I have 95 accord lx 4cly non-vtec (OBD1) that has the weirdest no start issue.

1) Fuel pump & filter replaced, new plugs & wires, new main relay(<--originally thought that was problem). Car started fine after each part was replaced and worked pretty much when it wanted to.

2) Original ECU/ECM was throwing out code 21(vtec solenoid), my car is non-vtec as stated earlier. Car eventually would not start with original ecu. Got a ECU at a local pick and pull, car started and worked fine for a day with no CEL. The very next day symptoms returned even with new ECU plugged in.

3) Very frustrated as this is an ongoing issue....just for the heck of it, I remove the new ecu and put the old ecu back in....Car starts with old ECU. Took it to shop, and no problems found. The mechanic put the pick n pull ECU back in and car ran fine for about a week. Which leads me back to where I'm at now.....car not starting with the new ECU, but starts with the old ECU

4) Every mechanic I have taken it to has not been able to figure out the problem....internet searches only lead me to bad main relay( which to me is not the problem because the car will still start when ECU's are swapped)

5) What would cause this.....SOMEONE HELP, thanks in advance

 

Get in the habit of turning the key to the II position and do not try to start the car. When the check engine light turns on to to the bulb check, you should hear the fuel pump prime for about two seconds. It is a faint buzzing/whirling sound that comes from the back seat, so turn off the radio, blower, etc and listen carefully. Let us know if that sound is or is not present when the car does not start.

When the car does not start, does the starter turn the engine? Or does nothing happen?

Reset the ECU by pulling the 7.5 amp radio/backup fuse. When the car does not start, recheck the ECU codes.

Do you have access to a volt meter? a timing light?

 

I've done what you mentioned several times. The car only starts when the fuel pump primes. My problem is the fuel pump primes when it wants to. When it does start the car works fine. I've tried to reset the ECU by pulling the fuse and disconnecting battery, but codes do not clear on the old ECU. The new ECU is now displaying code 0 which I believe is bad ecu.

Heres another thing I forgot to mention, I also tried a P28(OBD1 for integra) ECU from a friends car just to see what would happen. Car starts every single time with P28 installed but will not hold idle due to vtec/non-vtec IAC compatibilty as im told.

I dont have access to a timing light but can borrow a multimeter.

I've previously downloaded the service manual, and went through all flowcharts pertaining to no start conditions. I have spark and sometimes fuel. For some reason or another the fuel pump will only prime when it wants to.

Also with original ECU installed, car is sometimes driveable. By that I mean, one day it will start and work fine, next time it wont start, or it will start and drive as if a governor/limit switch is in place( car sputters at 3500-4000 rpm and eventually stalls)

When trying to start with any of the 3 above mentioned ECUs, car cranks fine. Its always lack of fuel that causes the problems.

 

Btw its a 5-speed not sure if that matters......

 

When you say code 0, what is happening when you short that connector and turn the key to the II position? See the thread called how to check CEL codes in the DIY section.

It sounds like this is a fuel problem, which means either the main relay or the fuel pump. The wiring/ground is always a posibility The main relay is controlled by the ignition switch and not the ECU.

Anyway, in your trunk near the back seat there is an access panel and a three-wire connector. The easiest way to test the main relay is to back probe the yel/blk wire in that connector and connect one end of a 12V test light to the back probe and connect the other end of the test light to a ground. You want to see if the light turns on when the fuel pump will not prime.

 

When connector is shorted CEL stays on with Pick n Pull/new ECU
With original ECU CEL flashes 2 long 1 short (vtec solenoid)

I opened both ECUs and noticed some bad components.

1) "Original" ECU (37820-P0A-A01)- found out that it is for a vtec model, therefore the code 21, some components were also damaged

2) New ECU (37820-P0B-A01)- non-vtec but some components were damage, which weren't before. Maybe the reason for my no start condition

With that said, I'm assuming its a wiring/ground issue somewhere or another. Also the components may have been damaged due to me probing around with test light earlier today (not for sure, but just throwing it in as a possibility). I took both ECUs to a friend who is familiar with them, he's going to replace the damaged components and I will go from there.

I'm still not ruling out the ignition switch as the culprit. I don't think its is the main relay or fuel pump. The fuel pump is brand new (less than 1 month old, recently replaced). I have 5 main relays all solder joints look good on each, and no burnt component smell from any of them. Hopefully when my friend completes the repairs on the ECUs, I will be able to trace the short/open wire from there.

As for your test for probing the yel/blk at the fuel pump....

1) Done it when I first noticed the problems a couple of months ago

2) As far as I can remember, everything checked out as it should. I will test again when I get my ECUs back this weekend.

I noted the part #'s for the ECU's above if that's any help. The ground for main wiring harness looks clean and free from corrosion. Another note, some things in the 94-97 service manual I downloaded doesn't correspond to my car. I've been using that in combination with information found on teggers to troubleshoot.

Don't want to sound like I'm rambling on, just want to pass along any information that may be useful for your diagnosis.

 

The check engine light staying on means that no codes are stored and the ECU is ok.

As for the testing the main relay, what happened with that voltage test?