Electrical Gremlins- Won't shut down + Slow crank

[Big69C20 Toy]

Okay folks i've been lurking here for a while and reading where i can. I picked up my '86 M1009 in 2011 down in TN and it's been a barrel o' monkeys ever since. This post might be a bit lengthy but i'm doing my best to describe things and man do i hate electrical stuff.

Drove her home and since i got back to MI it's been one thing after another. Was having electrical gremlins and did the Doghead starter relay after my one fusible link lit up like a sparkler and wouldnt let 'go'. That time it took my starter out (had it repaired) and since then no trouble. I'd replaced several of the fusible links off the Pos terminal with fuses (yes i realize now a no-no).

Recently I was having more electrical gremlins with no brake lights and decided to get the thing rewired with a painless kit. Being deathly afraid and incompetent (mostly) with wiring on vehicles i took it to a mechanic to get it done.

Before i took it in aside from the brake lights being out all other systems were okay. Got it rewired and it was doing some slow cranking- mechanic thought it a weak battery. Batteries are Optima red-tops and are 1 yr old each. Tested batteries and they are good, took starter in and found the attenuator (sp?) was bad and threw solder all over the guts. Bought a new starter and still same thing. Replaced the starter cable and figured well i should just do them all.

Now i have 2ga wires from: starter to terminal, batt 1 to ground terminal, batt 2 to pos terminal, batt 2 to batt 1. Still no good cranking speed but she fires up. All those lines are copper terminals crimped then soldered and heat shrink tubing around joints.

Now here's where i think i jarred something up- i take off wires again, check the terminals and reconnect. When i was putting the wire back to the 12v (rear batt pos neg position) to the engine block (12V) i put it on the + terminal of the rear batt (24V).

Truck fired up like a dream then i go to shut it off and she wont shut down... so i disconnect the grounds on front batt/#1. She shuts down. hmm i think, weird. It's never had the shutdown issue ever. I check the wires again and fix the issue - moving that wire to the 12V (batt 2 - terminal).

One thing i notice here when i reconnect the system; when i put either that 12V eng block wire on or the grounds to complete the system the starter relay (big 200A feller) it gives a big "thunk". It's never done that before even when cranking i never heard it (perhaps because the 6.2 is so loud).

Again she cranks slow as a dog but fires up. Now when i go to shutdown she wont die. Pull the grounds off bat 1 and she keeps going! Squeeze the tube and down she goes.

Now here's what i'm seeing when i check wiring.
1) Starter Relay with ignition in off; Red=12v, purple=12v, purple/white=12v. Same combination when the ignition goes to run or to start.
2) Pink wire on fuel pump shut down solenoid is showing 12V whether the truck is in ignition positions Off/run/start etc.
3) Starter has 24V+ on the big post and the purple starter solenoid line is getting 12V when keyed to start. I used the starter housing as ground during my check so that should have meant grounding through the block was fine.

I don't have the starter tail/support bracket on the starter- my truck never had one but i know i should/will find one.

Ahah methinks- something went wrong because that shutdown solenoid should only be "hot" when in start or run. I check that solenoid for the 'thunk' with voltage on/off and it's good. I fire up truck and again it wont shut down so i yank that connector and down she goes. Also the "door lock" fuse popped. I replaced it with another 20A.

Now the truck still cranks slow and wont shut down. Batteries i've had tested 2x each- both showing good though the 1st round i did see one battery at 90% and the other at 35% (rear was lower). I trickled them up for a couple nights then tried cranking again but same issue on slow crank. 2nd battery test showed 93% and 98% but i cant recall which was which.

So i'm thinking i torched my starter relay and possibly other things. I'm all ears ladies and gents so please educate me... I did do some wire tracing by splicing open my new harness so if that level of information is needed i can give it. (IE that doorlock fuse is part of the circuit going to my red starter relay line).

I probably am missing lots of 'brainless' items like shouldnt that red starter relay be 24V? Shouldnt the starter relay only show the red line hot until the ignition is put to start (IE purple/white closes the circuit to purple)?

Thanks all!

 

[Warthog]

Sound like your mechinic does have a clue on how to wire the Cucv 12v/24v system. Why use a painless harness when the Cucv system is very basic and does require special attention on how it is hooked up. You have the wrong voltages at the wrong places.

you may need to start over.

I wouldn't even know where to start wiring a painless harness for a 12v/24v system.

 

[MarcusOReallyus]

I agree with Warthog about your mechanic. Bad idea to take these vehicles to folks who are not familiar with them.

I have no idea what a "painless harness" is, but it sounds to me like you may have had a ground problem. Now you have MORE problems.

