ramius665

I'm going to jumper the alarm and DME again, just to ensure that I have truly taken them out of the equation.

I should have specified in my original post but no, the engine has never ran in this chassis. I bought it from the PO as a non-running swap and swapped in the proper wiring harnesses from an S2 that was running when parted. The long story on this engine is that the owner wrecked his 1989 S2 in 1990 on his first track day ever. The remains of the car were sold to the PO's uncle, who paid a shop to swap the entire drivetrain over into a 1983 944 chassis. The PO bought that car and then wrecked it a few years ago. He bought a 1987 chassis and tried to Frankenstein the 83-compatible wiring harness into the 87. He never got the car to run but it cranks over without issue.

The engine bay and DME harnesses are 944 S2. The ignition control module and injector ballast resistor units are installed and functioning correctly (tested on a running S2). There is no need to re-pin the firewall connector when both are from an S2.

#Fail. All 16V cars only have one sensor at the flywheel and a hall sensor on the exhaust camshaft. Since you read the above posts, you know that I have tach bounce and therefore the sensor on the flywheel is functioning. If the FSM is to be believed, a non-functioning hall sensor causes the DME to retard timing by 6*, hardly enough to prevent starting and certainly wouldn't cause the fuel pump to not engage.

Adker

Power to the coil comes directly from the ignition switch....direct feed through the fuse box.
The alarm kills the enable to the first DME relay (pin 86, should be 12V with ignition on) and the alternator.
Adding the two jumpers to the DME relay should start the fuel pump and supply power to the DME and injectors. But, if no power is going to the coil from the ignition switch, you will get no spark. The power lead for the coil is Black for some dumb reason.

pontifex4

Correct. I'm driving my 968 right now with no Hall sensor.

Adker, I didn't know that.

ramius665

I used a factory alarm bypass connector and it didn't make a difference, still no fuel pump, still no spark. I have checked pin 86 on the DME relay (ignition switch) and it gets 12V+ when the ignition is turned to accessory.

The 89-90 DMEs are the same. The 91 DME is a hybrid between the S2 and 968 DMEs.

Adker

If you have voltage at pin 86, no need to bypass the alarm.

ramius665

Update
I have performed the following:
- Removed/replaced fuse #34 (fuse was not blown)
- Replaced DME relay with a new unit (old DME relay tested good in another car)
- Jumpered DME relay (fuel pump did not run, car did not start)
- Replaced fuel pump (runs with 12V power at the terminals of the fuel pump)
- Tested continuity of the fuel pump harness (good continuity on +/- wires)
- Tested terminal 30 at DME relay (has 12V+ power with ignition on/off)
- Tested terminal 86 at DME relay (has 12V+ power with ignition on)
- Removed DME, tested by installing in another 89 944 S2 (car started/ran without issue)
- Tested pins 24 [ground from MP IX] and 37 [voltage from DME relay with ignition] (registered ~13.5V)
- Confirmed cap/rotor/plug wires are in good condition (all are new)
- Verified no spark using spark tester at each plug and from the ignition coil
- Verified ignition coil has ~13.5V from positive terminal to ground with ignition switched on and negative terminal to ground
- Installed factory alarm bypass

At this point I'm at a loss as to where to go next. I haven't verified that the ignition control module is reciving signal (FSM doesn't detail how to do this) but as near as I can tell it wouldn't affect the fuel system. It appears that the DME is receiving correct signals but for some reason still is not allowing fuel or spark.

On a side note, would the lack of an airbag control module cause a no start condition like this?

ramius665

bump. Any ideas why the DME wouldn't energize the fuel/coil circuits?

1933beer

[QUOTE=ramius665;10002455]I'm going to jumper the alarm and DME again, just to ensure that I have truly taken them out of the equation.



He bought a 1987 chassis and tried to Frankenstein the 83-compatible wiring harness into the 87.

The engine bay and DME harnesses are 944 S2.


Ramius this would be dificult to disect but frankenstein is the problem you need to know in great detail the difference between the wiring harness in the 83 and the 87 and the S2. Did the PO remove something thinking it wasn't needed? The first shop that did the swap made it work it can be done. If you can fine out what had to be done originally by that shop you can figure out how the PO messes up. look for some thing that was cut ( wires) KNow how the wire hardesses are different.

I swapped engines ( one year difference)on two toyotas years ago i made the car run but it took me 3 years to figure out the vacum differences to make run right when it was cold. I feel your pain

F18Rep

Ramius...A couple of little 944 things that I <think> apply to the S2 as well.... When you twist the key, you should see a ground at pin 85 of the DME relay. I'm thinking the DME is seeing the engine speed but not passing the ground to the enable the DME relay. I don't really think this is your problem though as you may have multiple problems which makes it much harder to troubleshoot. Assuming multiple problems, I think you have to work through them one by one.

On the fuel pump, you have jumpered the DME relay and you have confirmed the wiring to the pump is good, why not, also see that the jumpered 12vdc is getting back there. If if is and you have a good ground for the pump, then pump may just be bad. I had one do that once - in mine, I could even use a battery charger to get the pump to run but nogo off of the car's wiring - a new pump fixed it.

Over the years, I've seen weird loading kinds of problems too and maybe that what we have here e.g. the pump is pulling so much of the current that there is not enough for the coil to build spark. Its a long shot but you could jumper only the ignition side of the DME relay and see if you get spark. Likewise, you could jumper only the pump side and see if you get the pump to run....Good luck...Bruce
PS... reaching way back but seems like I got burned once with pump that wouldn't run because the o2 sensor was shorted.

mblaszak

My suggestion is to tackle one problem at a time and sort it out. It is the only way to trouble shoot this.

1) check the power circuits. Get the power to your fuse panel so that when the key is turned on and the jumper is in place, you get your fuel pump to run. This is very basic. Right now when you switch on your ignition, there is no power in the control power half of your fuse panel. If there was, then the fuel pump would run. I will surmise that once you track this down, all other problems will go away.

As to airbag, the car does not care. The airbag controller (which you do not even have in your car) does not kill the power.

Markus

joes

I did the same swap in my race car. There are at least three places that the DME needs to be powered up that you don't get from the the early cars. It's not "plug and play" the DME's are (WAY) different. You will have to tap the harness to get the power where it needs to be.The only way that you will figure it out is break down the wiring diagrams and you have to have a DME input/output list. I don't have my notes with me I'll try to get them tomorrow.

Dougs951

Some notes as the car is in my garage right now.

The car is getting power to the fuse panel

The dme is getting power on the key.

The fuel pump is not, I ran a new circuit to it and it runs. Brand new pump btw.

We have tach bounce, but no injector firing or spark

This car is hacked up in so many ways, it drives anyone who touches it insane.

mblaszak

Bet you do not have power on the power pin for the DME relay. If you did, you would have a running fuel pump when you jumper the DME relay (assuming that you are doing it right and the connector at the fuel pump is good... they fail often).
Find out why you don't have power at the 30 pin on the DME relay when you turn your key on and you will have found out why the car does not run.

michael2e

How About your ignition switch itself. I've had those go bad before.

Dougs951

Pin 30 is getting power. I think the harness is bad from the fuse panel to the pump.

All the checks for the ignition switch show it is good.