LS Fuel Pressure
- Thread starter custodian
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
Bextreme04
Full Access Member
- Joined
- May 13, 2019
- Posts
- 4,464
- Reaction score
- 5,630
- Location
- Oregon
- First Name
- Eric
- Truck Year
- 1980
- Truck Model
- K25
- Engine Size
- 350-4bbl
Those are the correct values to be seeing.
custodian
Full Access Member
- Joined
- Apr 15, 2016
- Posts
- 959
- Reaction score
- 556
- Location
- Catawba
- First Name
- William
- Truck Year
- 1973, 1985
- Truck Model
- C10
- Engine Size
- 5.3 LS, 350
I hoped I solved my running rich problem. Switched the two inlet for a three inlet sending unit. Can the charcoal canister be mounted horizontal?
You must be registered for see images attach
You must be registered for see images attach
Bextreme04
Full Access Member
- Joined
- May 13, 2019
- Posts
- 4,464
- Reaction score
- 5,630
- Location
- Oregon
- First Name
- Eric
- Truck Year
- 1980
- Truck Model
- K25
- Engine Size
- 350-4bbl
No, charcoal canister needs to be upright, unless you switch to one of the newer canisters from the LS vehicles. Those canisters are designed to be mounted horizontal right near the tank and then vent using a computer controlled signal to a point right above the tank fill point and purge to a computer controlled valve on the intake manifold. They use quick disconnects and formed hard line to get there, so it can be a problem to retrofit in swaps.
custodian
Full Access Member
- Joined
- Apr 15, 2016
- Posts
- 959
- Reaction score
- 556
- Location
- Catawba
- First Name
- William
- Truck Year
- 1973, 1985
- Truck Model
- C10
- Engine Size
- 5.3 LS, 350
So far the numbers are staying the same. Will have to remove a few things and mount the charcoal canister on the passener side under the air box.
87chevy_com
Member
- Joined
- May 7, 2023
- Posts
- 31
- Reaction score
- 19
- Location
- Texas
- First Name
- Clint
- Truck Year
- 1987
- Truck Model
- R10
- Engine Size
- L83
Just reading last posts... is your:
Tune stock
Intake tube stock
Mass airflow sensor stock
87chevy_com
Member
- Joined
- May 7, 2023
- Posts
- 31
- Reaction score
- 19
- Location
- Texas
- First Name
- Clint
- Truck Year
- 1987
- Truck Model
- R10
- Engine Size
- L83
Humm.. I had a slightly larger aftermarket intake tube and factory mass airflow and that made mybswap run rich. I wound up putting a wideband on it and tuning the airflow sensor table.
Bextreme04
Full Access Member
- Joined
- May 13, 2019
- Posts
- 4,464
- Reaction score
- 5,630
- Location
- Oregon
- First Name
- Eric
- Truck Year
- 1980
- Truck Model
- K25
- Engine Size
- 350-4bbl
Any time you change the intake tubing, you change the mass airflow readings and need to retune them. As long as you stick to the stock tubing it will be fine.
Hunter79764
Full Access Member
- Joined
- Sep 1, 2021
- Posts
- 344
- Reaction score
- 536
- Location
- Grand Prairie, TX
- First Name
- Shawn
- Truck Year
- 1987
- Truck Model
- Suburban V20
- Engine Size
- 350
Welp, I'd say that counts as stock...
FWIW, it isn't uncommon for even stock setups to be 10% off, although my experience is that it usually is trending lean and forcing more fuel to be added. Dirty MAF allows more air that isn't detected, dirty injectors allow less fuel than what the computer thinks, and ethanol fuel supplies less BTU than the early computers planned for (assuming it isn't flex fuel, but even the later computers seemed to default to accommodate 10% ethanol where my '01 stock setup was based on real gas).
All that said, 58/53 seems close enough, 100 psi is absolutely going to make it rich. I think you got rid of your 100 psi readings with the tank venting, correct? If you have pressure in the 50's, run it a while and you should be able to see if you are running right or not. If you don't have a way to check the computer, get an OBD2 bluetooth reader and something like the Torque Pro app and look at your fuel trims, long term and short term. If they aren't pegged out one way or the other (after resetting the computer with a battery disconnect) then you should be good enough. A good in-person tune will always help, but if you just want stock, reliable operation, you will be in as good of shape as any 10 year old Chevy truck out there.
