Hello Yotatech!

I have searched on this forum and on the web for possible answers and leads but can't figure this out. My truck died while I was driving it the other day and I can't get it started again. It's a 1981 Pickup SR5 4wd that is mostly stock. I did the weber 32/36 conversion, k&n filter, and Doug Thorley headers.

Hello Yotatech!

I posted this in the pre '84 section as well. I think it's more of an electrical problem than a mechanical issue.

I'm a bit of a newbie when it comes to 4x4ing and pickup trucks in general but it finally rained in southern calIfornia and I got excited. I took my truck to where I could find some mud and gave it a test run. I hit a few puddles here and there and one of them was a little deep but nothing I was concerned about; I didn't flood the cab or get water in my carburetor. The truck did stall out for a split second at one point and then kept running fine (maybe a little, little on the rough side) the rest of the night. I got sick and came out to start it the next day and there was no power, just a tick. I think I left the lights on but not too sure; I was a valet for 10 years...I probably turned them off. My neighbor jumped me and off I went to the dr. The sensor and battery light were on for about 30 seconds and then clicked off. I stalled or it stalled at a light but started right back up and the battery light cleared again. It started fine after the dr. and then didn't want to crank after the grocery store. I tried again 3 minutes later and it fired up. The sensor light came on one more time with the battery light but shut off again and didn't come back on. I drove it two times for about 30 minutes a piece while I was sick.


A week and a half later after I got better and I went out for a cruise. After a couple of hours of worry free driving, a few stops here and there, I pulled over to look at a view and left it running. When I got back in 2 minutes later it sounded like my blinkers were flashing but I didn't have them on nor would they cancel out. Then my fuel gauge started going to zero and so went the rest of my dash. I lost my tach, voltmeter, oil pressure gauges and all. My hazards went out and so did my lights. Then my truck started running rougher and rougher. Next I started to lose engine power and it backfired a few times. Then everything went out and I couldn't restart it. There were a few moments where it sounded like something was shorting out but there was not any odor or smoke to provide a clue where, just somewhere behind the radio and heater controls. I did use the defroster for the first time since I have owned it when I was out playing in the mud.

My first thought was, "great, my alternator just quit." I took my battery out and put it on the battery tender as soon as I got home. It charged for about 14 hours and finally gave a green light. I had it off the charger while I was at work and it read 13v when I got home today. I put it in my truck and it read at 9v on my voltmeter. That's odd. I checked my dash lights and tried cranking it anyways to no avail on either. I went ahead and checked the fuses, fusible links, and power to the starter. I also checked my ignition switch. Everything showed lower than 12v but so did the battery. At some point a few of the lights in my cluster came on (the brake light and I don't remember the other but it was kinda insignificant a not the sensor or battery lights). It still won't crank or tick. My battery is back on the charger again.

I am hesitant to think it is just the battery/alternator problem. The battery is a 1 year old optima yellow top that's always treated me well and the alternator is the same age but re manufactured. If it were a bad alternator I should still be able to start it and test for that off a charged battery.

I was pretty easy on her but did I do something stupid when I went playing in the mud and rain?
Is there anything else anyone can think of to check?

I'm trying to avoid "the man" here....

Thanks,
Nathan Price

 

Could have.

Handheld VM or stock?
13v is without anything connected to it, correct? This is open-circuit voltage, no load voltage. Even a bad battery could read that high without load.
Even a bad battery can make lights that draw very little power work. Optima may have a good reputation but don't bank on that. Have battery tested.

Yes. However, a bad alternator may have a short to ground that loads and drains battery. That's the reason that your battery voltage dropped when connected to your alternator.

If you could not take battery to get tested, try this to test:
1) Charge battery again until fully-charged battery,
2) Disconnect battery cable from alternator/regulator (you have external regulator, correct?). Disconnect every connector on alternator/regulator. This will isolate the alt/regulator.
3) Connect cables to battery (starter, fusible link to fuse block, and ground)
4) Measure battery voltage with hand-held (not stock volt-meter). Measure voltage at all points in fuse block that should have 12V
Lower or same as open circuit voltage? How much?

6) Turn on all electrical loads (high beams, air conditioner, hazards, step on brake), and measure battery voltage in that condition again. If it stays above 11 or somewhere around there, battery should be good. It should be able to crank and run. when my alt died, I drove my 22RE until batt voltage went down to 10 V, then had to recharge.

7) If all above tested good, look at your alternator. Measure resistance from battery post to ground. Expect mega-ohms there, lower and I'd suspect a short.

Keep us posted...

 

I had time to do a little testing today with my DVOM and the battery fully charged, 15.0V.

I tested the battery again a few minutes later before I hooked anything up to it and it still read 15.0V. Next I connected the battery with the key in the OFFS position and checked it again, still 15.0V. I waited a few minutes and checked again with the same voltage. Then turned the key to ACC and did the same thing with no change. I turned it to RUN and the voltage dropped 2V right away and continued to drop down to 10.6V while I was checking for voltage at the fuses, starter, and alternator. Everything read out over 12.4V but I still didn't have headlights, dash lights, running lights hazards, or any action at all from the starter so I can't test the alternator running.

Next I reinspected the fusible links and the positive cable. There are two fusibleq links; one is a single wire and the other is two, red and green. The red wire is hanging on by a few strands, problem number one. During this time the voltage in the disconnected battery rose to about 13.0V I disconnected the fusible links at the positive cable and reattached the cable on the positive terminal. No change in voltage. I waited a few minutes and checked again, and still had over 12.0V. Next I attached the single wire fusible link and repeated the process with no change in voltage. I connected the two wire and started losing voltage.

While waiting to recheck the voltage I tested what I could of the alternator according to the manual. I tested the connector for continuity on the back of the alternator by checking the L terminal with the F terminal. There was continuity and the manual says to check the alternator.

When I had the two wire fusible link disconnected and was inspecting it I checked for continuity between the terminals on the harness side of the connection to ground. What would be the green wires terminal read out .007 ohms and the red wires terminal read 0.004 ohms on the 2M setting of my DVOM. If I'm not mistaken that means I have a short in both circuits?

I can't find the paper I had all my notes on so I'm sure Im leaving a few bits of info out. Any ideas or anything to recheck? I have not tried getting a jump start with my battery charged yet but I'm not really sure if that would tell me anything or not.

 

It's difficult for people to visualize what you are doing, unless they have exactly same model truck as you have and IF you have stock wiring.

Why don't you find a schematic and post it to show us what exactly you're dealing with?

If you want to read resistance AND expect close to zero resistance that af fusible link wire should have, do not use 2Meg-ohm setting. Use the lowest resistance scale setting. Maybe 20 ohm.

Anyway, a .007 ohm resistance using 02-ohm scale is good. However, a few strands of wire may still read low but when current passes through it, it would heat up, increase in resistance, cause voltage drop, melt, or cause a fire if it does not melt soon enough. To figure this out, run whatever circuit is supposed to take power from that fusible link and measure voltage between the ends of that same fusible link.