At this point, you need to download the TMs, and start getting familiar with the system. Put things back the way they should be, and THEN you can start troubleshooting.

Because your truck is not stock anymore, it's almost impossible for anybody here to guide you through troubleshooting.

 

[Big69C20 Toy]

Bah- no fun. I figured what better method than using a new kit and since these things are essentially a hopped up K5 with a split 12/24V system and the 24V only being active in a few regions the Painless kit would be good. No one around here seems to do wiring, let alone know about these trucks. I was too dense to post something on here first and go after your guys help.

As much as i'd love to be able to break out the TM's and try to learn i have never been able to understand wiring diagrams- simple as they may be they baffle me. My 1 course in EE back in college never covered any practical things like diagraming.

Well the mechanic said he'd take care of any troubles that came up and i think he will. Can you guys give me some pointers on where he went wrong? I know of a few things he did that didn't make sense to me offhand.
1) that starter relay being 12V on the red wired to the doorlock- sounded reasonable once i traced it out since the solenoid merely needs to pull the big starter engaged and the door lock fuse is a constant 12v hot.
2) Glow Plug relay he said wasnt working because i had pulled the temp sensor to put in an analog- looking at the TMs i pulled 2 connectors in the back drivers side- one was what i thought was an 'oil dummy' light and the other a water temp 'dummy' light. He put in a manual switch for the GPR.
-- My analog water temp unit has never seemed to work (i tested it in water ahead of time and it was good) so only thing i can think there is it's in too deep and grounding out my reading.
3) pink shutoff solenoid is wired to the starter relay purple- that pink line is also spliced to the glow plug greens.
4) the purple/white line on the starter relay goes out in cab and turns into what i think is a faded purple(possibly purple/white) to the 'anode/cathode' which i think looks like a connector with a resistor across it in space right next to the fuel filter. That line is also spliced into the new harness "coil to power" which i would think is the ignition circuit.

So while i understand no man can undo this baffling splice job via net i'd appreciate any/all help i can to get my Mechanic/I to clean this thing up and get it back to normal! I have lots of pics if needed.

 

[MarcusOReallyus]

Well, I can throw a few general ideas your way. At this point, that's about it.

Bah- no fun. I figured what better method than using a new kit

Almost always, a much better way is to find out what's wrong with what's there, and fix it, before you modify it.

As much as i'd love to be able to break out the TM's and try to learn i have never been able to understand wiring diagrams- simple as they may be they baffle me. My 1 course in EE back in college never covered any practical things like diagraming.

Yeah, electrical is not for everyone. But remember the sage advice from that respected philosopher, Harry Calahan:

A man's got to know his limitations.



If you don't understand electrical stuff, the last thing you should be doing is modifying electrical stuff.

Well the mechanic said he'd take care of any troubles that came up and i think he will.

That's good news! Best thing you can do to help him is point him to this site. He can download the TMs for free, with all the wiring diagrams he could want.

I know of a few things he did that didn't make sense to me offhand.
1) that starter relay being 12V on the red wired to the doorlock- sounded reasonable

Uh, that doesn't sound at all reasonable to me. What has the starter circuit got to do with the doorlock? Do you have electric door locks? Even if you do, why would that be connected to the starter circuit?

once i traced it out since the solenoid merely needs to pull the big starter engaged and the door lock fuse is a constant 12v hot.

Okay, I get it now. Well, if grabbing 12v any place he happens to find it is your mechanic's idea of good work, you have a problem, because the guy who is promising to stand behind his work is an idiot, and nobody else is going to want to touch it.

The fact that he dove into this without first taking time to understand it does not give me warm fuzzies about him.

See Warthog's comment about not knowing where to start wiring in a Painless harness? Warthog probably knows more about these systems than anybody on the planet, with maybe a few people on this site being in his league. Think about that - he knows this system in his sleep, and he wouldn't know where to start.

That suggests to me that your mechanic doesn't know enough to know how much he doesn't know. That ain't good.

I'm pointing that out just so that you know you need to proceed with caution, and not just blindly accept what he says.

2) Glow Plug relay he said wasnt working because i had pulled the temp sensor to put in an analog- looking at the TMs i pulled 2 connectors in the back drivers side- one was what i thought was an 'oil dummy' light and the other a water temp 'dummy' light.

Please see the Harry Calahan comment above.

He put in a manual switch for the GPR.

Well, okay, if he did it right. Some like it that way. It's not needed if the GP system is working correctly, and it's a lazy man's way of fixing it if it isn't. (I know that some just prefer the manual method. Okay, fine.)

