69 L-36 Surging Under Full Throttle
Thread Starter
Instructor
Joined: May 2015
Posts: 133
Likes: 12
From: Maple Valley WA
69 L-36 Surging Under Full Throttle
Hello all !
I'm pretty sure I know whats happening but am looking for some confirmation. I took the vette for a 1 hr drive, I haven't driven it that long for some time. After driving winding surface streets at 25 mph and sitting at some traffic lights I floored it in 2nd getting on the freeway and the car surged, accelerating-decelerating-accelerating all within a second or two (I have given full throttle the same way recently but right after the car was warm with no problems) so I let off a bit and smoothly accelerated onto the freeway with not problems all the way home on the freeway and surface streets for about another 20 minutes.
I'm thinking vapor in the fuel? Thanks in advance
Dave
I'm pretty sure I know whats happening but am looking for some confirmation. I took the vette for a 1 hr drive, I haven't driven it that long for some time. After driving winding surface streets at 25 mph and sitting at some traffic lights I floored it in 2nd getting on the freeway and the car surged, accelerating-decelerating-accelerating all within a second or two (I have given full throttle the same way recently but right after the car was warm with no problems) so I let off a bit and smoothly accelerated onto the freeway with not problems all the way home on the freeway and surface streets for about another 20 minutes.
I'm thinking vapor in the fuel? Thanks in advance
Dave
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
I had similar symptoms with my 69 L-36. Coming on to the freeway and under heavy acceleration it would bog then surge and repeat. The entire fuel system was new. I was using one of those Napa anti drain back fuel filters in the quadrajet carb inlet and it did not allow enough fuel to enter the carb. The center spring loaded valve was binding in the filter making it hard to open all the way causing fuel starvation. I tossed it and installed the stock filter in the carb and it solved the problem. Last time I will use one of those....
Last edited by CanadaGrant; Dec 15, 2015 at 11:53 PM.
Thread Starter
Instructor
Joined: May 2015
Posts: 133
Likes: 12
From: Maple Valley WA
I had similar symptoms with my 69 L-36. Coming on to the freeway and under heavy acceleration it would bog then surge and repeat. The entire fuel system was new. I was using one of those Napa anti drain back fuel filters in the quadrajet carb inlet and it did not allow enough fuel to enter the carb. The center spring loaded valve was binding in the filter making it hard to open all the way. I tossed it and installed the stock filter in the carb and it solved the problem. Last time I will use one of those....
Dave
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Hello all !
I'm pretty sure I know whats happening but am looking for some confirmation. I took the vette for a 1 hr drive, I haven't driven it that long for some time. After driving winding surface streets at 25 mph and sitting at some traffic lights I floored it in 2nd getting on the freeway and the car surged, accelerating-decelerating-accelerating all within a second or two (I have given full throttle the same way recently but right after the car was warm with no problems) so I let off a bit and smoothly accelerated onto the freeway with not problems all the way home on the freeway and surface streets for about another 20 minutes.
I'm thinking vapor in the fuel? Thanks in advance
Dave
I'm pretty sure I know whats happening but am looking for some confirmation. I took the vette for a 1 hr drive, I haven't driven it that long for some time. After driving winding surface streets at 25 mph and sitting at some traffic lights I floored it in 2nd getting on the freeway and the car surged, accelerating-decelerating-accelerating all within a second or two (I have given full throttle the same way recently but right after the car was warm with no problems) so I let off a bit and smoothly accelerated onto the freeway with not problems all the way home on the freeway and surface streets for about another 20 minutes.
I'm thinking vapor in the fuel? Thanks in advance
Dave
If your gas tank had less than 1/4 full the gas could have been forced against the rear of the tank on hard acceleration and starving the fuel pump.
Thread Starter
Instructor
Joined: May 2015
Posts: 133
Likes: 12
From: Maple Valley WA
Had about a half tank so I don't think thats it. I'm not utilizing the return line right now, have fuel line going directly from the pump to carburetor so I believe the fuel was getting too hot. I'm going to re-plumb everything with a return off the filter to help circulate the fuel and see if that cures it. It will be a while till I'm able to get to it.
