Hey all, newby here. I swapped a LS 5.3 and a 4l60e into a 1962 C10 Pickup. Got it running a while back and started driving it last week. Here's my issue:
Truck starts and runs excellent when cold. As soon as it warms up (closed loop) it begins to stumble on accel. I have 60 PSI fuel pressure, fuel system is new walbro and filter, all new lines and tank was spotless.

I have no codes present. I recently changed the left O2 sensor, (DTC code) the spark plugs and the MAP because I thought that was the issue...

Had the VATS removed and the rear o2 sensors...

Any help appreciated. Thanks.

 

Is the engine stock? Are you able to read the o2 voltage swings from a scanner?

 

Yes engine is stock. I have a Bosch 1100 code reader that does live data...just don't quite understand what the data means...

 

Curious how you did your fuel system? Stock tank? When/how are you checking the fuel pressure?

Are you by chance dealing with a fuel quantity problem? Like the size of line in the stock tank is too small?

Most people check the fuel pressure at idle and call it good, but it is very possible to have 60psi at idle, but if the line size is too small, it will not maintain that pressure when engine demand(increased consumption) increases.

And, as mentioned, watching the fuel trim numbers on your scanner should provide valuable information.

 

what do you have for a fuel tank? sounds like seat tank - is it an in tank pump or external setup?
if external on a seat tank you are forcing the pump to suck fuel instead of pushing it which has its own set of problems as a wlabro wont suck some 23" of head from the bottom of your seat tank very well if at all, properly
what do you have for a tank vent - is it working properly
where are your fuel filters located? are they clean/new
how did you run the return line and what size?

 

I am using the "seat tank" Walbro pump mounted on the frame. Vented cap on tank. Fuel filter I am not sure will have to look..tank was hospital clean when I installed it. All new lines to factory regulator. I installed a fuel gauge tonite at the rail and will see...47 PSI at idle...when cold..

 

you will likely always have issues with the pump that far from the pickup point
there is room to make it an intank install for the pump as the sender/pickup flange hole is lots large ( we are buildign a 61 so I know this for a fact)
you didnt mention what size return line or how you have it installed
I believe 58 psi is needed at all times as the minimum for proper running
you are starving for fuel - see pump location issues

 

47psi is pretty low, you need at least 58psi at all times. Are tou using a return or returnless fuel rail?

 

Ok what pump are you using in the tank? This Walbro whine is driving me nuts...I have to turn down my hearing aids...

 

we started out with using the factory pump that was in the sierra we bought for the engine and trans - and ultimately switched to a fuel cell out back for weight transfer

 

If you're hearing an external pump and it bothers you, then you'll hate an in tank pump behind the seat in the cab, its going to be real loud. I have a buddy that did it and it was annoying to him. If it's getting loud though, I agree with the other poster, sounds like it's having a hard time sucking the fuel the distance it has to, electric fuel pumps are generally designed to push fuel rather than pull it.