3.2 DME schematic shows a yellow wire from the ignition switch to position #4 on the DME box. But that's for a 911 and this is for a 914 so I don't have that switch and don't know what that wire has and under what condition.

I thought it might be the same as the yellow wire to the starter solenoid. When I make that connection the engine won't start with the ignition switch, but if I use my remote starter switch across the starter relay with key "on", the engine will start and run fine. Anybody know what's going on here (besides my not knowing wht the heck is going on) ?

Sounds like you may be picking up power from the wrong terminal of the ignition switch. There is one pin that has power during cranking and running, and one that has power only when running.

The Cap'n

I ran a relay from my fuel pump wire to power my ignition module on my 3.0L!

The 2 3.2L diagrams I looked at both show the yellow wire to pin 4 of the DME control unit as coming from the T50 on the ignition/starter switch, same as the yellow starter wire on a 914. The yellow wire is just a signal to the DME that the engine is cranking.

Make sure you still have your ignition power from the ignition/starter switch while cranking. The T15 circuit in the ignition/starter switch should have power when in the ON position as well as the crank position. Some ignition/starter switches have a X circuit that has power when in the ON position but does not have power when in the crank position.

Jim

I'm actually making the connection at the starter, not the switch. I've confirmed the DME box is getting the start signal at DME #4. When using my remote starter switch it only serves to confirm that DME #4 is getting what it already has. But the engine only starts with remote and not key. That's what is crazy about it.

Someplace you have to be connecting to the ignition switch because the DME needs power that is controlled by the ignition switch. Typically the ignition switch energizes a relay that supplies power to the DME control unit. It is the power from the ignition switch to operate the relay that we are questioning whether it is connected to the correct terminal on the ignition switch. I believe the yellow wire just signals cranking so the DME will turn on the fuel pump.

Jim

Here:

On my iPhone so too hard to search. I have a thread dedicated to wiring a 3.2l motronic...including placement of my dme and wiring into the fuse panel etc. I put my dme under the passenger seat and tapped into the yellow wire that comes from the ignition switch and resides under the passenger seat that ties into that seat belt/ignition switch mess. Yellow ties into yellow...nice and clean. Of course this only works on the model years that had that "safety feature".

Found the link:

http://www.914world.com/bbs2/index.php?sho...7&hl=Wiring

I have ALWAYS followed the 911 wiring diagrams EXCACTLY!. That means that the yellow wire from the ignition switch is the yellow wire from the ignition switch (not the starter). The ONLY problem I have EVER run into electrically is the connection of the two flywheel sensors plugged into the wrong position. I have been running 3.2 conversions since 1986.

You can find the correct circuits by following the PORSCHE wiring diagrams. Heck, each terminal is LABELED with the SAME numbering scheme. One of the things I truly love about old Porsches.

Good luck in your endeavor, but please contact me if you have any questions, I may be able to help.

Edited to seem less picky

Mr. O'brien, your diagram is great. I thank you all for your responses. This place is great. I'm off this Fri and will have another crack at it.

Joe...I'm not debating the solution....I actually used your diagram and the 911 and 914 wiring diagrams to do mine. The thread I created only showed real pictures of where and how I used that diagram. I'm guessing you didn't even look at it to understand that. Man this place can get picky at times when all we are just trying to do is help this guy.

Done venting...brp986s, look at the diagram as it is very good and spot on. If you want pictures of how I implemented that diagram go to that thread.

Sorry, I wasn't trying to be picky. I couldn't get your link to work last night, but it's working now.

Oh, and that diagram is not "mine". It was given to me a long time ago. I don't know the original creator, but I share it because it was shared with me.

Does anyone know how to wire a Carrera tach in a 914 with the 3.2L?
The 8 pin connector on the back is labeled 1-8, not much help if you don't have the correct wiring diagram.

Yes.

Signal on #2
12v+ on #5
Ground on #6

Thanks Joe!

North Hollywood Speedometer will convert a non-DME tach for $160. May help with keeping visual consistency across gauges.

This is baffling. DME#4 is getting +10.0 V while cranking, but it won't start. If I disconnect the starter and turn key to start then dme#4 gets 12+ V. I thought maybe 10V wasn't enough so I tried connecting another battery in parallel. DME#4 now gets 11V but still won't start. There is no fuel pressure. I put in another dme relay. Won't start. The fuel pump is new. If I bypass the dme relay to operate the fuel pump the engine won't start. But, putting key to "on" and jumping 12V to dme#4 with no other assistance, the engine will start and run every time. Further confounding matters, I got a generic automotive relay to supply 12V to dme#4. The fuel pump will turn on, but the starter won't operate! Preparing to go Goober with push button switch. Ugh.

I guess I was lucky. I just took the Haynes 914 and 911 manual and figured it out on my own. After putting the whole thing together the car wouldn't start. I was all ready to tow it to Hergesheimer's when a friend said to sleep on it. I got up the next day checked the fuel pressure and it was twice what it was supposed to be. The problem was I pinched one of the fuel lines putting the tank back in. I replace the line and it started right up and has run great ever since. That was 10 years ago.

I wouldn't suggest bypassing the wiring components. I suspect you may have some issues with how you have your DME relay wired. The DME relay supplies power to the computer AND controls the fuel pump.

