How long do glow plugs stay on?

[jackmech2]

On the 4JB1 engine should the glow plugs stay on for a minute or so after the engine is started, of do they turn off as soon as the light goes out?
I would think they should go out straight away being direct injection, but would like conformation.

[geeves]

Not sure if the controls on your engine are the same as the older ones. There is a big age difference between your engine and the ones we have info for. In that time emissions rules may of changed things so the following may not be true in your case.
The 4jb1 as found in Troopers up to 1991 and Mus to 1993 and a lot of Isuzu/holden utes. The cold start system if the water temp is above 5C activates the glow plugs for about 5 seconds. Thats it. Below 5C they activate for 30 seconds and the injector timing is advanced to improve cold running untill the water warms to 5C. The 4jb1 is direct injection which is very easy to start and does not need anything more than this.A few people have had blown glow plug fuses and not noticed.

[jackmech2]

They do come on when the light is on and turn off when the light goes off, i was just wondering if they should stay on for a bit longer while engine is running to help with the poor start/idle situation.

[geeves]

Old style engine without the inbuilt smarts to do that.
Also on the later famous 4jx1 engine a few people have had problems with flat batteries. The reason is that the glow plugs stay on on that engine for about 10 minutes and draw 90 amps. This is to meet emissions requirements. If you do a lot of short trips the 60 amp alternator cant recharge the battery

[shylie]

my glow plug light only stays on for a split second! does that mean its nearly stuffed, cause the other night it reached zero here and still the plugs did not stay on for more than a second?? im also thinking this may be contributing to my excess smoke problem when i first start her of a morning because the diesel is too cold??

[geeves]

It might have a problem. It measures water temp not air temp. On the thermostat housing try taking the right hand wire off. It should glow about 20 sec. Dont drive it like this as it will knock terribly