420A No spark, results and confirmation

[bmxunderground]

I'd like to say for those who may frequently answer my posts, yes I still own five of these 420a eclipses, and yes a new problem

Car: 95 eclipse RS N/T
Trans: 5spd

Problem: No start (no spark)

Items checked:
- MFI relay
- ASD relay
- Cam sensor
- Crank sensor
- Coil pack, plugs, wires
- TPS
- wires near EGR tube (for melt through)
- capacitor (mounted on valve cover)-->front of block on other year models.
- VSS sensor has not been operable for quite some time

After reviewing almost every post I could find I wanted to see if I could get some professional/experienced confirmation on my findings.

The Red w/White wire coming from ECU to ASD relay (pin 4 i believe) shows 12 volts during KEY ON, as do pin 8 and 6. I understand that the ECU is to ground this wire (pin 4) when the starter is engaged.

Pin 4 remains at 12v even while starter is activated and engine is turning over. There is zero voltage to the Black w/Red wire (pin 2) at any time thus zero voltage to the coil pack center wire.

Does this confirm a dead ECU? or is there more inspection I should be doing

NOTE: while wiggling wires near the coil pack at one point I began to get spark. (had one spark plug connected to a plug wire) Vehicle has also been known to sit a few days then start up flawlessly.

 

[cookmeup272]

I would say it is a dead ecu but u said if u wiggle a wire, sometimes you can get it to start? maybe one of the wires is frayed or cut or something.

 

[YENKO]

Does the engine and chassis have a good ground signal?

 

[bmxunderground]

this car is a show car so I have gone through the pain staking trouble of ensuring every surface is neat and clean. As far as I can tell all grounds are attached firm and clean.

I'm really looking for information from those with experience on the behavior of this particular ECU and known issues that can be verified and tested.

I wish life were as simple with this car as swapping in a known good unit, unfortunately the five spare ECUs I have are for all newer model eclipses.

 

[bmxunderground]

it has taken me awhile to get a new ECU. Finally got one, plugged it in and same issue. NO start. no spark.

Red w/white wire is not showing ground at KEY ON.

Should I try to splice a new ground to pin 12? at the ECU

any suggestions would be helpful as I spend my day playing with all this wiring.

Thanks,

 

[#40Fan]

Don't wire the Red/Wht directly to ground. It will keep the ASD energized all the time.

I would start by unplugging things one at a time and see if there is a sensor that is goofed up and causing the PCM to do this. I would begin with the three wire sensors sense they normally are the problem when I have ran into this before.

TPS, Cam, Crank, Map, TPS, and VSS. Unplugg one, cycle the key, look for a ground at the Red/Wht. If nothing, leave the first unplugged and go to the next. If you find the Red/Wht grounds after unplugging one of the sensors, start plugging the others in one by one and checking the Red/Wht as you go.

With you having a VSS problem before, you might want to start there. Make sure the wires aren't split and touching eachother at each sensor too.

 

[bmxunderground]

yea, the VSS went out some time ago. It has driven unplugged for a while now. Before the car died on me, it had intermittent loss of spark and eventually quit all together. I had replaced the crank sensor before when it behaved in this same way. I guess I might try replacing that once more. I hate intermittent electrical issues....

 

[bmxunderground]

did what you had mentioned, unplugged each sensor one at a time and still the red/wht wire would show voltage, never a ground, each time the key was cycled on. This is the new ECU as well. I really don't understand what could be wrong.

After a day of probing wires, I found a short in the cooling fan. the motor had melted and locked up. Also found a fray in a new splice on the crank sensor. After the repairs were made, crank sensor showed fault via key dance. Replaced and car is running.

NOTE: autozone crank sensor was replaced only 1000 miles ago and died this soon. Who knew.

New ECU was a good investment given the cars age, never-the-less, problem solved.