Slow Crank, No Start When Warm

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RustyRatRod said:
Then get a remote starter switch. Any auto parts store will have one cheap.
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THIS. You MUST test under load "cranking." That is the way voltage drop works. If you can't measure the battery in the trunk by yourself, "rig" some wire from the meter up front to the battery. Use your head. You can use an extension cord, EG example: Get an extension long enough to reach front to rear. Voltage drop in that cord is not an issue because all it is powering is the meter measurement. Now pick a ratty short lamp extension, and cut it in half. Connect that extention, "plug" in to your long cord. Strip the cut ends, hook one of the cut ends to your meter, and clip the other end to the battery.

Yet another way is to do the opposite. Use your meter back at the battery, but use the extension cord lash up to trigger the starter relay. Hook one wire of one end of your cut end to the batter, hook the other wire to the spade on the starter relay where the yellow "start" wire goes. Just short the other end of the ext. cord together at the rear to crank.
 
Good info. I would check voltage drop cold before starting and then warm, to see a difference. On my car, I run the fans constantly before shutting off the engine. And sometimes run the fans after shutting off the engine, to cool down under hood temperature. I have not seen water temperature above 200* at any time.
 
Voltage drop when cold between starter+ and battery+ while cranking was 0.94 and between battery- and starter case was 0.36. I didn't even bother warming it up. Would this be bad connections or wires?
 
Tyler Fritz said:
Voltage drop when cold between starter+ and battery+ while cranking was 0.94 and between battery- and starter case was 0.36. I didn't even bother warming it up. Would this be bad connections or wires?
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You have to check and find out!!!

Voltage drop is just like a diagram---follows a road, follows a road map. If you hit a chuckhole (bad connection at a terminal) that is a drop right at the terminal. If you hit a narrow road (long length of wire) that is drop over a distance/ length of wire. How to check? Use your head

Once again, I suggest rigging up a remote switch long enough that you can reach the full length of from the battery to the starter.

"Let's say" you suspect a battery terminal/ clamp. First crank the engine and either feel it for overly warm, or use a "gun" thermometer. And or, clip your meter to the rear of the clamp, or stab a probe to the rear of the clamp, and stab the other probe into the top of the battery POST. Crank and read while cranking.

If you have a soldered/ crimped say, bolt on eye, like a ground, clip or stab a probe into the eye as close to the stud as you can get, and stab the other probe into the wire itself right next to the terminal. Crank and read.

Or maybe it's a rusty/ loose eyelet to ground stud. Stab/ clip a probe to the eye, and stab a probe "hard" into the metal next to the ground stud. crank and read.

Here's an example that threw me

Used to have a 86 Ranger. Ground cable went down next to the frame, where a factory "T" crimp in the middle of the ground cable, bolted to the frame. The cable continued on and bolted to the block.

One day it would not start, yet in the dim carport, the headlights remained bright. WTF? The voltmeter tells the story. A few checks and 15 min later I KNEW it HAD to be a bad cable. Cut the insulation around that "T" splice and there it was, cable all ate up and corroded inside the insulation.

Once you guys learn/ teach yourself a bit of power/ amperage/ voltage drop stuff, you can save a LOT of money throwing parts and money at a problem, and maybe even some time.

Ohmeters are not that much help sometimes, specially on large current type components.
 
By the way with that much drop, I'd start by feeling around the cable connections for "warm." Could even just be a dirty battery clamp at the posts
 
67Dart273 said:
By the way with that much drop, I'd start by feeling around the cable connections for "warm." Could even just be a dirty battery clamp at the posts
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I would've checked all connections first. I didn't read every post on this matter. If the OP just started having this problem then I rule out the cables being to small as the problem would've been reoccurring. Just from what I have read I'm thinking that possibly the starter is going bad. Also I think that the battery is kinda small, I always run a 1000 cold cranking Amp battery or at least as close as I can get. If all of this always has been discussed I apologize
 
Dan the man said:
I would've checked all connections first. I didn't read every post on this matter. If the OP just started having this problem then I rule out the cables being to small as the problem would've been reoccurring. Just from what I have read I'm thinking that possibly the starter is going bad. Also I think that the battery is kinda small, I always run a 1000 cold cranking Amp battery or at least as close as I can get. If all of this always has been discussed I apologize
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No, you're the first to make mention of a possibly too small battery.
 
A voltmeter AT THE battery will tell you that as well. That is part of the reason I emphasize voltage checks. Crank the engine cold and hot, with your probes stuck into the tops of the battery posts. If the battery is known to be charged, and the voltage sags anywhere near 10V or lower, have it load tested. By someone with a CARBON PILE tester, not a shirt pocket instrument. The battery could be somewhat discharged, old, defective, or too small.

If the battery load tests OK, but the V AT the battery still sags when cranking, then the starter is drawing too much current. This could be something in the engine bad-- drag, bearings, etc, bad starter, and possibly small cables.

Something I did not see mentioned is we were talking about too much timing advance. Easy to check for that. With it hot and showing the "slow" problem, ground the coil wire or otherwise disable the spark. If it spins up nice then too much advance.
 
I did that test a bit ago where disable spark and try turning it over after the engine was heated up. No change, still very slow crank, took out the spark plugs and it turned over free and clear so that leads me to believe it's not an internal issue such as bearings
 
I should have responded about your battery when you first mentioned it.

For a battery in the trunk install I still believe you need the proper size cables and battery.

1/0 will work, but for the difference in cost, I ran 2/0.

Your cables getting hot is a clear indication they are too small.
 
Since we’re on this subject, what is considered the best starter for higher compression small block LA engines?

Brand/Model number
 
MSD DynaForce or any starter that is rated 3.0 hp or more. Be wary of:
- a company that does not provide a HP rating for it's starters
- cranking tq #s quoted for the starter. Useless.

Just like a certain amount of HP is reqd to move the car, a certain amount of HP is reqd to 'move' [ crank ] the engine.
 
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