Glow plugs not cycling properly

[markrinker]

Just finished replacing glow plugs and glo plug relay on one of my plow trucks. This morning, tried a 20 degree start without block heater. Noticed that I didn't get any cycling of glo plugs after the first manual heat. The truck needed it, and it took a number of tries to finally fire up and run properly.

What gives? I have seen the plugs cycle properly since the relay was replaced. What determines if and when the plugs will cycle during start-up?

[chickenhunterbob]

Mark,

This may or may not be of some help to you,

you decide...

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005699

[markrinker]

Sure enough, both of mine are 1994's. Weird problem - I have only seen it happen on one of the trucks. The other always cycles properly???

[john8662]

Disconnecting the batteries as listed in the linked page will cause what your seeing, but its the first crank. Some on here will crank the engine with the short glow till it starts. All I do is after first connecting the batteries, go inside the cab and turn the key. The glow plugs come on for about 1-2 seconds and go off. I don't crank the engine, rather let the ignition key stay on for one minute. Then I turn the key off, then back on, then I get the regular glow cycle. I think that after a disconnect of the batteries the computer had to re-learn the glow system and some other systems to work properly. Thats why I just give it some time before I actually try and start it.

If your not seeing a normal cold start cycle or the afterglow on a really cold start it could be the temperature sensor on the water crossover. To test this, wait till its really cold, pop the hood, and unplug the two-wire connector on the water crossover (thermostat crossover), its near the passenger side on the crossover. Then go crank it, the glow time will be really long and the engine will be have a real diesel rattle to it, because the computer is assuming max cold temp. If you get somewhat normal glow time and an afterglow, that could be the problem, replace the sensor.

John

[markrinker]

Today everything cycled fine. It was much warmer out, and the truck probably wasn't completely cooled down from last nights late plowing. The plugs took about 5 seconds to pre-heat, the engine started in about 5 revolutions, and I got two short afterglows to help things along.

Go figure. Thanks for the input. I'll test it again when the temps dip back into the 'teens.

[ 02-12-2004, 01:08 PM: Message edited by: Mark Rinker ]

[markrinker]

8 degrees this morning, no block heat, parked outside. Full length initial glow, 5 seconds cranking, fired off, two short afterglow cycles and we were up and running, although normal cold rattle and LOTS of white unburned fuel smoke for the first minute or so.

Not sure what the scenario is that causes the 'no afterglow' scenario. When its cold and I don't get them, it is very hard to start and I end up cycling the ignition key and taking 3-4 attempts to get ignition.