Ok, my truck stopped running about a month ago. It cranks but wont start. Had a buddy come over and hooked up his snap on reader and it didn't spit out any codes. Got out the test light and checked the GP relay and the Air intake heater relay. When he was on the Air intake heater relay, the truck fired. Ran for 2 weeks and stopped again. I replaced both relays as they were looking a little shabby. still nothing. Checked the batteries, took them down to auto zone, charged, holding charge. Put them back in my truck and nothing. When we hooked up to the battery last night, the reading went from 12.6 volts down to 8. Tested the battery again and says its good (both batteries). hooked up to the battery again and turned key to on position to let glow light turn off and the battery dropped to 10 volts. What the heck is going on? I need help.

 

When u say tested battery, is that a load test? SOunds to me like batts are failing when the glow plugs load them up. Did u recheck the Gpr relay to make sure both big terminals have power when the key is turned on? Sounds like it. What happens when u put jumper cable to the truck? Will it spin and crank then?

I do not think the AIH kicks in until after the truck is running, afte rthe glow plus cycle off. a lot of the guys here have deleted it all together so I would not worry about that.

If u plug in the block heater, does it make a difference?

 

battery was tested from Auto Zone with their load tester. I plugged in the block heater and nothing. It does crank and spin, just doesn't start. Tried to jump start it also. I was told by the manager at Auto Zone that I should remove my starter and bring it in to have it tested????

 

Does it sound weak when starting? Sluggish? Did u check the GPR to make sure u had voltage on both big terminals? If u have a multimeter, touch one lead to the batteries and the other to each of the big studs on the GPR and see what the voltage is.

After the wait to start light goes out, the Glow plugs are usually still activated for a time after that-90 seconds or more which would drop the volt meter until they cut off.

What size battery and amp rating do u have? I guess u cleaned all of the terminals really well even down at the starter?

Do u get any smoke at all when turning over? It could be the CPS bad on it.

How long was block heater plugged in? Did the temp gauge move off of cold?

 

I am with Carlton on this, if it is not the battery, then you have a bad connedtion, dropping from 12 to 8 says bad battery/bad connections all day. WHere are you at?