I'm trying to trouble shoot why the engine doesn't start easily when it's cold. I figured the best place to start is with the relays. Are they the two relays next to the fuel bowl (I have an '02)? Each one has 4 wires. 1 going to the battery, 1 I assume goes to one bank of relays, 1 I assume is ground and 1 I assume is from the key. The ones coming from the battery have a boot on them that appears to be melted to the relay, and when checking with a light I don't see any power come out of the other large cable.

Is there a fuse somewhere that I can not find? Or should I bight the bullet and replace both relays?

Thanks

 

not sure on the 02 but on my o1 the relay that is closest to the firewall is the gp relay and should have current under the rubber boot all the time but the opposite large post should only have current when the key is first on and only for about 120 seconds max. The small post closest to the firewall should be the pcm lead and the opposite post is the key on post.

 

I have two relays that look exactly alike. Does the '01?

 

The one closer to the front of the truck is for the air intake heater and the one closer to the rear is the glow plug relay. You should see power to the booted post 100% and power to the one without a boot when the GPR is active.

One way to test to see if it's the GPR that's the issue is to take a screwdriver and cross the posts on the GPR for 30 seconds or so and then see if the truck starts easier.

 

 

As Said above..

12v under the big wire with a boot, Always. Turn the key on and the apposite Large post will will also get 12v. If the relay is working correctly.Using the negative on the battery for your negative for your light.. If no voltage on the opposite side large post when you turn your key on (with a cold truck) would suggest a bad relay. Very common.

Sounds like you have a bad relay.. I would replace it with a stancor. You will never have to monkey with it again.. Stancor is built for life.
Welcome to guzzle's Stancor GPR replacement Mod Web Page

 

Thanks I'll get out there next weekend and do some more trouble shooting based on the link above.

 

I assume both relays cycle about the same amount of time throughout the life of the vehicle. If I find that the GPR is faulty, should I replace both?

 

The AIH very rarely comes on. It is used to warm up the intake air in very cold climates to reduce smoke.

 

Thanks, Hopefully I will get outside this week to check the GPR. Most likely it will have to wait for the weekend.

 

LIke Jim said, the AIH relay is not worked nearly as hard as the GPR. I would not even worry about it. A lot of us delete the AIH system altogether.