectors separate and only disconnected them one at a time. So the "middle" connector shows open pin 1 to 2 when it s/b ~960 ohm so I guess this must be the bad sensor. Might as well replace both as long as I'm in there .....

If I can borrow a DME, and still no start, then it's got to be one or both of the position or speed sensors.

Funny, but I searched and could not find them listed for sale anywhere on Pelican, are they dealer parts?? Someone also said the BWM were the same and cheaper, are they the same part # as the 84 911?

Thanks .... Rich

[Joe Bob]

IF it's the DME, you can get it rebuilt. Ingo, 3.6@cox.net he's in Santa Barbara.....

[rusnak]

'84 - '88 Carrera cheap(er) DME speed and reference sensors available

You have to remove the left rear shock absorber, and glue a washer on the old sensor to get the right gap. Make sure the holder is clean. A drop of oil might help to install the new sensor.

[DRACO A5OG]

I'll show you which on is which.

And Yes, sometimes they both go out at the same time.

Jim

[rusnak]

If you have an old but still good sensor, plug it in and pulse it against a rear fender while cranking the engine. If it starts, then you need a new sensor.

[Crude Rudy]

So Jim/Draco was nice enough to stop by and lend me is DME to settle this problem. Jim is a great guy and very knowable about the mid-80's 911's. He pulled his DME in my driveway and we swapped it into my car with the same results ..... strong crank but no start, so it has to be one of the 2 reference sensors. By pulling the rear wheel and removing the shock in about 10 min I was able to remove both speed and crank position reference sensors. Jim also turned me on to a BM site where the replacement sensors, with the same connectors but cable ~ 1 inch longer were $56 each instead of $125. Parts are on order so hopefully I'll close this thread with the final solution and good news!

Thanks again to Jim for all of the help!

[wgirardot]

Originally Posted by livi

..running like a raped ape..

I just keep learning so much good English phrases on PP.

how about: "running like a scalded dog". that is another way to describe these beasts

[DRACO A5OG]

My Pleasure Brother!

Remember check to insure the new sensor's OD before installation.

Let me know if you need a hand :-)

Jim