Okay… To sort of tell
“The Story of a Failing Fuel Pump” as the possible cause of this
Shut-Down-Starts-Back-Up-Later Syndrome” … I’ll use Minimal Dialogue (ordinarily ...very rare in most of my responses) and use ‘discreet imagery’ as a better way to explain all of the things required for
Testing and Diagnosis of the GM Truck/SUV Fuel Pump as being the possible source of this problem:
Symptoms:
The GM Trucks and SUVs Start just fine and Run for around 5-10 Minutes ...before suddenly shutting down. After waiting brief periods ...the Vehicles WILL Re-Start and Run… and the sequence of events may return to having these Unnerving Shut-Downs happening :
Diagnosis:
First... For The Average Mechanic in possession of a GOOD Digital Multi-Meter that can read at or above 20 Amps… THIS is simple and expensive way to Diagnose a Failing Fuel Pump:
(1) Set your
DMM to read 20 Amps.
(2) Insert your
DMM Probes with Proper Polarity into the vacant PCM-B Fuse slot in the Power Distribution Center… Like this:
(3) Start the Vehicle and observe that the
DMM will be acting like the 20 Amp Fuse to Keep the Engine Running as long as the Probe Points are connected to the
PCM-B Fuse Insert slots like this:
(4) The
Fuel pump for GM Vehicles should only be Drawing around 5 Amps if it is Properly Functioning. However… if the Amp reading is ABOVE 5 Amps… You should begin to suspect that the Fuel Pump ‘innards’ are drawing WAY Too Much Current for any number of reasons… and it
GRADUALLY HEATS UP AND FAILS AS A RESULT. After brief periods when geing inoprative... The Fuel Pump Internals COOL DOWN and the Punp can begin to Work Again. Look at THIS High Amperage DMM Reading on a GM Tahoe with the Same 5.3L Engine as the OP’s and observe how much more Current is being Drawn by the Pump:
(5) This
Diagnosis Strongly Suggests that the Fuel Pump must be Replaced… HOWEVER… If you lalso ook at the
Very Poor Condition of the OVERLY CLOGGED AIR FILTER that came out of this same Vehicle…
Air Starvation and a Very Filthy MAF-IAT Sensor can ALSO cause Sketchy Problems in combination with a Failing Fuel Pump to make the Engine Misfire and Stall very quickly as soon as the Fuel Pump begins to Struggle:
(7) After
Putting in a New Air Filter and Fuel Pump… Clear any remaining Trouble Codes and Fire Up the Motor to see if things run Nominally.
And here... For the Privileged Few In possession of either a Snap-On Vantage Scanner or similar High End Scanner… are Additional Instructions on How to Do the Following:
(1) Shut off the Vehicle, Raise the Hood and Uncover the Power Distribution Center.
(2) Locate the
20 Amp “PCM-B” Fuse right next to the Fuel Pump Relay as shown here:
(3) Pull the
PCM-B Fuse like this:
(4) Insert a
Single Closed Wire Jumperin between the Two Fuse Terminal Connectors in the
PCM-B Fuse Position... like this:
(5) Set your
Snap-On Vantage Amp Clamp Tool to the
20 Amps Setting ...like THIS:
(6) After plugging in your Amp Clamp to the Vantage Scanner… Clamp it around the Single Closed Wire Substitute plugged into the
PCM-B Fuse port ...like this:
(7) Navigate to the Vantage Diagnostic Ssettings to read the Electrical Wave Graph Form and after Starting the Engine...
COMPARE the Known Good Wave Form (Nice, Regular, Round ‘Humps” Hi-Lighted in
RED) to the performance of the Fuel Pump Live Wave Form (Hi-Lighted in
Yellow)… Like This.
(8) If you notice that the
Wave Form gradually fades flatter and flatter, it could mean that the Amp Clamp needs to be properly re-positioned around the Single Closed Loop Probe Wire… or that the
Fuel Pump is FADING ...like this:
(9) If you observe a
“Clipped”Wave Form on the Live Feed from the Fuel Pump on the Oscilloscope Graph Screen… this also indicates a Failing Fuel Pump… Like this:
(10) The OBD2 Scanner showing
P0300 Code indicates
Random Misfires, possibly caused by a failing
Fuel Pump that LEANS out the EFI Fuel Spray enough to cause the Engine to Stagger, Stumble and even experience Shutting Down of the Motor ...from
FUEL STARVATION.
Tussen Takke... (A Thousand Thanks to the VOP Below...)
Props to the VOP (Video Original Poster) for making this very enlightening and inspirational Video these Screen Shots came from: