Voltmeter question

[bcrobbins]

I have an '85 M1009. It starts just fine after replacing the fuel sensor switch a few weeks ago, however now when I start it and watch the voltmeter, it goes straight up to mid-green for a few seconds and then I hear a click from the dashboard and the needle goes down into the yellow for a few seconds and the belts squeak. This happens every time I start it, but it doesn't last long and after 2-3 cycles, the truck runs fine and the needle stays in the mid-green the whole time. I'm wondering if there is a relay or something behind the dash that is responsible. It's not a big deal , but rather it's just annoying to listen to the alternator belt squeal on and off for the first 15 seconds, and I'd like to do something about it if I can. Any advice is appreciated. Thanks in advance.

 

[gungearz]

Tighten up the belts... maybe it's not pulling volts on start up... bad alt perhaps...?

 

[Warthog]

From your description, the glowplugs are kicking in for the afterglow. The clicking is coming from the GP relay mounted on the firewall.

Watch the glowplug operation sticky.

Sounds like it is operating correctly except for the belt squeal. A stretched belt or a worn pulley can cause that.

 

[bcrobbins]

Thanks to both of you. Warthog... I'm not sure exactly what you mean by glowplugs kicking in for the afterglow, or watch the glowplug operation sticky. Does this mean that the relay is sticking? Your reply seems like the plausible solution.

Could you expand, please? I'm new to working on diesels and only have a rudimentary understanding of how they work.

Thanks

 

[antennaclimber]

I agree with Warthog. Glow plugs draw a lot of current when cold.

Mine was doing the same thing.
Tightened up the alternator belts and the squeal was eliminated.
Karl

 

[2002ford]

Basic terms is that glow plugs cycle a few times after the engine starts. It sounds like you need to tighten your belts or replace them.

 

[Warthog]

Watch the video in the Glowplug Module Theory of Operation sticky.

http://www.steelsoldiers.com/showthread.php?62477-GP-Module-Theory-of-Operation

It explains how the GP system works.

Diesel engines do not have sparkplugs to ignite the fuel. Diesels use heat and compression to ignite the fuel. When you compress a gas or liquid heat is generated. With high enough compression the diesel fuel will ignite. Some engines will help with the heating of the fuel with glowplugs or air heaters. The 6.2L Diesel engine uses the glowplug system.


After starting a "cold" engine, the cylinders are not fully warmed up to support complete ignition of the diesel fuel. The GP controller turns the glowplugs back on a few times to help burn the fuel and warm the cylinders. This called the afterglow. When the fuel isn't completely burned it will show as white smoke.

 

[MarcusOReallyus]

Tighten up the belts... maybe it's not pulling volts on start up... bad alt perhaps...?

Mine was doing the same thing.
Tightened up the alternator belts and the squeal was eliminated.
Karl

Tightening up the belts is a good idea - if they are loose. That's not the only reason for belt squeal.


Too much tension = premature alternator failure.