Voltage drop with ignition switch on (3 Viewers)

[jakerudy]

Drove my 60 this morning with no issues. After sitting shut off for about 15 minutes it wouldn't crank. A few months ago I had a loose connection at the positive battery cable so checked that first with no improvement. I tried to jump the starter to bypass the solenoid which didn't work either. So here is what I've found. The posts and cable connections are clean. Battery is 2 years old.

Battery post to post 12.7V.
Ignition switch off 12.7V from positive to negative cables.
Ignition switch on 4V from positive to negative cables. Still 12.7V battery post to post.
Same voltage drop at the starter posts.
I noticed a slight hum or rattle type noise under the passenger dash around the heater fan with the ignition switch on. The noise is somewhat intermittent but is there more often than not.
Can't find any worn wires shorting to the body or frame.
None of the accessories or the radio will work with the ignition on due to the voltage drop.

Any ideas?

Thanks in advance.

 

[Seth S]

if you never see a voltage drop across the battery itself (key on or off) but you see a voltage drop across the cables.....

I would start by cleaning the terminals, clean the grounding locations. I'm wondering if the starter is stuck and is creating the voltage drop....its really the only major current drawing component in the truck....but if so I would expect to see a hit on the battery. And that hum you are hearing could actually be the starter solenoid.

Have you tried banging on the side of the starter?

 

[Zjohnsonua]

x2

 

[jakerudy]

I checked the battery terminals but not the grounds. The voltage drop occurs with the ignition switch in the on position before turning the key to start. One time when I shorted the starter terminals with the key off the started bumped but would not go ahead and crank. The starter is only about 2 years old.

Did not try to bang the started since it did bump once.

The started solenoid is mounted on the left fender. The hum does not sound like a solenoid clicking and is just a faint noise from under the glove box area. It may have been there a long time and I just never noticed it.

The key warning beeper still works but once the ignition is in the on position nothing works.

 

[Seth S]

My mistake on the starter solenoid....was thinking of starters with the solenoid mounted on it

I'd would still clean and inspect my battery cables both pos and neg and all ground locations. Its possible for those cables to fail internally with time....had a pos cable fail on me in an older saab years ago. driving down the interstate the car just died innexplicably. I was lucky in that I was miles from a indi saab garage and I got towed there. Bought a used bat cable off them, swapped it out, and was on my way again.

If your cables and grounds and connections seem to check out then I would try jumping the starter. If it cranks as it should then its time to consider the ignition switch or the wiring from the switch to the rest of the system

 

[jakerudy]

Update. Using my battery charger with a 200 amp boost I was able to jump the starter and get it going. 20 minute drive home and it ran fine. Shut it off and restarted it a couple of times just like normal.

Tested the battery and under load it shows borderline weak for a 500 CCA battery (my tester only shows up to 500 CCA but the weak indicator moves as the CCA goes up). My battery is 885 CCA to crank the 6BT so I'm leaning towards just a weak battery.

 

[tmxmotorsports]

Was wondering what you were talking about having the starter solenoid mounted separately you should have mentioned you have a 6bt swapped in the landcruiser if you don't mention it we all assume its stock well can't speak for everyone i did...

 

[tmxmotorsports]

How do like the 6bt swap?

 

[jakerudy]

Sorry for not mentioning the swap. It is in my signature line but I should have been more specific.

Love the swap. It will idle through rough terrain, more power than you need on the highway, and gets 20+ mpg. My 2F had California emissions so I was constantly chasing vacuum leaks and emission switch problems. I've put over 30k on it with the Cummins and would drive it anywhere. The engine compartment is actually cleaner with the 6BT.

 

[Seth S]

FYI signatures don’t show on the phone.

 

[jakerudy]

FYI signatures don’t show on the phone.

My mistake. I've got it running but still have an electrical glitch somewhere. The radio & tach are now intermittent.