My o1 wont cyle the glow plugs, if I jump the gpr it fires up. I have changed the relay no change. There is power to the timer and the relay but with the key on the relay wont power up the glowplug side and there is power to the small terminals with the key on. Checked all the fuses and fuseable links around the timer and the relay. What is next?
Thanks

 

Welcome to FTE. There are 4 posts on the GPR (glow plug relay) 1 large post is battery voltage in that is always hot. The other large post is voltage out to the glow plugs. The smaller posts sound like the ones you're having issues with. The way the GPR works is one of the small posts that reads hot with the key off will receive a ground signal from the PCM (computer) to activate the relay. Sounds like you've lost the ground signal from the PCM.

If you've got a volt meter, check the voltage both key on and key off at each of the 4 posts on the GPR and report back.