I have an 86 GX (auto) that has no spark and have been trying to fix for weeks now, the connector that plugs into the leading ignitor gets a reading of only 4-volts and 0-volts to the trailing (which I believe is normal till the car is running and at a certain RPM?)

The normal stuff has been gone over like battery being fully charged, all the engine harness has been gone over more than once to check for bad ground, all fuses have been replaced etc.

I decided to check the ECU since a mechanic suggested that was likely the problem (none of the idiot cluster lights come on) ECU turned out to be fried! so located a replacement and changed it. Did not fix the problem thou still reading 4 volts at the connector and no idiot lights coming on...

could really use some good knowledgeable help with this please (should I be taking apart the dash next and checking the inside harness for a short or bad ground?)
anything else I should be checking replaceing?

 

Do this go down to your nearest junk yard and pull a couple of coil's off a rex there. should only cost you 20$ find out if your's went bad.

Ive had coil's go bad just by sitting for a peiod of time. When i replaced my engine my car only sat for about a week. When i got it all back together i wasnt getting spark in one of my coil's for some reason. Turns out it just went bad...My buddie lent me one of his and whala fired right up.

 

I have two full sets of coils with ingnitors, now granted they have all been sitting for some time as well to know if any of them work or not has yet to be discovered, As stated above you can see my problem starts before the coil as the car is not providing the right amount of volts to the coils ignitor pack(s)

thanks for your suggestion thou

ps. would be nice if scrap yards exsisted within 200kms around here with 7's in them :P

 

You should be going to the SMALL, WHITE, TWO SOCKET connector at the LEAD coil assy.

There is a black/yellow wire there that should have battery voltage.

No batt voltage means the MAIN RELAY is not pulled in. The MAIN RELAY is pulled in when the key is to ON, and you have a good ENGINE fuse.

FORGET about the other wire in the SMALL, WHITE, TWO SOCKET connector at the LEAD coil assy.

FYI, the coils have to be bolted to the chassis for the coil assy to work. The ignitor gnd is thru the coil assy body. IF the coils are bolted down, then that's fine and don't go off on a tangent on coil grounding etc.

The ECU and hence the coils/injectors, gets it's gnd from a two wire ring connector on top of the rear rotor housing. You cannot see this without dismantling the top of the engine. So you go to the ECU connectors and take them off. You look at the FSM page called CONTROL UNIT and see which wires are the gnd wires and check them with a digital meter with the key to OFF.

Then you look at the pages called CONTROL UNIT and turn the key to ON and with all the plugs NOW connected to the ECU, you backprobe the plugs and compare YOUR readings with the values in the FSM pages called CONTROL UNIT.

CONTROL UNIT pages are found in the FUEL SECTION. Only use a S4 CONTROL UNIT PAGE for your car. No series five allowed.

 

The MAIN RELAY has two plugs on it.

Pull the one with four wires off. See if you have batt voltage at the wires that are black/green and white/blue. They should have batt voltage.

 

what if its a low voltage? 4.6-volts is what I get a reading of...

 

Bad meter/bad ground for the negative lead of the meter/bad Main Relay contacts (see the remarks about checking the black/green wire on the four wire plug I mentioned).

Or go to the MAIN RELAY and pull the four wire plug off. Jumper the black/green with the black/yellow in the plug and then go look at the SMALL, WHITE, TWO WIRE CONNECTOR at the lead coil assy. There HAS to be 12v there now or your wiring is cut in two. Car will not start in this configuration because the fuel pump is not powered with that plug off.

 

Thank you very much for your advice thus far, very helpful.

 

WHOOT!! Houston we have SPARK!

Still a no go on starting it thou cranking over and have smoke comming out the exhuast but thats it so far. Any ideas where to head next? recent fuel pump installed and have fuel, fuel is getting to plugs (I have pulled them out a few times and checked).

With plugs out and cranking there is strong pulses(however dont own a tester to know excattly what kind of compression it has) should I be trying the ATF trick anyhow?

ps. this car has not run in 5 years...

 

Well today is a good day indeed. the car Runs! finally it runs! its not idling on its own yet or starting without the aid of a boost from my camaro but the point is it runs! twice now I have started it up (lots of smoke coming out of her still and takes a lot of cranks before she fires) but did I mention it runs?...

Remember its been 5 YEARS! since anyone has had this car running and all it took was a fuel pump and ECU, and me pulling out all of my hair for weeks! :P

Im hoping to have it idling on its own before the night is finished so stay tuned the neighbors must hate me by now. lol