1999 C1500 GMC Suburban 5.7 fuel issue

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.

Mister1500

Newbie
Joined
Oct 5, 2021
Messages
34
Reaction score
32
Location
Naptown
Okay guys I need new help. Just received a new to me 1999 C1500 GMC Suburban. Has been sitting approx 2 years. It cranks an fires, runs momentarily 2-5 seconds then dies. I have 60 psi key on engine off. After it starts it drops to roughly 54-56 psi. Never drops below that. It wont take any throttle. If I spray a fuel source into the throttle plate it stays running until I stop spraying. Seems like maybe a SFI issue. Currently no codes. Not sure where to go from here. Never had a central SFI system before. Any suggestions? Is there a separate crank vs running signal to the SFI? Thanks for everyone’s time.
 

Mister1500

Newbie
Joined
Oct 5, 2021
Messages
34
Reaction score
32
Location
Naptown
I hadn’t thought of the VATS system being on this veh. I’ll check for a security light in the morning. Thanks. I’ll post my findings
 

df2x4

4L60E Destroyer
Staff member
Super Moderator
Joined
Mar 1, 2012
Messages
11,159
Reaction score
12,702
Location
Missouri
Definitely sounds like PassLock/VATS. That started in '98 on these trucks.
 

HotWheelsBurban

Gotta have 4 doors..... Rawhide, TOTY 2023!
Joined
Sep 18, 2019
Messages
9,686
Reaction score
17,583
Location
Houston, Texas
Definitely sounds like PassLock/VATS. That started in '98 on these trucks.
Yup that's exactly what my Burb did when the Passlock started acting up. Only way away from that, is to get it electronically deleted from the PCM with tuning software. The relearn procedures don't work consistently, and putting a resistor in the system doesn't work for long term either (the resistor gradually weakens and fails).
 

Pro439

I'm Awesome
Joined
Aug 1, 2022
Messages
154
Reaction score
141
Location
Rome,NY
If the security is your issue Wester’s Garage can help you out with that and for a reasonable amount. He can also remove the egr and down stream O2 sensors if you like
 

Mister1500

Newbie
Joined
Oct 5, 2021
Messages
34
Reaction score
32
Location
Naptown
Okay, update: It does light up with the security. I assume as part of the dash bulb check. After starting veh, it stays on. I might get 2-5 seconds before it dies. How quickly should the security light go off? If it is aVATS issue, would I still be able to keep it running with an external fuel source? It never takes any throttle. Appreciate all the help!
 

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
10,970
Reaction score
13,756
Location
The Seasonally Frozen Wastelands
Wester’s Garage can help you out with that and for a reasonable amount. He can also remove the egr and down stream O2 sensors if you like
Not legally. If the EPA finds out, he's in deep doo-doo. Whether they'd confiscate his client list and bring trouble downstream, I don't know.
 

Supercharged111

Truly Awesome
Joined
Aug 20, 2015
Messages
12,617
Reaction score
15,245
In my experience, it'll run for 1 second max with a VATS issue, not 2-5. You mentioned spraying fuel at the throttle blade, are you trying to run it with the throttle body bonnet removed and the MAF still plugged in? That'll piss it off for sure.
 

Mister1500

Newbie
Joined
Oct 5, 2021
Messages
34
Reaction score
32
Location
Naptown
No I removed the hose from the valve cover, plugged and spray in the throttle body bonnet at that point of access. However the security light does not go out.
 
Top