85 gmc suburban 6.2L electrical issues will not start

[DetroitDiesel]

Hello i have been browsing these forums while trying to find a solution to my problem.I came across the manual glow plug switch and came to the conclusion this would be a band aid to At-lest get the truck to start so i can move it from were it is.I will begin by trying to explain my issue ,i will have photos tomorrow when it is light out.Truck was runing fine up intill this point , i had just bought it drove maybe 600 miles.I had asked previous owner if this has ever happened to him and he said no.
1.Things started when one day i tried to use my horn and it would make a wierd sound , now base don what hAS HAPPENDED LOOKING BACK I WANT TO SAY IT MADE A CRACKLING TYPE NOISE.I can atleast say that the horn stoped working did make a noise and it sounded off.So i stoped using it.
2. 2 or three days go by and i stop at the gas station go inside come back out start the truck up and the head lights will not come on.So i check the fuses in the parking lot and find one blowen but i cant see what its for i assume headlights.I get one put it in and still doesnt work.Im driving to a friends house near by turning my lights on and off hoping they will work.Then when i am almost there about 1/4 mile away they come back on and i think im saved.
3.The next morning i come out get in turn the key on dash lights come on and go off glow plug light comes back on i try to start it and it doesnt.So i turn the key off and re try and this time the glow plug light doesnt even flash when i turn they key.I check the headlights they dont come on.Radio / power doors and locks blinkers everything else works.Just no interior light head lights or glow plug.
4.I check all the fuses one at a time and none of them are bad.I take the bulb from the water in fuel light spot and put it in glow plug spot thinking it may be the bulb still nothing.
5. i get on the internet look around and i see things on a manual switch , my friend said he had the relay deal for an old ford truck.I went and bought a switch.So on tjis relay ( forgive me if i am calling it by the wrong name i will get photos.) there are 2 fat studs and 2 skinny studs.I wired both fat studs to fat studs on glow plug controller.Then the switch inside the cab with 12volt going to fuse box middle/acc going to skinnt stud on relay ground going to screw in truck.
6. before this i used a test light and probed atound controller and got nothing. after i wired up the switch and it stilled didnt work i probled relay while key wa son and only got power from were it came from fuse box neigther fat connecters had power on controller or relay.

truck still will not start lights will not work and i can not figure out why , i will get photos of how i hooked up switch maybe that will help.
Forgive me if this is hard to read

 

[WarWagon]

Check your grounds.
Then check your grounds.
Then check more grounds...

Then check positive battery cables. This includes taking the connectors apart and looking for corroded cables.

Next check the fuse for headlights and see if it even has power. Headlights may be on a breaker and you had a fusible link burn up. The rear wiring for trailer plugs tended to have insulation fall off the wire, crack, and corrode the wires.

If you bypass the glow plug controller the original plugs will last about once before they burn out. You need the newer self limiting plugs.

You should check for a bad battery.

You have to have 100 RPM min for the engine to start. It will not start just hardly turning over like a gas engine can. You need 12v at the pink wire on the IP to turn the fuel on.

I'd check around the ignition switch for bad connections or burnt wires including the high/low beam switch.

Fuses blow from a short or age. Never hurts to pull all the fuses one by one and clean the connections on them.

The crack noise was a fuse blowing (incl fusible link wire) from a dead short. Look for wires worn through and shorting out. Bulbs can be the source of a short.

Fuel, rpm and glows for heat and she will run even on 7 of 8 cyl. Without glows she will start if you spin it fast enough.

The fuel systems had issues with the filter box leaking air at the restriction sensor and air in fuel is the next step to look for if you have enough RPM and 12v at the pink wire.

 

[just a number]

I wondering if it's the main power feed. IIRC it's a red wire,12ga comes off the starter. it has a fusible link on it. that wire controls all the power for the cab.


EDIT: you can check for power at the junction on the firewall. it's a block/mounting(plastic I think) with 2 studs on it. it'll be right above the drivers side head.

