87 Carrera ignition stopped

[superpilot27]

problem:
While driving my stock 1987 Carrera targa, the ignition quit. No sputter, no cough, just dead.

story:
I was doing about 45mph on sunny dry day when it quit and immediately pushed clutch in, tried all starting techniques (key, clutch out) and coasted through 3 green lights and about a mile into a safe parking lot. A nice save swerving powerless in tough traffic all the way until parked. That is the good news. Now the bad.

troubleshooting:
1. jumped DME Relay to confirm that the fuel pump is working, the ignition is not.
2. tested, no spark at plug, cap, or coil
3. checked bentley manual, test for coil shows no power at coil
4. checked ref sensor speed sensor and both check out same ohms 1-2 and infinity 2-3 and 1-3
5. checked all fuses, my car May 1987 does not have an ignition fuse in the fuse box

background:
last year I replaced DME relay, computer, cap, rotor, coil and both ref sensor and speed sensor.

need:
ideas.
has anyone had this happen?
I need to figure out how to troubleshoot/jumper thee ignition switch or wiring to the ignition switch, or maybe there is a sweet magical poschephile fix?

[techman1]

Did you keep the old cap and rotor and DME relay as spare? Do a quick swap to confirm the new stuff is still good.

Try to check behind ignition switch, all wires there look good?

[175mph951]

does your targa top leak at all....its common to get water on the floor and get the dme wet....ecu doctors will check your dme for $50 or swap yours with a known running car.

[Por_sha911]

-Borrow a relay and swap it out again.
-Pull the cap and make sure the rotor turns when the motor cranks (and look for signs of damage to the cap or rotor).

[DRACO A5OG]

When you said "computer" do you mean the DME? If so was it refurbed or new?

I would take it our and check the solder joints. Steve Wong posted on how to check and fix that issue.

[superpilot27]

Ok. Thanks for all your comments.

I read comments and have narrowed it down.
Here is where we stand.
Car will crank but not start.

It is getting fuel.
cap and rotor removed and reinstalled-visual inspection shows both are good (brand new 8 months ago)
DME relay two methods test relay as good (brand new 8 months ago)
Ref and Speed sensors test good via Bentley manual ohm method (brand new 8 months ago)
Grounds: confirmed all ground points and straps visually and cleaned the DME ground point, trunk floor gnd point and fuse box gnd point (none needed it but I'm being as through as possible)
main issue:
no spark at plugs or coil. tested and
no power is getting to the coil (terminal 15).
I did not remove the DME/ECM for now. It is dry, car has been garaged, targa top is new refurb and I even keep desiccant next to DME to keep any moisture off. (this is a refurbished DME/ECM installed 8 months ago)
My guess is:
1. ignition switch is bad or
2. wire from ignition switch to coil is bad
3. wire from battery to ignition switch is bad
I'm going through the wiring diagram now, but does anyone know the wires to check or a method to rule out these 3 items?
any other ideas or experiences?

[superpilot27]

PS: car has no aftermarket alarms and is totaly stock. it has the factory alarm and I've never used it in the 10 years I've had the car

[Steve W]

When you say you say you replaced the computer, do you mean the Motronic DME unit?

[rick-l]

Originally Posted by superpilot27

Ok. Thanks for all your comments.

no power is getting to the coil (terminal 15).

Wouldn't this mean a bad ignition switch?

[Por_sha911]

Other things to consider:
The factory alarm may have decided you needed it. Consider bypassing it (you'll have to search to find out where). Its a freebee to check.
Your DME (not the relay) may have a bad solder joint.

[lucittm]

I just had this happen to me this weekend. It turned out to be a burnt wire under the fuse panel in the front compartment. It was quite evident after I turned the fuse panel over.

Good Luck,
Mark

[superpilot27]

Yes Steve
on post #6 "refurbished DME/ECM installed 8 months ago"
hoping it is not the DME but some wire..
bentley open to wiring diagrams right now looking for the wires to test to figure out if
no power to terminal 15 is
fault from DME to terminal 15 or
fault from ignition switch to DME or
fault from battery to ignition switch

[ischmitz]

If your diagnosis of no power to the coil is correct you either have a bad ignition switch or a bad wiring harness. The power to the ignition coil is simply coming from the ignition switch (Term. 15). It has nothing to do with the DME relay. Use a DVM and check if your ignition switch is working properly.

