f150 won't start on just 1 battery

[rodbolt17]

a load test is done on the battery.
a voltage drop test is done on the cables between the +terminal and the starter and the - terminal and the engine block.
what the drop test is looking for is any unwanted resistance in a piece of wire.
be it the lug,switch,cable,solinoid or what have you.
in a perfect world it would drop 0 v.
typically the + side will drop about .7v and the - about .5.
remember the F motor must carry current through the soliniod to get to the brush assy not like the like two strokes.

[pstephens46]

think just a tad.
if the starter spions the motor normally when on both why would you suspect a bad starter?
if battery voltage is dropping to 7.4 AT the battery you have a massive short in the starter or the solenoid.

that would be a load test.

I was asking for a voltage drop test on the individual battery cable.

OP said a few back voltage dropped to 7.4 when starter was hooked up to jumper cables?

[rodbolt17]

think just a tad.
if the starter spions the motor normally when on both why would you suspect a bad starter?
if battery voltage is dropping to 7.4 AT the battery you have a massive short in the starter or the solenoid.

that would be a load test.

I was asking for a voltage drop test on the individual battery cable.

[gsdanno1]

I have it apart , it looked pretty good , spun in the direction it was supposed to , locked in the direction it was supposed to . I have continuity at the correct spots on the armature , per the manual ,and have no continuity on the brushes ,also per the manual. The brushes look good , I'm going to pick up a set of calipers to measure them as well as the commutator, but I suspect they will be within spec . I cleaned up the armature with some 600 grit , it was slightly dirty. Should I use something like acetone/compressed air to clean everything ? I'm trying to find some more info spec wise on the starter , like checking the solenoid , other than just hooking up a battery , since I know it will work , just not with the 1 battery

[TownsendsFJR1300]

nothing wrong with the motor , ran up to 4500 rpm full of fuel ,on plane , good oil pressure , water pressure/temp . I will now attempt to rebuild a starter. Did a GM one about half a lifetime ago. Going to look at the service manual tonight. Yamaha is too pricey to buy a new one , although I did find a company called Arco Marine who has this starter for about $200 less than Yamaha

Click on the Yamaha parts (in RED) above and see what's what.

I suspect, with what's going on, it's pretty obvious and unless something major, should be repairable.

With all you've done on that engine, that starter should be a piece of cake...

Did you happen to bench test it yet, see how/if it spins?

[panasonic]

Good to know the engine itself OK. Hopefully you can get your starter repaired and/or rebuilt at a reasonable cost.

Let us know the results.

[gsdanno1]

nothing wrong with the motor , ran up to 4500 rpm full of fuel ,on plane , good oil pressure , water pressure/temp . I will now attempt to rebuild a starter. Did a GM one about half a lifetime ago. Going to look at the service manual tonight. Yamaha is too pricey to buy a new one , although I did find a company called Arco Marine who has this starter for about $200 less than Yamaha

[TownsendsFJR1300]

Since you did a bunch of work on this engine BEFORE all this slow starter business got going, maybe there is one more thing you may want to look at before replacing/repairing that starter.

I am wondering if the engine ITSELF is harder to turn over, then normal, for some reason?

If you pulled all the plugs out, killed the ignition by pulling the emergency lanyard off, then put a 1/2" ratchet on the flywheel nut and turned the engine over by hand and see if it is very hard to turn and/or has a tight spot...

Now I know you probably don't have a baseline value of hard it should be to turn by hand, but I would think with plugs out it would not be that hard.

IF it was extremely hard to turn, that might be why it is taking both your batteries to turn that starter.


I am saying all this because a friend of mind had a 800cc Quad engine apart and made a mistake while reassembling it and it would not turn over using its small onboard battery. BUT if he boosted it with it with his large truck battery it would start and run. We discovered he had left out a shim on the crank and the cases where pinching the crank making the engine very tight to turn.

Might be worth a look.

Agreed on the above BUT he posted quote:"This has been an ongoing issue for some time" from post #92. I read this as it's been this way before the balancer/re-assembly...

[panasonic]

just hooked up one of my boat batteries that I have been working with , directly to the starter with jumper cables. Batt voltage 12.85 , would barely spin the motor , voltage dropped to 7.4 during cranking . Then I pulled the battery from my truck , hooked it up the same way , also would barely spin the motor over . Initial voltage on the truck battery 12.6 , dropped to 6.4 during cranking . I guess I could bench test the starter , but with the same result from 3 different batteries , I don't see the point . Time for a new starter

Since you did a bunch of work on this engine BEFORE all this slow starter business got going, maybe there is one more thing you may want to look at before replacing/repairing that starter.

