Fixinater2 wrote: ↑Fri Aug 21, 2020 11:07 am
We transferred the entire elect system from our parts car to the metro. It ran good for awhile but started dying on occasion. We traced it to the low voltage from the ecu to the injectors. Give her a shot of starting fluid she fires right up but dies due to no fuel. I don’t have a spare ecu to try. I
The engine wiring harness is rough having been repaired many times. I’m about to give it up and build a manifold and either put twin webbers or motorcycle carbs. This mod would allow me to remove a bunch of useless junk not needed to make the car run. This is the fourth gt I’ve had so I’ve a bit of experience with these cars.
I just happen to post up related information on the subject a couple days ago. I would say there is a good chance that it is the ignition signal to the ECM that is causing the low or no signal to the injectors. Here is a cut and paste of the same thing I posted. It starts with checking your sensors because they all feed information into the ECM for injector control.
You could test at the back of harness to see if the input conditions are within range. If not then I would test sensors, and then I would run a continuity test across from sensor to back of harness. This would save a lot of time testing and narrow things down fairly quickly. Read through the entire thing first especially the bold before starting your search.
I’m feeling generous and I’ll list the trouble shooting procedure for no start, no injector pulse.
First I’ll post the MAF sensor flow chart:
Disconnect AFS (MAF) coupler and remove coupler seal to test voltage from back of coupler.
Check voltage at “W” wire terminal of coupler with ignition switch ON. Is there battery voltage?
“W” wire open or poor A3 connection. If wire and connection are OK, substitute a known good ECM and recheck.
With ignition switch OFF, connect AFS coupler.
Turn ignition switch ON and check voltage at “Vout” terminal.
Is it within 0.2 - 0.8V?
Poor AFS to coupler connection. If connection is OK, faulty AFS.
Clean air cleaner element.
Connect AFM to AFM outlet hose as shown in figure and clamp it securely.
Start engine and check voltage at “Vout” terminal.
Does voltage rise as engine speed is increased?
Open “B” wire or poor A6 ECM connection.
If wire and connection are OK, intermittent trouble or faulty ECM. Recheck referring to “Intermittent trouble” on p. 6E-34.
I would also check the WTS, CAS, and TPS sensor also. For basic injection time the ECM uses both CAS and AFS sensor, but uses TPS, WTS, and battery voltage, and O2 sensor to make comresation to injector time.
However the injectors should go into fail safe mode if plug AFS is disconnected and still pulse. Same with o2 sensor.
Fuel injector circuit check
If none of 4 injectors makes operating sound. (low or no voltage would cause this condition)
Disconnect coupler “C” from ECM with ignition switch off.
Check continuity or volatage between such terminals as listed below. Is continuity or specified voltage obtained?
Terminals Coninuity or voltage
Between C3 and C8 continuity
Between C5 and body ground continuity
Between C2 and body ground 10-14V at ignition switch ON
If not in 1. Injector signal wire open or poor coupler connection.
If not 2. Injector ground wire open or poor engine ground.
If not in 3. Injector power wire open.
Poor both C3 and C4 connections, both C8 and C9 connections, both C5 and C10 connections, both C5 and C10 connections or both C2 and C7 connections.
If all above are OK, substitute a known good ECM and recheck.
Igintion Signal Circuit (ignition signal not inputted). Ignition signal is sent from the ignition coil primary circuit. Monitoring this signal, ECM detects whether the ignition spark is emitted or not and stops injector operation when this signal is not inputted. Make sure you are using the right ignition components for wiring harness and ECM. Post up a picture of your ECM, ignition wiring, and inside of your distributor.
Faulty ignition system
1.Disconnect ECM coupler with igntion switch OFF.
Is battery voltage applied to A12 terminal at ignition swithc ON?
Faulty noise suppressor or open circuit between ignition coil and A12 terminal.
Poor A12 connection.
If connection is OK, substitute a known good ECM and recheck.
This is from a 91 FSM. In 92 to 94 is similar but has some changes to ESA (electronic spark advance).
Do you have a FSM? Do you need the ECM pinouts?