Electrical: Avanti Slow Cranking

[tluz]

Hi, Guys,

It's been a while since I have posted, though I still lurk in the shadows.

I have completely reconstructed a basket-case '63 Avanti R-1. Engine rebuilt by a competent shop and gone through by one of the few guys left around southwestern Connecticut who still understands these engines.

Here's the problem: slow cranking although it cranked fine not long ago.

History:

Car came with a Thibeault/Chrysler HEI ignition. I duplicated what was in there rather than go back to stock or rewire for a Pertronix.

Sent the car to the shop for ignition setup and to get the car running. Shop returns the car in running condition, which is to say starts right up and pleasingly loud owing to the glasspack mufflers from Silvertone Exhaust, but carb and choke not yet tuned.

Shop man gives me homework, to wit, alternator is not charging the battery and power steering valve is leaking like a sieve. Keep in mind as you read on that she started up like a champion (no pun intended) as long as there was sufficient charge in the battery.

So here's what I did:

Replace alternator with a Nippondenso 60 Amp per instructions on Bob Johnstone's website. Very easy I add for those who are considering it and much cheaper than a rebuilt Prestolite. Added bonus, no need for a voltage regulator. But I digress.

Have Jon Myer rebuild power steering valve, which he does in a day. Turnaround is rapid and no more little pink puddle under the valve.

To get the valve out and then back in I have to yank the starter. Difficult on one's back but doable.

After everything is back in, replace the starter and reconnect the battery.

Charge battery to full.

Now the fun starts. Very slow cranking. Not enough to fire the engine, where it could do so before.

Take out the starter and spin it with no load. It spins rapidly.

Put the battery back in and jump from the +terminal on the battery to the starter post. Plenty of spark but no go. No spin at all. She won't budge.

Put the battery cables back. Recheck all grounds.

Pull the spark plugs and spin the engine with no compression. Spins acceptably well.

Put the plugs back in and restart. Sloooooooowwwwww crank.

So it seems to me either the starter doesn't have enough oomph to spin the engine under compression or there's not enough voltage getting there. Starter is the correct 4-pole Prestolite MDU model.

What do you guys think? Any thoughts are gratefully welcomed.

Tested for current draw and there is none.

Thanks,

Tom

[autoradiotech]

Suspect battery and/or cables first and dirty connections second. If cables are more than a year or two old, I've seen them where somehow battery acid 'climbed' up into the cable and corroded the wire under the insulation and ate up several of the wire strands! I know it's a reach but I've seen it happen.

[Skip Lackie]

You said you checked the grounds, but fiberglass-bodied cars are notorious for having grounding problems. You might try running a temporary ground wire (jumper cable will work) from the negative post of the battery to one of the bolts holding the starter and see if it makes a difference. Another possibility is that the starter is "cocked" at an angle and is binding. Stick shift? Did you use the special shoulder bolts to mount the starter?

[Gunslinger]

The timing could have shifted if the distributor isn't tightened down. If the timing is too far advanced it can act like that.

[tluz]

Hi, Skip,

Possible it's not exactly aligned although I tightened it up pretty well. I did use the correct shoulder bolts. If the starter is binding would it spin the flywheel with the compression off?

[tluz]

A gearhead friend suggested that maybe a smaller gauge cable might help. I'm using a set from AutoZone that is narrower than stock.

[WCP]

You want to use the largest cables available to minimum voltage loss to the starter. To illustrate, I recently started my R2 Avanti with the battery out of the car, using heavy duty jumper cables attached to the "in-car" cables. The engine was very slow to turn over, rather than it's usual good cranking speed. It doesn't take much voltage loss, particularly with an R1, to slow starter performance.

[Gunslinger]

A smaller gauge cable is the wrong way to go. I've seen smaller gauge booster cables used trying to start a car overheat and melt the plastic insulation. WCP is absolutely correct...use as large a gauge cable as you can reasonably get.

Let your gearhead friend try that on his own car.

[55 56 PREZ 4D]

Some of the insulation on new cables IS thinner than the insulation on the stock cable.
The wire INSIDE is what is of concern.
For 12 volt, # 4 is the smallest wire size to use.
#2 is bigger wire and would be a better choice.
You could go bigger [# 1] but would be overkill.

[ddub]

A smaller gauge cable is the wrong way to go. I've seen smaller gauge booster cables used trying to start a car overheat and melt the plastic insulation. WCP is absolutely correct...use as large a gauge cable as you can reasonably get.

