Strange Starting Problems

I've got a starting problem neither I, nor my mechanic, can figure out. It's an '83 Datsun pickup, Z22, 4x4, 5-speed with 140K miles.
About 30% of the time, it just starts to kick over and then stops. I switch off immediately [previously having fried one starter by holding it a few seconds a number of times] and hit start again. I do this from 3 to 20 times [probably average 6 - 10 times] before it turns over and starts immediately.
It does this with a new battery [12.6 + volts cold] and even with two jumpers attached - so it is not battery power. It will turn over with the spark plugs out.
I have replaced the starter, ignition switch, cleaned all under-hood connections and added an additional negative-to-block cable.
What's up with this thing? Would appreciate any comments/suggestions.

 

Assuming all the parts are in good shape - The starter may need shimming to correctly position it relative to the flywheel. It may need moved out or the angle of it may be off slightly. Either can cause the bendix drive to bind in the flywheel teeth.

The next time you have the problem, try loosing the mounting bolts of the starter slightly. If it will spin the motor over, binding was likely the problem.

If it needs shimming, do that and tighten the mounting bolts. Either way don't leave the mounting bolts loose.

If it is turning over fine with the plugs out, try spinning it over with the plugs in and the coil wire removed. If it turns over fine then, it would be the timing = too far advanced = stuck advance.

Hope this helps,

Bob

 

Have you taken a compression test of all cylinders, when you had the plugs out ? Are they even ? reason I'm asking is in case of hydraulicing in cylinder(s) from, fuel, oil or coolant leaking in when engine stopped. Did plugs all look the same ?
Did you measure the throw of the starter drive, & compare it to depth from bellhousing face where starter mounts, to flywheel teeth, in case a shim or 2 may be needed? (too long a throw & binding) Also try a small shim in a spot where it will change the angle of the starter drive, to flywheel.
If you have run the engine, and shut it off, and immediately try to restart it, what happens? When it sits for a while and then try to restart, what happens? Have you tried a heavier gauge start cable & ground? Remember, you can hook 4 sets of booster cable up to your battery, but all the current still has to run down one cable to the starter, perhaps it's weak where you can't see. Perhaps these new/rebuilt starters draw more amps than the original did, thus requires a heavier gauge cable set-up?
Just some thoughts!

 

All good tips: Shimming, advance, compression - leaking into cylinder, heaver start cable, plug condition - none of which I have previously addressed.

Regarding when it "locks-up": There is no pattern; it can happen at any time under any situation.

As to shims, do washers between the starter and the bellhousing on the attaching bolts qualify if the throw is too long? If it is binding due to angle, it would seem that a shim to change the angle should be placed so as to pull the bendix drive away from the flywheel. Right? What could I use for a shim in that case since I believe that would place it inbetween the [2] attaching bolts?

Lastly, what would plug condition tell me for this problem?

 

Washers will work, but start thin and add if needed. As far as shims, perhaps some thin sheet metal, (aluminum, galvanized or just tin.) cut like a half/quarter circle kind of,and placed between starter & bellhousing so as to angle the drive gear of the starter, away from the flywheel slightly.
Remember, not too tight at first, just snug. Spark plugs, if any differences in way they burn. For example, I had a Caravan that was hard starting after running, then sitting for a few minutes then try to restart. It sounded like it was flooding. Pulled plugs next time this occured, as planned in the driveway, and found one plug soaked in fuel, thus indicating an injector leaking after shut-off. Replaced that injector, problem solved. If all your plugs look like they are burning basically clean & the same & normal, then you may be able to eliminate hydraulicing etc, provided your compression is fairly equal as well, and start looking elsewhere. See links below on what to look for.

( http://www.nightrider.com/biketech/spkplghnbook.htm )

( http://www.championsparkplugs.com/sp...Fouling&mfid=2 )

hope that helps some.

 

I did all kinds of shimming with no success. I looked at the ignition and saw that it was way advanced. Retarded it and although it ran rougher there was no "lock-up" of the starter! I set it at a middle point and it's been running better with no start problems. Thanks again for the tips.

What I don't understand is HOW the advance affects the starters ability to turn over the engine. Does the advance setting close the valves enough so that there is added compression?

 

If you advanced it too far, the the thing could fire so prematurely it try to send the engine in reverse direction. The starter itself really has nothing to do with it. It would be due to the firing off process.

Pre-detonation caused by this or carbon build up where the carbon lights up when the engine gets hot, can also try to halt an engine. But this occurs after the engine has already been running for a while, and would not be the story in your case. Just thought I'd mention that while we were on the subject of that locking up business.

 

Don't know how many people are aware of this for carbon buildup, but it's for real.

With the engine running at a fast idle and your hand on the carburetor throttle, pour water down the carb throat {about 8 to 12 oz. total depending on size of engine} fast enough so that the engine runs really rough but not enough for it to stall. Use the throttle to keep it running.

Does no damage but the combustion combined with the steam from the water blasts the carbon out.

If you have fuel injection, you're out of luck except taking it to a shop with an expensive machine to do the same thing.

Blast away.