1986 F-250 Starting Issues and WTS/GP Light Issue
 

Hi guys, Im new here so I hope you can forgive any errant mistakes. Ive recently acquired a 1986 Ford F250 with the 6.9 IDI. Its having some issues.

First off the truck is a PITA to start. My dad and I determined the alternator was bad and replaced it. It has one battery running 850 CCA on the passenger side, and one older battery running 650 CCA on the drivers side. 9 times out of 10 the truck needs a jump to get going. My dad drove it for a couple of hours to my house from his. After a few succesful test starts he drove the truck here and when I shut it down and went to restart it was cranking but weak and didnt start before the batteries gave.

I do believe my Glow Plugs some or all may be bad. The WTS/GP light is always on. I havnt uyet found my test light to test the plugs. I did unplug the controller and the light is still on. Im curious if my relay may be stuck on and feeding the most likely cooked GPs juice, that would explain the restart and start issues tho. Any suggestions? Is there a way to disable the relay/gp system in case its draining the batts?

If the 86 is like my 85 there will be a second starter solenoid on the passenger fender (actually over the wheel, not on the side like the starter one) for the glowplugs. If you unhook the wire to the solenoid for the trigger wire it should stop it, otherwise unhook the power wire to it.

Thx Baradium there is a 2nd relay down there. Ive found out inadvertantly if I unhook the battery supply to the relay everything loses power. I unplugged the purple wire but my WTS light remains on

sounds like your GP cotroller is shorted and your starter may be pulling excessive amprage...... also do a continuity test on each glow plug..... there probably fine ... beins how it starts cold.... usually will smoke like hell for a bit of cranking and tghen fire if there all bad..... keep us informed :humm:

After more research it looks like the signal wire on my alternator got damaged so I need to replace that havnt focued too much on the glow plugs