Ignition electrical issue?

[BURRIS490]

I have a 2000 K3500 with the 7.4, went on a 2 week DET cross country, so the truck had to sit. came back to start and wouldn't start. replaced starter, and checked/cleaned all power wires from battery. truck fired, but now it has a weird intermittent issue where sometimes when I key on the ignition, it will not send power to the fuel pump nor gauges, it will still turn over, but acts like there is no fuel or spark. all lights and all other electrical works perfectly fine, so I know I have a good battery connection. sometimes when I key on it works fine and fires right up, or the power to fuel pump/gauges is delayed 5 to 10 seconds then it will fire. batteries are fully charged(its a dual battery) all fuses are good, all related relays are new, and starter is new. I did find a small mouse nest in dash under radio, but upon further inspection all wires seem perfectly fine both in the cab and engine bay, and again, nothing else is faulty... I'm stumped. any advice or ideas would be greatly appreciated. thank you.

 

[HotWheelsBurban]

Just guessing, I would say there's a grounding issue somewhere. The other day, my 99 Burb 5.7 decided that it would do nothing when the key was turned. Normally it fires up right away unless it's really cold. Tried 4 times, no dome lights or dash lights, no crank, no click. Tried it once more, lights came on, started right up just like it should. I was about to raise the hood LOL! (Funny now but at the time, not so much) Got home fine, and checked the battery connections the next morning. Ground cable was a quarter turn loose. Not only does it start better, but the power windows are faster too. I also had an issue earlier this year with the small terminal on the starter solenoid being a little loose.
There's so many things on these trucks that are electrical, and especially computer controlled, that grounds are super important. You could also have a situation where the starter or solenoid has a bad spot on it, or an ignition module or coil that is just beginning to go out. Good luck and have plenty of patience.

 

[BURRIS490]

I checked and cleaned all grounds and power wires when it started acting up, and also got a brand new starter. the relays in the under hood fuse box are new, are there any other relays that could potentially cause this? is never completely loses power, just fuel pump and gauges.

 

[thinger2]

Could be the ignition switch but I would fix all of the grounds first.
The side post battery cables will look great on the outside but can be internally green and rotted.
If you look at the battery side of the cables, they have 4 little tabs that stick out and are suposed to dig into the lead on the battery to keep the cable from coming loose.
they are often so worn down and corroded that they only stay in place when its cold.
Your starter is a super high reduction motor and draws a lot of amps so a weak connection makes that wire get real hot really fast and changes the nature of that connection.
You also have a ground on the manifold for the ECM and a ground from the back of the passenger side head to the firewall and then from the firewall to tbe frame.
Check all of those and check the hot side to the starter and the wire to the solenoid and I think you will find the problem.
I pretty sure its nothing serious just normal cruddy Chevy wiring

 

[Schurkey]

replaced starter, and checked/cleaned all power wires from battery. truck fired, but now it has a weird intermittent issue where sometimes when I key on the ignition, it will not send power to the fuel pump nor gauges, it will still turn over, but acts like there is no fuel or spark.

You dicked with the starter, now you have electrical problems.

First things I'd verify are any fusible links attached to the starter solenoid terminals. Wire condition, corrosion on the ring terminals, tightness of the connections, etc.

Any cables you loosened to change the starter are suspect.

Your starter is a super high reduction motor and draws a lot of amps so a weak connection makes that wire get real hot really fast and changes the nature of that connection.

The Permanent Magnet Gear Reduction (PMGR) starter motors draw LESS current than the non-gear reduction, field-coil starters they replaced.

 

[thinger2]

You dicked with the starter, now you have electrical problems.

First things I'd verify are any fusible links attached to the starter solenoid terminals. Wire condition, corrosion on the ring terminals, tightness of the connections, etc.

Any cables you loosened to change the starter are suspect.


The Permanent Magnet Gear Reduction (PMGR) starter motors draw LESS current than the non-gear reduction, field-coil starters they replaced.

Yep, they sure do. If I didnt have a bunch of Direct startes laying around I would go for the gear starter.
But, the same laws of physics still apply.
If you have bad connections or intermittant conections the reduced amperage to the motor can be directly attributed to an increase in heat due to longer crank times.
Heat raises the resistance in the wire.
It is a "feedback loop"
The worse your wiring is, the more amps it takes to gain the mechanical advantage needed to rotate the assembly.
The more that motor and wiring attempts to draw through the system,
The hotter it gets.
The hotter it gets, the more resistance in the wire.
The more resistance in the wire, less amperage available to "do the work"
Thermodynamic feedback loss of effective work applied to reduction gear systems.