1990 GSX No Start issue, thorough testing done...

[silvershark]

Ok, so I was helping a buddy try and troubleshoot his no start problem today and we were still unable to get it to start.

Here is what we tried.

Checked fuel pressure 43psi. Check spark, no spark. Air seems to be fine.

So we started troubleshooting the spark related stuff, checked the CAS, we get 12v on the red wire, 5v on the small black, 5v on the small white, and the ground wire looks fine. Cycled the CAS manually and can hear the injectors spraying, the 5v cycles 4 times as it should, and the other 5v cycles 2 times as it should.

We then checked the Coil Pack using resistance tests. I got 12.2ohms between the first pack and the second pack where the spark plug wires attach. This seems to be within range of 10ohm -14ohm. I then tried to check the 4 connector plug and it shows 0 ohm on all 3 of the connectors and 12v on the power supply wire for the 4th connector. So this seems legit. I even went down to the parts store to check with my multimeter and the new one read about the same.

We checked the 6 pin connector that connects to the coil pack using the 1.5v AA battery test with a light bulb and that worked fine. We have two of these modules along with 2 of the coil packs. We have tried swapping both and it still wont start.

The MPI relay works fine. I removed the MPI fuse and noticed on the 6 pin pack, you get 2.5v on pin 2 and pin 5 when cranking and when you remove you do not get any voltage. So it seems you need the MPI fuse or it wont start period.

So I pulled the spark plug wires and attached a brand new plug to the end and I see no spark. I am STUMPED. The only logical thing I can think of is the ECU is bad... This seems unlikely as the CAPS were replaced about a year ago.

The other weird thing, when I did the light test to the 6pin connector that connects to the coil pack, it requires 12v to either pin1 or pin6 to test the module.... At no time when cranking did I see 12v to either pin 1 or pin 6. Can anyone verify with their running dsm if they are getting 12v on either pin 1 or pin 6 of this connector? This seems like the only likely thing to make sense other than a bad ECU.

Please help, I want to get this car back on the road!

 

[luv2rallye]

The other weird thing, when I did the light test to the 6pin connector that connects to the coil pack, it requires 12v to either pin1 or pin6 to test the module.... At no time when cranking did I see 12v to either pin 1 or pin 6. Can anyone verify with their running dsm if they are getting 12v on either pin 1 or pin 6 of this connector?

You won't see 12v while cranking because it is a short pulse then and your meter will just read an average.

You can do a real load test of the coil by unplugging the PT and with the key on, short harness side pin 1 (yellow-green) to ground and then remove it at which time 2 plugs should fire. Repeat for pin 6 (yellow-black) for the other 2 plugs. Make sure you have the plug casings clamped to ground. If ok, sounds like the problem is in the ECU (or wiring) since you've tested everything else. Try swapping ECU's.

 

[river]

So I am on my buddies account... We grounded out plug 1 and plug 6 and then simply shoved a copper wire into the coil pack to eliminate the plug wires. One in inside the coil pack and the other side to ground on the car. I didn't get any spark. I did this with all 4 banks while grounding out pin1 and then repeated while grounding out pin6. So at this point does it sound like the coil packs or the ECU?

Thanks!

If i ground out pin1 on the Power transister harness It sparks, I get the same thing when grounding out pin6. I took my meter and read 11.5v both times when I did it. So it looks like pins 1 and pins 6 are getting 12v like they should.

 

[luv2rallye]

Ya remember you touch it to ground and then remove it and that's when you get spark. It sounds like it's working though. I would suspect the ECU. Try to swap with a friend's ECU to test or send in for repair.

 

[river]

After we did the above test we hooked everything back up to see if we were actually getting spark out of the coil pack. We unplugged all the plug wires and just put a piece of thick copper wire into the coil pack on both 4/1 and 2/3, we just held the wire close to a ground, cranked to see if we got spark, which we did. So, the power transistor, cas, and coil pack all have tested good and working. I know I'm getting fuel because the plugs were getting washed with fuel at first (then I unplugged the fuel pump to not wash out cylinders with fuel).

I also even took apart the timing belt side and made sure it was all in time. Everything is perfect.

So, there's great compression, fuel, and the coil pack is creating spark. Im going to do one more test with the plug wires and a spark plug. It really seems odd to me that we get spark when going directly through a copper wire to ground, but we don't see spark with the spark plug wires hooked up and plugged in to a spark plug. If the plug wires check out....looks like it's time for a new ECU.

There's tons of 91+ ecus here...but no 90's. Going to have to order one in...

 

[NYCRedlineTalon]

I'm Having that type of problem too But im not getting spark at all. My core pack isnt getting power at all i think itz da wiring harness but im not sure.......my cam position sensor isnt gettin power nor is my crank. it cranks but don't start of course. I looked for shorts but i dont have one. I had to wire a few plugz back together under the car that just like ripped off but i'm tryna figure out what would stop me from getting spark or stop power from getting to my sensors and coil. It's actually a headache, Been tracing wires for like $dayz straight and still no luck. Anyone might have an idea?

 

[river]

Couldnt find a 90 ECU locally, so I just swapped pins 6 & 14, then put a known good 91+ ecu in. Car started up and runs great again. The tach is screwy, but I'm going to buy one of those boards from DSMChips and install it to fix that issue. It's good to have this car on the road again!