FWIW, it isn't uncommon for even stock setups to be 10% off, although my experience is that it usually is trending lean and forcing more fuel to be added. Dirty MAF allows more air that isn't detected, dirty injectors allow less fuel than what the computer thinks, and ethanol fuel supplies less BTU than the early computers planned for (assuming it isn't flex fuel, but even the later computers seemed to default to accommodate 10% ethanol where my '01 stock setup was based on real gas).
All that said, 58/53 seems close enough, 100 psi is absolutely going to make it rich. I think you got rid of your 100 psi readings with the tank venting, correct? If you have pressure in the 50's, run it a while and you should be able to see if you are running right or not. If you don't have a way to check the computer, get an OBD2 bluetooth reader and something like the Torque Pro app and look at your fuel trims, long term and short term. If they aren't pegged out one way or the other (after resetting the computer with a battery disconnect) then you should be good enough. A good in-person tune will always help, but if you just want stock, reliable operation, you will be in as good of shape as any 10 year old Chevy truck out there.
custodian
Full Access Member
- Joined
- Apr 15, 2016
- Posts
- 959
- Reaction score
- 556
- Location
- Catawba
- First Name
- William
- Truck Year
- 1973, 1985
- Truck Model
- C10
- Engine Size
- 5.3 LS, 350
Vent is fixed and hooked back up to a charcoal canister. Not flex fuel. Reset the computer yesterday. I carry an OBD2 scanner with the the truck. Checked everything and was in normal ranges. Will drive it tomorrow and see what happens. I programmed the LS tune myself.
custodian
Full Access Member
- Joined
- Apr 15, 2016
- Posts
- 959
- Reaction score
- 556
- Location
- Catawba
- First Name
- William
- Truck Year
- 1973, 1985
- Truck Model
- C10
- Engine Size
- 5.3 LS, 350
Drove for about an hour, no codes, runs good, stopped and checked the fuel trims and were okay, what a stupid oversight on my part.
Hunter79764
Full Access Member
- Joined
- Sep 1, 2021
- Posts
- 344
- Reaction score
- 536
- Location
- Grand Prairie, TX
- First Name
- Shawn
- Truck Year
- 1987
- Truck Model
- Suburban V20
- Engine Size
- 350
Good deal.
I had a coworker who did an EFI conversion on his mustang. Ran great, for about 30 minutes at a time, then started running lean and eventually died. A few hours later it would be fine, but do it all over again. It was a head scratcher for weeks, I think he replaced the fuel pump a couple of times, diagnosed wiring connections, ran the thing on jackstands until it got hot enough to see if something was changing when warm, rerouted his fuel lines to keep them away from the exhaust, and a bunch of other stuff. Turns out his tank vent wasn't right and it was pulling vacuum as fuel was removed, causing it to lean out from low fuel pressure. Since then I always keep an eye out for things like that.
I had a coworker who did an EFI conversion on his mustang. Ran great, for about 30 minutes at a time, then started running lean and eventually died. A few hours later it would be fine, but do it all over again. It was a head scratcher for weeks, I think he replaced the fuel pump a couple of times, diagnosed wiring connections, ran the thing on jackstands until it got hot enough to see if something was changing when warm, rerouted his fuel lines to keep them away from the exhaust, and a bunch of other stuff. Turns out his tank vent wasn't right and it was pulling vacuum as fuel was removed, causing it to lean out from low fuel pressure. Since then I always keep an eye out for things like that.
- Joined
- Feb 5, 2014
- Posts
- 4,341
- Reaction score
- 3,393
- Location
- Kentucky
- First Name
- David
- Truck Year
- 1986
- Truck Model
- K10/LM7 5.3/4L60e/np208/3.73/32"
- Engine Size
- 10 yrs Air Force
my recent "used" replacement LS it's acting a bit funny and have been thinking about how to troubleshoot it.
I ordered a fitting to hook up to the fuel rail. Then I plan to hook up an oil sender to it (weld if needed to so it don't leak), then put a switch to the oil pressure gauge to switch between the 2. I'd like to monitor mine when it's acting funny. I might have a filter/regulator or pump going bad.
Thought I'd share cuz it might help troubleshooting ur issue. If you beat me to it, make sure it doesn't leak at the sender obviously.
I ordered a fitting to hook up to the fuel rail. Then I plan to hook up an oil sender to it (weld if needed to so it don't leak), then put a switch to the oil pressure gauge to switch between the 2. I'd like to monitor mine when it's acting funny. I might have a filter/regulator or pump going bad.
Thought I'd share cuz it might help troubleshooting ur issue. If you beat me to it, make sure it doesn't leak at the sender obviously.
