superpilot27

Hey rusnak, a checklist for "no start" would be great. Thanks for your input. all pitching in sounds good too. I have the Bentley wiring diagram open right now looking for the wires to test to figure out if
no power to terminal 15 is
a fault from DME to terminal 15 or
a fault from ignition switch to DME or
a fault from battery to ignition switch

Lorenfb you say in your post"Terminal 15, now where does that come from?"
Where does it come from? and what is a good test to check it?

I may be posting silly questions on this forum to some, but sharing information is why I am here and one way or another if it takes reading 50 wiring diagrams and 100 posts, I will fix my 911. then I'm calling those chip guys for more fun and Dr. Pepper.

I'm looking for the post of what to look for with the DME removed, hoping that it is not the DME.
and the Ischmitz "Ingo" one
note: battery is now freshly, fully charged with cleaned terminals.

superpilot27

rusnak
thanks for the post- reading it now.
my ICV vibrates.

rusnak

ICV is the Idle Control Valve - the silver cannister that is on the front of the engine.

Ingo mentions that when you turn on the key, before cranking, the cannister will hum. The Bentley manual outlines several resistance and visual checks of the ICV.

When you say you have fuel, did you put a pressure gauge on the fuel rail? The jumper wire on DME relay is merely to test if you have power to the fuel pump, not whether it is running while the engine is cranking. These are two different things. The fuel pump is controlled by the dme relay. If no pressure while cranking then you dme relay is bad.

Amber Gramps

This is your ICV. It's that little hummer right in the middle of things. Mine is new. Not even brake cleaner could get my original one to hum like I wanted.

(sorry for the interruption....I have always wanted to try to figure out how to put text in a photo-shop image.)

rusnak

Here's a draft of the checklist.

Guys, please feel free to look it over and make any additions or deletions that you wish. Then add your name to the author list, and change the date modified.

Thanks!

Lorenfb

A lot of non-applicable posts in this thread!

If there's no power to the #15 on the coil, then don't waste time with
the DME relay, the DME ECM, the fuel pump, & etc. The Bentley manual
should indicate that #15 comes from the ignition switch which gets its
power from the battery.

So if there's really no #15 power on the coil, it's that simple!!!!!!!!!!!

rusnak

The coil gets power separate from the dme, that's true. But I see no reason to not check the other stuff.

When the key switch goes bad, usually other things start acting funny as well because the cylinder controls many contacts, not just one. For example the windows may not work, or the lights may not work. You may have noticed that the engine will not shut down even though the key is off and out of the ignition switch.

I don't have a wiring diagram on me at the moment, but it makes sense that you can isolate the switch with a multimeter.

rusnak

ok found it. Check fuse #8. If it has power, it's not the switch but the wiring to the coil. No power, then it's the switch. Good luck.

superpilot27

Yes there is a god of Porsches and this god has been good to us. The car started.
Thank you rusnak, douglas bray, Lorenfb, J. Brinkley, theiceman, cal44, 2002M3Drew, old man neri
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 it
before so either something else is up or we had a bad ground the other times we checked this voltage.
Frustrating.

The car still would still not start, so I had a friend crank the car while I beat on the DME with a 14mm 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 from moisture. 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.

rusnak

To answer your question, I think you'll be ok. Cleaning your battery and grounds probably eliminated the problem.

I went through something very very similar this past Fall. I knew about the corrosion on the positive battery connector, as I have advised others about it many times. I cleaned every single terminal and connector that I could reach in order to perform the voltage and resistance checks. The car just started on it's own.

After that, I bought a spare dme computer, another dme relay, changed all of the injectors and the intake rubber boot. I have since then also tracked down and eliminated all vacuum leaks and now I am in the process of learning how to check and adjust the fuel and air ratio.

I seriously doubt in your case that knocking on the dme had any affect on corrosion. You may have a cracked solder joint, but that would not have any effect on the coil.

Either you still have a bad switch, or your corrosion on the positive battery connector had caused the problem. I would guess it is probably the latter unless it happens again. If it does, then check the coil power again.

superpilot27

thanks for the info on your experiences. the idea of cracked solder joints seems to loom larger.
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 and clean corrosion or solder cracks as needed.
but first, I'm going for a drive.

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 it home.

When it fired up I immediately drove it to my garage, pulled out the DME, disassembled the DME and soldered 3 solder joints that 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? I'm not sure I want to go through my PCA call list again to avert the tow truck.
Any ideas on this?

rusnak

The time it did not start, did you check the ICV in the "accessory on" position to make sure that the dme is in fact not sending a signal? Were you able to hear the dme relay click? Did you have a multimeter with you to check the power to the coil? I'm just asking because it could still be a bad switch vs. bad dme relay or bad dme.

superpilot27

rusnak, I didn't do my due-diligence this time when it wouldn't start.
I smelled lots of fuel during cranking and could hear the fuel pump but I should have:
- checked ICV with key on
- listened for DME relay click
- checked power to the coil (I had a multimeter with me)
instead, I just beat the crap out of it with the 14mm (actually used the 13mm side and it didn't work, flipped the wrench to 14mm and went nuts and it worked. I laughed at this point.)
Your comments are greatly appreciated. if I had checked the list of your suggestions above, I would know where I stand. As it is, I am tentative about driving the car, since I only know it runs, but not that it is fixed. I did confirm cracked solder joints on the bottom of the lower DME board and I did fix them. but as you said, I don't know if there is another problem. I am glad it runs.

superpilot27

One year later.

No restart issues on this daily driver.
soldering the three cracked joints seems to have fixed this issue.
I was expecting it to need more work so I have the nuts for bolting the DME to the floor in a
bag under the seat. Maybe it is time to bolt the DME down now..