Rotten 1
Full Access Member
- Joined
- Jan 9, 2024
- Posts
- 50
- Reaction score
- 66
- Location
- Tennessee
- First Name
- Chris
- Truck Year
- 1974
- Truck Model
- C10
- Engine Size
- 350
Hey guys,
I read through a few older threads and have a couple of ideas, but wanted to summarize things here and see what I might be missing.
Rebuilt Rochester 2GV because the truck would not start in the cold, choke plate would stick, and acceleration was lethargic (and I have a Quadrajet and new intake on the shelf in the garage but thought I'd get my feet wet without adding new parts). Rebuild was; new float, new idle mix screws, new gaskets, new accelerator pump seal, a lot of carb cleaner and nylon brushes *bought the little brush kit from Mike's). Got everything bolted back on and the truck died about 100 yards down the road, backfire and stall; but started right back up again and I limped home. Found one vacuum line was not completely seated so I reattached.
Then, while in park, engine would rev up fine but backfire and stumble as RMP dropped. Visually confirmed that the accelerator pump works, solid and immediate squirt when I bump the throttle. Replaced vacuum lines to the advance, checked timing (8 degrees BTDC) and confirmed timing does advance with a timing light. Replaced the fuel filter. Replaced lines to the PCV and the EGR, where I thought I heard a leak if I barely moved the vacuum line. There are also two lines that attach to a unit where the top radiator hose enters the block, and I cannot find what those hoses do or what that unit is. My assumption is some kind of coolant control based on RPMs.
With the engine running and warm, I was able to reach under the EGR and try to push up the diaphragm and it made no difference but was very dirty with what I assume to be carbon buildup.
Now I warm the engine up and get occasional backfire as RPMs are going up, but everything if fine coming down; the backfire is not every time I rev the engine, but I cannot estimate if it's 1 in 10 or 1 in 5 yet. Easy data to get if that helps. My main concern is getting out on the road and it dies in traffic.
I also found that the end of the hose that goes from the carbon canister to the carb is not connected, but I cannot find an empty vacuum port to attach to. I could see how a bare vacuum port would cause me problems, but I just cannot find it. I have not read or heard anything that tells me the disconnected canister is going to do anything other than allow for the lovely gasoline smell to fill the garage
From what I have been able to find my next steps are:
1) Pull EGR and seal off the holes and vacuum tube, if the EGR is bad then the backfire should go away and I buy and install a new EGR.
2) adjust the float for more fuel in the bowl. The old float was rubber/plastic, the new one is brass. I set to the same height but maybe different material acts differently and a slight adjustment here solves the problem.
3) tee into the brake booster vacuum line (or other manifold vacuum source and hit it with a vacuum gauge).
Am I missing anything else? Any recommendation on EGR v. float or just work through all of them?
thanks
I read through a few older threads and have a couple of ideas, but wanted to summarize things here and see what I might be missing.
Rebuilt Rochester 2GV because the truck would not start in the cold, choke plate would stick, and acceleration was lethargic (and I have a Quadrajet and new intake on the shelf in the garage but thought I'd get my feet wet without adding new parts). Rebuild was; new float, new idle mix screws, new gaskets, new accelerator pump seal, a lot of carb cleaner and nylon brushes *bought the little brush kit from Mike's). Got everything bolted back on and the truck died about 100 yards down the road, backfire and stall; but started right back up again and I limped home. Found one vacuum line was not completely seated so I reattached.
Then, while in park, engine would rev up fine but backfire and stumble as RMP dropped. Visually confirmed that the accelerator pump works, solid and immediate squirt when I bump the throttle. Replaced vacuum lines to the advance, checked timing (8 degrees BTDC) and confirmed timing does advance with a timing light. Replaced the fuel filter. Replaced lines to the PCV and the EGR, where I thought I heard a leak if I barely moved the vacuum line. There are also two lines that attach to a unit where the top radiator hose enters the block, and I cannot find what those hoses do or what that unit is. My assumption is some kind of coolant control based on RPMs.
With the engine running and warm, I was able to reach under the EGR and try to push up the diaphragm and it made no difference but was very dirty with what I assume to be carbon buildup.
Now I warm the engine up and get occasional backfire as RPMs are going up, but everything if fine coming down; the backfire is not every time I rev the engine, but I cannot estimate if it's 1 in 10 or 1 in 5 yet. Easy data to get if that helps. My main concern is getting out on the road and it dies in traffic.
I also found that the end of the hose that goes from the carbon canister to the carb is not connected, but I cannot find an empty vacuum port to attach to. I could see how a bare vacuum port would cause me problems, but I just cannot find it. I have not read or heard anything that tells me the disconnected canister is going to do anything other than allow for the lovely gasoline smell to fill the garage
From what I have been able to find my next steps are:
1) Pull EGR and seal off the holes and vacuum tube, if the EGR is bad then the backfire should go away and I buy and install a new EGR.
2) adjust the float for more fuel in the bowl. The old float was rubber/plastic, the new one is brass. I set to the same height but maybe different material acts differently and a slight adjustment here solves the problem.
3) tee into the brake booster vacuum line (or other manifold vacuum source and hit it with a vacuum gauge).
Am I missing anything else? Any recommendation on EGR v. float or just work through all of them?
thanks
