bound to happen, carrera no start, possibly speed sensor?
 

Hello all,

After 10 years of uneventful and blissful ownership, my 85 Carrera (107k miles) left me stranded for the first time at a red-light a few weeks ago with the dreaded "no start". It has been running fine for years. Got her home and did research here a lot. I am now suspecting the speed sensor, but unsure if that really will cause a no start/spark? here is what I've narrowed down:

Car turns over fine, not starting at all
Possibly a very little fuel smell after cranking but not really strong
No spark at a test spark plug, or off of coil wire to a ground.
New dme relay installed, feel it softly click once on start
ICV valve vibrates when ignition on
Fuel pump runs (I hear it) when fuse is jumpered at fusebox
12 volts gets to coil when ignition on
Can't see a pulse from coil though across posts with test light when starting
Tach is not moving when cranking

so unless I'm missing something based on research, I am suspecting reference/speed sensors are not letting spark/fuel happen.

Just checked resistance across bottom two posts of the reference/speed plugs in engine bay. Reference sensor I get 1k ohms (bottom I think), speed sensor (middle) I get no resistance at all. And the rubber around the plugs started crumbling when I unplugged them, imagine from old age and heat, obviously making me suspicious (pic below). Question: does a bad speed sensor stop any spark/fuel like a reference sensor (which reads ok I think)? am I missing something else to check before I make an order?

http://forums.pelicanparts.com/uploa...1426636858.jpg

gratuitous pic
http://forums.pelicanparts.com/uploa...1426638921.jpg

Search here for cracked solder joints on the DME, it's an easy visual check once you open the DME...

The solder going to the coil transistors that are up off the board are under vibration and crack after time.

Chuck.H
'89 TurboLookTarga, 392k miles

DME relay is an easy swap and you should be carrying a spare anyway. It can be fixed by resoldering if your handy. Lots of info on the interweb.

Speed sensors are a PIA to change.

Turn the factory alarm off and on a few times. That solved my no-start issue.

It may not work for you, but it is easy and free.

To test the DME, find a 3.2 Pelican and ask if you can test your DME in their car. If it starts then it may be the sensors, replace both. Note do not not put their DME in your car.

BTW, she is a Beauty :D

I would recommend changing the sensors if they have never been replaced. They got me twice in the past, one at a time. The first time, I wasn't too far from home when the car started revving wildly. I turned around to go back but the engine quit shortly after. I coasted into a gas station and changed out the dme relay but no go. I had the car towed back home and started troubleshooting. One of the ref sensors didn't check out and there was no spark. The car fired right up after replacing the sensor. The second time, the car just didn't start at all. No tow needed that time as I was at home. Replaced the second sensor and all has been ok since.

If you are getting different ohm readings on the speed/reference sensors, then one is bad. My 84 died at the track with the exact same symptoms: no spark. I changed both sensors when I got home and she fired up 1st try.

It is a fiddly repair, as working position is awful, but easily doable at home. I also changed CHT sensor while I was in there.

I believe I have a spare speed/crank sensor if you want to try swapping it out.
Let me know.

Yes, DME relay first, but don't be surprised if a brand new one also doesn't work.

Shoddy workmanship abounds!

I just changed my oxygen, speed, ref, and CHT sensors. Did this mainly because of age, while I am also chasing the cause of an occasional temporary no-start problem/stall problem when the motor is warm. DME relay is next.

As others have noted, the last three sensors are a bit awkward to replace and take some time. For the ref and speed sensors, it is easiest if you just remove the whole bracket with the old sensors in it, though this means you will have to gap the new sensors properly (see below).

The crucial step is to leave the cylinder/flywheel ends of the old sensor wires dangling by the flywheel so you can use those old wires to pull the new sensor wires through the engine bay and up to where the sensors plug into the connectors for the wires that feed the information to the DME. Another important step is to gap the sensors properly, which can be done easily by cleaning off your old sensors and gluing a 0.8 mm washer to the end; then slip that old sensor back in your bracket, position the bracket so that sensor, with washer, is up against the flywheel teeth; tighten down the bracket; remove the old sensor and insert you new sensors, and then pull the plug ends of those new sensors up through the engine bay.

Good luck and please don't hesitate to send any specific questions you may have as my memory is very fresh on this job.

Jonathan

OP and 89PS911 - to easily check for cracked solder joints, you can also try this test; unbolt the DME and shake it slightly, this should cause/fix your no-start issue, even if temporarily...

Hope this helps,
Chuck.H
'89 TurboLookTarga, 392k miles

Thanks to everyone for the info so far.
I will check on the DME solder joints this weekend. Thanks Chuck.H for the shake test idea
It sounds like I should replace the speed/ref sensors, they are original and now the rubber around the plug is crumbling! Targa Me I definitely appreciate the offer to swap, but all things considered I think I will bite the $ and time bullet and order and replace both, just to be sure. It is evidently a pain to replace them, and 89PS911 appreciate the tips. Maybe while i'm in there i'll do the CHT sensor and get all three.
I never thought of the factory alarm being an issue, but I don't think mine is hooked up though will need to look.
I also never thought about a new DME relay possibly being bad! I do feel a soft click, would be a real shame to go through all of the sensors and that be it. :rolleyes:

ouch.
these sensors are very expensive.
assume I need two of these for both speed and reference: 911-606-215-01-M14
I read an older post that a bmw sensor is the same but cheaper. 12-14-1-708-619-M14
is that true and has anyone use the BMW one? the BMW part sold here is half as expensive. sorry if this question offends the host.

The BMW part is the same but with a slightly longer wire.

The DME relay is easier to swap and I would start there. The URO made ones have been known to be bad out of the box.

