No excessive heat anywhere. The ground is a little warm, but to be expected. I'll try the new wire to the solenoid.
An new 911 starter sounds like a good idea. Although it is nearly a 100.00 more.

Mike,
If you're going to change out the starter you might want to look into getting a high torque starter just to save some money. I'm pretty sure that Performance Products (who I wouldn't recommend to my worst enemy) sells them. Sorry, I don't know their price off the top of my head, but I believe they are less expensive than the 911 starters. I think most later model 911 Starters I've seen are about $200 more than the early starters for the 912.
I'd make sure that it is the starter though. Usually when something is wrong with the starter you turn the key and you hear either nothing when the selenoid has gone bad or you hear click-click-click-click-click but the engine doesn't turn over. It just seems weird that the starter works fine, and then the engine running stops the starter from working. Still, if you said you noticed it's barely turning the engine over you could be right. Good Luck.

Andrew

Hello

OK please keep in mind that only generators will survive runing without battery. A alternator will get shoot within secounds ( Overheat and then the diodes go to hell ).

OK maybe Wayne will kick me now spoiling his biz ;)

A guess is that you have somwhere a little interuption and that maybe killed already your alternatoor ( Not all 912 have alternators, in fact most came with generators )

BTW check if the generator is magnetizized and in the correct direction....


Grüsse

Don’t make things more complicated than they need to be.

You were almost at the answer. The reading at the battery (12.26V) with the car at idle is LOW it should be above 13 volts and above the standing battery reading. This points to a diagnosis that the charging system isn’t working corectly! To confirm the diagnoses of a malfunctioning charging system you need to check the battery voltage with the car at about 3000RPM if it is not 13.5 or better you have a bad charging system. (14.5 volts is normal) If this is so, changing cables, starters and or batteries will do nothing but cost you $ and time. If you follow thru previous post for test sequence you will be able to see if it is the battery loop or charging system. When you come back with a positive answer one wat or the other then it is time to test why and where the problem is. This is a simple thing to track down!

Pulling the battery cable with the car running is a way to test to see that the charging system is working for the 912. Be careful with this method and use it only on some cars. If you do this to a modern car (our 912 are not included in this list unless certain ignition systems are added) you stand a very good chance of frying the ignition or charging system. Also, some charging systems require the battery to be in the loop or they will cut out even when working correctly.

The correct place to test the charging system is at the battery not at the generator. If you have correct VOLTAGE at the battery all is good. Only if the voltage is incorrect do you start testing “up stream” from the battery.

Big bore kits normaly do not add much, if any, cranking load to the starter but compression can and very high compression motors will start just fine with a stock starter. You run high comp and big displacement with no problems from a stock starter.

If the battery is in backwards the starter will try and turn backwards but will be unamle to crank the motor, and funny things will happen in the regulator.

Funny thing, you can spin a 924 motor backwards and it will start and run (poorly but run) to do this correctly you have to assemble the starter incorrectly not flip the battery. Never tried to start a 912 motor backwards and I hope not to any time soon.

The battery has over 14 vdc at 3000rpm. The generator appears to be functioning properly. The entire ignition system appears fine aswell. I tried wiring in a new battery with all new wires and still had the same problem. I've concluded that once the engine is warm, she doesn't want to start. whether theres no fire or the engine is harder to turn i don't know. Could the new rings cause this?

No, rings will make it a little stiff at first but even more so when cold unless the ring gap was set way too small then you will do all kinds of bad things to the P&Cs . Is the motor tight when hot? Is it hard to turn by hand and harder hot than when cold? Turn the motor until you hit TDC then you will be able to feel the crank and its bearings without feeling the compression as much. Then slowly turn the crank around 4 or 5 cycles feeling each piston coming up to TDC and past. Does it feel even for all 4?

What is the battery voltage when you hot crank? Have you checked the connectors on the starter and the starter itself to see if it is getting hot? Missing any tin on that side? Does the battery run down during use? What work was done to the motor since it last worked and now? When hot does the starter click and try to crank or just click or nothing?

Green912,
When i bought the car it ran but there was a noise on the driver side of the engine. I removed the valve cover to find the a valve keeper failed and there was spring parts everywhere, and bent a few pushrods. So i had the heads rebuilt, new valves and new rings.
All cyclinders feel even to me. I haven't noticed if there is a difference when its hot or cold. I'll check.
When she is hot the starter does turn over, just doesn't pop and quickly drains the battery.
The battery connectors are clean. The starter is brand new.
What do you mean by "tin"??? sheet metal??
I'm not sure what the voltage is when hot but its 11 something at the starter when its cold.

