Hello everyone, having a hard time figuring out a small issue I've been having intermittently. About a month ago I noticed when I filled my G up with gas when I got back in the car to start it it would just crank and crank and crank but not fire. I would cycle the key a few times and after a few minutes the car would start. I figured the stock fuel pump was on its way out so I bought an AEM 340LPH pump to replace it. When I installed the new pump it is a little bit longer than the stock one so I was not able to clip the plastic basket on the back of the fuel pump to hold it in but the pump is already jammed inside that plastic housing and the rubber grommet holds it pretty well in place. Another thing that might be causing this issue is I've been getting an EVAP code for the vent valve saying wrong direction of flow. I already replaced the part under the hood that is bolted to the back of the intake plenum and I also replaced another plastic vent valve that was attached to the charcoal canister box.

Just this morning I filled up and when I got back into the car it took a minute or two of cycling the key on and off and just cranking the car for it to fire. Is this EVAP code causing this? And how would I go about diagnosing the problem or figuring out why the car is doing this. It's not an immediate problem more just irritating than anything. My car has 156,000 miles, is it possible the charcoal canister is completely clogged and I need a new one? Also the valve I installed on the intake plenum was from the junkyard so maybe that one was bad too? The other part I replaced was new (and it was a newer style I guess there was a TSB for it at one point).

Or is my new pump that flows much more LPH a problem for the stock fuel pressure regulator?

I'm pretty mechanically inclined but tis issue has me stumped. Any recommendations or ideas would be greatly appreciated. Thanks

 

Did you modify the swirl jet and regulator? You can't just put a higher flowing pump in on the stock system without modifying them or it's going to cause low rpm fueling issues. That's a TON of fuel pump for a stock VQ btw, the Walbro 255LPH pump is considered the biggest pump you would ever need for NA use, it flows significantly more fuel at higher rpm compared to the stock 255LPH Nissan pump. You're going to really be drilling out the swirl jet and regulator to get that AEM unit down to the right flow.

Personally I think you need to be troubleshooting these as separate issues, if you suspect fueling is the problem then you need to start by checking fuel pressure, you will need a sandwich adapter for the fuel damper like the one sold by Z1 Motorsports to be able to read fuel pressure on the VQ. Otherwise you're just introducing more potential problems, like swapping to a completely different fuel pump that WILL require some custom drilling to get it to flow properly, even though there's other problems that need to be addressed first.

Yes EVAP problems will cause the car to not start, or to stall out immediately, that needs to be addressed first. Needing to prime the pump multiple times is definitely an indicator of EVAP problems, super common on LS1 Chevy trucks btw.

Exactly which codes is the car throwing?

 

Yes, sorry I didn't mention that but I did drill out the venturi pump with a 7/64th drill bit I believe it was. I did not drill the other part out, I think I found out about that after I had already installed the pump. You are talking about the metal part under another plastic clip/cap off to the side on the housing?

EDIT: Also my car is far from stock but yes still naturally aspirated. I had the car e-tuned by limp mode tuning because I run their huge 4" intake. Would tuning on the old pump mess with the new pump or is that not a factor because of the fuel pressure regulator/damper?

EDIT EDIT: Also I haven't gotten the code in a while, so I can't remember exactly what it was but the next time it pops up I will be sure to write it down.

 

Yeah the plastic part is the swirl jet / venturi, 7/64 should be fine for it.

The other metal part (under that plastic cap at the bottom) is the regulator, the same 7/64 would be a good starting point for it just make sure you're only drilling through the thin metal opening on the outlet side (part that points back up into the pump housing), you're not drilling through the entire thing.

EDIT: You probably need a retune on that new pump. Even being off by a couple of psi makes a difference in how much an injector will flow, if you were on a fuel return system then you could just adjust the regulator to match the stock 51psi. Run it first and see how much correction the ECM is actually making, you might get lucky and it's only a minimal correction and won't be an issue.