Starting problems

Hello,

It sounds like a classic fuel pump going out. Here is a guide that will show you what you are in for when doing the job and some diagrams (below) of what it will take on your car.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

you will need to jack the car up.

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Please let us know what happens.

Cheers, Ken

Nice work, we are here to help, please use 2CarPros anytime.

Cheers, Ken

With key on engine off you should have battery positive power at the injectors?
If not check wiring from fuse box and ignition switch, check fuses and fusible links by the starter solenoid

Check fuel pressure first must be 9-11 psi at least.

Check the fuel pressure to rule out the fuel pump and also look for injection pulses.

You need to find the fuel pressure test port-that's where you hook up.

When fuses are shorting out, NEVER use a larger capacity fuse. It can result in the electrical wirings starting a fire or melting and causing all the wires to be fused together.

The ECM-B fuse provides power to the fuel pump relay, fuel pump switch and PCM. Any of these components or their wiring can be faulty causing the shorting.

You're welcome.

PCM = Power Control Module also known as ECM (Engine Control Module ) meaning the engine computer. It is located under right side of dash.

The ECM would be less likely to be the cause as they seldom shorts out.

Which engine variant do you have, 5.7 or 7.4 L?

The fuel pump circuit would be more likely to be the cause. As the wires runs from fron to rear of vehicle, there could be a possibility of some wires being damaged to external elements such as abrasion or rodent damages. Intermittent shorting is never easy to detect and a stroke of luck helps.

Fuel pump relay is located on right side of firewall in relay box.

I could not find any detailed diagrams and description of the relay box or other components.

Unplug the fuel pump relay.
Use a 10 A fused wire apply battery voltage to terminal B.
Alternatively you can use the fuel pump test connector locatred near relay box to connect the wire.
Start engine.
If fuse blows, you have a short in the fuel pump circuit.

Another components wiring that could cause the shorting of the fuse would be the fuel pump oil pressure switch, located at left rear of engine for 5.7L and at front side of engine block near oil pan for 7.4L.

Don't replace any parts until they are confirmed to be faulty.

Shortings usually are due to wiring faults and the only component that can cause it would be the fuel pump.

Btw if your vehicle is equipped with dual fuel tanks, switch to the other pump and retest.

How long since a tune-up? Any applicable trouble codes? When the problem occurs can you turn the crank or flywheel by hand.

Check the starter circuit. I have heard of chevy hot start issue. They used to use a ford starter relay, place high on fender lining, wire to starter.