Refer to
Fuel Injectors
for an electrical diagram of this circuit.
The Injector Flow/Voltage Drop Check compares the fuel pressure drop when each injector is pulsed for a set amount of time. Since each injector is pulsed the same, the fuel pressure drop for each injector should be approximately the same. Suspect fuel injectors can be identified by either too high or too low fuel pressure drop. This check also determines if the voltage drop of the injector is within specification. Injector voltage drop out of specification can cause driveability conditions that are intermittent or that do not show up during an injector flow check.
Tools Required
J 34730-1A Fuel Pressure Gauge, J 39200 Voltmeter, J 39021 Fuel Injector Tester.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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Commanding the fuel pump on for 5 seconds will energize the fuel pump to build fuel pressure. Then selecting individual injectors will allow you to see the fuel pressure drop associated with each injector. If all eight injectors drop some pressure then the circuit is not open. Any injector that drops no pressure has an open in the circuit or a faulty injector.
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Checking if a fuse was open causing either injectors 2, 3, 5, 8, or 1, 4, 6 and 7 not to operate.
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Checking if ignition positive voltage feed is open from the fuse to the connector.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |
2 | Has the Fuel System Check been performed? | -- | Go to Fuel System Diagnosis (Fuel System Check) | |
Does fuel pressure drop when each injector is tested? | -- | |||
4 | Do two or more fuel injectors have no pressure drop? | -- | ||
Are both fuses OK? | -- | |||
6 |
Do both pins measure greater than the specified value? | 10V | ||
7 |
Did voltage reading for any injector exceed the specified value? | 9.5V | ||
8 | Inspect the highest reading and subtract the specified value. Was the voltage for any injector less than this value (more than .55 volts less than the highest)? | 0.55V | ||
9 | Have any injectors been replaced up to this point? | -- | ||
10 | Were the fuel pressure drops recorded in Step 3 for all injectors within the specified value? | 2 PSI | Go to Fuel Injector Balance Test | |
11 |
Does coil test voltage measure between the specified value? | 5.74-7.0 V | ||
12 |
Does voltage measure the same or greater than the specified value? | 10V | ||
13 | Check fuel rail harness for opens or shorts in suspect injector circuits. Open or short found? | -- | ||
14 | Check CKT(s) ignition positive feed circuits for shorts to ground. Was a short found? | -- | ||
15 | Measure resistance at the fuel rail connector (fuel rail side) across suspect injector circuits. Do any measure less than the first specified value or greater than the second specified value? | 8 to 25 ohms | ||
16 | Connect fuel injector tester to suspect injector(s) and select Coil Test. Does voltage reading from coil test measure between the specified values? | 5.74-7V | ||
17 | Repair open ignition positive feed circuits between the fuse and the fuel rail connector. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
18 | Replace injector(s) whose voltage reading exceeded the specified valve. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
19 | Replace injector(s) whose voltage reading was more than 0.55 volts less than the highest voltage reading Was a repair made? | 0.55V | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
20 | Duplicate conditions under which customer complaint occurred and verify proper operation. Is the system operating OK? | -- | System OK | -- |
21 | Replace injector(s) whose pressure drop was not within the specified value of the others. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
22 | Check PCM terminal contact and if OK, replace the PCM. Refer to PCM Replacement/Programming . Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
23 | Repair open between the fuel rail connector and the PCM in suspect circuit. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
24 | Repair circuit. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
25 | Replace injector. Refer to Fuel Injector Replacement . Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
26 | Repair short and replace blown fuse. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
27 | Replace blown fuse. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
28 | Repair fuel rail harness for suspect injector. Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
29 | Replace suspect injector. Refer to Fuel Injector Replacement . Was a repair made? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | -- |
