Fuel pump and A/c relay issues

[OneofFew]

A while back I had a no start condition, swapped the Fuel Pump relay with the DRL relay and all was well for weeks. Then I discovered the A/c relay wasn't kicking in. After messing with it's relay, it kicked in. It seems when the relay is seated all the way, it doesn't connect well. I keep having to mess with it to get the compressor clutch to kick in. A few days ago, I took the housing off the relay center and checked out the wiring on the underside a little, but found nothing obvious. Then the A/c relay worked seated all the way. Today I had another no start and again the fuel pump relay was not closing. It took me a good while messing with it and finally the relay connected. I have one brand new relay. The relays for the DRL, horn, A/c and Fuel pump are all the same, swapping them around seems to not make any difference but for disturbing some bad connection in the relay box- I assume.
Is there a common issue I need to check? It looks like one large connector below the relays.

 

[Doubeleive]

sounds like maybe there is some kind of crud built up on the connectors, I would try to clean them up somehow, I don't know if some contact cleaner would be enough but it's worth a try autoparts store should have it (maybe) if not you can order some online or see if there is a electronics store near you. you could probably get away with using some maf cleaner

 

[OneofFew]

Makes sense to check and try cleaning the contacts. I am thinking I need to look closer at the big connector that comes in from the bottom of the relay center. Maybe loose or corroded connections.

 

[OneofFew]

I am thinking that I may have a pcm issue here. Intermittent fuel pump not kicking in and a/c compressor not engaging. I wish I had a tech2. I may try to pick up a used pcm. Would any pcm off a 00-06 tahoe 5.3 work, or...?

 

[Mechanic421]

Will need a reflash

 

[merlin1128]

I have been reading through some posts and I see you started to swap out relays. When you swapped them out did you look and see all kinds of different numbers on where the go on the bottom of the relay and where they plug in?

When you put the relay back in we both know it can go in 2 different ways, but you have to look at the bottom or the relay and the terminal block to make sure all the numbers match and are plugged in correctly to that. Plus, make sure the relays are the same too as you will see different numbers on them that do not match up where they plug in. They have to be exact like that with all numbers matching up and plugged in correctly.

Another thing I would check for sure is all your ground wires on the frame to make sure they are all clean and making a good contact. I know for sure their is one on the front underneath the frame due to mine was starting to lose its ground and it made my back wiper on the hatch possessed just turning on for no reason. Then as it got worse I got the tighten fuel cap intermittently too. With getting those on occasion I think next was my gas mileage was horrible, then I go an air bag light, and all kinds of things were coming up on the dash. Basically all kinds of things were going wrong.

Then I remembered what my mechanic told me a long time ago is if you start to get things that are going bad and more keeps happening as it will come slowly as the ground loses contact with the frame "check your grounds on the frame".

He told me this is often overlooked and everyone can go in circles and rely on the scan tool seeing all the codes popping up and they are popping up due to they lost ground or have a weak ground.

Not sure if that is your problem or not, but it starts slowly as it starts to lose a ground and I did not think of what he told me until everything and anything was coming up on the dash and my horrible fuel mileage. I found my ground on the front of the frame hanging off due to the bolt holding it rotted away. Got out the Dremel tool and got all the rust off the frame with a stainless steel bolt to put it back on when it was all cleaned up. Plus the ground on the front of the frame goes up to your battery negative and you will see tons of wires it goes with. Their are also two more grounds underneath the drivers door too. I cannot recall if I cleaned up another one or if it was just the hanging one and the ones under the door.

Once I got the front one all cleaned up and back on nothing on the dash came up at all and took it by him to see what codes had stored and WOW losing that ground it was loaded with them which he cleared out and took it back a week later to scan again after driving it a while now that I had that ground wire back on and not one single code stored. Gas mileage went back up too.

So I would check your relays you swapped out and look at the numbers so they are all correct and check your grounds. Something this simple solved my problems and read horror stories and seen them on You Tube of when a ground starts to loose connection and all the havoc it can play with all kinds of weird stuff going on where you and just like me were going in circles until I remembered what he told me a long time back about the relays and check the grounds.

 

[rockola1971]

Its aliens! Nah, its not. Check your flat ribbon ground going from rear of engine to the firewall. They are notorious for corroding to the point that they break off. Be sure to check the connection at the rear of the motor of that flat ribbon ground. Remove it and wire brush all connection points on the engine, firewall and the lugs of the ribbon ground. Replace if ribbon is getting crusty, green or is crumbling.