Car will only start when glow plugs light up

GABOE83

MEMBER
VOLKSWAGEN

I have a 1999 volkswagen jetta 1.9l TDI with 174,000 miles, the car will only start when the glow plug light on the dash comes on, I think it may be a bad switch or sensor. It only does every so often and I tried to bypass the automatic glow plug switch by putting a manual switch in but that didn't work. Also it dies on me while I am driving but like I said it is only when the light does not come on

1 Reply

FRIEDEMANN

MEMBER
47 POSTS

The light comes on when the sensors sense the engine is too cold. Under 160 F. It is not necessary to wait until the light goes out (especially if you had shut the engine off 10 minutes ago so you know the coolant and the oil is still quite hot.
Just give it a quick turn and the engine should start. Do not step on the "gas pedal" while starting. It will start much faster if you don't.
First thing in the morning after an overnight cool off, do wait till the glo plug lite goes out before turning over the starter. It should only take 6 seconds tops for the lite to go out. Mine doesn't go out so I count 6 seconds and start the car. Otherwise you will burn out the glo plugs. Let a cold engine warm up. If it is a really cold day(snow and the like) you need to let it warm up a couple of minutes for if you try to drive off on a cold engine, the additional cold diesel and cold air will be too cold to keep on burning and your vehicle will die on the road. It needs to be adequately warm enough.(If you see the coolant temp needle start to move you should be ok at that point)
Do yourself a favour and don't mess around with the glo plug relay system. It works the way it is suppose to.