serious short circuit somewhere

[GentleGiant]

Hello:

1984 CUCV. Drove home yesterday, no problem. Changed the oil.

Near freezing point this morning. Started it without plugging in block heater... running a bit rough in the cold, but running... then stalled. Didn't want to start again, so I said, "OK, I'll plug you in." Plugged in the block heater. Waited an hour.

Went to start it. NOTHING. Not even lights on the dash. Testing revealed two flat batteries. Flat like 5 and 7 volts. Flat. Charged batteries. Tested batteries with a load tester (push and hold the button for 10 seconds and the battery heats a coil to test it under load). Both batteries good.

Noticed a serious spark when putting the cables back on the batteries. Enough spark to make a small puff of smoke. Yikes.

Got truck started. Ran a minute or two. Aftermarket Ammeter on dash showing very low. Shut truck off. Checked batteries. 11.4 volts and thereabouts. Could watch the voltmeter dropping when keeping the voltmeter on the battery.

There must be quite a short somewhere, I think. Not blowing a fuse.

So, any suggestions where to look for the solution to this problem?

Thanks to all.
GentleGiant

 

[richingalveston]

Is your truck stock. you should have close to 24 volts on second battery. if a 12v conversion has been done, we will be shooting in the dark.

 

[NovacaineFix]

I would ditch that ammeter for sure, they are prone to all sorts of problems, may be your culprit.

Disconnect the ammeter and see what happens. Voltmeters are way better than ammeter simply because voltage is like electrical pressure where as amps are like flow.
Ammeters have to run through a circuit so if the gage fails or shorts, it will cause a short into the system unless adequately protected, whereas voltmeters can run across a circuit for measurement.

It may not be your issue, but they are not good reliable sources for voltage or electrical diagnosis unless you are looking for full potential or load factors of a device.
Just my

 

[GentleGiant]

Thank you for replying, kind sirs.

Is it 24 volt? I certainly believe so. The batteries are connected positive on one battery to negative on the other, so they are in series and that must mean 24 volts.

I apologize about the ammeter.. it was late when I was writing and upon examination in daylight, it is a volt meter.

My thought is that there must be one heck of a short somewhere. The batteries are drained deeply in a very short time and the big spark and puff of smoke upon connecting the batteries to their cables suggests to me we aren't shorted on something small.

Also, no fuse is burning, so I wonder if its not something with glow plugs or the starter. What circuits in the truck are not fuse protected? That spark indicates enough current flowing to burn a fuse in a second, I would think.

Does anyone know of a common CUCV problem I might be encountering, or tests I could perform to find the short?

Thanks very much,
GentleGiant

 

[Hal O'Peridol]

I have had problems with the starter dong this.

 

[richingalveston]

sounds like you may have gotten starter run on. your solenoid sticks causing your starter stay engaged. with the truck running you don't here it. it burns up the starter and since the solenoid is bad, you truck is trying to start but your starter is shorted.


That is the first place to look. IF this is the case, you need new starter and need to check wiring for anything burned.

read up on doghead mod, there is another relay under dash that controls solenoid and it can have problems

one more edit, the only other thing to put that kind of load on batteries is the glow plug system. IF your GP relay is stuck, it will keep your plugs on and cause a drain. It won't do that for long before all plugs are burnt up and no longer pulling any power.

 

[GentleGiant]

Thank you again,

I disconnected the leads from all 8 glow plugs. Gently started hooking up the batteries. No spark. Tested voltage on a glow plug lead with key not turned on: 12.8 volts.

Ah-ha!

So, not that there can't be two problems at once, but it looks like the glow plugs are a problem. Correct?

1) Can anyone confirm that it must be the GP relay, or is there another element of the GP system to also check/replace.
2) If is the relay, what NAPA part number to replace it with?
3) I believe there is a glow plug modification which is recommended to be done. Can anyone direct me to instructions for that mod?

Thanks very much. I remain indebted to and impressed by this forum.

GentleGiant

 

[richingalveston]

I believe ST-85 is a good part number for the relay, it has been a while. you don't want to use the stock relay it is crap.

send us some pics of your wiring, If you are getting 12 volts on the green wires when all the glow plugs are unplugged, then either you are converted to 12 volts or your resistor is bypassed. Most likely resistor bypass which is good.

just want to confirm you have stock set up so we don't give you bad advice.

Does the smaller red wire from the Neg. of the rear battery go all the way to the glow plug relay or does it connect to a part on the fire wall right behind engine then to glow plug relay. That part is a resistor. Just curious if you are still using the resistor.

things to look at on this site to help you are the stickies at the top of the cucv section. look at the doghead mod and the resistor bypass and it will help you to understand some of the wiring.

 

[GentleGiant]

Hello and Thank you Rich,

Here is a picture.



