Sluggish starter
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Joined: Nov 2008
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Sluggish starter
I've got a '66 F100 w/ 240. It recently has become increasingly slower turning over while starting, like it has a low battery. I checked the battery. It's showing a little over 13 volts. The lights dim and heater fan slows while at idle, but brighten and speed up when increasing RPM's. A friend told me it may be the voltage regulator. Any ideas?
Postmaster
Joined: Oct 2008
Posts: 3,026
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From: Renton, WA
You have 2 issue's the slow starting and idle power issues are seperate.
On the starting issue the first thing to do is measure voltage at the battery (not the cables but the battery posts) while cranking, if it drops below about 9v you got a weak battery if not it's in the cables or starter.
On the dimming at idle issue, one it's not uncommon. If it has always done it then the alt is to small if it's recent, chances are one or two of the diodes have gone. Alternators are composed of three A/C generators that use diodes to rectify (make DC) the juice. These diodes falling is what usually causes an alternator to go bad, but they don't generally fail at the same time. For each diode that goes out the alternator looses 1/3rd of it's ability and it's ability is taxed most at low engine speeds and high draw, like idling with your headlights and fan on. And if while running at a high idle with everything off the voltage is around 14 the voltage regulator is fine.
On the starting issue the first thing to do is measure voltage at the battery (not the cables but the battery posts) while cranking, if it drops below about 9v you got a weak battery if not it's in the cables or starter.
On the dimming at idle issue, one it's not uncommon. If it has always done it then the alt is to small if it's recent, chances are one or two of the diodes have gone. Alternators are composed of three A/C generators that use diodes to rectify (make DC) the juice. These diodes falling is what usually causes an alternator to go bad, but they don't generally fail at the same time. For each diode that goes out the alternator looses 1/3rd of it's ability and it's ability is taxed most at low engine speeds and high draw, like idling with your headlights and fan on. And if while running at a high idle with everything off the voltage is around 14 the voltage regulator is fine.
Postmaster
Joined: Apr 2002
Posts: 3,613
Likes: 6
From: Coal country
Your voltage regulator and alternator have nothing to do with your starter being sluggish if your battery is fully charged.
I would put the battery on a charger overnight first. If the battery takes the charge well, then you have a battery cable or a starter problem.
If the battery still shows taking a heavy charge after sitting overnight, it isn't holding a charge anymore, and may need to be replaced.
If the battery shows fully charged the next morning, but voltage is low while cranking, it will no longer accept a charge, and may need to be replaced.
Before you go replacing parts, I would inspect the starter and battery cables for corrosion (don't forget to peek inside the wires, under the insulation behind the clamps), for loose, burned and arcing connections.
Check the the starter for any evidence of burned wiring, broken teeth, lots of crud in the Bendix and the like.
Good luck to find the problem!
I would put the battery on a charger overnight first. If the battery takes the charge well, then you have a battery cable or a starter problem.
If the battery still shows taking a heavy charge after sitting overnight, it isn't holding a charge anymore, and may need to be replaced.
If the battery shows fully charged the next morning, but voltage is low while cranking, it will no longer accept a charge, and may need to be replaced.
Before you go replacing parts, I would inspect the starter and battery cables for corrosion (don't forget to peek inside the wires, under the insulation behind the clamps), for loose, burned and arcing connections.
Check the the starter for any evidence of burned wiring, broken teeth, lots of crud in the Bendix and the like.
Good luck to find the problem!
