Hello forum!
I'm a long time reader, first time poster. Recently a friend of mine asked to store a 94 Civic LX at my house as it was going to be towed from his apartment. After it sat for a while, I offered him a couple of bucks and now I'm trying to get this thing running. I've done some basic troubleshooting but am kind of lost as to where to go next. The car's a 4 door (not that it matters) with an automatic transmission. To the best of my knowledge, it's bone stock. After charging the battery, I can get it to crank, but don't get any fuel smell from the exhaust. The CEL stays on when the key's in the 'run' mode.

I have no voltage at the fuel pump connector. I've verified that I have continuity from the main relay to the fuel pump connector as well as from the chassis ground (seat belt bolt) to ground connector for the fuel pump. So the wiring seems fine and I'm guessing the chassis ground is fine, as well.

I've deduced that the fuel pump WILL run as I hot-wired it and it makes a whirring sound. However, even in hot-wiring it directly to the battery, when I crank the engine, it doesn't start.

I've done the main relay test and it checks out fine. Even after replacing it (which was completely unnecessary,) no difference. I do have voltage at the main relay connector on pin 1, and when the key is in run, pin 5. Not sure if there's a test from the ECU to see if that's functioning.

Am I maybe looking at an ECU that's gone bad? Any direction would be helpful.

Thanks!
Matt

 

If you unplug ECU connector A, turn the key to ON(II), and ground ECU connector pin A7 or A8, does the fuel pump run?

http://www.phearable.net/tech/wiring...schematics.gif

 

I haven't even gotten as far as troubleshooting anything with the ECU. Even finding it, for that matter. It's under the carpet on the passenger side, right? I will certainly try that once I get to it and begin troubleshooting. That does seem like a culprit, though, right?

 

...

 

I got the ECU accessible. Checked connector A. Fuel pump starts when I run from pin 7 to the chassis ground. 8 does nothing.

 

It's possibly an ECU problem. Some multimeter tests would help to verify. Interested?

 

Absolutely. I have two multimeters and am pretty decent with electronic troubleshooting.

 

Appreciate all your help, by the way.

 

Test 1

1. Unplug MAP sensor
2. Turn key to ON(II)
3. In the 3-wire MAP sensor connector, measure voltage to body ground at the Wht wire terminal and the Yel/Red wire terminal individually.
4. Post the two voltage readings.

 

One of them has 5.5v and one of them has 8.2v

 

Both should read around 5V. Which has 8.2V? Double check that reading.

-----------------------
Test 2

Unplug ECU connectors A and B.
Turn key to ON(II).
Test whether ECU connector pins A25 and B1 have battery voltage to body ground.
Turn Key OFF.
Test whether ECU connector pins A26, B2, A23, and A24 have continuity to body ground.

http://www.phearable.net/tech/wiring...schematics.gif

 

Just tested again. White = 4.6v Yellow/Red = 6.76v

 

Yel/Red (reference voltage) is a little higher than expected but is probably okay. Move to test 2.

 

Have voltage on A25 and B1. When testing continuity to the body ground, I have continuity on A26, A23 and A24, but not B2.

 

I took apart the ground at the thermostat housing and even cut it back some. Brown / black wire looks good. Spliced in a piece. No difference. Still no continuity. Even cut the brown (B2) wire going into the ECU and ran it directly to the battery. Still no fuel pump kicking on, no start. What next?

 

Does the B2 pin in the face of ECU connector B now read continuity to body ground?

 

Yes, I have a temporary wire ran directly to the negative terminal of the battery. Still no priming of the fuel pump when turning the key on.

 

Doesn't answer the question.

 

Yes, now I have contiunitiy. It's temporary, but I do have continuity on that pin to the chassis ground.

 

Repeat the A7 test. Does the pump still prime?

 

I'll have to check it when I'm home. At work currently, but I'll test when I return. Thinking maybe I blew a fuse?

 

Yes

 

Yes, the pump does prime when I jump the A7 pin to the ground and turn the key to "on." Checked fuses 24 and 31. Neither are blown.

 

Any other suggestions on what to test?

 

Redo the voltage and continuity to body ground tests on the ECU connectors. If all is fine and the pump still won't prime with the key, then the ECU is likely bad. What makes me somewhat uneasy with the bad ECU diagnosis, however, is the fact that B2 lacked continuity to body, indicating 2 separate problems were at play.