2G Car won’t start

[JKD06]

This will be a bit of a long one so huge thanks to everyone who reads this whole thing and offers their input.

I have a ‘97 GSX that blew its engine and I’ve recently bought a new one, built it, and replaced it. Since replacing the car no longer starts. OBD scanner doesn’t recognize any system in my car as being active or installed besides my SRS system and no check engine light comes on when I switch the ignition on.

Starter is wired to a separate “push to start” button and was like that when I bought it so the starter will engage and crank the car but nothing else happens. I’m seeing no voltage to my spark plugs or my injectors. And this is all the case with 2 different ECU’s.

I have 3 grounds in my engine bay: Battery-Chassis, Battery-transmission bell house, and chassis-intake manifold. Any and all help is appreciated! Brand new battery as well, no blown fuses

 

[steve]

Sounds like your not getting power to the MPI relay or it's not getting activated by the ECU.
Make sure you have 12v to the backup power pin on the ECU and that you're getting getting 12v from the ignition switch when you turn the key to run position.

 

[JKD06]

The car is a no crank no start. All the grounds have been double and triple checked. New battery and terminal connectors, new starter, new mpi relay in passenger footwell, new crank position sensor. I also have no power to my OBD port. Please help!

 

[pauleyman]

How To Diagnose A No-Start

Diagnosing a No-StartI've been seeing a lot of No-Start related threads popping up lately, and I figured a basic Tech Article for diagnosing a few of the most common No-Start problems might be in order. Any images posted are courtesy of my 1990 GSX your setup may differ slightly; refer to...

www.dsmtuners.com

 

[steve]

Sounds like you've been throwing parts at it vs diagnosing the problem.

Read https://www.dsmtuners.com/threads/2g-basic-ecu-mfi-mpi-relay-circuit-function.497188/ and work through the process to see where things fail and let us know what you don't understand or what you find.

The no start checklist is also a great resource but you still sound like you have electrical issues getting the ECU to turn on.

 

[MattiaFTW]

Are the Fuel Pump and MPI relays clicking? Located at passenger footwell left side.

 

[cyclops755]

What, if anything, aftermarket or modified do you have on the car electrically? You mentioned the push button start - what else?

 

[JKD06]

Sounds like you've been throwing parts at it vs diagnosing the problem.

Read https://www.dsmtuners.com/threads/2g-basic-ecu-mfi-mpi-relay-circuit-function.497188/ and work through the process to see where things fail and let us know what you don't understand or what you find.

The no start checklist is also a great resource but you still sound like you have electrical issues getting the ECU to turn on.

The only thing I’ve thrown at it is that mpi relay. Everything new I have is because I’ve done a full engine build and I did a lot of “while I’m in there” type of work

What, if anything, aftermarket or modified do you have on the car electrically? You mentioned the push button start - what else?

I uninstalled that push start and wired it back to the key. Still no joy unfortunately. I do have the fuel pump wired to its own switch.

Sounds like your not getting power to the MPI relay or it's not getting activated by the ECU.
Make sure you have 12v to the backup power pin on the ECU and that you're getting getting 12v from the ignition switch when you turn the key to run position.

I’m not getting any power to the ecu, I have my OEM one and an ecu I bought from someone nearby that has ecmlink already installed, and neither are receiving/putting out power. No CEL when the car is turned on.

 

[steve]

I’m not getting any power to the ecu, I have my OEM one and an ecu I bought from someone nearby that has ecmlink already installed, and neither are receiving/putting out power. No CEL when the car is turned on.

It's for issues like this that I wrote the post in the link above. It explains how the MPI circuit works and tests to help you figure out what's failing.

 

[JKD06]

It's for issues like this that I wrote the post in the link above. It explains how the MPI circuit works and tests to help you figure out what's failing.

I’ve read the post. I do still need a little help in what my next plan of attack should be. I know my mpi relay is new. All my fuses are good and I still get no power to my ecu. What should my next steps be?

 

[pauleyman]

I’ve read the post. I do still need a little help in what my next plan of attack should be. I know my mpi relay is new. All my fuses are good and I still get no power to my ecu. What should my next steps be?

You stated you've checked stuff. Checked how? With a meter? Ypu need a volt/ohm meter and go through your mpi circuit. I wouldnt have even replaced the main relay before I did that.

 

[steve]

I’ve read the post. I do still need a little help in what my next plan of attack should be. I know my mpi relay is new. All my fuses are good and I still get no power to my ecu. What should my next steps be?

"The 2G ECU receives backup power on pin 80 from Dedicated Fuse #11 (room) in the relay box in engine bay. This is used to maintain the RAM in the ECU's CPU and allow the ECU to power itself up. It also provides power to the radio to maintain it's settings and to the cabin lights. Like MFI relay input pins the backup power on ECU pin 80 should be present all the time. In other words it's unswitched.

The ECU sits dormant in a powered down state waiting to see pin 82 (IG1 from ignition switch) go high (to battery voltage). When the IG1 from ignition switch goes high the ECU pulls pin 38 low (to ground). This causes the the MPI/MFI relay to activate and switches the MFI power from the input to the output pins providing power to the ECU on pins 12 and 25 along with various sensors, solenoids, injectors, ISC, and O2 Heater in the engine bay.

Shortly after battery voltage shows up on ECU pins 12 and 25 the reset circuit in the ECU wakes the ECU up, the CEL will come on for about 5 seconds and then turn off, the boost gauge will display 0 (Stock ECU software on turbo cars) and the ISC on the throttle body will move in and out to rehome.

The next interesting condition is when ECU pin 71 (indirectly START from the ignition switch) goes high (to battery voltage) causing the ECU to do the things it needs to do the start the engine.

Once the engine is spinning (CAS is pulsing) the ECU pulls pin 8 (The Fuel Pump Control signal)) to ground and continues to hold it low until you turn the car off or the engine stops (CAS stops pulsing for 10 seconds), to keep the fuel pump powered."

Which part of this isn't doing what I describe?