I am wondering if the engine ITSELF is harder to turn over, then normal, for some reason?

If you pulled all the plugs out, killed the ignition by pulling the emergency lanyard off, then put a 1/2" ratchet on the flywheel nut and turned the engine over by hand and see if it is very hard to turn and/or has a tight spot...

Now I know you probably don't have a baseline value of hard it should be to turn by hand, but I would think with plugs out it would not be that hard.

IF it was extremely hard to turn, that might be why it is taking both your batteries to turn that starter.


I am saying all this because a friend of mind had a 800cc Quad engine apart and made a mistake while reassembling it and it would not turn over using its small onboard battery. BUT if he boosted it with it with his large truck battery it would start and run. We discovered he had left out a shim on the crank and the cases where pinching the crank making the engine very tight to turn.

Might be worth a look.

[99yam40]

Those drop readings while cranking are over the .5 volt Rod mentioned.
too long and small of wire being used, too many questionable connections, or a combination of these .

by putting to both, it draws less from each battery and their cable to the switch.
from the switch on to the starter seems to be Ok if the starter spins good set to both

[TownsendsFJR1300]

just hooked up one of my boat batteries that I have been working with , directly to the starter with jumper cables. Batt voltage 12.85 , would barely spin the motor , voltage dropped to 7.4 during cranking . Then I pulled the battery from my truck , hooked it up the same way , also would barely spin the motor over . Initial voltage on the truck battery 12.6 , dropped to 6.4 during cranking . I guess I could bench test the starter , but with the same result from 3 different batteries , I don't see the point . Time for a new starter

Sure sounds like the starter, or your engine is seized up...

IMO, I'd bench test, then pull the starter apart and inspect first before dropping the big bucks...

Go to the purchase parts section in RED above and bring up your starter/ parts fisch. That should help...

[gsdanno1]

just hooked up one of my boat batteries that I have been working with , directly to the starter with jumper cables. Batt voltage 12.85 , would barely spin the motor , voltage dropped to 7.4 during cranking . Then I pulled the battery from my truck , hooked it up the same way , also would barely spin the motor over . Initial voltage on the truck battery 12.6 , dropped to 6.4 during cranking . I guess I could bench test the starter , but with the same result from 3 different batteries , I don't see the point . Time for a new starter

[pstephens46]

He gets good cranking with switch set to both and switch is new. #1 definitely has more voltage drop than 2. I assuming set to #1 it doesn't crank much at all and set to two probably cranks much better?

Maybe Rodbolt can comment on his testing above.

[gsdanno1]

Starter has the 2 big cables coming from the console connected to it , 1 positive , 1 negative . No separate ground strap . I removed both of those cables as well as the wiring to the solenoid when I did the test . Engine has 881 hours , it was run from the ramp back to my lift , where it sits now . This has been an ongoing issue for some time . If I didn't mention it , starter spins very normal in the "both"position

[TownsendsFJR1300]

I also removed my 5 month old *****ing motor battery with less than 1 hour run time , fully charged @ 12.89v , attached it to the starter , turned the switch and it would barely turn the motor . I will repeat this last test tomorrow with one of the batteries that I have been testing , as well as the battery from my truck . During the cranking procedures , there were times when the solenoid wasn't able to kick out the starter drive , but most times it did. I also noticed that I had to reverse leads on my meter depending on if I was going from the + side or the - side . Depending on time tomorrow , I may go from batt to batt switch and repeat , I will also try and get enough cable to take the switch out of the equation , and hook the field cable directly to the battery , and disconnect the other cables going to the switch as well

The voltage drop with BOTH batteries looks good but your test with ONE battery and the voltage drop-CRANKING (which your going to do) should tell us something.

A good battery hooked directly to the ENGINE's pos and neg cables (no switches, long runs, etc) should tell the story and crank normally.

How many hours on the engine?


Too lazy to read back, but the engine has run since the rebuild correct?

Also, prior to the balancer failing, did the starter itself work fine-no issues?

Depending on what results you come up with(batteries pass load test-wired direct to engine), you may end up pulling the starter and checking that specifically... Wouldn't be the first time brushes wore out