Search the Bosch part number for the speed sensors. They can be had for about $60 each. I just bought 2...

bosch 0261210002

Do you mean, rubber band the old sensor head to the new sensor wire plug?
Then pull on the old sensor cable from above to fish up the new sensor wire plug?

I used the BMW parts when I swapped my sensors, have worked perfect for last couple yrs

If you're thinking of pulling the sensors, I'd hit them with some penetrating oil and let them soak. Mine pulled out like a mofo and I had my engine out when I replaced them. If you can salvage one of the original I believe you glue a washer to the bottom and set your gap with it, then pull the old one and install the new ones.

BTW, I'm also running with the BMW sensors.

thanks all very much, I will try the bmw sensors

Same here - I should have just changed the sensors right off - after all the car is over 25 years old, instead I went ahead and did the DME inspection and walked down a few other dead-ends first.

just ordered 2 bmw sensors and a coil from the host. It may take a few weeks to get the time to install them, but I will circle back and let you guys know how it is going.

You didn't order the silver Brazilian coil, did you?

Wow, very timely...been running into same issue on my '88. However in my case the "no start" would happen after a 30 minute drive where I let the car sit for a few minutes then tried to restart. It would turn over fine but never fire. I took the relay out and noticed a broken/missing chunk of solder and ordered a new one from Pelican (KAE). BTW, I popped in the old "working" relay I kept in the glove box and car fired up. Then installed new relay but had same issue, car would (on occasion) not re start after 30-40 minute drive. I shook the relay and it fired right up...so assumed the new relay was buggy out of the box, which seemed really unlikely. Pelican promptly sent me a replacement and SO FAR has worked but I'm still suspicious. Tested the RPM/Reference sensors but I did it at the DME connection itself, both tested perfect and are the BMW versions installed during rebuild 2 years ago. Question to OP...did you car die at the red light? In my case the car runs perfectly while its running...only had issues on restarts. What confuses me is what to test on the relay if it happens again.

Hi Sugarwood,

On the flywheel/cylinder end, I left the old wires dangling there poking through the hole leading into the engine bay (where the big rubber grommet fits), but cut off the sensor heads. I then just, one-by-one, tied the old wire ends around the plug side of the new sensor wires and then, as you say, fished them up through the engine bay to where the plug connectors are. That worked very well, and I am sure rubberbanding them would be even better so that wires don't separate from each other somewhere inconvenient in the engine bay.

Jonathan

Twice in nine years my car wouldn't start, the first in 07 the second in 2013.
On both occasions it was the speed and reference sensors, replace both not one at a time like me.

Nine years of ownership that is had the car since 06.

oh not sure, I ordered this bosch from the host. it has a silver body and red top. did I make a mistake?

944-602-115-00-M14

yes 88911coupe, mine died while I was sitting at a red light.

Just to confirm - it's the same part for both speed and reference sensors... correct?

Yes, same part for both sensors. They can be a BI*CH to replace. Mine were corroded into the brackey so I had to remove the bracket requiring a regap which is easy. If you have to remove the bracket you wll need to take a corect diamete washer that you make into the correct thickness. Use a removable glue to glue the washer to the sensor, install the bracket and the gap is correct. My old sensors were destroyed in the removal process so i used the new sensors to set the gap. Its an akward place to get to and work on but be patient and don't get frustrated.

I used 2 of the BMW sensors form my local BMW dealership at $60.00 each. They are well aware of the issues with these sensors which either work or don't, no in between. The wire is about 8-10" longer so be sure to tie up the extra on the ENGINE side of the shroud.

Good news is this will correct things and you will be back in business.

Ok, some progress. I won't receive my new sensors till mid this week, but went ahead and wanted to try and get the old ones off the engine. After lots of awkward positioning, pb plaster, wiggling, cajoling, more pb blaster with some choice words, I was able to loosen and remove the two sensors without removing the bracket!!Definitely not easy, but the pb blaster was the trick. I will stop here until next weekend when I have the new sensors, I was satisfied today to get this far. :D

http://forums.pelicanparts.com/uploa...1427054664.jpg

No mistake on your part; you probably just joined the wasted money club. These particular Brazilian made coils have a poor rep for durability. Don't throw your old coil away yet.

Hi there, why new coil?

oh great, thanks for the warning, I should have researched the good/bad coils more. with all of the noise on shoddy DME relays and other components, I guess buyer beware.

I only bought a coil because I could not verify mine was good in the current situation, and with being 30 years old, well It is suspect. I will definitely save my current one as backup/original.

Can you measure the resistance on both your newly ordered coil and the old one when you have them both? just to see if there is a difference. The Bentley's got good instructions and datatables. Also, Can you start off by changing the sensors first? If I were you I would only change the sensors, and if they fix you problem, not swapping the coil if you do not have any starting issues...

yes lars i will replace sensors first since I've already pulled them out and try with old coil. I will also measure coil resistance of both. will be this weekend earliest

News alert
 

I literally just replaced both sensors, and it FIRED RIGHT UP! I did not replace the coil, I will either return it or keep it as a spare.

I am stoked, appreciate everyone's help here!!!! Pelicans are the best :D

Fantastic!!
6 years ago when this happened to me, nobody on the forums were pointing toward the sensors as a problem area. As a result, I spent months doing all of those other suggested fixes before finding the problem. Glad it worked out for you.

Did you happen to measure the resistance at the harness connectors in the engine compartment with the bad sensors? Would be interesting to see what those readings were vs the readings on the two new sensors. Maybe higher resistance levels could be a clue that sensors are going bad...

From his first post
The later is definitely an indication of a sensor going bad :)