Can You Check For Clogged Injectors With Fuel Pressure Tester?
02-03-2003, 02:51 PM
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Can You Check For Clogged Injectors With Fuel Pressure Tester?
Hi--I just bought an 86 camaro z28 305 tpi and it doesnt want to run right, it wants to die at idle. This car has sat for 3 years or so maybee, could the injectors be clogged? how can you test it using a Fuel pressure tester? Thanks For Help.
Brandon
Brandon
02-04-2003, 08:33 AM
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Blue 86,
There are a few tests you can perform on your injectors to help determine their condition.
The first is an electrical resistance test. This will determine if the operating solenoid coils are intact. Bosch injectors (which you likely have) can be serviceable down to 12 ohms. The flow has no relationship to the resistance of the solenoid (unless the resistance is zero or infinite, of course).
You can perform a "go/no-go test" to determine if any fuel is getting through the injectors in a couple of ways.
1. One method is to perform a power-balance test. Start the engine, allow it to reach operating temperature, then unplug the IAC electrical connector while the engine is idling. Unplug the electrical connector from one injector and monitor the engine RPM as it is disconnected. The drop in idle RPM should be relatively equal through the firing order. Replace the electrical connector and go on to the next injector. You need to realize that the ECM will sense the RPM drop and attempt to compensate by adjusting the IAC, which is why it was disconnected in the first place. Compare the RPM drop at each cylinder. Don't forget to replace the IAC connector. If one or more injectors caused little or no change in RPM, it is not flowing fuel at the correct rate. NOTE: This test will not be accurate if the ignition system is not in good order or compression is low on a cylinder.
2. The other method is done with a fuel pressure gauge, test connector, and stopwatch. You can fabricate a test connector from parts available from your local auto parts store. Connect the pressure gauge to the test valve on the right fuel rail. Turn on the ignition until fuel pressure stabilizes (about 45 PSIG). Turn off the ignition and monitor fuel pressure. If the pressure drops rapidly, your test results will be inconclusive and you cannot use this method. If the pressure maintains without dropping, connect yout test connector to an injector and to a 12V source. The pressure should begin dropping. Measure the amount of time until the pressure drops to 20 PSIG and make a note of this time. Disconnect the test connector and turn on the ignition to rebuild fuel pressure. Move to the next injector and repeat the process. Compare all the times when you're finished. If one or more of the injectors takes a significantly longer time to bleed off fuel pressure, it is not flowing at the same rate as the others.
Neither of these tests will indicate any problems with spray patterns, only flow. But if an injector isn't flowing properly, you can bet the spray pattern is poor. If you determine that you have a weak injector, I'd advise contacting Rich at Cruzin' Performance.
Later,
Vader
There are a few tests you can perform on your injectors to help determine their condition.
The first is an electrical resistance test. This will determine if the operating solenoid coils are intact. Bosch injectors (which you likely have) can be serviceable down to 12 ohms. The flow has no relationship to the resistance of the solenoid (unless the resistance is zero or infinite, of course).
You can perform a "go/no-go test" to determine if any fuel is getting through the injectors in a couple of ways.
1. One method is to perform a power-balance test. Start the engine, allow it to reach operating temperature, then unplug the IAC electrical connector while the engine is idling. Unplug the electrical connector from one injector and monitor the engine RPM as it is disconnected. The drop in idle RPM should be relatively equal through the firing order. Replace the electrical connector and go on to the next injector. You need to realize that the ECM will sense the RPM drop and attempt to compensate by adjusting the IAC, which is why it was disconnected in the first place. Compare the RPM drop at each cylinder. Don't forget to replace the IAC connector. If one or more injectors caused little or no change in RPM, it is not flowing fuel at the correct rate. NOTE: This test will not be accurate if the ignition system is not in good order or compression is low on a cylinder.
2. The other method is done with a fuel pressure gauge, test connector, and stopwatch. You can fabricate a test connector from parts available from your local auto parts store. Connect the pressure gauge to the test valve on the right fuel rail. Turn on the ignition until fuel pressure stabilizes (about 45 PSIG). Turn off the ignition and monitor fuel pressure. If the pressure drops rapidly, your test results will be inconclusive and you cannot use this method. If the pressure maintains without dropping, connect yout test connector to an injector and to a 12V source. The pressure should begin dropping. Measure the amount of time until the pressure drops to 20 PSIG and make a note of this time. Disconnect the test connector and turn on the ignition to rebuild fuel pressure. Move to the next injector and repeat the process. Compare all the times when you're finished. If one or more of the injectors takes a significantly longer time to bleed off fuel pressure, it is not flowing at the same rate as the others.
Neither of these tests will indicate any problems with spray patterns, only flow. But if an injector isn't flowing properly, you can bet the spray pattern is poor. If you determine that you have a weak injector, I'd advise contacting Rich at Cruzin' Performance.
Later,
Vader
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