1998 Trans Am LS1 fuel pressure low
09-19-2017, 05:07 PM
#1
1998 Trans Am LS1 fuel pressure low Hi, my TransAm just recently began having trouble starting. It cranks for like 10 seconds and then fires up. If I prime the pump twice it works pretty well.
So, I checked the fuel pressure, first prime was like 14PSI...... if I do it twice it goes to 35~PSI, and then RAPIDLY drops to 20PSI, and then slowly over a few minutes down to 9PSI. When the car starts up and idles, it stays at 42PSI consistently for over 5 minutes of testing, but on shut off it IMMEDIATELY starts to dive into the 20s, and then back down to 9PSI. Is my fuel pump fucked? Or something else? Or what the hell?
I just spent all my money surviving Hurricane Irma FFS.
So, I checked the fuel pressure, first prime was like 14PSI...... if I do it twice it goes to 35~PSI, and then RAPIDLY drops to 20PSI, and then slowly over a few minutes down to 9PSI. When the car starts up and idles, it stays at 42PSI consistently for over 5 minutes of testing, but on shut off it IMMEDIATELY starts to dive into the 20s, and then back down to 9PSI. Is my fuel pump fucked? Or something else? Or what the hell?
I just spent all my money surviving Hurricane Irma FFS. 
09-20-2017, 09:27 AM
#3
Would buying a new fuel pump fix all of those collectively? Also, is the backdoor method, you know, safe? Between the sparking, and then the exposed fuel pump to the cabin where my wife and kids are? Otherwise, the shops want 4 digits in labor because of how ******* stupid these F-bodies were designed with dropping the tank to access it.
09-20-2017, 10:12 AM
#4
'Also, is the backdoor method, you know, safe?' I did the 'trapdoor' 14 years ago,since the tank is underneath the hatch floor,it can be sealed(the trapdoor) to keep separate the outside to the hatch area. I didn't 'seal' mine,I just have a small road sign covering the hole underneath the carpet. Never had an 'odor'. The replacement pump went after a few years while I was on I75 down in Florida. Since I carried a extra pump,15 minutes and I was back up running.
09-20-2017, 03:24 PM
#5
LS1Tech Administrator
iTrader: (3)
Join Date: Nov 2001
Location: Schiller Park, IL Member: #317
Posts: 32,046
Likes: 0
Received 1,493 Likes
on
1,075 Posts
Sounds like you need a new pump, it should be at 58-60psi at all times when running. If you get a complete module it will contain everything mentioned above (pump, FP regulator, check valve.)
There is no safety concern with the trap door method. You can cover the hole with sheet metal and seal it with silicone or rope caulk if you wish, but as long as you install the pump properly in the tank you won't have any gas fumes to deal with regardless.
There is no safety concern with the trap door method. You can cover the hole with sheet metal and seal it with silicone or rope caulk if you wish, but as long as you install the pump properly in the tank you won't have any gas fumes to deal with regardless.
09-20-2017, 06:13 PM
#6
Would buying a new fuel pump fix all of those collectively? Also, is the backdoor method, you know, safe? Between the sparking, and then the exposed fuel pump to the cabin where my wife and kids are? Otherwise, the shops want 4 digits in labor because of how ******* stupid these F-bodies were designed with dropping the tank to access it.
As others have stated cover the hole up with something. I bought some thick weatherstripping and put around the hole, then placed the metal I cut on top of it. I had my carpet out to track a water leak and without carpet or cover, I could smell exhaust fumes coming in while stopped, plus that pump is loud when it's 5' from your head lol.