Let your gearhead friend try that on his own car.

Am I right that smaller gauge # is actually larger wire? Perhaps that is what the "gearhead" meant by smaller.

[Gunslinger]

The smaller the number means the heavier the wire diameter...or gauge. The gauge is the overall diameter or wire thickness, not the thickness of each individual strand of wire. Automotive wire is stranded to various gauges as required for the purpose and to be pliable...unlike household wire which is solid core where being pliable isn't a concern even if equivalent gauge.

Maybe we're misinterpreting meanings here. Maybe we should simply say heavier gauge wire might be better.

[55 56 PREZ 4D]

# 16 American Wire Gauge = .0508" diameter
# 8 AWG = .1285" dia
# 4 AWG = .2043" dia
# 2 AWG = .2576" dia
# 1 AWG = .2893" dia
"1/0 or 0" AWG = .2893" dia
"2/0 or 00 AWG = .3648" dia
So, Yes. Smaller number, bigger wire. Till you get to the "0"s, then the more 000 the bigger the wire.
These dimensions are for the wire only, no insulation. Actual wire with insulation will be larger and that will vary with manufacturer and insulation type.

[Dan Timberlake]

Before I change a cable, and often before even cleaning connections I check (measure) voltage drop start to end, and then in steps along the positive and negative starting circuits.

http://reconitelectric.blog.com/files/2012/03/voltage-drop-test-points1.jpg

More than about 0.2 volt DC when cranking requires attention.

Oh, and the voltage across the battery posts (not clamp connections) should not drop much below 10 volts when cranking, or the battery is likely either undercharged or defective.

[R1 3137]

When I was getting the R1 running I made the 'discovery' that just cause a jumper cable LOOKS beafy doesn't make it so. I had two batteries and sets of cables trying to get the thing to turn over faster when I realized the jumper cables were all insulation and only what seemed like 10 strands of wire half of which were broke, which got me looking closer at the battery ground and starter to battery cables.
A new woven ground strap and 1 or 0 gauge battery cable made all the difference in the world and I gave the useless cables to someone I didn't like...

[altair]

slow crank

Hi, Guys,

It's been a while since I have posted, though I still lurk in the shadows.

I have completely reconstructed a basket-case '63 Avanti R-1. Engine rebuilt by a competent shop and gone through by one of the few guys left around southwestern Connecticut who still understands these engines.

Here's the problem: slow cranking although it cranked fine not long ago.

History:

Car came with a Thibeault/Chrysler HEI ignition. I duplicated what was in there rather than go back to stock or rewire for a Pertronix.

Sent the car to the shop for ignition setup and to get the car running. Shop returns the car in running condition, which is to say starts right up and pleasingly loud owing to the glasspack mufflers from Silvertone Exhaust, but carb and choke not yet tuned.

Shop man gives me homework, to wit, alternator is not charging the battery and power steering valve is leaking like a sieve. Keep in mind as you read on that she started up like a champion (no pun intended) as long as there was sufficient charge in the battery.

So here's what I did:

Replace alternator with a Nippondenso 60 Amp per instructions on Bob Johnstone's website. Very easy I add for those who are considering it and much cheaper than a rebuilt Prestolite. Added bonus, no need for a voltage regulator. But I digress.

Have Jon Myer rebuild power steering valve, which he does in a day. Turnaround is rapid and no more little pink puddle under the valve.

To get the valve out and then back in I have to yank the starter. Difficult on one's back but doable.

After everything is back in, replace the starter and reconnect the battery.

Charge battery to full.

Now the fun starts. Very slow cranking. Not enough to fire the engine, where it could do so before.

Take out the starter and spin it with no load. It spins rapidly.

Put the battery back in and jump from the +terminal on the battery to the starter post. Plenty of spark but no go. No spin at all. She won't budge.

Put the battery cables back. Recheck all grounds.

Pull the spark plugs and spin the engine with no compression. Spins acceptably well.

Put the plugs back in and restart. Sloooooooowwwwww crank.

So it seems to me either the starter doesn't have enough oomph to spin the engine under compression or there's not enough voltage getting there. Starter is the correct 4-pole Prestolite MDU model.

What do you guys think? Any thoughts are gratefully welcomed.

Tested for current draw and there is none.

Thanks,

Tom

You mentioned that you connected the + to the starter, that would be a dead short try the neg terminal to a lug bolt.