wiring help

jamess2 · 08-17-2011, 11:12 AM

Ok I swapped a s2 engine into my 87 944. Me and my mechanic friend wired the ignitor and have monster spark on the engine now. I have no tach bounce the fuel pump runs but i have no power to injectors. I know we are missing something simple. We supplied power from fuse 7 like the rennlist wiring changes thing said to we also done the rest of the wiring. I have looked over the diagrahms and just cant figure out what we are missing. The only thing I can see is that it say we need to have 12 volts running from the passenger side footwell to the dme? But niether plug on the s2 harness or the na harness has this? PLEASE HELP!!

jgporsche · jgporsche's Garage

How does the reference sensor on the bell housing look? That is where the tach bounce comes from. On the earlier cars just shaking the reference sensor plug will make the car start.

John_AZ · 08-17-2011, 12:07 PM

This is unfamiliar to me.

Did you do the same as post 7?
S2 and 968 Engine Swap wiring Notes - Rennlist Discussion Forums

GL
John

jamess2 · 08-17-2011, 01:23 PM

I can't get the link from post 7 to work. I have spark and the fuel pump runs when engine is turning over but the injectors are not firing and I have no tach bounce. It has to be something.g simple. I've searched and seems most people have trouble getting spark and I can't get fuel. My mechanic wants a pinout for the s2 dme but I can only find early 944 stuff. He followed the wiring changes and it wont run.... I'm baffled.

bazar01 · bazar01's Garage

Do you have 12V power to injector plug on one terminal?

jamess2 · 08-17-2011, 01:45 PM

I do not

bazar01 · bazar01's Garage

12V to injectors come from DME relay term 87. It also supplies the DME computer.

Use a triple jumper and see if that solves your issue. Jumper 30, 87 and 87b.

jamess2 · 08-17-2011, 01:54 PM

I don't mean to sound dumb but what do I need to do? I can turn wrenches but this wiring stuff blows me away

jamess2 · 08-17-2011, 01:55 PM

OK ill try that.

bazar01 · bazar01's Garage

Quote:

Originally Posted by jamess2

I don't mean to sound dumb but what do I need to do? I can turn wrenches but this wiring stuff blows me away

Make a triple jumper wire like this.

Pull the DME relay.

Insert the triple jumper into the DME relay socket on terminals 30, 97 and 87b.

The fuel pump will run and the injectors will be supplied with 12V.

Start the car and see if it will run.

If it does not run, remove jumper on terminal 87b to turn off the fuel pump.

With a digital meter, test for 12V at the injector plug. It should have 12V. If it does not, you have a wiring issue.

Ga 951 · 08-17-2011, 07:35 PM

is the S2 supposed to have tach bounce? If so, isn't that the first place to look? I thought 200rpn signal was req for the fuel pump???

jamess2 · 08-18-2011, 07:07 AM

After seeing what you were talking about my mechanic did jumper the dme relay. Does any one have a pinout for the dme for a 90 s2? I can some one look at the wiring changes from rennlist to walk through and explain each step in wiring? I don't think it is showing all the info needed for the swap. I know this engine has been put in regular na's but know one has really documented the exact changes to the wiring

bazar01 · bazar01's Garage

Quote:

Originally Posted by jamess2

After seeing what you were talking about my mechanic did jumper the dme relay.

And...........

I may have the DME pinout in my home pc, but I am at work....

johnkoawood · 08-18-2011, 09:09 AM

The tach bounce is a signal from the DME that the refference sensor is working, this is also the signal that powers the DME relay second side to turn on the injectors and the fuel pump..

Not sure HOW you report the fuel pump is running, but not the injectors.. this portion of the wiring should remain untouched.. as the fuel injector 12VDC is supplied directly from the relay (jumpers).. the DME switches GROUND to the injectors, not power.

If you have no power to the injectors, while the jumper is installed, it is a wiring issue in the engine harness between the central electric board and the injector connectors.. I would suggest you reseat all the connectors into the central electric board, then trace the wiring from the central electric board to the injector connectors (likely it is a bad in line resistor on the wiring.. this is found inside the boot at the firewall by folowing the injector harness untill you see the wires all tied into one feed wire... YES all the injectors fire together at one time.. there are two ground leads but they are tied directly together inside the DME)

I can pull the wiring diagrams up when I get home later today, and post teh colors of the wiring, and their locations at each point along the harness to check.. but that will be later this evening!

jamess2 · 08-18-2011, 11:13 AM

I greatly appreciate the help. I look forward to seeing the diagrams you guys have. I'm also going to verify that my crank sensor is working. I guess it's time for me to purchase a multi meter.

johnkoawood · 08-18-2011, 12:19 PM

Quote:

Originally Posted by jamess2

I greatly appreciate the help. I look forward to seeing the diagrams you guys have. I'm also going to verify that my crank sensor is working. I guess it's time for me to purchase a multi meter.

Multi meter wont really help you other than to check the resistance of the sensor.. the pulse is VERY short, and not too many multi meters will capture it correctly..

IF you dont have 12VDC at the injectors with the jumper in place, it is a wiring problem, not that teh sensor isn't also causing a problem, but make sure the injectors are getting the proper voltage first!

jamess2 · 08-19-2011, 05:39 AM

I guess the next step is I'm going to pull the harness back thru the fire wall and inspect the harness. I can only seem to find a wiring schematic for a s and not an s2. I know I shouldn't assume they are the same.

bazar01 · bazar01's Garage

Quote:

Originally Posted by jamess2

I guess the next step is I'm going to pull the harness back thru the fire wall and inspect the harness. I can only seem to find a wiring schematic for a s and not an s2. I know I shouldn't assume they are the same.

you're still not telling us if you have 12VDC at the injectors with the jumper installed....only after you know there is no 12V at the injectors that we can tell you what to do next.

jamess2 · 08-19-2011, 10:09 AM

I did not have power with the jumpers installed.

jamess2 · 08-19-2011, 12:34 PM

Well I think I might have figured out why I have no power to the injectors. According to an old post on rennlist about the s cars had a ballast resistor for the injectors. A Guy was having the same problem when he put an s2 engine in an Early 944. He plugged this into the car somehow and instantly had power at the injectors. Where was the resistor located on the car? It was close to the cruisecontrol on the passengerside under the Hood but I can't remember seeing this on my donor unless I just missed it? Also were oldies it plug in?