Hard start '61 sedan

[brkdncr]

Symptom: Starts fine when cold
When hot, as in driving for a while, if i stop for gas then start it back up, it turns a few fan blades then stops. after a few trys the battery can't get the engine to turn over.
If it's warm from idling for 15 minutes it will start fine, although it seems to strain a bit.

Details:
rebuilt engine.
Rebuilt/replaced start 3x. Most recently the starter put in was "high-torque"
Battery replaced 2x
wiring from battery to starter and solenoid is welding cable and is nearly an inch thick.
Battery terminals replaced with audio grade terminals.

What i'm thinking:
I think the rebuilder did a great job getting a tight seal with the valves and rings.
Solenoid is unknown. I think it's some cheap part that isn't flowing enough current to allow the starter to overcome engine compression. Every mech I've taken it too says it's not possible, then they look at how hard it is to replace the solenoid and then tells me it's the starter. Unfortunately I've not had the option to take it to the same mechanic so i've just been setting dollar bills on fire.

Any hints on getting the solenoid out? Looks to be really cramped and hard to get at.

[action]

Other concerns for hot engine slow crank speed besides low current level to starter

Base ignition timing too advanced
Engine oil viscosity too low and not providing lubrication (Too low viscosity or the oil is breaking down)
Piston to cylinder wall clearance too tight

Electrical -
Both sides are important. Positive AND negative
Cabling exterior isn't a good indication of current capacity. It helps. Positive cabling may need to be 1gauge or zero. All + cables from the battery to the starter need to be the larger gauge. Ground side should be the same. Engine ground to frame (or unibody) may be something to checked out depending on battery - cable attachment point to vehicle. (I am not familiar with the '61 wiring)

>>>>Action

[brkdncr]

Thanks. I've played with timing and setting it within 3 degrees of 6 has no effect.
oil is fine.
engine turns freely when some of the spark plugs loosened.
I've added grounding ribbons between engine, battery, body. i'ts welding cable.

[tomo]

You need to perform a few tests to see if you can isolate the problem. All of these can be performed on an engine that is at room temperature (above 60F), except the timing test. That need to be performed in failure mode.

Battery cranking test: Disconnect the coil high tension lead, connect your voltmeter across the battery and crank the engine and determine the voltage reading. If it is less than 10 volts, your battery is either not at full charge or defective. Have the battery tested.

Starter voltage drop test will determine the condition of the components in the starter circuit. Voltage drop in the + side of the circuit should be a max of 0.1V for each connection. The ground side should be 0.1 volt total from the starter case to the NEG battery post (not the cable) Here is a link to the test.

http://www.aa1car.com/library/voltage_drop_testing.htm

Starter current draw will check the condition of the starter. The current draw is specified in the Shop Manual. Typical draw is about 150 -200 amps. If the engine turns freely when not in the hot start condition, it probably is not too tight.

You can check if the timing is your problem by disconnecting the coil high tension lead when the engine is in the failing mode and then cranking the engine. If it cranks freely, you have a timing issue.

Another possibility is a leaking carburetor causing a hydraulic lock. A cold check is to look for excessive carbon or wet fuel on the plugs.

[blkmk69]

To try and assist by eliminating variables:

"engine turns freely when some of the spark plugs loosened."

Is that with the engine warmed up?

After install of rebuilt engine, has there always been a slow cranking when warmed up problem?

Is there a slow cranking problem with a cold engine?

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Joined: 05 Aug 2009 18:41
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