Power Issues

[Robw34]

Ok so I just picked up a 95 GMC 1500 from my Uncle, drove fine until it got dark and turned headlights on, truck then start sputtering, then take back off, kept acting like it wasnt getting enough fuel..but it only does it with the headlights on, anyone have any Ideas what could cause this, Ive replaced battery, alternator, plugs n wires, and brakes for good measure....

[98GMCClubCab]

I'm surprised nobody has commented. I can't be sure but I have found these issues in other vehicles and it came down to the ground system. Everything gets grounded in a car or truck to the frame and if the connection is not good you will get very erratic voltages on the positive side of the circuit. I would start there. Good luck!

[Robw34]

I'm surprised nobody has commented. I can't be sure but I have found these issues in other vehicles and it came down to the ground system. Everything gets grounded in a car or truck to the frame and if the connection is not good you will get very erratic voltages on the positive side of the circuit. I would start there. Good luck!

ty I will check that....

[thx1138v2]

Check the fuel filter. That truck probably has a high pressure fuel pump and turning on the lights might lower the voltage to the point where it has a problem pumping through the clogged filter.

 

You still probably have a grounding problem but you'll need a fuel filter anyway if that is the problem.

[barry G]

the lights.

I have mentioned this in other posts...must be ac ommon gmc thing.

 

I added the parking to be 40 amps nominal ..that is before turning on the headlights.

 

I swapped 33 bulbs out, most of which are dash and parking, all LED.

 

those tungsten bulbs in the active sun..

I won't babble. I worked airplanes.

 

I see gmc is the make, those are the culprits more than the others. The blinker has a unique pattern up front.

 

My own just went for a ride today in just the second rain in 90 days, after a record cold and snow... faultless. I intentionally hit grooves of water in the road until a belt squealed, alt gauge did not wiggle.

 

I won the same battle.

 

and plug wires. go for some good grade, aftermarket.

 

it is all conquerable with modern stuff. If you do not want to get into it too much, find a relay called "ep29", plug it right in to be the new flasher, and go from there.

[2018GMC]

trace and clean ground from battery to frame to engine. If your truck has an aftermarket tow package check ALL connections to the tow plug and ground on back of truck of course. All my tow wires were corroded but ground was good. My Volt gauge would act funny until I cleaned and re-spliced all corroded wires to 6 pin tow plug. Now Volt gauge is dead on.