1976 Cadillac Eldorado fuel injection ECU

[R.B]

Are there any here who have a ECU for for sale ?
I want also to know how I can check if the speed sensor and trottle position switch is defect or not.

[TJ H 20664]

The TPS on those can be checked with an ohm meter. They are not like modern ones that are a constant variable signal.  Im going from memory but if you want me to I will dig out the manual and confirm but this is what I remember.  5 pin plug.  Middle pin is the common or wiper contact.  Top is either wide open or closed, bottom is either closed or wide open (I cant remember which way it goes).  The last 2 inner middle pins are alternating contacts so as you move the throttle the signal should alternate between the two.  It doesnt know what position the thottle is in other than wide open or closed it only knows movement.

I think there was something about the speed sensor but it required a o scope.  Does the cruise work?  I think it was the same sensor.

[R.B]

I did not know if the cruise work. Not possible to test since the car not will run.

[TJ H 20664]

Ahhh... not running at all.  I doubt the speed sensor would have anything to do with keeping it from running unless by not running you mean as soon as the car moves it dies?

Those systems are fairly simple by todays standards and only require a few things to work.  Did the thing ever run or did you buy/find it like this?  By speed sensor do you mean the pickup under the distributor? That pickup is just 2 switches that tell each bank of injectors when to fire.  Again from memory 3 pins, one of them is common the other two are the contacts that are normally open and pulse closed each one time per turn of the dizzy.  Do you have spark?  Can you hear the injectors clicking?  Do you have fuel pressure?

Give us as many details as you know about how this problem started and what you tried already.  I will grab my manual (regular shop manual)and see if it any help.  The few of these I have messed with the ECU has never been the problem, just like on todays cars you still need the old fashiond mechanical basics for them to run.  I parted out one that didnt run because the plastic cam gear had fallen apart so the cam and distributor were not even turning.  That one sounded real strange turning over.

TJ H
20664

[R.B]

The car did start, run 10 secund then died. If I put some gas in the trottle did it run but if I move the gas pedal did it died.
I guess the car have a problem with the ECU, cooling water sensor, air temp sensor, trottle switch , speed sensor or fuel pressure. I have changed the fuel filter. The fuel pump works but I have not checked the pressure. I will like to know how I shall check the speed sensor under the distibutor and the trottle position swicth. It looks like that the cooling temp sensor maybe is defect. I have put on a jumper with a resistance on 1000 ohm there when I am waiting for a used temp sensor I have ordered but this did not help but the car will only run at low speed and died if I move the gas pedal.

[TJ H 20664]

According to the 77 shop manual:

There are two temp sensors and they are the same. Air temp sensor is located on the intake manifold and the coolant sensor is located on the right side of the block below the thermostat.  There is a graph of the ohms vs. temp.
-20*F=650 ohms
0*F=700 ohms
60*F=950 ohms
180*F=1300 ohms
240*F=1600 ohms

There are 2 fuel pumps, one in tank, one on chassis.  They both appear to run off the same wire from the ECU.

Injectors are group 2 3,4,5,6 & group 1 1,2,7,8

Distributor trigger has 3 pins.  #3 white is the common.  #1 black is group 1. #2 red is group 2.  they should pulse on and off as the distributor turns.

Throttle postition sensor is shown as a 5 pin connector.  For some reason the book shows it B A D C E as the order of the pins but this may just be the way its drawn.
E pink      common/wiper
C lgt green group 2
D tan       group 1
A black     wide open
B blk/wht   closed
you should get 0 ohms between E & B when closed
between E & A when wide open
there are 4 1s and 4 2s starting with 1 and altenating all the way up to wide open.

There is a fast idle valve that seems to work like an electric choke.  There is also something called throttle body air bypass that controls the air when the throttle blades are closed.  I dont have one of these to look at so I dont know what this is or if its something that could be stuck or adjusted.

There are several pages of tests but they all refer to using a fuel injection analyzer so I dont know if they would do you any good without one.

Hope this helps.  It has been a while since I worked on one of these. The fuel injection section of the manual is 76 pages but most of it doesnt look like it will do much good without the tester they keep talking about.  

TJ H
20664

[R.B]

Thank you for the information.