Only two injectors fire during cold start?
Thread Starter
Staging Lane
Joined: Mar 2024
Posts: 78
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Only two injectors fire during cold start? I’m having some really really strange issues with my LS swap. It’s an LS1/T56 out of a 2004 Pontiac GTO, it’s in a 1981 Corvette and I’m using the Holley Terminator X as an ECU.
A few months ago, I got it started and running with the Terminator. It would start up right away but “hot start” was kind of an issue. I then sent it out for paint, re-wired the whole car, and now I’m having issues. At first, it would start up right away, but restarts were still tough…much tougher than when I first got it running. Revving was also really rough and it would bog down a ton.
Called up Holley and realized my IAC was 0, so they had me raise the throttle adjust screw to open the throttle blade a bit and get IAC between 2 and 10. That pretty much fixed the hot start issue - now it restarts no problem when it’s hot and revving is perfect. AFR is about 14 at idle, but will drop to like 9 while revving, although it runs and drives great. However, adjusting the throttle adjust screw also affects throttle position (as the computer now thinks your foot is on the gas). When I go to zero out the TPS, my IAC drops back down to 0…but it still runs well.
Anyway, the real problem is after all that I’m now having cold start issues. The engine just does not want to start on its own, but if I put starter fluid in the intake, it starts right up and runs great. Looking at my data logs, it looks like AFT is at like 35, which means it’s basically getting no fuel whatsoever.
Called up Holley and we did some troubleshooting. Noticed that my primed fuel pressure is about 48, but jumps up to 60 when running. When revving, fuel pressure drops from 60 to about 45, but again, it still runs great.
But the real kicker is Holley had me take the fuel rails off to see if the injectors were actually firing during cold start…and only injectors 3 and 4 pump fuel! But the second it turns over, all 8 injectors fire, no misfires whatsoever. When I told this to Holley they were absolutely baffled!
At this point, I think I’m going to try replacing the fuel pump to see if that helps at all. But if not, I’m out of ideas.
Anyone ever heard of anything like this?!
A few months ago, I got it started and running with the Terminator. It would start up right away but “hot start” was kind of an issue. I then sent it out for paint, re-wired the whole car, and now I’m having issues. At first, it would start up right away, but restarts were still tough…much tougher than when I first got it running. Revving was also really rough and it would bog down a ton.
Called up Holley and realized my IAC was 0, so they had me raise the throttle adjust screw to open the throttle blade a bit and get IAC between 2 and 10. That pretty much fixed the hot start issue - now it restarts no problem when it’s hot and revving is perfect. AFR is about 14 at idle, but will drop to like 9 while revving, although it runs and drives great. However, adjusting the throttle adjust screw also affects throttle position (as the computer now thinks your foot is on the gas). When I go to zero out the TPS, my IAC drops back down to 0…but it still runs well.
Anyway, the real problem is after all that I’m now having cold start issues. The engine just does not want to start on its own, but if I put starter fluid in the intake, it starts right up and runs great. Looking at my data logs, it looks like AFT is at like 35, which means it’s basically getting no fuel whatsoever.
Called up Holley and we did some troubleshooting. Noticed that my primed fuel pressure is about 48, but jumps up to 60 when running. When revving, fuel pressure drops from 60 to about 45, but again, it still runs great.
But the real kicker is Holley had me take the fuel rails off to see if the injectors were actually firing during cold start…and only injectors 3 and 4 pump fuel! But the second it turns over, all 8 injectors fire, no misfires whatsoever. When I told this to Holley they were absolutely baffled!
At this point, I think I’m going to try replacing the fuel pump to see if that helps at all. But if not, I’m out of ideas.
Anyone ever heard of anything like this?!
