Please help! Problem with fuel pump wiring(?)
01-26-2008, 01:28 PM
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Please help! Problem with fuel pump wiring(?) Guys:
I really hope that someone can point me in the right direction. My car is a hybrid ('70 Datsun 240Z with LT1/T56 - http://forums.hybridz.org/showthread...&highlight=248) and am close to getting it running, but having some frustrating issues.
I'm using a Speartech modified harness and wired the Aeromotive pump using the relay coming from the stock harness. I have power at the ICM, the coil and at the injectors. Also, when the key is turned on, the pump primes and then shuts off. During cranking, there is no power to the fuel pump and Zero fuel pressure.
Am I missing something basic? Any thoughts that you could send my way would be really appreciated.
Bryan
Dat240zg
I really hope that someone can point me in the right direction. My car is a hybrid ('70 Datsun 240Z with LT1/T56 - http://forums.hybridz.org/showthread...&highlight=248) and am close to getting it running, but having some frustrating issues.
I'm using a Speartech modified harness and wired the Aeromotive pump using the relay coming from the stock harness. I have power at the ICM, the coil and at the injectors. Also, when the key is turned on, the pump primes and then shuts off. During cranking, there is no power to the fuel pump and Zero fuel pressure.
Am I missing something basic? Any thoughts that you could send my way would be really appreciated.
Bryan
Dat240zg
01-26-2008, 02:10 PM
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Well, in doing more testing, with the key on, I have power at the injectors (positive side). However, under cranking, I should be getting a pulsing signal through the negative side - which I'm not.
Sends me back to the optispark. Maybe more to come.
Bryan
Sends me back to the optispark. Maybe more to come.
Bryan
01-26-2008, 03:50 PM
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Here's a try, not sure what year LT1 you put in the 240Z, but the principals are the same for PCM, ECM. Looks like you have a couple of problems 1- the fuel pressure dropping to zero quickly AND 2- the fuel pump not running during cranking. Once you build initial fuel rail pressure by turning the key a few times the fuel pressure regulator should hold the pressure for quite a while (over 15-20 mins). If your pressure goes to zero the regulator may be defective (I assume your custom build has a regulator). Also you have a check valve somewhere in your setup to prevent fuel from draining back into the tank (maybe in your Aeromotive fuel pump). Both the regulator and check valve contribute to correct fuel delivery during initial cranking. Secondly you need to investigate oil pressure and/or correct signals to and from the PCM to keep the pump running. Below is a cut past of generalized fuel delivery during cranking and initial startup. Your setup should have the same concepts if you are using OBD1 or 2 in your 240Z. By the way nice build so far, good luck..
Fuel Rail Pressurization:
When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.
Initial Crank Action:
If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.
Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).
The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.
ECM Reaction:
If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).
The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).
The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)
Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.
Fuel Rail Pressurization:
When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.
Initial Crank Action:
If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.
Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).
The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.
ECM Reaction:
If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).
The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).
The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)
Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.