You need to measure @ Fuse #7 and check for +12 Volt with the ignition in ON position. If you do see it there then the wire from the fuse box to the ignition coil is interupted. Nothing else. If you do not get +12 Volts there (also means a whole bunch of other things such as instruments, wipers, etc. are not working properly) you have a bad ignition switch.

Cheers,
Ingo

[superpilot27]

Yes there is a god of Porsches and this god has been good to us.
Thank you ischmitz, lucittm, Por_sha911, rick-l, steve w, DRACO A5OG,
175mph951, techman1 for your posts. The god of Porsche threw a wrench in the deal
but we came out ok.

Here is what I did after all the earlier tests to make my '87 black/black Targa Carerra start.

I charged the battery over night. I cleaned the ground points to the DME and the
positive battery post and terminal. I checked the voltage at terminal 15 on the
coil and got a 12V reading. We measured no V at the coil both earlier times we checked
before (either something else is up or we had a bad ground the other times we checked this voltage).

The car still would still not start, so I had a friend crank the car while I beat on the DME with a a14mm wrench. The car started. I know, cave man approach, but it is running.

The car has started now 4 times. I don't know how long it will last.
Does anyone have any experience with this sort of fix?

The theory is that there was corrosion on the circuit board in the DME. The banging from the wrench
vibrated this corrosion off. Also I've been told that if I remove the DME and open it, that I
will see a white water mark on it. The suggestion has been made to lightly brush off
any water mark or corrosion on the solder. This will be my next chore. I think there was
a recent post to this forum but I haven't found it yet. Does anyone have any tips for this?

The reason for this corrosion is that I have a Targa. Does anyone have one that doesn't leak?
I will be adjusting my windows to fit better right away. Looking for posts on that now.
thanks for all your input.

[andyu911]

I had the same problem years ago. Replaced and checked everything possible. I tapped the DME connector by accident and the car fired right up. I had the DME checked by a Bosch technician and found hair-line crack on solder joint. It seems like a common problem for our aging Carrera.

[xlr8]

My '88 cab had similar symptoms. I was able to isolate the problem to the DME computer by swapping it out with another.
The DME had three cracked solder joints here-



Bright sunlight and a magnifying glass were necessary to see the cracks, I did not see them the first time I looked.



The three solder joints connect this component-



To gain access, I had to disassemble these plastic supports-













I found a butane soldering iron easier to use because you can grip closer to the tip and there is no cord in the way.



Good Luck!

[ischmitz]

You have the classic symptomes of cold solder joints. And unfortunately, your "repair" will not last. The ductile solder now makes contact after the banging but vibrations and temperature cycles will make it fail again. So you either need to solder it yourself or have to have it rebuilt.

Let me know if you need help. BTW, our host sells a rebuilt service for the 3.2 DME with warranty.

Cheers,
Ingo

[superpilot27]

thanks for the info on solder joints and pics
the car has started on 5 occasions now but I haven't gone anywhere in it yet.

I am going to take my DME out, open it up and see what I've got. clean corrosion or solder cracks as needed.
but first I am going for a drive.

[rick-l]

our host sells a rebuilt service for the 3.2 DME with warranty.

Holy crap $449 to re flow three solder joints?

Not to disparage our host but I would think twice about getting a rebuilt unit that has an unknown history, possibly a box full of latent failures, intermittent failures and questionable parts substitutions.

[superpilot27]

Why is it that I am addicted to Porsches? Why does this affliction make me want to drive?
The car ran but was not fixed of course but I just had to take the car for a drive. bad idea.

it started the first 4 times and the fifth it would not start. This is the same thing it was doing last year right before I paid $3G to a shop that was throwing parts at it, including a "refurbished" DME.
I used the 14mm wrench trick again to get my aggressions out on the DME while cranking and it started on about the 5th time doing this after many calls to friends trying to borrow their DME to get home.

When it fired up I immediately drove it to my garage, pulled out the DME, disassembled the DME like XLR8 shows in the pictures and soldered the same 3 solder joints. the outer two were visibly cracked on this "refurbished" DME. I took pics.
The car starts easily with the soldered DME re-installed.
but will it start consistently?
Any ideas on this?