 

[dieselfuelonly]

I wondering if it's the main power feed. IIRC it's a red wire,12ga comes off the starter. it has a fusible link on it. that wire controls all the power for the cab.


EDIT: you can check for power at the junction on the firewall. it's a block/mounting(plastic I think) with 2 studs on it. it'll be right above the drivers side head.

I ran into this same problem with the truck I just bought over the weekend. Would not start because of major electrical and wiring issues. That red 12 gauge wire is down at the starter, not connected with copper showing at the end...just hanging there. Could only get the truck to crank over by jumping the one side of the firewall juntion block to + side of the battery. There is a wire installed at that junction block on the right side stud, but no wire on the left side stud. Also had no dash lights...as in glow plug indicator, etc., or working guages. I know for sure I'm not getting any power in the cab...ahhh what fun! :rolleyes5:

 

[dieselfuelonly]

just a number, do you happen to know where that 12 gauge wire is supposed to mount to at/or around the starter? I have that wire there just inches from the starter, with the copper strands exposed at the last 3/4" of an inch on the wire...it is not connected to a stud or any power, just hangs there. I have no power in the cab and also the junction block at the firewall has no wires installed at the leftside stud (looking at the firewall from the grille view), but do have them at the rightside stud. I have major wiring issues and anyone happen to have an 87 or 88 Chevy 6.2 wiring diagram? The truck is an 88...thanks!

 

[just a number]

IIRC it did mount to the same post as the main batter cable. I just routed mine straight to the battery itself. make sure you keep the fusible link on it.

as for the wiring diagram I haven't got one, but have dealt with alot of it.

EDIT: you should have 3 wires at the starter, a battery cable, one from the IGN switch and then the main power lead. do you have all 3 down there?

 

[dieselfuelonly]

Thanks for your reply. I do have 3 wires at the starter, but only 2 are hooked up. One I know is coming from the passenger side battery, the other is the wire at the solenoid, and the last one is that thick red cable that now that I think about it is larger then 12 guage more like 4 guage trying to take my best guess. That wire is hanging there just inches from my starter and not mounted or connected solid. I have no power in the cab until you turn the headlight switch on all the way out I do get one or two dash lights... This truck was tampered with a good bit and apparently I bought it from a shop that was supposed to be a diesel shop working on trucks, mainly these size trucks. The guy told me it needed a starter because it was bad and he needed to push start it when we went to pick it up. Turns out after I got the thing home the starter is perfectly fine and it only had one starter bolt installed and it was loose! Of course it's not going to start if you don't have two bolts in it and torqued properly! Wasn't too impressed with dealing with what they thought was "bad". That's why I'm likely going to need a wiring diagram....

 

[just a number]

oh boy, you are in for some fun.:rolleyes5: Hmmm, I'm kinda stumped for the night. I thought there was only 1 power feed in so it's strange that the headlights work. all the dash lights should come on with the headlights.

on the main studs for the glowplug controller, is there just one wire in and one going to the plugs. just wondering if they tapped into there.

 

[WarWagon]

I think you solved your problem. They dropped the starter with that wire hooked up and it stripped out of the crimp connector. Or the wire is too short and engine movement is pulling it out.

I am guessing the stripped or broken wire goes to the main power from the battery. Could just be to the glow plugs. Check it with a volt meter. Then risk your amp meter fuse and check it with the key off: stranded wire testing to the positive battery lug on the starter or positive battery whatever is easier to reach. If it doesn't pop the fuse it is safe to assume it isn't a ground or shorted. It could be going to the glow plug controller and I think there is another junction before the glow plug controller. My 1988 started and ran without the glow plug controller in place.

I think you have other issues to hunt down after this wire.

You should have a starter brace on the rear of the starter to the block. This keeps the starter from kicking the rear out and breaking the bolts and/or block. I bet it is 'missing' and yes it is "Critical".

Edit: :mad2: the thread says 1985 and we have another member posting about his 1988. The glow plug controller is different on 1988 than 1985. It is a good conversion to the 1988 or 1993 controllers from the 1985 round thread in can "mess".

