Start - No Run AGAIN
Thread Starter
On The Tree
Joined: Mar 2007
Posts: 113
Likes: 14
From: Calgary, AB
Start - No Run AGAIN I've had an L33-swapped 97 C1500 running well for a couple of years, then started glitching out -- ran perfectly for 3 sec on startup and then just died. Sometimes it would prime up again and start, but not always. Diagnosed that problem to a shitty fuel pump relay housing connection in the PSI harness. Rewired that = OK, started and ran like a new pickup. This was last summer, drove it that way right til snowfall when I parked it.
Fast forward to present. Started it up in storage and drove it home, parked it on the lift to do some brake work. Went to start it ... here we go. Fires instantly and dies just as quick. Runs for one vroom, about one second, exact same every single time. Rechecked and cleaned up all the grounds, wiggled all the wires and harnesses, checked those relays. Jumpered the fuel pump relay so it ran continuously, still exact same, starts but quits immediately. It feels to me like something is telling it to start but not to keep running. Remember this is after running fine for a few thousand miles, and 2 years before that. 1997 Chev 1500, 5.3/4L60e, 2002 Silverado factory ECU, PSI harness, VATS deleted.
Should I start checking things like cam sensor? Crank sensor? Maf sensor? WTF else? Can these be diagnosed with a 2-way scanner?
How do I tell if the injectors are shutting off, or the spark?
Fast forward to present. Started it up in storage and drove it home, parked it on the lift to do some brake work. Went to start it ... here we go. Fires instantly and dies just as quick. Runs for one vroom, about one second, exact same every single time. Rechecked and cleaned up all the grounds, wiggled all the wires and harnesses, checked those relays. Jumpered the fuel pump relay so it ran continuously, still exact same, starts but quits immediately. It feels to me like something is telling it to start but not to keep running. Remember this is after running fine for a few thousand miles, and 2 years before that. 1997 Chev 1500, 5.3/4L60e, 2002 Silverado factory ECU, PSI harness, VATS deleted.
Should I start checking things like cam sensor? Crank sensor? Maf sensor? WTF else? Can these be diagnosed with a 2-way scanner?
How do I tell if the injectors are shutting off, or the spark?
Last edited by Blacksix; Feb 21, 2026 at 06:29 PM.
Thread Starter
On The Tree
Joined: Mar 2007
Posts: 113
Likes: 14
From: Calgary, AB
Rechecked all. Fuel pressure steady 60psi. Crank, Cam, MAF etc all showing signals in that 1 second of run time. All external power is correct with no interruption when cranking is over. Confirmed VATS inactive.
How do I tell if the ECM is cutting fuel or spark?
What else can I look for? Could it be ECM-related, or am I up the wrong tree?
How do I tell if the ECM is cutting fuel or spark?
What else can I look for? Could it be ECM-related, or am I up the wrong tree?
Last edited by Blacksix; Feb 23, 2026 at 03:09 PM.
Thread Starter
On The Tree
Joined: Mar 2007
Posts: 113
Likes: 14
From: Calgary, AB
So I've found I can get her running every time with starting fluid sprayed into the intake. So something is telling it to start, but not keep running unless its kinda running on the starting fluid then takes off. Any ideas?
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