LS Swap stalling under load
10 Second Club
Joined: Nov 2005
Posts: 933
Likes: 75
When you get the fuel pressure fixed and want to run it in SD, go to engine diagnostics and make P0101,102 mil on first error like 103 already is. You can uncheck the boxes if you don't want to see the light. Go to Dynamic airflow and make high rpm disable something like 8000 rpm so the computer will not hunt for the maf sensor. If you run a O2 sensor, make sure you have about 2' of exhaust pipe past the sensor.
Agree this happens between the pump and the sender occasionally Start in the tank, make sure all lines are connected properly with the correct hose type and clamp and work your way forward. Check for vacuum leaks also
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
I just don't understand why the lines would have anything to do with it if the problem only arises when the engine is warm. I also don't smell a strong gas smell when I prime the pump so I don't believe it's leaking.
TECH Enthusiast
Joined: Jul 2010
Posts: 593
Likes: 29
From: Florida
When you turn the key to activate the pump (without starting the motor) than turn the key off, does it still show 58, if it drops than you may have a bad check valve on the pump or the regulator is gone.
Show us a the video of the gauge under pressure "turning the key, wait 5 seconds than off" it should hold a long time.
Show us a the video of the gauge under pressure "turning the key, wait 5 seconds than off" it should hold a long time.
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
TECH Enthusiast
Joined: Jul 2010
Posts: 593
Likes: 29
From: Florida
I had a car come here that had a similar issue, It started but the gauge dropped pressure when you stepped on the gas. I disconnected the bleed line from the regulator and capped it. I wanted to see if it hold, it didn't. Now it's between the injectors and check valve in the pump. Next I installed a check valve between the pump and injectors, pressure held. Came back a hour later it still had pressure, reinstalled the return line on the regulator it slowly bleed off, replaced regulator, turned the key pressure remained strong (which mean the injectors were not leaking). Long story short, check valve on pump and regular had leaks.
Check valves are cheap,
Check valves are cheap,
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
I had a car come here that had a similar issue, It started but the gauge dropped pressure when you stepped on the gas. I disconnected the bleed line from the regulator and capped it. I wanted to see if it hold, it didn't. Now it's between the injectors and check valve in the pump. Next I installed a check valve between the pump and injectors, pressure held. Came back a hour later it still had pressure, reinstalled the return line on the regulator it slowly bleed off, replaced regulator, turned the key pressure remained strong (which mean the injectors were not leaking). Long story short, check valve on pump and regular had leaks.
Check valves are cheap,
Check valves are cheap,
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Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Replaced the regulator. Not sure if this has to do with replacing it but now the truck isn't holding pressure at all.
Edit: was trying to go to sleep and realized I left an extra o ring in the regulator. Went out there and removed it today and now it still doesn't hold pressure but doesn't drop immediately.
Edit: was trying to go to sleep and realized I left an extra o ring in the regulator. Went out there and removed it today and now it still doesn't hold pressure but doesn't drop immediately.
Last edited by bm23; Nov 21, 2020 at 06:54 AM.
Thread Starter
Staging Lane
Joined: Nov 2020
Posts: 55
Likes: 5
Update: So I replaced the fuel pump today and noticed it was holding pressure again. Took it for a drive and it drove like never before. Drove it a half hour away and back today with no issue. Moral of the story: don't trust fuel pumps even if they're brand new. Thank you all for helping me out and I hope to be posting on here again soon.
The more you peal a build down the greater chances for something to fail right away. I always say a builds not done until you've driven it a full year ironing out the kinks and chasin away gremlins and whatnot. Bit of a diatribe there lol