[Bert John]

NNN. Fuel System Troubleshooting

This is a two-part problem: 1) Determine if the fuel pump works, and 2) Determine why the PGM-FI Main Relay doesn't work properly.

If you don’t hear the fuel pump run, when the ignition switch is turned to ON (Position II):

Problem 1: Determine if the fuel pump works.

1. Disconnect the main relay from the main relay connector. Jump main relay connector Terminals 5 and 7, turn the ignition switch to ON, and listen for the fuel pump in the gas tank. If you can hear the fuel pump run, which is usually the case, it is likely good and you should proceed to Problem 2. If it doesn’t run, go to Step 2.

2. Turn the ignition switch ON. Measure voltage between main relay connector Terminal 5 and ground. If there’s not battery voltage, test/replace the ACG (ALT) (S) (15 A) fuse in the under-dash fuse/relay box. If necessary, repair an open in the wiring between the main relay and the ACG (ALT) (S) fuse. Verify that you now have battery voltage to Terminal 5. If the fuel pump still doesn’t run, however, go to Step 3.

3. Check for continuity between main relay connector Terminal 7 and the fuel pump. If necessary, repair an open in the wiring. If the fuel pump still doesn’t run, go to Step 4.

4. Check fuel pump. Even though it's certainly possible, I have never seen a Honda fuel pump fail. They are very reliable. Clean connections and thoroughly test pump motor, prior to replacement. Before going any further, all efforts must be focused on getting the fuel pump to run (i.e., solve Problem 1 first), when main relay connector Terminals 5 and 7 are jumped and the ignition switch is turned to ON. If the main relay and fuel pump still don’t work properly together, however, go to Problem 2.

Problem 2: Determine why the PGM-FI Main Relay doesn’t work properly.

5. Check for continuity between main relay connector Terminal 2 and body ground, with the ignition switch OFF. If there’s no continuity, clean the main ECM ground, which is usually located on the thermostat housing. Look for 3 wires going to a brass connector. Remove the 10 mm bolt, clean with No. 240 abrasive cloth, and apply dielectric grease. If necessary, repair an open in the wiring between the main relay and the main ECM ground. If there’s continuity, go to Step 6.

6. Measure voltage between main relay connector Terminal 1 and ground. If there is not battery voltage, test/replace the ECM fuse (15 A) in the under-hood fuse/relay box. If necessary, repair an open in the wiring between the main relay and the ECM fuse. If there is battery voltage, go to Step 7.

7. Turn the ignition switch to START. With manual transmissions, depress the clutch pedal. With automatic transmissions, the gear selector must be in Neutral or Park. Measure voltage between main relay connector Terminal 6 and ground. If there’s not battery voltage, test/replace the STARTER SIGNAL (7.5 A) fuse in the under-dash fuse/relay box. If necessary, repair an open in the wire between the main relay and the STARTER SIGNAL fuse. Should the main relay and fuel pump still not work properly, go to Step 8.

8. Perform the K-Test on the ECM. Remove the MAP Sensor connector and turn the ignition switch ON (not start). Using a multimeter, check for 5 volts going between the MAP Sensor connector’s reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into a cleaned main ECM ground on the thermostat housing. If the voltage is low, it’s probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate. The ECM controls grounding to main relay Terminal 8, which affects when the second relay inside the main relay opens and closes. If the ECM cannot control grounding to the second relay, the fuel pump will not run. The only alternative is to replace the ECM.

SUMMARY OF MAIN RELAY PROBLEM AREAS:

Terminal 1--Test ECM fuse in under-hood fuse box.
Terminal 2--Clean main ECM ground on thermostat housing.
Terminal 5--Test ACG (ALT) (S) fuse in under-dash fuse box.
Terminal 6--Test STARTER SIGNAL fuse in under-dash fuse box.
Terminal 7--Test continuity to fuel pump.
Terminal 8--Test ECM (K-Test).

Many hours of research, thought, and experience went into designing this easily understood approach to troubleshooting one of Honda's most complex systems. I consider this the most thorough coverage of this subject anywhere--it doesn't get any easier or better than this. I'm proud of this work and hope it blesses many people.

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How do you make a jump tester?

[ddollinger]

A jump tester is simply a piece of wire.

[Bert John]

How do you make a jump tester?

I tried the jump tester on the main relay fuse the fuel pump runs, but when I put back on the new main relay and I also just purchased another Ignition switch. But none of these work my car still won't start. I was thinking that it could be my computer box? Is there a way that I could easily test for my computer box to see if it's working properly? I appreciate all your help!:)

[Stratmando]

I would see if it has an inertia switch(resettable)that opens power to fuel pump. This may be under the dash.
A good test:
With the key on, see if voltage is going in and out of inertia switch.
I have seen cars that had a relay that needed a pulse from engine turning to energize.
Not %100 sure of what you have.
Good Luck.
Will dig out manual tomorrow.

[Bert John]

I would see if it has an inertia switch(resettable)that opens power to fuel pump. This may be under the dash.
A good test:
With the key on, see if voltage is going in and out of inertia switch.
I have seen cars that had a relay that needed a pulse from engine turning to energize.
Not %100 sure of what you have.
Good Luck.
Will dig out manual tomorrow.

Where's this inertia switch located at under the dash passenger or driver and also how does it look?:)

[Stratmando]

On my Ford, it is on the passenger side panel.
Since you can jump at relay socket. 2 thing also need to happen, the coil of the relay needs a hot from ignition on, and a ground. Both need to be verified.