relocated fuel pump... could cause no spark?
01-24-04, 06:10 PM
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relocated fuel pump... could cause no spark?
Hi, it's me again. Over 2 months of troubleshooting, replaced ECU, leading coil, countless other things, and I still can't get a spark from the leading ignition.
When I bought my car, the fuel pump was taken out of the fuel tank and relocated to the front. What i'm wondering is, is there any way the ecu can detect that there's no fuel pump connected at the fuel tank level, and possibly cut spark to the leading coil? Or are they completly different things? Thanks.
When I bought my car, the fuel pump was taken out of the fuel tank and relocated to the front. What i'm wondering is, is there any way the ecu can detect that there's no fuel pump connected at the fuel tank level, and possibly cut spark to the leading coil? Or are they completly different things? Thanks.
01-25-04, 02:14 AM
#3
They are mutually exclusive actually...
With the Ign ON, awhile the Check Connector (yelloe plug at the right strut tower) Grounded, are you hearing whirling sounds coming from the Fuel Pump? You should be.
If you are not getting Spark from the Leading Coil, your car won't start, as obvious In your case. Trailing Is different though. How are you determaining the lack of spark at the Leadings?
With the Ign ON, awhile the Check Connector (yelloe plug at the right strut tower) Grounded, are you hearing whirling sounds coming from the Fuel Pump? You should be.
If you are not getting Spark from the Leading Coil, your car won't start, as obvious In your case. Trailing Is different though. How are you determaining the lack of spark at the Leadings?
01-25-04, 02:52 AM
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The only things going to the fuel pump are a relay, microswitch (inside the AFM), and an ignition-switch power wire. Generally, if you can jumper the YELLOW connector with a black rubber boot around it (next to the boost sensor, variable resistor, and air box), and hear the pump turn on, then everything should be working properly.
If you have a turbo, then there is a second relay that runs to the ECU from the Fuel Pump Relay and resistor. This adjusts the voltage the fuel pump gets when at idle and at various stages of boost. It is also tied into the Main Relay and the circuit opening relay.
If it's an N/A, it goes from the pump to the circuit opening relay. The circuit opening relay (same thing on TII models) will only operate when the Air Flow Meter's internal microswitch creates a ground.
At any rate, if you can crank the car, and the fuel pump is working while trying to start, then all is good.
If you've not got spark on the leading coils (the pack closest to the battery), check all this stuff:
CAS. If the hall-effect sensors aren't working, it won't fire spark at all. The Resistance between the G (green) and B (black) terminals (on the CAS's plug) should be 110-210 ohms. Resistance between the R (red) and W (white) terminals should be the same (110-210ohms). Between the same pairs, while the engine is running you should see fluctuations in voltage/resistance.
To check that the coils are seeing battery voltage, disconnect the 2-prong connector (B/Y and G/Y). Connect a volt-meter and you should see 0 volts (on the engine side of the harness, not the coil side). Turn the ignition switch on, and you should see ~12volts. Try to start the car. Every time the coils are supposed to fire, the ECU breaks ground and the coils fire (ECU pin V; the wire's color is G/Y). Check the resistance of the coil's two terminals (where the spark plug wires go). It should be below 1 ohm.
Make sure you don't have a damaged Front harness. Make sure the engine harness is plugged into the ECU as well as the other 2 emissions harnesses (they get all the sensor data and fire the injectors). The ECU is located under the passenger side carpet.
Check all that and tell us where you're not getting a proper reading.
If you have a turbo, then there is a second relay that runs to the ECU from the Fuel Pump Relay and resistor. This adjusts the voltage the fuel pump gets when at idle and at various stages of boost. It is also tied into the Main Relay and the circuit opening relay.
If it's an N/A, it goes from the pump to the circuit opening relay. The circuit opening relay (same thing on TII models) will only operate when the Air Flow Meter's internal microswitch creates a ground.
At any rate, if you can crank the car, and the fuel pump is working while trying to start, then all is good.