 

[just a number]

the glow plug controller gets it power from the alternator/battery wire. it's doubled up on the ALT stud.

 

[BBB82]

I just rewired by whole engine bay about six months ago I am deployed so I would post a diagram but cant. All I remember is the power wires make one big circle. Stating with pass battery down to starter, up to alt off alt back to fuse on firewall two wires off fuse right side one goes in the cab, the other runs over to glow plug sol, then hot side of the sol goes to drivers battery then to pass battery. That sounds about right I would do like I did and replace them all at one time mine had so many brakes in them tape up from a owner before me.

 

[just a number]

well I stand corrected. there are 2 wires, both come off the block on the firewall. one runs the headlighst,taillights and ecm power. the other is the IGN side.

at the firewall connector the bottom right corner(looking from the front) is the headlights.halfway up the right side is the IGN wire

 

[dieselfuelonly]

Well, it very well could be a crimp connector still attached at the starter and the wire did pull out of it...true. When I was down there looking at the starter I didn't really see anything that stood out like the wire pulled away from something. But in order to get this thing to start and run we had to take a jumper wire and run it from the + terminal on either battery to the junction block at the firewall on the leftside stud (that had no wires attached to). The rightside stud had wires installed and after we jumped it I still had no lights come on in the dash when you turned the ignition to the "ON" position to pre-start and glow the engine. But when we jumped the stud we also heard clicking after 10 seconds telling me that the glow plugs were getting power, but it would not start after cranking for a little bit. We had fuel but didn't actually get it to start until we removed the rightside wire at the glow plug controller and jumped it to the leftside stud. Then it cranked and started...running engine. Just definitely a wiring nightmare, but I'm used to a lot more wiring and electronics working on these newer Freightliners at work. I haven't got a chance to get back to the truck and look it over to update what I've found but I know that red wire down at the starter is probably causing 99% of my problems!

 

[just a number]

the wire at the starter can cause a ton of problems. that's why mine ended up wire straight to the battery. no major sources of heat and alot easier to keep from chaffing.

the firewall 'block' has 3 wires on it. one comes up from the starter and is 'doubled up' at the connector. the other wire is on the other stud.

the 'doubled up' wire is the one that supplies the IGN power. the other is headlight/taillight. I bet you have a cigarette lighter and horn LOL. they're on the same power supply.

 

[dieselfuelonly]

I know it would make it a lot easier if I had pictures, but I do plan to go over to check out and work on the truck tomorrow. I can tell you for one thing I do not have any other wire(s) installed on the one stud....it has nothing on the one side. And I think the doubled up wire is on the other stud. I think I also may try to pull the starter down and check to see if there is the remnants of a crimp connector for the thick gauge red wire "not installed and hanging there". This truck also doesn't have A/C so there are no wires that run over to and through the HVAC assy. because there isn't one there. The simplest thing I can probably do at this point is run the same guage wire from the wire down at the starter right to the positive stud on the passenger side battery? Would this work and I also wonder could I get a large enough butt connector to tie the wires together...it is like 2 or 4 guage I think??

 

[just a number]

why not run it to the drivers side? shorter run is the way I see it. there is a couple of wires for the HVAC setup, just for the blower setup.

if you want to eliminate the block connection, there is a multi wire connector that'll work. you'll have to use the 10-12 gauge version

 

[dieselfuelonly]

Well, turns out this is going to be an easy fix. In my work on pulling the stock N/A manifolds off on Thursday I found the red wire down at the starter just pulled out of a crimped ring terminal on the starter. So new end and crimp job and it should be back in business...still probably going to need to run a wire to the one stud on the junction block on the firewall because the leftside stud is empty. With the passenger side manifold off I can get right to the starter for the repair and install the much needed front support bracket too!

 

[BBB82]

I would just get a roll of wire and replace all your large pos wires,the factory likes to run them on top of the manifords and bad places, just do it right the first time and not worry about them again. My 2 cents.