97 accord, 4cyl, lx, not a v-tec.

If the car sits for 2 or 3 days it does not want to start sometimes. It has fire, fuel injectors getting signal, but it looked like the fuel pressure is very low. So I put a new fuel pump in it, but that did not fix it.

If you try to start it a few times, let it sit for an hour and try again, it will start right up (so far).

I was thinking regulator, or maybe even the injectors were leaking down. So I tried to pinch the supply and return lines off at the injectors and see if pressure went down after cutting it off, but there was no pressure drop.

But it doesn't do it all the time.

Anyone?

 

Probably Main Fuel Relay (MFR).

When you turn keyswitch to ON, the ECU activates MFR to engage fuel pump for 2-3 secs, and then cuts fuel pump off. If you listen carefully, you can hear MFR relay click closed and fuel pump buzz for 2-3 secs. If you don't hear those sounds, it won't start, and MFR is the culprit.

good luck

 

The relay seems to be working fine. I can hear the pump kick on and run for a few seconds. Still, no start.

 

You said it doesn't happen every time...
Can we second-guess about having spark? Did you verify a good spark even when it failed to start?

And you mentioned fuel pressure. Did you measure it?

(I'm just trying not to take anything for granted)

 

If you hear MFR and pump run, fuel pressure is likely OK. How did you measure fuel pressure?

When no start occurs, suggest checking for spark w/ a timing light on one spark plug lead. No flash = no spark.

Since engines runs normally most of time, compression is not the issue, but rather spark or fuel.

good luck