slow crank only when cold

[kirk knighton]

When I turn the key when cold it barely cranks. Try a couple more times and it suddenly lurches to life!
Let it run just one minute, shut it down and then try again and the starter spins merrily away and the engine starts right up.
Battery? Starter?
Actually both are new, but maybe one or both is defective?
This 412 has dual carbs, not FI.

[raygreenwood]

OK...how cold is cold?

Lets say its a new battery and starter....as you have. Is it the correct size battery (in cranking amps)?

One of the biggest issues with this is grounding. Typically the chassis is not as great of a ground as you might think. You need to check the ground braid on the tail cone of the transmission,

Also....that term...ground braid. Its a problem.

I found this out in my industry. Lots of machines use ground "braids" similar to our automotive ones. We tend to think of them as big fat "wires". They are not.

They are collections of little copper wires...in groups...braided into a sheet of copper cloth...technically. Over time each little copper wire in each group gets green or white corrosion on it. They no longer touch....both within each bundle and from bundle to bundle.

This makes for a VERY high resistance ground. So....ideally...getting rid of the actual ground braid to the pan from the battery and going with a solid copper core wire....can make a HUGE difference.

We see this same problem in insulated battery wires. You get green corrosion growing back up under the insulation from the clamp on battery post terminal....and it can almost be a dead short.

Bear in mind that power flows from positive to ground. The more resistance there is to ground....the less power flow you get.

Here is a short article speaking about the same issue on Pelican forums for BMW.
https://www.pelicanparts.com/techarticles/BMW-X3/7..._Strap.htm

If you are going to be keeping an actual ground braid...replace it with a "tin" plated one.

This add I just pulled in for the picture.

Note that it is silver colored.

https://www.zoro.com/grote-ground-strap-braided-24...nsQAvD_BwE

Why does all of this happen....because...the patina that copper develops....from the dark brown like a penny...to green or white corrosion.....is a NON-CONDUCTOR. Its not conductive. This is why fuel injection terminals at a minimum are tin plated...and best are gold plated.

Its also why in medical devices like defibrillator pads.....we are not allowed to use copper connectors or copper circuit traces. They must be silver at a minimum...because when silver tarnishes...that tarnish or patina is still conductive....while tarnished copper is not.
Ray

[kirk knighton]

I have new cables, ground and positive.

Like I said this only happens with that first cold crank in the morning. Turn the key and it grunts and stops, as if the battery is dead.
Then turn key off, try again, another grunt.
Third time another click and grunt and - whoomph! Starts!
Run the engine for as little as one minute, turn off, then try again, and it starts right up, the starter sounding like it's getting 100% juice.

And then go for a drive, park, shut off engine, go for a walk for a few hours, come back - it starts right away!

Hmmm. Maybe the wrong battery? Do you know what the cranking requirement is for a 412?

[Pepperbilly]

First of all make sure that new battery is good. Not all new things are good. Ray is spot on about the grounds...you need proper ground from transmission to chassis and proper grounding from the battery to the chassis. This is an old car so all your connections need to be rust free, clean, and tight. Also check the starter connections... again clean, not corroded, and tight. Look at all those.
Bill

[raygreenwood]

Yes.....just to reiterate......there IS something in the system that is either physically dragging.....or high resistance.....or low current feed.

Ok lets think through a few things....brainstorm a little.

1. Starting at the battery.....its new right? What cranking amps does it list?

Is it a standard lead acid battery? If its not maintenance free.....can you pop the caps and check each cell with a hydrometer? What you are looking for is low strength or a weak or dead cell. It can mean.....that until its "stressed".....it does not put out full cranking power.

Next.....make sure that if you are using dielectric grease.....it is ONLY on the outside and there is no grease between the post and clamp on terminal for either + or -. Dielectric is. Non-conductor and makes for high resistance.

If the + battery terminal is the type that is a seperate terminal that bolts to the wire.....its very possible and common that even when new it has corrosion between the strands and under the clamp. Remove the end and check, clean and reclamp.

What happens is that the first cranking session.....heats up the high resistance connection and either displaces water or corrosion....and makes for better current flow on subsequent cranking.

Same process on the ground braid to chassis.

2. Same process on the ground braid to the tail of the transmission. Also realize.....by looking at how the stud (I think its a stud if memory serves) that the transmission ground braid goes to on the body.....this can be high resistance over the eons because it gets rust in the threads between the stud and body. Again.....if it heats up when cranking....it improves the connection.

