Back from shop, now GP's not working!
 

In my ongoing saga to get better starting in the cold weather we are having, I took my 85 300TD to the local indy to have the valves adjusted. I also had a block heater installed.

So I pick up my car today and start it up without looking at the GP light. It was a hard start, but it went. I drive home and it seems to run well. I go out later and I see that the GP light is not coming on. I looked at the fuse, it's good. A quick look at the plugs and they seem fine, no obvious loose wires. I imagine that they knocked something loose then they were doing the valves or block heater.

I called them and let them know about the problem, they say they will take a look monday, but if it is something simple I would rather fix it myself and save the hassle of taking the car in.


Any idea what it might be?

It's dark now, I will look at it tommorrow

Thanks

Pull the fuse out and actually look at it in your hands. Sometimes you just can't tell......
And while I hate coincidence, you might want to disconnect the connector to the glow plugs and ohm out each wire and make sure they all test good.

I can't think of anything that would have been disturbed by either of those jobs that would effect the glow system. Maybe you just have bad glow plugs?

While ohming out the glowplugs, jiggle around the wires at the gp end. They can be real fragile with poor connections. Mine are finnicky, and after adjusting the valves, my glow plug wires must have gotten knocked around, making poor connections at the end. I haven't swapped out the harness to glowplugs yet, but using some contact cleaner and strategic positioning helped me.

Was it working before going to the shop?

The light was working fine before I took it to the shop. The GP's were replaced last year.

I'd ohm out the plugs. I've had plugs fail in less than a year.

Before replacing anything bring it back to the shop where the work was done and have them check their work. Its quite possible they screwed something up and also its possible the relay or gps failed but the shop should check the work.

You've been here for three years. Isn't it about time that you did the maintenance on the vehicle yourself...........including valve adjustments..........then you wouldn't have these ongoing "mechanic" problems.

When you do it yourself, you know that it's done right.

Asking us to diagnose how the mechanic screwed up the system is an unrealistic approach to the problem.

I agree completely!!! I was considering doing the valve adjustment but I don't have a garage to work in and it is a bit chilly here lately. I guess I should plan to adjust the valves on a nice warm August day. I did do the GP's myself :D

I have a garage and I still let the SD sit...........too cold to do any front end work.

But, that's the benefit of six vehicles............:o

just a quick update and some more questions.

I unplugged the GP wires and turned the key on and the GP light turned on, so I know that the light is not burnt out. When I plug the wires back in, the GP light still does not work. Does this narrow down the problem. I still think it is a broken or loose wire.

Do all the wires and GP's have to be working for the light to work?

I tried to Ohm the wires but it is still really cold out. I have a good Fluke meter that automatically adjusts scale. I was getting resistance on all wires (1-3 ohms) but I was not sure what wire went where? But I didn't see any "open" wires. I was checking between the plug on the relay and the thread on the end of the GP. Is that right.

The fuse is good, it shows 12v on both sides. I inspected it closesly but did not take it out.

I can hear something (relay?) click on and off when I turn the key with the GP harness unplugged?

One other thing, they put a new block heater in and the mechanic mentioned there was a temperature sensor on that side. If it was knocked loose, would it affect the glowplugs?

Thanks for the help and advice

OK, what's the sixth vehicle?

Replace the 80 amp fuse. I think it got sick of being cold.

No, you should check from the 5-pin large plug that you have unplugged from the GP relay to ground (the blockor battery negative). Should be no more than 1 ohm. My Fluke 8800 generally gives around 0.5 ohm. If one GP measures high, confirm by measuring between the tip of the GP and ground, in case you have a bad wire.

If the light does not come on, you have (a) bad light, (b) bad GP relay, (c) bad #1 GP, or (d) bad any two other GPs.

Jeremy