I believe that you may be dropping out one of the voltage carrying wires required to run the car when you turn your ignition switch to the start position. (Your description of the problem seems to confirm this when you state that when the key is in the run position and you jumper the starter, that the car runs.)

It almost sounds like a circuit that should be powered with the key on and also with power while cranking. That sounds like circuit 15 to me.



Circuit 15 at a standard 914-4 ignition switch is hot in both start and run positions. This terminal usually has a Black/Blue Stripe wire. This terminal feeds Fuse #9. On 1974 cars, there is also a Red wire connected to this same terminal that feeds power to the seatbelt warning lamp.

The DME relay PIN 86 needs to connect to circuit 15. In a 911 wiring harness, this wire is BLACK. Circuit 15 feeds both the DME relay and powers the coil (also terminal 15). The circuit is +12V in both start and run key positions.

I hope you get your 3.2 wired correctly (running and starting with the key).

I have done a number of these and can potentially help.

John, thanks for offering. I made some measurements today at the dme relay.

measurements versus ground (engine doesn't start, no jumping to dme box #4):

key off - #30 red = 12v and 85 brn = ground

key on - #87 red = 12v, and 85B blk/wht = 12v, and #86 blk = 12v (also 12v at coil)

key start - my dvom gives weird readings. Probably need a scope for #87 for injectors. But reading was ~0 fwiw. #87b grn/red ~0.6v

When everything is hooked up normally, 10v to the #4 while the starter is turning is totally normal. The starter is using a lot of energy. 10v is plenty of voltage to tell the computer what's happening, so let's forget about that.

It's unlikely that you have two bad DME relays, but not impossible. It sounds like either a DME relay, or the wiring to the relay.

The bottom line: you can make the engine run, so all that wiring is fine.

There is a lot of great info in this thread!
I just wanted to clearify (maybe) the function of the DME relay.

DME Relay is actually 2 relays inside a single housing. 1 section powers the DME system and 1 section powers the fuel pump.
Here are the wire descriptions and there functions, as best I know.
Note: You may have to unplug the DME relay to read the terminal designation to determine the wire positions.
T30 - 4mm Red wire from the battery, provides power to the relay for DME system. Everything powered from the DME relay goes thru these wire.
T85 - 1mm Brown wire to ground
T85b - 1mm Black/White wire to pin 20 on DME Control unit (DME grounds this to power fuel pup)
T86 - 1mm Black wire from 15 circuit, 12volts with Key ON AND while cranking. (From the ignition switch)
T87 - 6mm Red wire to DME Control unit, injectors, idle control valve (power out of the relay)
T87b - 2.5mm Red/Green wire to fuel pump (power out of the relay)
also .75mm Yellow wire to O2 sensor heater (later cars)

Power from the ignition switch in the ON position AND in the start position goes to T86 on the DME relay. If T85 is properly grounded the relay then outputs power to T87 to the DME and injectors etc. It also provides power internally to fuel pump portion of the DME relay and when the DME control unit grounds the wire to T85b the DME relay outputs power to T87b to the fuel pump.

To me your symptoms seem like the wire to T86 at the DME relay is not getting power while cranking, only while in the Key ON position..
But never under estimate the havoc bad grounds can cause and double check them all.

Jim

It also COULD be a bad ignition switch....

There's a tiny spring inside the switch that is supposed to carry a trace current, but a short in other parts of the vehicle circuitry can cause the spring to burn up.
When the spring is damaged the switch may no longer engage all the circuits in start mode that it normally does.
If you replace the switch, the new one will fail as soon as the key is turned on, unless the short is discovered and corrected in advance.

I'm fully onboard with this theory and it will be easy to verify once I get home tonite. I had the same idea after Jim's post. Thanks to all.

No 12v at relay 86 or 85b at key start. Ign switch is dead. Now why would the switch choose the moment of the engine conversion to crap out? This thing may have further tricks up it's sleeve, but I'm on the right path now. Thanks again!

weird stuff happens. Glad to see you just might be on the right path to success!

So is your car working correctly now?

Yeah, don't you hate how threads evolve to climax, then...nothing?!

Yes, the car is running. The ign switch was replaced. Also, I measured 0.4 ohm from starter solenoid to ground. Is that an internal short or normal? That would pull alotta juice thru the switch - maybe not good for it. I had a spare low mile rblt starter that was open circuit at these terminals. So I swapped that one in, resulting in

Now the problem is the motronic. I bought a rblt motronic box from 911chips.com. (the rest of the set up I bought separately). Starting from cold or coming to stop the engine will often do 15 or so 500 to 1300 rpm rev cycles before settling to normal idle. I have another motronic box that doesn't result in this feature. I'll see if I can return/swap the 911chips box w/o alotta . Sigh. I thought that going to motronic from cis I would be free from quirky old fuel systems. Instead it seems more of the same, but different.

You may want to check the idle stabilizer as well. These have a tendency to stick causing idle hunting as you describe. Sometimes they can be freed up by removing them and spraying through them with some sort of solvent/cleaner. I have replaced several of these over the years. They are a little pricy, but it does fix the hunting idling. Tapping on them tends to get them temporarily freed up and helps with diagnosing them as the problem.