So while i understand no man can undo this baffling splice job via net i'd appreciate any/all help i can to get my Mechanic/I to clean this thing up and get it back to normal! I have lots of pics if needed.

All I can suggest is that you get the TMs downloaded for your mechanic. Put them on a CD for him. He's got some work to do.

There are a lot more knowledgeable people than me that might chime in, but it's quite possible that none of them wants to try to untangle this mess over the 'Net.

Maybe after the holiday somebody will offer more help.

 

[Big69C20 Toy]

Thanks for the advice fellas. There was some hack/splice stuff before i took this thing home the more i look and i understand about the warm fuzzies on my mechanic. I know my limitations so i thought i'd farm the work out... that didnt turn so well thus far but i'm hopeful.

Sadly i know less but you guys are helping. That GP module of operation video- wowza... i get it but only on the fringes.

He did put in a temp sensor on the water pump along with the manual glow plug switch... i'm not sure how that got spliced in but when the GPR wait light comes on the truck doesnt want to start- i get that dead 'clunk' most of the time.

Like Warthog said i think there are voltages in the wrong places and i think (dangerous) i'm getting some of where;
1) starter relay red should be 24v constant. i got 12 constant
2) starer relay purple/white should be dead when off and 12v when key is in start position. right now i get 12v constant.
3) purple starter relay should be dead when off and 24V when keyed over on relay in start. right now i get 0v in off and 12v if connected torelay (since i'm showing constant hot on purple/white)

Can you guys confirm for me if i'm reading the F7 diagram right because i may have just had another "Duh" moment. Lookin gi see the 2a circuit coming from the 24V into the resistor bay and then going to the GPR (i have one of those 470's). So does the GPR see 12V via those resistors 'leaching' down? I notice I do not have one of those resistor panels anymore and my GPR is hooked direct to my engine wiring harness block (see photo). In 'theory' i would think that using the engine block would still supply the 12V needed for the GPR... right? seems odd (and i'm sure there's a reason!) for that resistor piece that was there before.
Thanks for the help.

 

[wayne pick]

I have no idea what a "painless harness" is, but it sounds to me like you may have had a ground problem. Now you have MORE problems.
Because your truck is not stock anymore, it's almost impossible for anybody here to guide you through troubleshooting.

The painless harness is an aftermarket generic replacement for the OEM harness. They do often come with a few extra wires that are not needed to add to the confusion. I would botch it up ASAP, LOL!

 

[cpf240]

It looks like someone has already done the "12v bypass" for the Glow Plug relay power supply. This is an often recommended mod, so I think you are good there. You'll still need to get out there and measure the voltages on either side of the relay's big terminals. It is not uncommon for the relay contacts to be carboned up, and not pass the voltage/current through to the glow plugs.

In the stock system, one with the resistor bank, yes, the voltage seen by the glow plugs is about 12v. That comes from the combination of the resistance of the resistor bank AND the resistance of the ALL the glow plugs. Thus if one glow plug fails, then the voltage seen by the other glow plugs goes up. Leading to more glow plugs failing and more voltage seen by the remaining glow plugs. Often called the "cascade failure" and the reason many do the 12v bypass.

 

[MarcusOReallyus]

A few questions here:

1. Are we talking about the starter relay or the GP relay? Or both?
2. Do you know if your beast has the GP resistor bypass done? (I'm sure cpf240 is right, but I want to make sure you know which system you have)
3. Have you verified the integrity of the engine block ground?
4. Have you verified cranking voltage at the starter?

 

[Big69C20 Toy]

Thanks gents.
I'll look into the GPR bypass mod- i'm not sure what i've got. I DID pick up all 4 sizes of fusible links and i'm going to replace all the fuses i put in back to proper + a few more! I notice my Glow Plug connectors are loose as all end.. so those might all get done too.

For the discussion with MarcusOReallyUs
1) Depends what part you're talking about. i've got issues possibly at starter relay and glow plug relay. i was mainly focusing on the starter relay earlier as i KNOW i have voltages wrong there
2) gotta read- i'll let ya kno
3) No- i'm not sure how to do that... i read some things on with truck running and headlights on (mine blew out in the previous woopsie when i touched the 12V eng block red wire to 24 and fired the truck up).. so with running i should see <50mV's right? or is there some other test? i'll look in the TM's too
4) Yes- 24V at the starter motor and 12V when keyed on... this is part of my starter relay issues i think.

 

[Big69C20 Toy]

Ohh i also bought some of that NOALOX stuff yesterday. Plan to slather it on grounds and connectors. PS this thing has from what i can tell at least 4-5 grounds in the engine bay; block to frame, block to negative bus panel, ground strap on block to firewall, frame to front clip, front batt to negative bus panel