3. Many years ago.....I found that on a pretty fresh, high compression engine....in weather below about 15°F.....with oil thicker than 10w-20......in the automatic cars.....the combined drag of transmission oil and engine.....could do this......make it drag on the first set of cranks ....unless the battery and starter were perfect.

4. Once you get it started and warmed up......check your ignition timing. Specifically.....if yours has vacuum retard....pull both the retard hose and advance hose off and check at idle below 800....about as low as you can idle......what your initial advance setting is. Then test it with advance hose plugged in.

What you are looking for is excessive advance. Im not saying that yoiur advance setting is excessive....because we all know what kind of slightly different than stock tuning works......but it can be excessive compared to design.

If your ignition timing is set up with vacuum retard.....there may not be enough vacuum to retard during cranking. So now you have about 5° extra advance at starting. If your throttle is cracked just right and you are somehow getting a few degrees of vacuum advance as well.....and if you are set a bit more advanced by position anyway......you can have something like 10° of advance....plus a cold engine with cold oil.....and if there is any minor weakness in grounds or + supply line or battery.....it makes it really drag.

5. With any starter....new...rebuilt...old. it can have high resistance inside. Usually due to rust or grease or wear.
Try this....tomorrow before starting.....reach down and rap on the starter a cew times with a hammer. Wiggle it. Then try it. If it makes a big change......its probably worth stripping and cleaning it.

6. Disconnect the positive cable and connect a volt meter. Check it end to end. You are looking for high resistance. It can have anywhere in its length a little knick in the insulation where ot has gotten water in and started corrosion between the strands.

7. You could have a ground or power drain. A quick test.....is to get home at the end of the day.....and just for the heck of it....disconnect both cables from the battery. In the morning...connect them back up. Make note either when connecting or disconnecting.....whether you get any small sparks.

If it starts better....you have a power drain. It could be the clock or ground system or even other small items that stay powered with the key out like stereo or even wires to the emergency flasher or headlight switch.

Ray

[Hawker]

I had this very issue back in the 80’s.

I eventually traced it to a loose battery terminal. Try this: Turn the interior light on and see how much it dims when initially cranking. If it dims excessively or extinguishes completely, you have a bad connection. Of course you don’t have to use the interior light but any low wattage consumer will suffice.

BR,

Rob

[ClassicCamper]

Perhaps the starter is binding? Can you see that the gears are engaging properly?

I‘d triple check to make sure its the correct starter for the application (you mentioned it’s new) and verify it‘s mounted flush and not cocked to one side. If it has a bushing that the pinion goes into, make sure there’s no crud in there. The bushing may be expamding after a few attemps and allow the starter to spin free once warm.

Just another perspective.

Good luck, hope this helps.
_________________
1973 412 Wagon
1976 Westy
1978 SB Vert

[raygreenwood]

[kirk knighton]

Ah, all of these are excellent observations - thanks!

This morning I was going to try that cold start with the addition of a jump-starter battery hooked up to it, to help boost the battery and see if that is indeed the problem.
It's a new battery I got at Costco in September. Of course they didn't have the "official" battery for a 412, but they did have one that was a bit bigger than the one in there, and of course the terminal posts were in the right places and it fit right in there under the seat.
Well I decided to try starting without the jumper battery hooked up, and wouldn't you know it started right up! Again a bit slow and creaky for a second or two, but then it started.
I let it run for 5 minutes, shut it down, cranked again and started instantly.
I shut it down for about 6 hours and went again - vroom! Started right up!
I drove it about 10 miles, stopped for 2 hours, started again and came home.
I'm guessing the same will happen tomorrow morning: that initial "reluctance" to turn the flywheel; turn the key back off, try again and a nudge or three and it starts.
Sounds so much like a battery problem with that early-morning weakness. Should I go ahead an attach the jumper cables and see if that doubling of battery power makes the starter spin fast on that first try?

[raygreenwood]

[kirk knighton]

So even a "new" battery may be "partially" defective?
Partially, because it only seems challenged with that first crank of the day?
And running the engine for even two or three minutes is enough to charge it so that the next crank works fine?

I'm guessing virtually every battery one buys is in fact remanufactured, not "new". So, yeah, people ( or machinery ) fuck up or cut corners or use faulty materials.

I'll try the extra jump in an hour or so - fingers crossed!

