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(Changed to) Which coil should I get? '87 911

 
Old 05-29-2011, 02:35 PM
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Carrera3.2LG50
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Question (Changed to) Which coil should I get? '87 911

For the first time in 18 months, my venetian blue baby has let me down.
I'm trying to diagnose the dreaded "no start" problem.
(At least she chose not to start in my garage.)

I've already read many many posts on this and I've been following the Bentley as well, so I'm not asking what to check. I already have various lists and items I'm going through.

My problem is with the understanding of how to check each item. I'm somewhat over my head, but I'm slowly learning as I go.

I'm at the point where I did the spark plug test and it appears I have no spark. Now I need to test the voltage and resistance on the coil.

The coil has a black plastic "protective cap" on top of it.
How does that come off? Do I first have to remove the coil from the bracket and then take the cap off? The cap does not appear to simply lift off.

It might be a silly question, but knowing-thy-self, I figured I'd better ask before I break something...

Thanks.

Last edited by Carrera3.2LG50; 06-03-2011 at 11:33 AM.
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Old 05-29-2011, 03:46 PM
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The coil cap clamps together on the side that the coil wire and Power/Ground wires enter.

I pull gently below the power/ground wires to separate it and then lift if off. It is a little tricky but not bad. You an even use a small screwdriver to assist in the separation. Slide it between the two halves and then gently twist. No other sides will separate. When separation occurs, then keep the halves pulled apart while you lift it over the top.

You don't need to remove the coil.

BTW, have you tried replacing the DME relay?
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Old 05-29-2011, 04:53 PM
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Thanks Scott.
I didn't want to break the cap.

Yeah, first thing I did was replace the DME relay. Still no start.
I can smell fuel every time I try to start it, so I assume I'm getting fuel to the cylinders.
Battery is always on a smart charger and checked out OK.
I did the 'spark plug with grounded lead' test and I didn't get a spark.
Checked the Dist Cap and Rotor. Looks OK to me. New last year.
Next up is the coil although that was new last year as well.
Ignition switch? DME failure?

I'm trying to run through the logical steps from the many "No start" posts I've found on both RL and PP.
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Old 05-29-2011, 05:29 PM
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Does the icv hum w key in the run pos? The dme relay should click twice, second time while cranking.

You might clean and check grounds. If the dme relay does not click the second time, then the ref sensor is not sending pulses to the dme.
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Old 05-29-2011, 10:43 PM
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Ed Hughes
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Grounds, especially the bundle to the manifold, and sensor connections on the LH side are often culprits.
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Old 05-30-2011, 06:13 PM
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Thanks guys... I appreciate the input - I've been searching many posts on "no start". My intention was not to revisit all that here, but I appreciate the help.

Got my coil protective cap off. Duh. That was easy. Thanks again Scott.

1. DME relay clicks on ignition. Clicks again when cranking.
2. ICV does hum on ignition.
3. Cleaned the ground in the trunk. Need to clean the others.
4. Tested the coil per Bentley instructions. Getting 12.46v when ignition on and the resistance test is in spec. (Coil is one year old.)
5. Eyeballed dist cap and rotor. Slight burn marks, but nothing unexpected due to the arcing of the spark. (Dist cap and rotor also one year old.)
6. I can smell fuel when cranking, but I have not yet fully tested the injectors.
7. Did the spark plug test and I am getting NO spark.
8. I have also not yet tested the crank sensors.

I may need to revisit this at a later time due to work and an upcoming vacation.

Next things I need to check:

a. Fuel pump to be sure it's coming on.
b. Fuel injectors.
c. Reference sensors.
d. I'll also do some testing on the pins on the DME based on some posts I saw from both RL and PP.

I am going to think of this as a learning experience...
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Old 05-31-2011, 11:05 AM
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If its not getting spark forget the other stuff with fuel . that aint it .. i have a pretty simple question actually .. ( I actually think you may find it is a reference sensor . it wont fire spark without the sensor. I think Loren would be outstanding help here this is his domain ) . But my simple question is this ... when you crank it is the distributor turning ?
oh your one year old coil .. doesnt happen to be a silver bosch one does it made in Brazil ?
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Old 05-31-2011, 02:14 PM
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Iceman,

I'm at work right now... I'll check later.
My shop replaced the coil, so I'll have to check the source and where it was made.

I did find some posts from loren and others both here and on PP that were very helpful. I'm going through this very slowly so I can understand what I'm checking, why I'm checking it, and what the results mean. I am learning a lot with this experience - still sucks that my car won't run, but it's a toy, not my DD.

So how can I tell if the Distributor is turning?

Thanks,
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Old 05-31-2011, 02:51 PM
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The second click while cranking "should" indicate that the reference sensor is sending signal to the dme. I wonder if you just have a bad dme relay? Could be a bad dme brain too.
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Old 05-31-2011, 06:14 PM
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Acutally, the distributor question is a good chance to remind people to check distributor bushing wear. Grab the rotor center shaft and check for radial play. If there is any, then time to take the distributor in for new bushings. The rotor can hit the cap and get destroyed. To see it turn, just remove the cap and turn the engine over via the fan pulley.

I would probably press on with all of the fuel and electrical test readings anyway. The information written down Is useful record keeping, as well as helpful to formulate a composite picture of what failure mode your L-Jetronic is in.
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Old 06-01-2011, 12:21 AM
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Iceman,
Hmm... Evidently my coil is indeed a silver Bosch unit made in Brazil...

A non P-car buddy found a link for a way to test the coil output. It's from Clark's Garage, a 944 centered site, but I followed his test and determined that the coil is still good and producing spark using my test spark plug.

His Coil Test procedure is here:
http://www.clarks-garage.com/shop-manual/ign-04.htm

Tomorrow night... Next check will be the Speed and Reference Sensors.
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Old 06-01-2011, 01:08 AM
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replace the coil
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Old 06-01-2011, 01:51 AM
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Man, I have to agree. That coil is a failure waiting to happen. If not already.
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Old 06-01-2011, 08:40 AM
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I would try to source a Bosch non-silver coil and keep the silver one on the shelf as a spare or paper weight.
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Old 06-03-2011, 11:37 AM
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So I've checked various sources and all the coils that come up for my car from Bosch all look just like my existing silver "brazilian" one. Funny how the suppliers don't say where they are made, nor do they show a clear picture of the label...

I emailed one of the major suppliers directly and they said theirs was made in Brazil and that Bosch no longer makes coils in Germany.

With that said, what do you guys suggest as a good coil to get for my '87?
My existing one may be OK, but I'd like to get a new one to keep around as a spare.

I know there are other brands besides the Bosch one. John suggested MSD as a viable option... I'm just polling the list for some suggestions.

Thanks,
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