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Electronic Oddity, any in depth ideas?


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180 replies to this topic

#176 sparkyboy

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Posted 21 January 2018 - 04:36 AM

i think that your biggest points here are:

1- The main relay needed replacing (a likely reason for the parking lot failure)

2- you are getting erratic action for both spark and fuel, but something at least

3- you were having a problem prior to your current problem.

4- you have an ecu, cam and crank sensor, igniter, and coil that worked in other cars.

To me it seems like a bad ground that finally crapped out...particularly an ecu ground. or maybe a fusible link? I dunno, but I will certainly bet that this problem has something to do with why your main relay went bad.

I will also bet that all your old sensors, coil and ecu are still fine

 

 

Now someone correct me if I am wrong, but the fuel injectors always get voltage with the key in on, when the tooth on the crank passes the sensor that causes the voltage to drop to whatever injector corresponds to crank position? Thus opening the injector for a brief moment?

 

You checked that you were indeed getting 12v to all three power supply pins in the harness with the key on

The fuel injectors are getting 12v as well

You checked the starter switch as well? That one is supposed to get voltage only during cranking (pin 81)

 

Just for grins check the voltage at the throttle position sensor. It's one of the few sensors you can test without the car running and that isn't a pain to get to. If you are getting 5 volts at the positive and whatever voltage at different throttle openings then that is a good sign because the ecu is sending something. 

 

This kind of wacky electrical work is why I like using a power probe instead of a multi meter. All you have to do is touch the probe to a wire and it tells you whether its a ground, a pos (with or without voltage) or a faulty wire if there is no sound. and you can push the button to supply 12 volts instead of screwing with a jumper wire. The only con is the cord is kindof a pita

 

If I were in your shoes (meaning in no particular hurry ha), I would just start at the top of that pinout and check as much as I can without the car running. I would take a couple of hours to look at the diagram and find the wire color as well and label the important ones so I don't have to look at the stupid pinout so much. Lol

If I found any goofy readings, (especially any of the circuits that get voltage only when cranking) I would cut the wire for the grounds and ground it nearby to see if it changes.

Then I would ask General Disorder if I can borrow his cool scope haha

 

Just a side note, While stripping and testing my wiring harness, I noticed that the grounds tend to be rather sensitive. At first I just gathered them all together, I believe there were five wires and three body ring connectors to put a bolt through. Well, at first I stuck a bolt through the rings and vice gripped it to the negative terminal. That didn't work well. Neither did simply vice gripping them all at once to the terminal.

Only when I separated them and vice gripped them one at a time did they work reliably. And I was kindof freaking out because I was getting weird action at the main relay, and faulty readings at the ecu. There were wires f**ckin everywhere! haha.

 

I guess the point I am trying to convey is that by all appearances those grounds were fine and would have even tested fine, and were indeed (at times) fine! But just the slightest movement of any wire would cause one or two of those grounds to act up and it would frustrate me to no end. Until after about two whole days of struggling I finally realized that half assing the ground wires the way I did is what caused me a pile of grief


Edited by sparkyboy, 21 January 2018 - 04:45 AM.


#177 koolminx

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Posted 21 January 2018 - 04:40 AM

, why should I scope the crank and cam sensor with both the crank sensor and the cam sensor are new and the cam sensor is brand-spanking-new right out of the box and the cam sensor is off a running driving motor this issue if not the crank of a cam sensor in the does not need a scope for that particular thing while the engine cranks it gets no signal but as soon as it is released it gets crank signal so between the ACM and the crank signal to the injectors what causes the injectors to flash because I have literally had the key in the on position and jumpered the crank signal down at the solenoid on the starter and it still does not Flash the injectors until after the engine stops turning.

#178 sparkyboy

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Posted 21 January 2018 - 04:46 AM

Just a thought and this might be a stupid question, but did you check that all three of the plugs (on the engine) for the ecu are plugged in?


Edited by sparkyboy, 21 January 2018 - 04:47 AM.


#179 GeneralDisorder

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Posted 21 January 2018 - 05:30 AM

No question that the sensors are good. They almost never fail. And have been swapped, etc. Now - assuming your other tests are all correct and you havent missed anything (power and ground to ECU whole cranking) then I have no choice but to assume the cam and crank signals cannot be understood by the ECU, or are not present. 

 

What needs determining is if the signals are getting to the ECU and are in alignment with one another, not missing any triggers, sufficient amplitude, and signal integrity. 

 

Do not take for granted that the valve timing is correct. I have seen the marks all line up and it still be out of time more than once. Remember the pulleys have the marks on them - the shafts are not gauranteed to line up with those pulleys unless the keys are intact. Something you only find out upon tear down. 

 

GD



#180 koolminx

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Posted 21 January 2018 - 10:58 AM

Just a thought and this might be a stupid question, but did you check that all three of the plugs (on the engine) for the ecu are plugged in?


Yes everything is plugged in and it is not a stupid question

#181 koolminx

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Posted 21 January 2018 - 11:08 AM

The timing marks on the Craig and both cams are good the bolts holding the cam sprockets in place are intact the Locking pins on the camshaft holding the camshaft sprockets in place are good this is not a timing event this is an electrical event and I am just missing something but I will find it




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