Sluggish crank/no start/runs fine when jumped *FIXED* (1 Viewer)

[HawkGunner]

78 FJ40, 2F, Webber 38/38. 70k miles on the clock.

My LC has been running fine for the last few weeks since I started driving it.

Recently the battery died, so I replaced it. It fired right up and I drove away. The next day it cranked a little sluggish as if the battery were low, it started and I drove off. The following day it was the same. This progressed until about three days later when the turn signals quit working, and the headlights dimmed. I got it home, and the next morning I had to jump it to start it.

I thought the alternator was going bad. So I ordered a remanned alternator and voltage regulator from SOR. Installed it, jumped the LC from my wife's jeep, it fired up, and ran just as good and smooth as it's been running. I drove it around a little, came back and turned it off. Immediately tried to crank it again.... and it's cranking sluggish as if the battery were worn down. More sluggish/not turning over at all as if driving it killed the battery.

My battery is at parts store getting charged/checked at the moment, just in case I got a bad battery.

I'll feel pretty stupid if it's just a bad/worn down battery. But, any help or suggestions would be greatly appreciated.

 

[1969FJ]

Simple checks.;

1.) When running, voltage meter on battery terminals, should be 13.5 volts ~
2.) Overnight, remove hot terminal on battery, connect inline current meter to see if something is draining the battery. Should be less than .030 amp.

 

[HawkGunner]

Simple checks.;

1.) When running, voltage meter on battery terminals, should be 13.5 volts ~
2.) Overnight, remove hot terminal on battery, connect inline current meter to see if something is draining the battery. Should be less than .030 amp.

I'll do those tests shortly. If I'm not at 13.5 volts, what might the problem be? Considering that I just changed the alternator and voltage regulator.

If something is draining the battery, I'll trace it to the source and fix that issue.

 

[1969FJ]

Could be alternator, voltage regulator, and/or wiring issue.

 

[HawkGunner]

Could be alternator, voltage regulator, and/or wiring issue.

I replaced the alternator and voltage regulator thinking that was it. The problem persists exactly as before.

Where should I start with the wiring? What should the ohms be on the battery/starter cable, what about from the alternator to the battery?

I can use a multimeter, and know how to check voltage drop, resistance etc. I'm no guru, but working on it.

 

[HawkGunner]

@1969FJ

I ran the voltage test on the battery. Only reading 10.74 volts after about 10 minutes of idling.

Any tips?

 

[Casey E]

Sounds like a bad battery. So battery died, jump started and then sluggish after shutdown and restart? Try charging battery.

 

[Casey E]

Never mind, missed you have battery charging at parts store.

 

[thebigredrocker]

If your battery turns out good, there is some discussion on how to adjust voltage regulators on the last two pages here: 76 Fj40 Face Lift

I imagine BJ40green and coolerman have posted tips elsewhere as well.

 

[pithicus]

Fusible link? Or charge fuse or relay if it has one.

 

[hedgehog23]

perhaps a bad ground/loose connection causing the lack of charge?

 

[1969FJ]

@1969FJ

I ran the voltage test on the battery. Only reading 10.74 volts after about 10 minutes of idling.

Any tips?

If the battery is good, and the alternator is "verified" as working, then the voltage regulator is suspect. The voltage regulator monitors battery voltage and does its thing to allow alternator voltage rectified to go to the battery to charge it back up. If you are reading 10.7 after idling that long it is wrong for sure. Another check, engine off, all electrical items off, and battery at full charge should read 12.8 or higher. That is first.
The alternator can be checked out at an electrical shop or auto parts store to verify.

If the battery is known good, and upon connection there is less than 12.8 volts, then a short is somewhere. If that is the case, remove all unnecessary fuses and see if it still the same.

Where did you buy the alternator and regulator ? Also, do you have electrical add ons over stock.

 

[coonassjohn]

The starter could be bad. Has the same symptom as a bad battery. Check the amperage draw with an amp meter before you throw anymore parts at it.

 

[JAFO2014]

@1969FJ

I ran the voltage test on the battery. Only reading 10.74 volts after about 10 minutes of idling.

Any tips?

One thing about these old trucks, they are easy to work on for the most part. If the alternator system is working the truck should stay running if you remove the positive terminal from the battery. I stopped to help someone years ago that was broke down. Their charging system was failing. Back then (70's) you could go about 100 miles on a full battery. Started my car, left it running. Then took my battery and put in their car. Started their car. They were able to drive to a parts store for a new alternator. If your charging system is working the 40 should stay running if you remove the positive terminal.

 

[Tommy Shumpert]

I bet it’s the starter as well. I had a similar issue. Took battery to get replaced and it was fine. I had a spare starter so I replaced it and it cranks like a charm.

 

[pithicus]

probably a good idea to make sure it's charging first. Test the battery voltage without the engine running, and test again when running. Should be 1 volt or more higher when running.
if it's charging, do what 1969FJ said above to eliminate drain.
If it's not charging check the fusible link and fuses/relay.

 

[swelltimes]

Alternator belt tension is good?

 

[rkymtnflyfisher]

I think it was lack of cold beer, there was never a mention of cold beer, so that must be the problem. I would start with a cold beer, then troubleshoot with the multimeter.

 

[coonassjohn]

As long as you can still read it!

 

[HawkGunner]

I think it was lack of cold beer, there was never a mention of cold beer, so that must be the problem. I would start with a cold beer, then troubleshoot with the multimeter.

I'm more of a liquor man. Maybe a shot or two down the carb and it'll start right up.