tjm6

Everyone - first thanks in advance for any and all help.
I have a 96 Civic EX. It will crank over but does not start. I have done quite a bit of troubleshooting based on info in some of the threads here. Here's a rundown and details of what I've done and figured out so far:
- Cranks over fine
- no fuel comes from fuel filter if I loosen it while turning key
- CEL comes on and stays on when key is turned on
- checked plug at fuel pump with digital meter and it shows voltage when key is turned on and when cranking (approx 7 volts the best I can tell with my meter)
- checked/replaced fuses and all seem to be fine
- I hear the click of the main relay within a few seconds of turning the key on.
- I do not hear the fuel pump kick on (have the back seat bottom removed for access and listening).

I have replaced the main relay with a brand new one. I also replaced the fuel pump previously. I thought this corrected the problem since it seemed to crank fine for a short time. Then it intermittently began having the same issue - turning over but not starting. Now I have been unable to get it to start at all - it just cranks over.

I have seen a few suggestion on jumping certain pins on the relay to force the fuel pump to start but I haven't been able to find specific instructions. Should that be my next steps and if so, what would that tell about correcting that actual problem? Any help appreciated.

tjm6

Update:

I have done some additional troubleshooting.

-- Unplug the main relay connector. Jump terminal 1 to 7 in the connector and the fuel pump primes.
-- Unplug the main relay connector. Turn the key to ON(II). Jump terminal 5 to 7 in the connector fuel pump does NOT prime.

Plug the main relay connector back in and unplug ECU connector A.
-- Turn the key to ON(II). Ground terminal A16 to the chassis. Fuel pump does NOT prime.

Does this indicate that the main relay is bad or is it an ECU issue?

Former User

15A dash fuse 13 is probably blown.

By the way:

You're probably mixing up the pin numbers here^. For your car, you would be jumping 7 (fuse 44) to 4 (pump) [key off] and 5 (fuse 13) to 4 (pump) [key in ON(II)].

tjm6

I replaced 15A fuse #13 under dash (old one did not seem to be blown but I replaced it anyway).

My main relay doesn't seem to have a pin 4. The layout is:
1 3 5 7
2 - 6 8 There is no 4. I wasn't able to load a photo to show.

Thanks for the info so far.

tjm6

I always put a meter on the new fuse to make sure I am getting proper voltage on both sides of the fuse. Forgot to mention that...

Former User

If this^ is true for fuse 13, and there's no voltage detected at pin 5 of the unplugged main relay connector with the key in ON(II), then the Yel/Grn wire is broken somewhere between pin 5 and the dash fuse box or the dash fuse box is bad.

Here is your main relay connector pin out:

Former User

This^ test tells you that the main relay is fine and also that the ECU is not the problem.

tjm6

Thanks for that diagram. I will retest the relay to verify the wiring.

This is a photo of my relay and I was originally going off the numbers shown on it for the pin layout.

Former User

Your pic is not displaying. Upload to ImageShack or equivalent and then paste the link.

tjm6

New update:

Using the diagram provided, I verified:
On main relay plug:
- jumping 7 and 4 with the key off makes the fuel pump prime.
- jumping 5 and 4 with the key ON also makes the fuel pump prime.

On the ECU Plug A:
- grounding A16 with the Key On also makes the fuel pump prime.

So all three of these result in the fuel pump priming.

After reconnecting all the plugs, turn the key on, hear the click, CEL stays on and fuel pump does not prime.

Former User

Do you have a multimeter?

Have you cleaned and tightened the G101 ground attached to the thermostat housing?

tjm6

I have cleaned and tightened the G101 ground connection. There it appeared solid but I cleaned it anyway. Still no difference in the cranking. Is it useful to run another wire to this location and connect to the body for additional grounding or is that just overkill?

I do have a Greenlee DM-20 multimeter.

Here is a picture of the Main Relay with the numbers I referred to earlier if it helps anyone in the future.

Former User

With ECU connector A unplugged:

Turn the key to ON(II). Do you measure battery voltage to body ground at pins A11 and A24 in the connector?

Turn key off. Do you measure continuity to body ground at pins A9 and A22 in the connector?

tjm6

With Key ON:
There is battery voltage on both A11 and A24 (the voltage seemed to vary on A24 a little, like there was a voltage drop occasionally but it could have been that I was trying not to push the probe in too far and damage the connector.)

With Key OFF:
There is good continuity to body ground on A9 and A22.

Former User

Looks like the ECU may be bad. Open it up to expose the circuit board. Inspect for any signs of blown components or circuits.

How did this problem come about?

tjm6

Drove it home from work one day and all was fine. Went to start it the next morning and it would just crank over. I first thought it was the relay and fuel pump and like a dumba$$ spent the money to replace both of them. That seemed to correct the problem so I wasn't too upset. Then the problem started occurring really intermittently. I couldn't predict it or reproduce it. I've now been to troubleshoot it to actually get it repaired and back up and running.
Thanks for all your help! Most appreciated!

I'll open the ECU case and see what I find. Will post photos...

Former User

Is the problem still intermittent or is the car now dead in the water?

tjm6

It seems to be dead in the water at this point. I have not been able to get it to crank regardless of what I've tried now. Before, it would just surprise me and crank... playing a nasty joke by making me think I corrected something! LOL!

Former User

In a troubleshooting sense, dead in the water is good by making test results meaningful.

tjm6

I agree. At least it doesn't continue to give false hope that it is corrected.

There is no visible evidence of damage to the ECU but I know it may not can been seen.

Here are a couple of photos of the ECU board itself:

Former User

Yeah, all your results are pointing to a bad ECU. Shop for a replacement.