I just wanted to share this with the community for research purposes. In researching and digging I found countless threads with similar symptoms to mine and everyone said replace main relay, or replace ECU. After several saying "this didn't fix it" and going unanswered, I wanted throw one more out there to help some not lose hope.
The symptoms were no fuel pump prime, and later discovered the injectors weren't firing. So I ran through everything I could think to test.
1995 honda del sol 1.5 manual, no power to fuel pump, injectors not firing. tested fuel pump, can hot wire to make fuel pump run, and has fuel pressure, replaced main relay, twice, brand new, has power at the 1 and 5 pin, if jump power to 7 pin fuel pump runs, still no injectors. pin 8 has 11.4volts on the fuel pump relay, it should be ground, If I introduce ground using a power probe, the fuel pump will run, I traced the wiring diagram to pin A7 on the ecu, has voltage (11.4) at A7 should be ground signal. nothing(no ground signal) coming out of pins A1 A2 A3 or A5 for the injector controls.
Replaced ECU with a Reconditioned one. Same exact issue.
Didn't have access to a scope to check signal from distributor, so I took a gamble and replaced the distributor. Still same symptoms.
It has spark.Is the power loss consistent, or does it fluctuate? constant, no power at the pump. voltage at injectors, no ground signal to fire them. I checked all grounds on the chassis, including the main 101 ground on the thermostat housing, cleaned and tightened, new battery. checked all fuses, seems to stem back to the A7 pin on the ECU having voltage and not ground.
If I introduce ground I can make the fuel pump alone run, unfortunately no injectors. However, the first time I made the fuel pump run, I was able to start the car, I shut it off over night to get a main relay assuming that was my issue. I installed a relay the next morning, and no injectors after that, reinstalled old relay, same issue.
After talking this over with someone else, I was told I should check the Throttle Position Sensor for 5v reference signal. I disconnected the TPS and within a few seconds, I heard the fuel pump prime. I reconnected and it fired right up. Shut the Key off, tried again, no start, disconnect TPS, It fires up.
After checking into this a bit more, the TPS is bad, shorting out the 5v reference to the computer, blocking it from sending a signal to the pump and injectors. I was told if the computer detects a "flood clear signal" or throttle wide open it may shut off the pump and injectors during startup.
So replace the TPS and recalibrate and its good to go. I also included the TPS calibration procedure.
Loosen the 2 screws that hold the tps sensor in place. Now u might have to notch them or cut them to be able to loosen them. next, backprobe the tps sensor ( the middle wire) which is the signal wire. Next turn the car to the on position but don't start it. Now check the voltage coming through the wire, it should be .45V at idle. If not, turn the tps sensor clockise or counterclockwise until the voltage reaches .45V. Once u reach the specific voltage tighten up the screws, and then check the voltage to make sure it's still at .45V
closed .45
wot 4.5 volts
With the TB closed, sensor disconnected, ign off:
Pins 1 and 2 = 0.5-0.9ohms
Pins 2 and 3 = 3.6-5.4ohms
You also need to be sure you have correct voltage, sensor connected, ign 'on':
Pins 1 and 3
0.5volts with the TB closed
4.5volts with the TB fully open
I hope this helps someone out there that may end up in the same situation as me.
The symptoms were no fuel pump prime, and later discovered the injectors weren't firing. So I ran through everything I could think to test.
1995 honda del sol 1.5 manual, no power to fuel pump, injectors not firing. tested fuel pump, can hot wire to make fuel pump run, and has fuel pressure, replaced main relay, twice, brand new, has power at the 1 and 5 pin, if jump power to 7 pin fuel pump runs, still no injectors. pin 8 has 11.4volts on the fuel pump relay, it should be ground, If I introduce ground using a power probe, the fuel pump will run, I traced the wiring diagram to pin A7 on the ecu, has voltage (11.4) at A7 should be ground signal. nothing(no ground signal) coming out of pins A1 A2 A3 or A5 for the injector controls.
Replaced ECU with a Reconditioned one. Same exact issue.
Didn't have access to a scope to check signal from distributor, so I took a gamble and replaced the distributor. Still same symptoms.
It has spark.Is the power loss consistent, or does it fluctuate? constant, no power at the pump. voltage at injectors, no ground signal to fire them. I checked all grounds on the chassis, including the main 101 ground on the thermostat housing, cleaned and tightened, new battery. checked all fuses, seems to stem back to the A7 pin on the ECU having voltage and not ground.
If I introduce ground I can make the fuel pump alone run, unfortunately no injectors. However, the first time I made the fuel pump run, I was able to start the car, I shut it off over night to get a main relay assuming that was my issue. I installed a relay the next morning, and no injectors after that, reinstalled old relay, same issue.
After talking this over with someone else, I was told I should check the Throttle Position Sensor for 5v reference signal. I disconnected the TPS and within a few seconds, I heard the fuel pump prime. I reconnected and it fired right up. Shut the Key off, tried again, no start, disconnect TPS, It fires up.
After checking into this a bit more, the TPS is bad, shorting out the 5v reference to the computer, blocking it from sending a signal to the pump and injectors. I was told if the computer detects a "flood clear signal" or throttle wide open it may shut off the pump and injectors during startup.
So replace the TPS and recalibrate and its good to go. I also included the TPS calibration procedure.
Loosen the 2 screws that hold the tps sensor in place. Now u might have to notch them or cut them to be able to loosen them. next, backprobe the tps sensor ( the middle wire) which is the signal wire. Next turn the car to the on position but don't start it. Now check the voltage coming through the wire, it should be .45V at idle. If not, turn the tps sensor clockise or counterclockwise until the voltage reaches .45V. Once u reach the specific voltage tighten up the screws, and then check the voltage to make sure it's still at .45V
closed .45
wot 4.5 volts
With the TB closed, sensor disconnected, ign off:
Pins 1 and 2 = 0.5-0.9ohms
Pins 2 and 3 = 3.6-5.4ohms
You also need to be sure you have correct voltage, sensor connected, ign 'on':
Pins 1 and 3
0.5volts with the TB closed
4.5volts with the TB fully open
I hope this helps someone out there that may end up in the same situation as me.