injector wires shorted, what could it damage?

[blown 944]

Did you install an 02 sensor withthe new DME? I bet no

Does it idle perfectly for a long period of time? Or does it start to surge after warmup and longer @ idle (w/o driving it)?

I have ran w/o an o2 sensor for about 10 miles and seen a very rich condition even with a supercharger on it so I bet it is really flooding it out on yours being na.

[Voith]

I had identical problem with injector connector on cylinder 4. the car started and died instantly. the problem was short connection in ruber boot on connector..

I'd post a picture but it's raining really hard outside

[onZedge]

In your first photo, you show a plugged nipple on the throttle body. That is not correct. That nipple is THE vacuum source for the FPR, FPD and the metal EVAP control valve. The other nipple is for the rest of the EVAP system.

Did you find a vacuum line diagram? It is the same for a 924S and 944. If not, download these FSMs for the 944/924S:

http://www.eucc.dk/manuals.htm

I gave a thorough description of the EVAP system and plumbing here:

http://forums.pelicanparts.com/showt...ghlight=vacuum

[Keithr726]

I had a similar idle problem in my old 83 944. It would only do it sometimes. Also, it too would occasionally not start when it was hot. I ended up selling it that way.

[soxnail]

In our conversation earlier you had said that you could get hold of a scope. I think the time is now. Shotgun trouble shooting is going to fix it but you will end up spending a lot of money on parts you don't need. Get/borrow a scope and I will help you trouble shoot..don't give up on it
Sox

[924sownerga]

I fixed the vacuum lines correctly. I tested the resistance to each of the injector wires and the injectors and they are all the same. I am convinced that because the car ran well when I first replaced the computer that there is something sending errand signals to the computer. I think the scope is a good idea. I will hunt for one. I am going to replace the o2 sensor (by replace I mean put one on the car).

[924sownerga]

I would like to test the voltage at each wire into my DME at each wire. I found a good diagram so I know which ones are grounds but I wonder if anyone has a good testing plan for the wires coming into the DME.
At the least, does anyone have a list of what the voltage should be for each wire into the DME?

Thanks, Brad

[soxnail]

Brad, To test the voltages on the dme other than the fixed ones is very hard without a scope, as the signals are variable and you need to look at the time as well as amplitude. How ever there are some pins that have fixed voltages on them to drive sensors etc. You can measure these.

Pin 2 idle sw. 4.3V to 5V
Pin 4 12V plus
Pin 9 airflow 4.5V to 5V
Pin 13 DME temp sensor 4.5V to 5V
Pin 18 12V plus
Pin 22 air flow temp sensor 4.5V to 5V
Pin 35 12V plus
Sox

[924sownerga]

New set of problems and update to old:
I replaced the oxygen sensor and the injector under the shorted wire (found a good deal on a single new injector and decided it was worth the $20.00.) I tested the injectors by placing a clear baggy around each of them and using a tie wrap I closed the bags. Then while cranking the car it was easy to see that each injector was firing and they were not leaking with just pressure in the line. The car started right up and idled fine. I test drove it and all was good with the world.
On the second test drive the car would die if I red-lined it. The oil pressure was low for both runs but seemed to continue to go down. At 60mph the car was reading an oil pressure of 2. It would go up some but would not go up like before to 5 if at speed. On the way home the car just seemed to shut down and would only idle at about 500rpm. The engine oil light was on. I pulled over, checked the oil. It was at an appropriate level and the engine was not running hot. The car restarted still with a low oil pressure on the guage but drove fine for about two blocks then did the same thing. The surge seems to be gone.
One other symptom, sometimes when you start the car cold it has no power but if you continue to drive it the car seems to click and all of a sudden it runs great. It is like a switch was thrown.
Thoughts????
Is it possible the oil pressure switch is telling the computer to shut down the car?
I will read to see how you test the oil pump. Any quick ideas.

[soxnail]

Originally Posted by 924sownerga

New set of problems and update to old:

One other symptom, sometimes when you start the car cold it has no power but if you continue to drive it the car seems to click and all of a sudden it runs great. It is like a switch was thrown.
Thoughts????

Look at the DME temp sensor...

Is it possible the oil pressure switch is telling the computer to shut down the car?
I will read to see how you test the oil pump.

The oil pressure does not shut the car down (no connection to the dme).

I would pull off the oil pressure sensor and hook a ohm meter to it, then use compressed air to actuate the sensor (no more then 10 psi or so and see if the if the sensor is working. (the resistance goes down with pressure iirc)

Any quick ideas.

Sox

[924sownerga]

any idea what the oil pressure relief valve does and what goes wrong when it stops working?

[soxnail]

OPR allows the oil to recirculate by bypassing it when the pressure gets above a certain point (kind of like a thermostat but for pressure). When it stops working you can get excessive pressure or no pressure depending on the failure.
Sox

[924sownerga]

I replaced the temperature sensor and the DME relay. The car started great, Purred at idle and ran for about 3 miles. Then it started doing the same thing as before.
I have lost patience and will scrap this car today. I really appreciate all the help on this site. Thanks to all,

[soxnail]

Sorry to hear that..good luck.
Sox