If you've not got spark on the leading coils (the pack closest to the battery), check all this stuff:
CAS. If the hall-effect sensors aren't working, it won't fire spark at all. The Resistance between the G (green) and B (black) terminals (on the CAS's plug) should be 110-210 ohms. Resistance between the R (red) and W (white) terminals should be the same (110-210ohms). Between the same pairs, while the engine is running you should see fluctuations in voltage/resistance.
To check that the coils are seeing battery voltage, disconnect the 2-prong connector (B/Y and G/Y). Connect a volt-meter and you should see 0 volts (on the engine side of the harness, not the coil side). Turn the ignition switch on, and you should see ~12volts. Try to start the car. Every time the coils are supposed to fire, the ECU breaks ground and the coils fire (ECU pin V; the wire's color is G/Y). Check the resistance of the coil's two terminals (where the spark plug wires go). It should be below 1 ohm.
Make sure you don't have a damaged Front harness. Make sure the engine harness is plugged into the ECU as well as the other 2 emissions harnesses (they get all the sensor data and fire the injectors). The ECU is located under the passenger side carpet.
Check all that and tell us where you're not getting a proper reading.
Last edited by black_sunshine; 01-25-04 at 02:57 AM.
01-25-04, 05:49 PM
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ok, here's what I'm working with. I ohmed the CAS wire, got about 130ohms in both the red/white cables and green/black cables.
The fuel pump is not even connected to anywhere the ECU would see that it is..it is simply plugged into a 12v that I have no idea where it came from (bought it like this) Here's a pic:
I'm about to check compression... I have exensevly checked alot of things, hailers and others helped me alot, I have narrowed/elimitated a bunch of possiblities. Here's the post: (kinda long)
https://www.rx7club.com/showthread.p...hreadid=254925
It's an n/a 86gxl btw. Could this fuel pump setup work fine? I don't want it running yet, I just want to get a spark for now. The fuel pump comes on when the key is ON position, so it shouldn't matter, right? (it pumps fuel in etc)
The fuel pump is not even connected to anywhere the ECU would see that it is..it is simply plugged into a 12v that I have no idea where it came from (bought it like this) Here's a pic:
I'm about to check compression... I have exensevly checked alot of things, hailers and others helped me alot, I have narrowed/elimitated a bunch of possiblities. Here's the post: (kinda long)
https://www.rx7club.com/showthread.p...hreadid=254925
It's an n/a 86gxl btw. Could this fuel pump setup work fine? I don't want it running yet, I just want to get a spark for now. The fuel pump comes on when the key is ON position, so it shouldn't matter, right? (it pumps fuel in etc)
01-25-04, 10:15 PM
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No, you can cut the fuel pump wires and throw the pump in the back yard and the ECU has no idea you did so. There's no relationship b/t the spark and the fuel pump.
The picture above almost makes me think the cas plug is not connected together. I must be wrong on that.
There is one gruesome thought that goes thru my mind. Do this: get your digital meter out. Go to your boost/pressure sensor and pull the plug off. With the key to ON, put your meter to dc volts, one lead in the brown/white wires socket in the plug, and the other lead on the meter on a good ground. You should have 5Volts approx. 4.5 is just fine. But if you read some absurd figure like one volt or .6534 then there is a problem we don't wanna talk about.
You have checked the 30 and 40 amp fuses in the engine bay? The EGI something or other fuses???
The picture above almost makes me think the cas plug is not connected together. I must be wrong on that.
There is one gruesome thought that goes thru my mind. Do this: get your digital meter out. Go to your boost/pressure sensor and pull the plug off. With the key to ON, put your meter to dc volts, one lead in the brown/white wires socket in the plug, and the other lead on the meter on a good ground. You should have 5Volts approx. 4.5 is just fine. But if you read some absurd figure like one volt or .6534 then there is a problem we don't wanna talk about.
You have checked the 30 and 40 amp fuses in the engine bay? The EGI something or other fuses???
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