Odd electrical deal

[sandrow]

I had my mechanic, "josh" do a bit of work on my truck. Fantastic mechanic by the way great guy with the bill too. One of the things we did was replace the glow plugs in the truck. I have noted the usual tick in the voltmeter directly after starting the truck but now it's doing something more. When it is warmed up and I start it directly after I get in, the voltmeter drops even while the engine is running for about 25 seconds like it is still trying to cycle the glow plugs and it takes all the alternator can put out just to heat them up. Is this normal? None of my other 7.3's have done this. I'm thinkin maybe this is why I am blowing glow plugs? Or is it just an idiosyncrasy of the system. I would think that a sensor would read that the glow plug cycle is unnecessary and NOT draw power down to heat them up. Seems like common sense to me .... but what do I know I'm not a diesel mechanic... or a Ford engineer. Any and all advice would be welcome I hate to bug the guy with trivialities that are just foibles of the year truck and motor. By the way my genuine thanks to this site for hooking me up with an awesome mechanic with a real world grasp of what folks need as opposed to plain old greed. God Bless im

 

[rhkcommander]

AFAIK the glowplug controller clicks on even after startup to aid in warmup... I ditched the auto system for manual control.

How old are your batteries? Just curious

 

[f-two-fiddy]

Is normal. Emmision deal.

 

[oldmisterbill]

Do you mean the plugs stay on for 25 seconds after the engine is running? They should click on & off briefly till the engine is a little warm. If they stay on longer that a couple seconds you have a problem.

 

[OLDBULL8]

Always WAIT for the WTS light to go out, no matter what the temp is. No GP controller will stay on for 25 seconds unless it has a defective timing circuit in it which is highly unlikely. Maximum on time is 15 seconds, then it could be up to 2 minutes with the ON/OFF cycling. On your 94 it should have the updated GP controller that does that. If all glow plugs are working, on a normal cycle they will draw up to 160 amps and the amps will decrease as they heat up, that is why the cycle is limited to 12-15 seconds or the wiring to them will burn up. Your alternator is only putting out about ~70 amps at idle, all the current draw comes from the batteries, the alt is just trying to replace (charge) the batteries from starting and GP cycle. Of course the GP's will get hotter from the combustion, and possibly burn out if you start the engine before the GP cycle is completed.