TPS

[mp470]

Dug the old girl out of the snow, barely made it home.  Stalling at stops...

Anyway, my TPS has no function whatsoever at the moment.  Wonder if that is part of the issue. No 5V ref., nothing. Two of the wires go right to the MAP sensor, not sure why.  One goes towards firewall in a loom under the air box.  
I may have completely misunderstood where the ECA is, I thought it was on the passenger side near the MAP sensor.  How I wish it was a carb...

Suggestions, please and thanks.

[Gary Lewis]

You can see the wiring here: Electrical/EVTM/1986 EVTM/Electronic Engine Controls.  Page 63 says the ECA is near the center of the instrument panel, so what you thought is the ECA is probably the ignition module on the left inner fender.

And if there's no voltage to the TPS then that is a big part of your problem.  One wire does go to the MAP sensor and another wire goes to a junction of wires close to that sensor.  The third wire goes to the ECA, and would have to go through the firewall.

But, I don't know how to test the TPS.  I'll look around, but hopefully someone who does know will come along soon.

[85lebaront2]

First issue is to diagnose the lack of the 5V reference circuit, it is not to ground directly, but goes to the sensor signal return. 1985 wiring is different in the color codes, the wire will have a base color and a hash or dot for the second color.

5V reference is circuit #351 and should be orange with white and comes from pin #26 of the EEC, signal return is circuit #359 and should be brown or black with white and is pin#46 on the EEC. These wires go to the TPS, EGR position sensor and MAP sensor.

Testing, in order to get a good test on the TPS, you need to unplug it and using an analog multimeter (I have a cheap one I bought at Autozone) measure first from the black with white to the orange with white, I do not have the actual resistance value handy, I do have a chart for the voltage vs rotation angle, which is tested with it connected and key on, engine off and measured at the dark green/light green wire. On yours, closed throttle needs to be as close to 1.0V measured to the signal return side or the system literally goes batshit crazy trying to run.

Best way to read the voltages with the connectors plugged together, use paper clips, and slide a straightened leg carefully through the back seal on the connector until it hits the pin or socket depending on which side you are on.

Good luck with it!

[Gary Lewis]

And now we know.  I'll get the '85 wire colors off my EVTM in a bit.

[Gary Lewis]

The 1985 EVTM shows:

Circuit #351 is Orange/white and goes from the TPS to the EGR valve position sensor, pin 26 on the ECA, and the MAP sensor

#355 is Dark green/Light green and goes to pin 47 on the ECA

#359 is Black/White and goes to splice S168 and thence to pin 46 on the ECA

[85lebaront2]

Thanks Gary, I pulled the colors off the EEC pinout information I have from AllData, which supposedly is taken from OEM manuals.

[Gary Lewis]

Oh!  I thought you were saying you needed the wire colors.  

[85lebaront2]

If you read through, I gave the wire colors as I had them, my info was wrong on #359, everything else matched.

[mp470]

I use sewing T-pins, they can also pierce the wire gently if necessary.

So, the only wire that I traced back to the EEC is the dark green one strangely.  Both the orange and black/white were traced to the MAP sensor. I assumed from this that this green wire would be the 5V reference since it's the only one going to the EEC. Not a hint of voltage on it backprobing the EEC pin (not sure which pin number, just used continuity and jumper wire to trace).  Very confusing.  I've got the Haynes manual but they're not terribly helpful since they show diagrams and wire colors from sometimes only specific years and models and they do vary quite a bit.

Edit, oops, had to refresh the page to see the newest posts. Back to it.

[85lebaront2]

Try not to pierce the insulation, it will allow moisture in and corrode the wires. Orange/white is 5V reference, remember to measure to black/white not ground. The dark green may have had a light green 33 years ago, that is the TPS output and it should be around 1 volt to the black/white at closed throttle, rising to 4+ at WOT.

If you are getting no voltage on the green wire, TPS is probably bad, and I don't envy you changing it.

Haynes manuals, if they are on regular paper can be used in lieu of a Sears catalog as a TP substitute, especially when it comes to wiring.

[mp470]

Thanks kindly. I will put liquid electrical tape on all the piercings I did under the hood. 5V checks out both at EEC and at the TPS. Voltage changes properly with opening and closing throttle plate. Resistance is within spec at rest (between 3 and 4k ohms). However there is no change in resistance when opening and closing the throttle. Sensor toast?

[85lebaront2]

If the voltage is changing it is working, when checking resistance, where did you check? orange to black/white will be constant, orange or black/white to green will vary, green to black/white will be quite low at closed throttle and increase as you open it, green to orange will be high at closed throttle and decrease as you open it.

Throttle Position Sensor
Rotational Angle Signal Voltage
0 Under Travel 0
10     0.45
13 Closed Throttle 0.901
20 - 1.44
30 1.9
40 2.37
50 2.84
60 3.31
70 3.78
80 4.24
84 Full Throttle 4.538
90 Over Travel 4.538
100 5
Values were calculated for VREF = 5.0 volts.
These values may vary 3 percent due to sensor
and VREF variations.

Maybe these will help, it didn't completely copy the way I wanted it too, all the voltage values were supposed to be all the way to the right, in a column.

[mp470]

You're right, I realized I was checking the wrong wires. Everything checks out OK with the TPS end to end. Now onto other sensors.

[85lebaront2]

If you need the other values, I have them also.

[85lebaront2]

Ok, maybe Gary will want to put these in a reference area, but here are the values for some of the sensors, I may have to dig to find the EGR position values.



ACT values are the same as the ECT. I hope this will help in troubleshooting. The voltages are measured to the sensor signal return, circuit #359, not to ground, on the ECT and ACT resistance is across the two pins with the harness unplugged.

[mp470]

You read my mind here, after doing all that, I got a code for the ACT.  Whereabouts is it located?

[Gary Lewis]

Bill - That's good info.  But is it for all Bullnoses or for a specific year/engine combo?

[85lebaront2]

Actually, the information I found was generic to Ford EFI systems, primarily speed density ones.

[85lebaront2]

In the driver's side of the intake, I believe in #6 cylinder runner, it and the ECT will look quite similar, but the ACT sits in an intake runner and the ECT in a cooling system section.

[mp470]

Well that code went away, but messing with that whole harness is revealing some issues for sure. Now, back to square one with no start hot or start / stall. Not even terribly hot, starting it cold which it does like a dream, idles perfectly for 5-10 mins, shut engine off, crank no start.  Spark is good at distributor so I can't imagine it would be the ICM (distributor-mounted).  Fuel is coming through based only on the smell and the engine sounds flooded after multiple attempts.  Stored codes are 31 and 63, both related to the earlier mentioned splice of orange/white wires and not to a starting issue. Never get a chance for KOER testing unless I do it cold which I understand is not recommended.