[halfassleatherworks]

As far as a new starter being good, it all depends on the source. back in 1974 or 75 I went thru 9 new rebuilt ford starters before I got one to work. The shop owner had a few choice words for the rebuilder and went some were else to get parts.
_________________
Halfass Leatherworks*****GOT LEATHER Made to order Leather crafts, you can find us on that face book thing

Belts, wallets, mouse pads, drink coasters, Engraving, most things made in leather.

personal items if you want it in leather in Reno Nv, *****

[kirk knighton]

Okay just did it.

And....the jumper battery seemed to have little effect. The engine cranked slow but then fired right up. Ran it one minute, shut it down, started again and then again like a full charge.

It's just and only that initial morning crank.

The engine IS high compression, a custom-built 2.1 litre with carbs and hydraulic lifters. 20W-50 oil. Outside temp today 35 degrees.

So far as my battery jumper thing goes: it is 15 years old. Is it still any good? Also has an air compressor in it for inflating the tires, works okay. But maybe the battery in this unit is too old to have any effect for jumping another battery?

[ClassicCamper]

Kirk - I'm more and more inclined to believe that outside of a defective starter, you are going to find that there is an issue with this starter binding.

If I'm not mistaken, you have two T4's... if you have some time and patience, you may want to swap them (if they are compatible) and rule out a voltage issue or high compression.
I'm not really a betting man, but if I were, a binding starter is where I'd lay my chips!

Keep us posted!

- Ron
_________________
1973 412 Wagon
1976 Westy
1978 SB Vert

[Pepperbilly]

That’s a very good point Ron. A new starter that he has installed may not be quite the correct fit. That could cause the binding for sure.
Bill

[raygreenwood]

[kirk knighton]

Today I drove to work and the car sat out in the cold for 6 hours.
With a little trepidation I got behind the wheel and turned the key.
It whirled with full power and started instantly!

Great!

But also - what the hell??

Reminds me of a nagging ongoing problem I had with my Honda 500-Four back in 1973. The thing kept conking out in the rain. I went around siliconing things like the points cover, plug wire caps....all over the engine and checking all wiring. Still conked out in the rain!
I kept at at, my Honda dealer kept at it, for weeks. They even did all they could and then started the engine up and turned a hose on it and it continued to run just fine.
Then I went out riding in the rain and it conked out again!
Went back to the shop, just about in tears of frustration ( I was 17 ), and one of the mechanics suddenly had a new idea.
He peered under the back side of the engine and said "aha!" He got a little knife, did something down there, and then told me to get back out on the wet road.
I did, and the damn thing did just fine!
So what was it after all that time??
Each of my four carburetors had a rubber breather hose that trailed down behind the engine, to breathe down to the ground. The hoses on my bike were an inch or so too long; when I rode on wet pavement water would fly up and temporarily seal off those hoses and create a dead vacuum in the carbs and effectively shut off fuel flow. The mechanic had simply snipped an inch off of each hose. No charge!
Damn!
And all that time we were thinking/presuming "electrics" being the problem.

Later in my life I had a '69 Squareback with fuel injection. A problem arose one day whereby two of the four cylinders would stop firing now and again, seemingly randomly. We tried tuneups, replacing various FI components like injectors, all to no avail. And every time I took it to the shop the car ran just fine and they could find no problems with it.
Finally, after several months of this the problem seemed here to stay, and I happily limped into the shop on two cylinders. They quickly diagnosed a cracked circuit board in the "brain". Cracked just enough to randomly shut off power to two injectors every now and then. So a new brain was installed and off I went!

Head Scratchers - that's what our beloved vehicles are. To be charitable about it!

And so I ponder all the ideas you guys have been kindly offering me...the starter is sluggish only in the morning first start. It was ice cold this afternoon after work. It sat for six hours in cold weather and yet started instantly. Tonight it will sit in my cold garage for twice that and will probably be sluggish in the morning.

[raygreenwood]

[kirk knighton]

So does the fact that my attempt at jump starting it this morning - in essence doubling up my battery power - had no effect say anything about my battery?

I got the battery at Costco - it's an Interstate - and so I guess I can simply take it out of my car and bring it back to Costco and get a refund?

Then whether I should buy the same battery from them again, or go to O'reilly's and get a different one? That way I might lessen the chance I get a defective battery?

I used to run Die Hards in my Type 4s, but with the demise of Sears that brand has been taken over by Advance Auto Parts. The nearest Advance store is quite a ways away from me...

[raygreenwood]