Tracking a slow-cranking problem

[41woodie]

I'm not going to ask for help diagnosing a slow cranking problem on a specific car I just want to make sure that I understand the testing procedure.  I'm trying to pinpoint the specific source of high resistance that is reducing the cranking voltage to a point that it won't spin the engine fast enough to start.
 
If I connect a multi-meter to the positive post of the battery and the Batt post on the solenoid then crank the engine is the multi-meter displaying the voltage between the two meter probes or is it showing the voltage in the entire circuit?
If it's displaying the voltage in the entire starting circuit it's only confirming what the slow cranking is demonstrating and is doing nothing to pinpoint the specific source. Yes?

If it's displaying the voltage between the two meter probe then it's identifying the location of the high resistance as being in the part of the circuit between the probes , Yes?

Trying to help a friend get and old 6volt stocker up and running and it's really kicking our butts getting it to start from the seat and run down the road.

[Harry]

Does it still have the large size battery cables?

[41woodie]

Does it still have the large size battery cables?

Postitive cable is size 1/0 welding cable (brand new), ground strap is 1 1/2" width flat braided strap, also new.  Ground location on engine block was ground to bare metal.

[enjenjo]

Connect the multimeter to the starter post on the solenoid, and the negative post of the battery if negative ground. That will be the voltage the starter is seeing.

[wayne petty]

yes... battery POST.. to starter solenoid threaded post..  cranking..  volt meter set to 20 volts DC ..

you can measure the battery voltage while cranking from positive to negative post..  use the 2 figures to calculate how much resistance the wire has..

please don't stop there for the testing..  do the Negative battery Post to the starter housing.. perhaps the starter thru bolts sticking out the end plate..  while cranking..

to warm up to voltage drop testing .. please print this page and perform it if you can get the engine running.. or even better perform it on several other cars..

linked to make it easy to bookmark for you.. and easy to drag a save the image to your hard drive for printing..

http://i.imgur.com/WMDprhm.jpg

just for kicks.. do you have a set of jumper cables.  i am taking this is a NEGATIVE GROUND SYSTEM.

hook both clamps to the negative battery post.. hook the clamps on the other end to a good ground spot on the engine.. see if it still cranks slow..  if it cranks fast then.. you could have a bad ground connection that will show up on test 2 when you perform it while cranking..  that is not listed but described..

lastly... are you sure its a 6 volt starter..  the armature and windings might have been converted at some point into a 12 volt starter and that could explain the slow cranking..

these are just thoughts.   the voltage drop test is a life saver.. actually an alternator saver..

[41woodie]

Thanks to Wayne and all.  The car is a '52 Pontiac Catalina straight 8 hydromatic, bone stock.  It is a 6 volt negative ground car.
Part of my problem is learning to trust what my diagnostic tests are telling me.  We tested the 1 1/2 year old battery with a load tester which showed it to be fine.  We took the battery back to NAPA and their test showed it to be defective, they stood nothing to gain as the battery was under warranty.

I have used jumpers to bypass virtually every device in the starting circuit.  I installed a push button Ford solenoid as you would on a chevy hot start problem.  The Ford solenoid will crank the starter and start the engine almost immediately if you use the push button on the Ford solenoid.  For those of you that aren't familiar with 52 Ponchos they have a keyed ignition switch and a starter push button on the dash.  The ignition switch only switches current to the coil and accessory circuits and does not activate the starter solenoid, that is done by the push button.

Finally this afternoon I think I may have isolated the problem to the neutral safety switch as I bypassed it and the starter cranked properly and fired the engine up immediately.  Strangely every wiring diagram I've found for early fifty Pontiacs omits the neutral safety switch completely as if it doesn't exist.  We've studied the factory manuals and I'm still searching the interweb for info and schematic of the safety switch.  I realize that they are simply a mechanical switch that is operated by the shift linkage but a schematic would be helpful.  The battle continues, it keeps old brains active and gives us something to cuss other than politicians.

[wayne petty]

have you got a picture you can either upload here.. or over at Imgur.com  so i can see it.. i have an amazing amount of old car info scattered in boxes that keep getting rearranged so i never know what or where i will find anything.

at least you have it narrowed down..

its amazing with a little application data what one can find in 2 minutes..

http://i.imgur.com/9O3Ox4C.jpg

http://i.imgur.com/V0Q6yb8.jpg


does it look like this..

http://www.ebay.com/itm/1953-1954-1955-1956-Pontiac-Neutral-Safety-Switch-Reverse-Light-NOS-RARE-1998039-/252515362598?hash=item3acb16a726:g:T7gAAOSw6btXR7Z8&vxp=mtr

[41woodie]

Wayne thanks for the additional information.  I found the imgur images a little earlier this evening.  The diagram that shows the neutral safety switch shows it with two wires.  The switch on the particular car has three wires, I believe the third wire is actually the power source for the back up lights but I wanted the schematic to confirm that.

The switch on eBay is for a 53 and newer and of course they are different on 52's.  In 53 and subsequent years Pontiac eliminated the dashboard starter button which required a different ignition switch and a few other changes.

I do think that the 53 switch would work using the two screw contacts, the 52 doesn't have the male plug terminals.  I'd take a photo of the 52 but it's at my uncles home about thirty miles away where I've been commuting to work on the Poncho.

[Bruce Dorsi]

OK, I'm confused now!

If the neutral safety switch is between the starter button and the solenoid, how does bypassing the neutral safety switch make the engine crank faster?

Does the continuity of the solenoid vary with the voltage applied to the small post of the solenoid?

Of course, if there is inadequate voltage to activate the solenoid there will be no continuity, so no cranking.

If there is sufficient voltage (and amperage) available to activate the solenoid, why would voltage to the starter be affected by a faulty neutral safety switch?

41 woodie said: "The diagram that shows the neutral safety switch shows it with two wires. The switch on the particular car has three wires, I believe the third wire is actually the power source for the back up lights."

Why would there be power going to the neutral safety switch?  ....If the power was coming from the starter button, the back-up lights would only work while the starter button is pushed.  ....There should be no constant power at the small terminal of the solenoid.

Which style of solenoid is on the car?  ....Grounded (requires positive power to the small terminal to activate) or UN-Grounded (power for solenoid coil comes from battery post of the solenoid, and requires small terminal to be grounded to activate the solenoid) ?

I'm here to learn, so please further my education.

[41woodie]

Bruce, this is a diagram of 52 Cadillac wiring.  The hydramatic and safety switch are identical or very similar to the Pontiac in question.  It appears (to me) that the safety switch is the point of high resistance that is causing the voltage drop and resulting slow cranking or chattering of the solenoid.  By jumping the safety switch the solenoid engaged properly and cranked as it should.[/img]

[41woodie]

I was mistaken, the dirt and general nastiness on the neutral safety switch was hiding things from me.  There are actually four contacts on the safety switch, two are screw type that accept ring terminals and two are male push-on type.  That allows for two different sources of + voltage.  One is carried on to the starter solenoid, the other powers the backup lights when the car is in reverse.

[BFS57]

Hello;
Had this problem on my Vicky not too long ago.
Cure:
Mini high torque starter (Remy)
Optima red top battery!
STARTS EVERY TIME! USES LESS JUICE TO START!, SPINNS FASTER!!!
Problem cured!!!!!

Bruce