 

[luv2rallye]

I'm Having that type of problem too But im not getting spark at all. My core pack isnt getting power at all i think itz da wiring harness but im not sure.......my cam position sensor isnt gettin power nor is my crank. it cranks but don't start of course. I looked for shorts but i dont have one. I had to wire a few plugz back together under the car that just like ripped off but i'm tryna figure out what would stop me from getting spark or stop power from getting to my sensors and coil. It's actually a headache, Been tracing wires for like $dayz straight and still no luck. Anyone might have an idea?

For the 2gT the MFI relay (turned on by the ECU) supplies power to the sensors and coil. For the 2gNT its the ASD relay. Not sure what you have now since you list a NT engine with turbo.

 

[NYCRedlineTalon]

For the 2gT the MFI relay (turned on by the ECU) supplies power to the sensors and coil. For the 2gNT its the ASD relay. Not sure what you have now since you list a NT engine with turbo.

itz a 420a n\a motor....with a turbo kit

For the 2gT the MFI relay (turned on by the ECU) supplies power to the sensors and coil. For the 2gNT its the ASD relay. Not sure what you have now since you list a NT engine with turbo.

where is this MFI relay, and ASD relay located? do they normally go bad?

 

[luv2rallye]

NT has ASD relay (T has MFI relay) and is 22 b in this pic: http://www.dsmtuners.com/forums/attachment.php?attachmentid=23588&d=1075582725

 

[NYCRedlineTalon]

NT has ASD relay (T has MFI relay) and is 22 b in this pic: http://www.dsmtuners.com/forums/attachment.php?attachmentid=23588&d=1075582725

What is A, B, and C? And could the ecu cause this issue cause the two relayz I have are good....I.don't have a third one. Is that a problem?

 

[luv2rallye]

What is A, B, and C? And could the ecu cause this issue cause the two relayz I have are good....I.don't have a third one. Is that a problem?

A is the Fuel Pump relay, B is ASD relay, C is ETAX relay (present only if an auto). If the ASD relay is not clicking on, yes the ECU may the problem since it drives it.
Make sure the 30A "engine" fuse in engine fusebox is good.
Also you can temporarily touch a ground to the ASD relay's red-white wire to see if it works.

 

[NYCRedlineTalon]

A is the Fuel Pump relay, B is ASD relay, C is ETAX relay (present only if an auto). If the ASD relay is not clicking on, yes the ECU may the problem since it drives it.
Make sure the 30A "engine" fuse in engine fusebox is good.
Also you can temporarily touch a ground to the ASD relay's red-white wire to see if it works.

Yea it's a manual. And I have a 40amp fuse for the engine fuse. I tested the ASD fuse and even replaced it with a ford one just to see what it does and they both test good but still no start. What reading should the ECU have if I was to test it? Is there a certain way to test? I got some readings but it was jumping all over the place. I just want to cover all my basis cause I don't want to just start throwing parts I don't need into it. And Ecu's for my car seems to be costly I just figure i'd invest in a modded ecu if that will garentee a start.

 

[luv2rallye]

I'm not familiar with a turbo kit on a NT so first I need to know if you have a turbo or NT ECU (or something custom)? And if turbo ECU, has the entire engine harness been changed to a turbo one? I need this to reference wires in the wire diagrams manual.

Next when you temporarily touch a ground wire to the ASD relay's red-white wire or tab (with other wires connected) does it click on (and +12V appears on its black-red wire)?

The ECU cannot be tested other than to swap it and/or look inside for leaking capacitors and broken/melted foil paths. But when it's ready to turn on the ASD relay it grounds pin 67 (assuming you have a NT ECU) which is that red-white wire (NT ECU pinout: http://www.dsmtuners.com/forums/420a-bolt-tech/283950-2gnt-pcm-connector-views.html).

 

[NYCRedlineTalon]

I'm not familiar with a turbo kit on a NT so first I need to know if you have a turbo or NT ECU (or something custom)? And if turbo ECU, has the entire engine harness been changed to a turbo one? I need this to reference wires in the wire diagrams manual.

Next when you temporarily touch a ground wire to the ASD relay's red-white wire or tab (with other wires connected) does it click on (and +12V appears on its black-red wire)?

The ECU cannot be tested other than to swap it and/or look inside for leaking capacitors and broken/melted foil paths. But when it's ready to turn on the ASD relay it grounds pin 67 (assuming you have a NT ECU) which is that red-white wire (NT ECU pinout: http://www.dsmtuners.com/forums/420a-bolt-tech/283950-2gnt-pcm-connector-views.html).

it's a non turbo ecu. As far as the turbo wires were just added. I still have to try touching ground to that relay wire. My boss said my ecu was bad thru his own investigation but i just want to cover my basis.

 

[luv2rallye]

Ya if the relay works on the test and you then get voltage at the injectors and coil, I'd say the ECU being bad is then a large possibility.

 

[NYCRedlineTalon]

Ya if the relay works on the test and you then get voltage at the injectors and coil, I'd say the ECU being bad is then a large possibility.

The crazy part is the injectorz shoot but not the coil pack....

 

[luv2rallye]

Well the ECU controls (turns on/off) the coils and injectors. If the injectors work then the ASD relay must be working since it supplies power to them (ECU just completes the circuit to control them as it does for the coils). The ECU also supplies power to the sensors. Still sounds like the ECU is the problem.

 

[NYCRedlineTalon]

Well the ECU controls (turns on/off) the coils and injectors. If the injectors work then the ASD relay must be working since it supplies power to them (ECU just completes the circuit to control them as it does for the coils). The ECU also supplies power to the sensors. Still sounds like the ECU is the problem.

okay thankz im test some more friday and keep u updated. Thankz for all you help sir