The smaller red wire from the negative of the rear battery turns blue and connects to a two-studded part on the firewall before getting to the relay. I think its clear in the picture above. Interestingly it connects to the left stud, and the picture in the "resistor bank bypass" thread it connects to the right stud.

The large gray wire crossing the photo has to do with the brake controller for trailers.

Here is a picture of the wiring to the left of the air filter.




Thank you for the tip on looking at the stickies. I will check them over.

If the photos are too small to see well, let me know. I'll try to figure a way to attach them larger. It takes a little figuring to use a new-to-me website here.

Looking forward to your experienced advice (or that of others as well).

Thanks,
GentleGiant

 

[richingalveston]

you already have a non stock relay, that one looks like the more recommended relay. I still not sure st-85 is correct, I think that may be the Napa number.

everything looks stock. your resistor is there and must be working. That is the black thing on the fire wall. It lowers the voltage on the glow plugs from 24 to 12 when all glow plugs work.
Read about the resistor bypass. I think it is a good thing and the doghead relay mod is a must.

All the info is here to fix anything on the truck yourself.
just a note, where the wires change color the small section is special wire called fusable link. These sections of wire are actually the fuses in your wiring harness.

good luck

Rich

 

[cpf240]

Make sure the GP relay has the small terminals electrically isolated from the relay's mounting tabs. Otherwise, in a stock system, the relay will be engaged when it shouldn't be.

 

[GentleGiant]

Thank you Rich,

I will replace that relay. ST-85 appears to be the correct number, as I have seen it elsewhere on the forum. I am impressed with my little Canadian small-town NAPA for having it in stock.

I do appreciate your suggestion to look at the stickies, etc... I spent a few hours getting more familiar with the website, and it is truly a gem. I appreciate the wiki, the stickies, and all the threads, not to mention to excellent advice from persons such as yourself on my own particular truck issues.

I will, by the way, absolutely do the doghead starter relay mod. It sounds utterly essential. And I will do the gp resistor bypass while I am in the business of snipping and re-attaching wires.

Thanks so much, Rich.

I will let you know how it goes.

GentleGiant

 

[eme411]

is this the truck that was on KIJIJI this past week?

 

[GentleGiant]

eme411: no, I've had this truck for almost 10 years.

cfp240: I would like to be sure I know what you mean by "electrically isolated". I plan on getting the st85 relay at NAPA tomorrow and swapping it with the identical looking one currently in the truck. I would make sure that any connections on the relay are not touching ground, naturally. Is that sufficient? Here are two pictures of the setup as it is, which I would duplicate with a new st8t relay. (Except that today I set up the wires to bypass the resistor... also set up for the doghead starter relay mod...just need parts on Monday.)



Thanks so much to all,
GentleGiant

 

[richingalveston]

you should see some plastic isolators around the terminals. The correct relay has the internals isolated from the case. some of them use the case as ground and thus when you mount it to the fire wall it grounds and causes it to engage. The relays look the same but if it have connectivity between the solenoid case and the terminals you are connecting to then it is not the correct relay.

 

[cpf240]

What rich said.. use a meter and make sure there is no continuity between the mounting tabs of the relay and either of the small terminals... heck, there shouldn't be any continuity between the mounting tabs and the big terminals either...

 

[GentleGiant]

Hi Rich,

It seems that NAPA ST-85 is recommended on several threads here as the proper relay and also it is mentioned in the CUCV Wiki:

Glow Plugs

• DH recomends AC Delco AC60G glowplugs and installing new 1/4" terminal ends on your wires
• Wellman 070 (original 3/16" terminal) direct fit replacement
• Wellman 050 or AC 60G glowplugs (1/4" blade terminal)
• Control Card/Controller is available from Antennaclimber
• GP Relay is NAPA# ST85, Advance Auto #S603 (AA is much cheaper)

In any case, before I install it, I'll look for those plastic isolators.


But, it seems likely that the NAPA ST-85 has the internals isolated from the case and has the isolators around its terminals, doesn't it?

What do you think?

Thanks,
GentleGiant

ps. sorry about the bold face... computer wouldn't let me make it normal typing.

 

[GentleGiant]

cfp240: I will make the continuity test you suggest on the ST-85.

Thanks to you and Rich for your guidance,

GentleGiant

 

[GentleGiant]

Hello all,

Thank you very much for your expert guidance. I have replaced the glow plug relay (after checking continuity between the various terminals and the mounting tabs) and I also replaced the starter relay as per the Doghead Relay mod instructions. I also bypassed the glow plug resistor while I was at it.

The truck is running very well now.

I remain grateful for your help and very impressed with this forum and the entire website with all its pertinent information so easily accessible.

Thank you very much,
GentleGiant

 

[richingalveston]

Glad you fixed it: look at all the other info here, it will help you to keep the truck running right for a long time.
We were all in your shoes once, that is why most are eager to help.
good luck
Rich