Intermittent Starting Problems

[beatnavy]

Today is one of those Washington DC days where the heat and humidity aren't crazy, it's not supposed to rain cats and dogs later this afternoon, it's not snowing/icing/sleeting, the trees have taken a slight pause in their pollen attack, and I don't have to drive all over the beltway to meetings. In other words, it's a rare day: a good day to drive my teener to work. But it didn't happen, because the starter wouldn't crank. There are probably 12.238 days left before crushing summer humidity arrives around here. Need to fix this soon.

This has been a periodic problem since I got it running last winter after its long hibernation. I thought I had it solved back in January when I cleaned up the ground strap connections and battery posts. But in the last few weeks, it's reared it's ugly head again. I've read and tried to use the troubleshooting guide on the site here previously, but honestly I didn't appear to be getting reliable data on the volt/ohmmeter, and the problem seemed to go away.

Basic facts: 72 1.7L, stock FI. Problem is totally intermittent. I turn the key, hear the fuel pump, and sometimes I hear a very slight whine, but no crank from starter. All other electrical stuff works fine. If I jump it from another car, it will start fine, although it may take a minute.

Battery: It's been somewhat abused during the process of getting this car running again, but FLAPS told me in Jan/Feb it was solid when I had them test it. It reads at least 12.8 volts sitting still. I charged it overnight with battery charger the other day, and I didn't have a problem - for about 2 days and only about 2 actual short trips in the car - until this morning.

Grounds/Terminals: Tried to clean the transmission ground strap, battery posts, battery ground cable connection real well the other night. The positive cable and clamp are admittedly old and may be suspect.

Charging system: At low idle, charging light comes on dimly and goes away at actual driving speed. I get roughly 14.5 volts across the terminals at high idle.

Any help on prioritizing how I eliminate each of the variables and/or which parts I replace? Based on the symptoms, can I rule out charging system, ignition switch, solenoid or starter or bump them up or down the prime suspect list?

I know there's tons of info out there for the googling, and I've read a fair amount of it, but I need help narrowing my focus.

Thanks for the help in advance.

[Kirmizi]

I would start with the ignition switch, replace with a known good one and see if the headaches stop.

[beatnavy]

Thanks for the input.

Some update: I don't think my problem is so intermittent now. No crank at all now. Also:

Brand new battery
Cleaned all battery connections
Put new terminal clamp on positive wire
Cleaned all connections on solenoid
If I "jump" between two posts on the solenoid starter spins.

Bad solenoid and/or ignition switch?

Thanks.

[Kirmizi]

Do your gauge lights illuminate (oil pressure and alternator) when you rotate the key?
Are you getting voltage to the solenoid?
I have a '75, and I remember when the ignition switch started going out it presented the same problems you described.
One thing you can do to try and isolate the cause is remove the switch from the column, reconnect the plug and operate the switch with a screwdriver.
If everything works ok, my next guess would be to check to see if the mechanical portion is excessively worn.

[jess p]

My car is carbureted and a 71 with new batt, starter, etc. On occasion my car
does the same thing, however, when I put a charger to it for 10 minutes
then it starts and I have no problem for the rest of the day. I am going to
replace the starter switch soon. Many years ago an upgrade was suggested
to use a small starter relay. Have never done that route but until you get
it resolved I might suggest you carry a set of jumper cables and maybe
even a spare batt in the trunk to give yourself a jump when you need it
or until you can resolve this issue. Sometimes a few volts gets you that
reduced potential difference that you need.


1976 911S
1981 911SC
66 912 V8
66 912 type 4 project
67 912
71 914 2 L
73 914
95 vette
87 vette

[The cap'n]

When you put a jumper across the "posts" on the starter, it spins? How about between the starter battery post and the tab connector for the switch wire? The engine should crank. If not, you have a solenoid issue. A '71 uses a completely different ignition switch than a '75 (actually, '73+) While they fail, it's less common. First thing to check is voltage at the tab on on the starter (with the wire still connected). Get under there with a good volt meter and have someone turn the key to the start position. 11v+? No?, look at the connections in the relay board (position 6 on the 12 pin connector, position 1 on the 14 pin connector). 11v+ there? No? Move on to the ignition switch. 11+v going in ("30")? No? Go to the small wires on the battery positive connector. Check/fix them (there are 4 in 2 pairs). If yes at the switch "30" terminal, then check the "50" wire on the switch with the key in the start position. No? Bad switch.

You can start at either end of the circuit, but I prefer to start at the "user" and trace back to the power source.

Good luck! The Cap'n

[beatnavy]

Awesome, thanks Cap'n and all. Yes, when I jumped between solenoid posts the starter spins freely. My troubleshooting activities are on hold this weekend (visiting in-laws), but I will try this when I get back home. I'm going to go ahead and order an ignition switch for $8. I also have a '75 1.8L sitting in my garage now (next project) with a solenoid/starter that I know cranks. Not sure if it's the same starter, but if so I may swap out to test.

[beatnavy]

Again, thanks for everyone's help here. For those keeping score at home I swapped the known good starter I have from a 75 1.8L I'm going to start working on with the one in my 1.7L. Fired right up. I'm pretty sure it was a bad solenoid. Only challenge I had was the 1.7L upper starter bolt seemed to be put in backwards at one point. In the engine bay it was the head of a bolt, not a nut, which made removal and installation a little more of an adventure than it otherwise would have been.

Now I'm sure I've solved all problems on this 42 year old car and nothing will go wrong for another 20 years or so. Or not.

[GregAmy]

Originally Posted by beatnavy

If I "jump" between two posts on the solenoid starter spins...

Originally Posted by beatnavy

I'm pretty sure it was a bad solenoid.

Does not compute...but if it's working now, knock on wood!