Short Story then a couple questions if you Please

Dkelly914 · 06-09-2012, 08:39 AM

Back in the early 70"s my car just died. I started out, and in about 3 minutes it quit. I could crank the heck out of it with no inclination it would fire. I just happened to have a couple of friends that I worked with that worked on German cars in their off hours. What they did to fix this was jump a wire from a post on the brain to another post on the brain. Just kind of pinched it under the leads. I worked fine for over 30 years

until I started restoration. I inadvertently pulled it out when I stuck my club like hands in there for something. I am back to the point of cranking the heck out of it with no indication of it firing. Would and one of you scholarly types know what the two pins in the brain I might be talking about? I'm obviously bypassing something but what? My second question is. During my relocating of my fuel pump and subsequent purging of the system by jumping the fuel pump, I have lost my 1.5 second zip when I turn the key on. I read somewhere here that I screwed something up while jumping it maybe in the FI part. Can I get it back? If not and I rewire it can I tap into a key on hot so that the pump with turn off when I stop or should I put in some sort of switch? 1973 1.7 stock.

John Rogers · 06-09-2012, 10:40 AM

You can jumper the plugs #30 to #87 and the fuel pump will start when the key is on. It only means that the pump is running all the time and only stops when the key is off. Many 914 FI owners carry a wire with banana plugs on each end in case the relay dies and need to get home. The only down side is if the injectors, including the starting one leak the engine can flood so if you do that I would suggest pulling all 5 injectors to see if they are tight.

Dkelly914 · 06-09-2012, 12:08 PM

Thanks John

Dave at Pelican Parts · Dave at Pelican Parts's Garage

On my 74, jumpering the fuel pump relay resulted in a pump that ran no matter what the position of the key.

Sounds like Dkelley had a wiring harness problem that was kludged to work years ago. I would suggest taking the FI wiring harness out of the car (requires dismounting the brain and unplugging the harness from all of the FI parts; label all connections first!!) and checking the wires from end to end with an ohmmeter or continuity tester. Or even a test light. Replace any wires that check out bad.

Or just talk to Jeff Bowlsby and get a "rebuilt" harness that is 99% new parts and better than the factory made. Replacement Porsche 914 Wiring Harnesses

--DD

Dkelly914 · 06-09-2012, 04:07 PM

Thanks for the the reply Dave. The Wiring Harness is a bit to pricey for me. I'm kind of looking for the Kludged solution it worked well for me for many years. Would you know where I can get a simple description of the brain posts? Maybe I can find what they jumped around. It also sounds like I'll be putting in a switch for my fuel pump

Thanks again Dave

John Rogers · 09:33 PM

I would imagine if you used a fairly large magnifier you might be able to see when wires were inserted in either the plug or the brain. Generally when that happens the wire/connectors/plugs/etc will change a little over the years. As a note, the diagram is for the relay board and I would bet that the jumper that was put on the FI connector did the same thing as jumping the fuel pump relay? Note that the large collection of wires at the top of the diagram is the large connector that is usually called the front connector and the collection of wires at the lower right is usually called the rear or outlet connector.

If I remember correctly (it has been a while) the connectors have a number for 1 or possibly all of them? You could also match the color of the wires to the pin number and if the wires are dirty, faded, etc, clean them with a small amount of lacquer thinner on a rag. When I did this back in 1996 or so I made a drawing of each connector and some time after that I actually posted here on Pelican so it may still be around? Anyways, when you "cleaned up things" hopefully the wire positions did not get moved!!??

In thinking back, we finally did a bypass on Julia's 74 2L FI car as the fuel system had firing troubles when using the relay and getting rid of it was the cure.

Hope this helps.

Dkelly914 · 06-09-2012, 06:17 PM

Everything helps John, thanks. I have totally redone the relay board because I thought it was a loose pin. I will look at the plugs as you suggested. I would really like to find something that would tell me what each pin is. I'm having a hard time following the wires.
Thanks again for taking the time
Dennis

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The diagram posted in your first post is not the "brain" or the ECU, it is the relay board. Just making sure that when you say that your friends "jumpered a connector on the brain to another one on the brain" you do mean the ECU in the right-front corner of the engine bay.

The diagram of the 1974 EFI wiring harness can be found here:

The numbers inside the big block at the top of that diagram are the pin numbers in the connector to the ECU. The same numbers are also printed onto the wires, so you have a bit of extra help that way. The five connections at the left side of the page are to the four-pin connector on the relay board (at the left-rear), and to one of the pins in the 12-pin connector (at the right-rear).

The Jeff Bowlsby site also has diagrams of how long the various wires are and what they connect to.

--DD

Dkelly914 · 06:27 AM

Sorry for the confusion. I am talking about the relay board. The wire was jumped from the 14 pin connector to the 12 pin connector.
Thanks
DK

John Rogers · 06-10-2012, 10:32 AM

If a wire was used to jump from one connector to the other then somewhere in the circuits is a break. You could spend lots of hours trying to figure which one it is but I would say a wise move is to buy another board.

Dkelly914 · 06-11-2012, 04:42 AM

The thing is I've redone the relay board. All the pins are solid and it has been all re soldered. I have continuity throughout. They really are a simple board. I think it's in the wireing between the 14 and the 12 pin connectors, I'll check for continuity there, do you think that would help?

DK

John Rogers · 06-11-2012, 06:24 AM

No, as I said, save yourself a bunch of time and frustration and get a good one. I remember an owner of a 74 2L FI car that spend months trying to get the replay board to work and missed a whole summer of driving and auto-x sessions and finally got so frustrated he SOLD the car. The new owner put in a replay board and within 20 minutes of owning the car was zooming down the road!

It is up to you

Dkelly914 · 06-11-2012, 09:19 AM

Thanks again John. Sometimes when I don't want to hear something I have to be beat over the head with it until it sinks in. After all we are just talking one silly wire

. Let me ask you this, In my parts basket I have a 2.0L relay board. Not sure of the year car it came out of tho. Would that work in place of the 1.7L board?
I'll leave it at this and won't bother you with it anymore.

Thanks John and Dave for taking the time to educate me.
I'll be back with more questions about something else I'm sure.
She is so close
DK

Dkelly914 · 06-13-2012, 07:44 AM

Found what I was looking for, a better detailed RB. Thought I would share
DK