Leaning out in boost after driving a while
On The Tree
Joined: Feb 2011
Posts: 120
Likes: 20
From: Tucson, AZ
MY 97 Camaro had pretty much the same problem. It would run great when cool, if I drove it for extended periods or was always in boost it would slowly start to run leaner and leaner and the car would have no power while in boost. It would generally take about an hour or 2 for it to start happening.
One night I pulled in my driveway and heard a noise from the gas tank, so I popped the fuel cap and it dang near blew the cap out of my hands and vented for minutes. I seriously thought it was going to blow up or something. That happened only once, but it was the longest I had ever driven the car and I was being pretty hard on it.
My fuel lines were just too close to the exhaust manifold, one time (different ocasion) they even managed to shift and melt the protective loom. The way the Camaros rout the lines is stupid and is was about 6 or so inches away from the header pre turbo, and there were a couple spots under the car where they got close as well. I wrapped the lines (only the areas close to the exhaust) with header wrap and then one of those reflective heat shields. The other thing was my return line inside the tank fell off and it was spraying fuel right out of the top. I fixed the heat issue and it got significantly better, fixing the return solved the issue for me.
One night I pulled in my driveway and heard a noise from the gas tank, so I popped the fuel cap and it dang near blew the cap out of my hands and vented for minutes. I seriously thought it was going to blow up or something. That happened only once, but it was the longest I had ever driven the car and I was being pretty hard on it.
My fuel lines were just too close to the exhaust manifold, one time (different ocasion) they even managed to shift and melt the protective loom. The way the Camaros rout the lines is stupid and is was about 6 or so inches away from the header pre turbo, and there were a couple spots under the car where they got close as well. I wrapped the lines (only the areas close to the exhaust) with header wrap and then one of those reflective heat shields. The other thing was my return line inside the tank fell off and it was spraying fuel right out of the top. I fixed the heat issue and it got significantly better, fixing the return solved the issue for me.
Last edited by Max78; Mar 9, 2021 at 10:19 PM.
TECH Enthusiast
Joined: Dec 2017
Posts: 676
Likes: 72
the one I worked on was even worse. Fuel.pump to regulator straight to driver's fuel rail and then a cross over between the drivers rail and the passengers at the rear. Return on bottom of regulator. I guess other people do it that way no problem but it really effected that vehicle. It was a 5th generation camaro so it had that weird saddle tank and the return they added was on the same side as the suction.
TECH Regular
Joined: Jul 2019
Posts: 460
Likes: 44
I would assume it would make huge problem with holding steady pressure... the fuel reg should always be last part of system. Putting pump into reg would bleed down some fuel before it evens gets good pressure to the rails.
So after reading and thinking about this, I think that at idle I'm having alot of fuel being bypassed and its just recirculatiing the fuel, building up heat.....so ways i can cut that down?
I'm going to insulate the fuel line in the engine compartment. That may help a little bit. But say I'm idling in traffic for some time..the fuel pressure regulator is hot from the engine temps and its mounted to the fuel rail. However, factory trucks had the regulator mounted on the intake/rail so maybe thats not as much of an issue. Maybe I should replace the aeromotive 340 with a smaller pump? What about cutting the voltage to it and jump it back up at wot? But then maybe the pressure would be less? The heat in the pump could actually become greater because a lower voltage will work the pump more possibly? I bet it would be a bitch to tune it too...
Maybe a stock pump and a large secondary pump might be the best bet?
I'm going to insulate the fuel line in the engine compartment. That may help a little bit. But say I'm idling in traffic for some time..the fuel pressure regulator is hot from the engine temps and its mounted to the fuel rail. However, factory trucks had the regulator mounted on the intake/rail so maybe thats not as much of an issue. Maybe I should replace the aeromotive 340 with a smaller pump? What about cutting the voltage to it and jump it back up at wot? But then maybe the pressure would be less? The heat in the pump could actually become greater because a lower voltage will work the pump more possibly? I bet it would be a bitch to tune it too...
Maybe a stock pump and a large secondary pump might be the best bet?
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Verdad Gallardo Are we sure the fuel is getting hot enough to cause the lean issue in boost? I'm returning a lot of fuel at idle with a 4303 and do not have any issues with the fuel system street driving.
That is exactly why I brought up battery voltage at the pump. I thought I was having the same issue and it ended up being voltage drop to the pump over time as stuff got hot.
TECH Fanatic
Joined: Feb 2015
Posts: 1,080
Likes: 178
Not doggin ya but, you can guess what it might be and try some things or define a test plan and measure a few things to identify root cause. Hot fuel is not a good thing. Is that the root cause of your problem? Likely not. How hot is your return line at the tank? How hot is the fuel at the regulator? Insulating a fuel lines that run next to 400+F exhaust would be wise or reroute them. Side note - Hot fuel returning to a fuel tank should never generate tank pressure and blow fuel out when removing the cap. If so, the tank is not effectively vented.
What datalog capabilities do you have on the car? Can you capture fuel pump voltage? Fuel rail pressure?
What datalog capabilities do you have on the car? Can you capture fuel pump voltage? Fuel rail pressure?
Alright. I’m back at it. Cars been sitting, had to finish the other turbo car and a truck I built an intake for and tuned. Pulled the tank out yesterday. Yep, the return was right at the pumps pickup filters. Probably wasn’t the best idea to do that.
Like dis
So I cut the line shorter and put a 90 degree fitting on it and put a radium engineering one way nozzle (if you disconnect the fuel tank with fuel in it, the return fitting is lower than the tank level and it will constantly siphon fuel out....don’t ask how I found out!)
here’s some pics of the pump bucket I built just for gp
Like dis
So I cut the line shorter and put a 90 degree fitting on it and put a radium engineering one way nozzle (if you disconnect the fuel tank with fuel in it, the return fitting is lower than the tank level and it will constantly siphon fuel out....don’t ask how I found out!)
here’s some pics of the pump bucket I built just for gp
I drove around last night for a while. Got on it. 21psi and afr was good. I’m gonna have to ride around on a hot day for a while and see what it does. I still need to wrap the line up front.