MikeP wrote

"Starting with a fully-charged battery the engine starts in just 3 or 4 seconds of cranking. I'll run the engine for 10 minutes in the garage, shut it down, and the battery is too dead to start again. I barely turns over. I tried another battery. Same process same results. "

When you put the second battery in, and it started, was the motor hot then? Maybe the charging system is still in play. I ran around this summer for about one week (200 miles) without my generator working. Never had a problem restarting with the battery only.

I think the starter will still run the right way even if the battery is in backwards. Heres a link to a great story about a backward cranking 912. They rev. the battery leads and it still cranked backwards !!!

http://www.hcpresearch.com/912_crank.html

GoodLuck

Brett

Just a thought-have you checked the ignition switch? A defective switch will discharge your battery pronto. Duke, 69 912.

“When she is hot it turns over but doesn’t pop and drains the battery” All the previous posts are disregardable if CRANKING IT is draining the battery. If it is cranking correctly then it is not the starter. You probably have a carb or spark problem if you cannot start the hot motor. Do you have a choke? Is it staying on? You might be flooding it.

Duke. Funny one on Pellow’s starter story. The other way to make a starter spin backwards is to reverse the magnet housing.

I got a headache.

Yes it does crank when hot! Just seems slower and drains the battery quick! I don't have a lot of experience with car engines. But i know how long a battery will crank a v8, which should be a lot harder to turn than a little 1600. And this engine will barely crank for a 30 seconds before the battery is to low to turn with any speed.
What in the carbs would cause the it not to start when hot? Doesn't seem like it would flood when hot and not when cold.

MikeP
Guess what ? went out in the cold and tried my old starter to see if you rev. the battery on the starter and if it would run backwards. Either way, it ran the same way.

Brett

Wow Brett thats odd. What did your instruments do?

This was with the old starter, out side the car.

Tell me how ?

Just to prove it would spi n the same way.


Brett

Cool, I learn something good every day. I will have to see why a 912 starter will spin same way regardless of polarity and the 12V motors I work with will reverse and run backwards. I wonder if you can flip the magnet case on a 928 starter and use it in a 912?

A motor needs a richer (more gas, less air) air/fuel mixture when cold. This, on some cars, is done with a butterfly choke. If the choke is left on after the motor has started and is warming up then as the motor warms up it will become too rich and most likely will not run well.

There are many other things that can disable a hot motor. Ignition, timing, vapor lock, choke, incorrectly jetted carbs, carb float settings and float valves, bad connections that increase resistance when hot and lots more. When the problems pop up after major work has been done it is even harder to diagnose as the work done and systems involved have to be considered suspect as well. To test further you will need a good grasp of what you are looking at and for. It might not be simple or even just one thing.

Hey guys, just an fyi... I told you the car would start normally with the battery in backwards. Green and Brett, don't try it anymore though. For one you can't charge it if it's in backwards, and you can permanently damage the individual cells within the battery. The reason it works is because you aren't actually reversing the flow of electricity or polarity outside of the battery itself.
I wish I had more advice on the problem, good luck Mike, I hope you get it figured out.

Thanks, but I had no intention of installing the battery backwards. I make enough errors without trying too. ;)

When you flip the battery you are reversing the polarity and direction of flow. Most devices are not sensitive to this but some are.

Hello

To prevent "backwards" mounting the battery posts have different sizes so the connectors will not fit.
( To big and to small, but such things always get "adoptet" ).

Said that I still would check if the generator is loading into the correct direction.

Grüsse

Clean and/or replace the ground strap from the transaxle to the chassis-make sure both ends are clean and tight to bare metal. If the hot start problem persits, replace the starter solenoid.

The ground strap carries ALL the current when the starter is being used (over 100 amps, usually.) If it's old, corroded, and/or loose, resistance to current flow will be high enough to prevent the starter from turning a hot engine.

Remember, current (AMPS) is what does the work in an electrical circuit-and don't forget it's a CIRCUIT-current has to make a complete loop from the battery, through the wires/cables, through any connections, through any components, and BACK to the battery.

So many problems are caused by people forgetting (or just not considering) that ground sides of a circuit are just as important as the hot sides.

Your high-speed engine miss sounds like weak coil to me-replace the cap, rotor, points & condenser while you're at it-they're so cheap and easy to replace it'd be ridiculous not to. Ohm out the plug wires and make sure they're not more than 1Kohms per foot.
Also, pull the plugs and check the gaps.