Double Dead Exp

[cucaracho]

Folks,

Things went bad. My 91 Sport 4X4, 5-Speed Stick provides 11, 11, followed by 1, 11, 11 five seconds later. Nothing should be wrong. But there is no spark on any plug and the plugs show no wet signs of fuel. Due to the manner in which the failure occurred, I think one item is at fauld---I hope it is not the EEC-IV in the kick panel.

The initial codes after the truck went dead while driving on the street were 67, 16, 67, 16, followed by 1, 11, 11 five seconds later. I got rid of 67 by placing the stick in neutral and 16 went after I wiggled the wires on the EEC-IV module. Replacing both the EDIS-6 and Coil Six-Pack units did not help.

Any thoughts or ideas on things to try will be very much appreciated. I dread the thought of towing this puppy to the dealer.

A Dead Cucaracho

 

[cucaracho]

Still Dead Exp

I had some time available today to check a few things and found good connections between the EDIS-6 and EEC-IV's PIP and SAW wires. I noticed the PIP wire out of the EDIS has 11.2V and there is no apparent voltage on the SAW wire Key-On, Engine Off position. Looks more and more like the EEC-IV bit the dust but I remain hopeful and will bring out the o-scope tomorrow to check for the signals indicated in the manual.

Next I am going to clean the sensor on the crankshaft as the engine has leaked oil onto it and as a result of that leak the engine is down one and one-half quarts of oil.

Any suggestions for an EEC-IV source and for additional troubleshooting ideas will be greatly appreciated?

Still dead Cucaracho

 

[Bwana Bob]

How about the EEC relay?
Bob

 

[cucaracho]

Bwana Bob,

I have double checked on this one and think this particular relay is operating correctly with 11.3V on pins 37 & 57 of the EEC unit with the key ON. I do not know why 11.3V instead of 12.8 on the battery. Could this be relevant?

Any other thoughts that will help me clarify the problem?

Thanks for your help

Cucaracho

 

[cucaracho]

OK. Had some time available today and put the o-scope on the EDIS module's VR sensor inputs. I got a flat trace---either the Hall Effect device is shot or I have a open circuit. This could be the reason why I get 11-11 on the codes yet the engine has no spark.

I have tested the VR sensor and it appears to be shot. I made a circuit with a 12VDC PS, a buffer to drive an LED, and a resistor to limit the LED current to about 4mA. I placed the VR sensor in series with the input to this circuit and then passed a screwdriver blade by the tip of the sensor---and nothing happened. I need another sensor so I can continue.

I have learned so much about this vehicle with this problem, that I may be hard pressed to get rid of it after I am done.

The Roach

 

[cucaracho]

The VR-sensor came in and so today I will have an opportunity to install it in the truck.

I have taken measurements on the new unit using the previous setup and the new one definitely has a working Hall Effect device in it. Passing a screwdriver in front of the magnet causes the output to change states. The old unit is open with near-infinite Ohms across its terminals.

I will report what I find after I get the part replaced.

The Roach

 

[cucaracho]

And so it was folks. Replacing the CKP (Variable Reluctance) sensor solved the problem of no-spark and no-fuel in my X. I connected the o-scope to the PIP line with the engine running and it and other points are sequencing as shown in the papers I got from some outfit in England.

As a point of interest; I am installing a remotely-actuated relay to the wires that connect the CKP sensor to the EDIS-6 unit. There is no way in hell anyone can start the truck with that circuit open!

World of thanks to Bwana Bob for throwing his $0.02 into this issue.

A very happy Roach :exp:

1991 Sport; Manual Trans.; J&B Headers; F/R LSDs Dana/Auburn 4/10s; Rancho 3" Lift

 

[Bwana Bob]

Thanks, Mr. Roach for sharing your experience. I'll be sure to check that sensor if I ever have a similar problem. Your troubleshooting procedure sure beats replacing the EEC just on a hunch.


Bob