Hi everyone, i just picked up a 2005 civic si with 183000km today and I noticed this long cranking issue today when I got low on fuel. Originally when I test drove the car and today when I picked up the car it had no issues and would crank normally... A couple hours later after picking up the car it started fine also. Eventually when I got home the fuel level was getting closer to the fuel light illuminating. After a couple of hours I went to start the car and the cranking took at least a good 5 - 7 seconds. I wanted to see if it would the same thing if I shut it off an turned it back on and the engine fired up right. I went to fill up, left the car to sit a couple hours and when I went to start it cranked normally. What's the usually culprit in these scenarios? My sister has an 03 civic lx and I've never seen her have this issue when low on fuel

 

Weak fuel pump, bad injector(s), possibly gunked up fuel filter in-tank... a bunch of potential problesm.

 

I realized it could be all those things after a bit of reading... My question is how do I diagnosis what it is? I figured I could add an additive to the fuel to clean the filter/injectors and see if that makes a difference

 

You could always try something like seafoam, to see if the problem subsides a bit.

 

Check fuel pressure at the rail, if it is within spec, you'll know your problem lies within the injectors.
If not, the problem will be something along the lines of toyomatt's first response.

 

When it happens again, low fuel and long cranking, before you crank cycle the ign. a few times, turn ign. on, wait till fuel pump cycles off, turn ign. on again and wait again, do this a few times then crank, see what happens. 94

 

do you just crank it right away or do you let the fuel pump prime?

 

I think it is due to low fuel level in the tank causing the pump to have to work harder to get that fuel. My EP3 does the same thing and there's nothing wrong with the fuel system. Once I refill it is fine--only does that when is low on fuel...and I replaced the built in filter a while back so that is not the issue.

 

Using seafoam at first is always a common and smart approach.