3.6 conversion question - no power to coils during cranking

mjshira · 12-27-2009, 04:40 PM

I am having a bit of a challenge with my 72 993 conversion. I have power to the coils with the key in the on position, but when I turn the key to the crank position, no power to the coils.

With the key in the on position and cranking I have power at position 86 and 30 on my DME relay.

Anybody have an idea?

stonec3047 · stonec3047's Garage

I had the same problem with my conversion. I found a hot ignition wire which stays hot during crainking. I wired it to the same ignition hot wire just like you described above.

Mine was position #8 on the fuse block (77 S Targa). It was easy to find with a volt/ohm meter and a set of alligator clip equipped jumpers. Took about 10 minutes to fix once I spent two hours scratching my head.

Not a well documented issue in the 964 DME manual.

call if you like 706 294 5057

Kevin Stewart · 12-27-2009, 09:16 PM

I have you looked to see if there is a fuseable link thats went bad, Kevin

tctnd · 12-28-2009, 07:26 AM

Most of the outputs from the ign switch are meant for various accessories. These all shut off during cranking to preserve power for the ignition. Only the dedicated ignition terminal remains live during cranking. I don't remember which one that is, but can check (I have a spare switch) this evening when I get home.
regards,
Phil

skinnerd · skinnerd's Garage

Quote:

Originally Posted by tctnd

Most of the outputs from the ign switch are meant for various accessories. These all shut off during cranking to preserve power for the ignition. Only the dedicated ignition terminal remains live during cranking. I don't remember which one that is, but can check (I have a spare switch) this evening when I get home.
regards,
Phil

What Phil above said.
There are some locations on the fuse panel that shut off when you turn the ignition switch to crank the starter.
I had my 3.2 conversion wired into one of these, and it took awhile to figure out what was really going on.
When it was rewired into a location that remains hot during cranking, the engine fired right up.
Hope it's as simple as this.
Good luck.

NoEardGoat · 12-28-2009, 11:38 AM

This might help. I haven't finished my motor yet, but I have my 1981SC body wired (1st diagram) a combination of Ingo's diagram and the diagram below (2nd diagram)

I can check my harness for anything you like, but I haven't installed the motor yet so my car isn't a proven setup.

mjshira · 12-28-2009, 02:27 PM

thanks guys. update for today and based on your reminders/help, I have spark, but no power to the fuel pump from the DME. I suspect it is the DME relay. My conversion harness relies on a DME relay from an 84-89 911. I have the part ordered from our host. I also checked fuel and oil. Prior to parking the car I had changed oil and filter so both are new. The fuel has been recently topped off (via gas can) and I checked the fuel rails.

So it seems that once I sort power to the fuel pump she will run!

Thanks for the wiring diagrams and PM's. They helped a great deal.

DW SD · 12-28-2009, 03:17 PM

James,
I had the same issue where things were initially wired to the wrong fuse block terminal.

Can you run a jumper to manually power up the fuel pump? I'd try this to see if things fire up. The fuel pump runs non-stop when the engine is running, so you don't run the risk of harming anything.

Doug

mjshira · 12-28-2009, 05:32 PM

Hey Doug! Great to hear form you man.

So we determined tonight that when we put power directly to the fuel pump, the fuel pump doesn't come on... so either the wires to the pump have come off OR the pump is bad.

Not sure how that happened from sitting. I am going to have to put the car in the air and see if the pump is getting power or not. If it is, I am into a new pump.

Do any of you know what the proper pump would be for a 993 engine?

It serves me right for letting such a fun car sit so much...

Kevin Stewart · 12-28-2009, 05:49 PM

ya know i had the fuel pump wires corrode once, Kevin

DW SD · 12-28-2009, 08:30 PM

James,
I run the blue 3.2 bosch fuel pump. I believe there are aftermarket pumps which can be purchased cheaper and are direct bolt-ins.
You can research pumps on the megasquirt DIY - EFI website, if you want to save a few hundred $. I would think you could also safely buy the 993 pump. First, I'd find yours and take a picture, post it here. Someone will recognize the pump and then you can decide what to do.

I had a pump freeze up. I squirted some PB Blaster in it and let it sit for a few weeks and it came back to life.

Happy Holidays!

Doug

mjshira · 12-29-2009, 05:55 PM

Turns out one wire of the two that go to the pump is broken. So I have to raise the tank to replace the wire. Fuel pump works when wires are removed and power is put to the pump directly.

mjshira · 01-03-2010, 03:41 PM

update - she is running!

thanks fellas. I basically had to re-check all my wiring because I'd taken it apart and frankly just forgot how and what went where.

next stop for this car is LA!!!!!!!!!!!