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PostPosted: Wed Sep 05, 2018 9:02 pm 
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I have a 1979, gas powered, Datsun pickup. Just had it completely rewired, and the carburetor jets, etc were cleaned about 6 months ago. Fuel filter is not clogged and elec fuel pump works. The timing chain, chain tensioner, rings and valves were replaced 3 years ago, with only 2,000 miles driven since. The distributor cap looks OK and the coil is only a few weeks old. The points are a bit pitted, and the spark from the coil looks yellow, not blue in daylight. However, the truck ran fine, until I hit a 2' deep pothole in the road at about 15mph, and it simply died.

Will not start, and it backfires during the starting procedure. What could be causing this problem? I thought that the distributor or points might have shaken loose and moved, but all screws seemed tight. Chain tensioner loosened and chain tooth slipped? Possible, but no wierd sounds from the timing chain. I have heard that a "vacuum leak" could be the problem, makes sense given the shock of the impact, but where to look? Could a hole in the exhaust pipe cause such a problem? Please help.


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PostPosted: Thu Sep 06, 2018 11:27 am 
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Joined: Wed Jun 01, 2011 1:43 pm
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Location: Mornington Peninsula
If I had to guess it sounds like a vacuum issue, check the hoses from the block, intake manifold etc... Could be the intake or exhaust manifold is loose too. Hole in the exhaust down the end shouldn't cause the issue you describe so I'd suggest the problem is under the hood


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PostPosted: Thu Sep 06, 2018 12:39 pm 
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Thanks mate, will do.

G2L


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PostPosted: Thu Sep 06, 2018 9:18 pm 
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Did the car die as soon as you hit the pot hole, or a little after?
First place I’d be looking would be for a spark issue.
Maybe look to see the distributor rotor hasn’t come loose and slipped on the dizzy shaft?
Also be sure the dizzy is turning when you crank the engine.


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PostPosted: Fri Sep 07, 2018 12:43 pm 
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Coz22a wrote:
Did the car die as soon as you hit the pot hole, or a little after?
First place I’d be looking would be for a spark issue.
Maybe look to see the distributor rotor hasn’t come loose and slipped on the dizzy shaft?
Also be sure the dizzy is turning when you crank the engine.


It seemed to die immediately. Can't see how it could be a spark plug issue as truck ran perfectly seconds earlier. As noted in earlier post, all related screws etc. were tight, but will check dizzy rotation anyway. Thanks for the tip.

Checked the wires: seemed to be tight and were fine minutes earlier. Rotor was tight, hard to get it off. Am replacing the pitted points today, just on GP, but don't think that fact will change the situation much.

Thanks for your input,

G2L


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PostPosted: Fri Sep 07, 2018 1:14 pm 
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Hatchman wrote:
If I had to guess it sounds like a vacuum issue, check the hoses from the block, intake manifold etc... Could be the intake or exhaust manifold is loose too. Hole in the exhaust down the end shouldn't cause the issue you describe so I'd suggest the problem is under the hood


Here is a thought. If I have a vacuum leak and cannot find it, will adjusting the mixture at the carb to make it richer solve the immediate problem and get the truck running again?

It is stuck out on a country road, and I am afraid it will get vandalized if I leave it where it is for long. Need to get it closer and get somebody who really knows his or her stuff to look at it, if I can't solve the problem myself.


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PostPosted: Fri Sep 07, 2018 6:20 pm 
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Location: Zombie-free unfluoridated town in QLD
does the engine spin or turn over with starter with no noises?


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PostPosted: Fri Sep 07, 2018 10:36 pm 
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If the car died immediately, it sounds electrical / spark related.
I say that because if it were fuel, I would expect the car to run for another 20 or 30 seconds or so on the fuel that’s in the carby float bowl/s then the car slowly die as it runs out of juice.
After hitting a 60cm deep pothole, it could have jolted the car enough so that a wire has come loose or maybe earthed out, preventing the spark from being made.
Take a Mate, pull a plug lead off and make sure you have spark.
If you have spark, spray some ‘start you bastard’ down the carby and see if it will start.
Good luck.


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PostPosted: Sun Sep 09, 2018 11:16 pm 
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Thanks folks for your help.

Trying to make a bit more sense than an episode from the Twilight Zone, let me report the following:

As mentioned earlier, the only item that I could find amiss were my points, which were somewhat pitted. Though I was sure that this could not be the root of the problem, I decided to replace them anyway. Did not bother to reset them as when the engine died, they were completely closed, so I simply put them back in exactly, or very darn close, to their original position.

Before reinstalling the points, however, I noticed that the PARKING LIGHTS were on. That was very strange, because I had left the truck overnight with all lights off, the ignition key completely turned off, and the key pulled completely out of the ignition switch. Not knowing how the parking lights could possibly be on the next morning, with the key out, and suspecting some kind of short, I pulled the fuse which governed the parking lights, and, as expected, they went off.

After a few minutes, I put the fuse back in, just to see what might happen, and, inexplicably, the parking lights STAYED OFF. I had (and have) no idea how this could be possible, but not wanting to risk any type of electrical complication, I pulled the parking light fuse once again.

After that, I cleaned up the dizzy cap and rotor, both of which were a bit greasy and worn, then installed my new points in the same position that the old ones were in. I cranked the ignition switch, and "viola" the truck started.

I drove it home and today, reinstalled the fuse, installed a new brake light and started her up. No problem whatsoever, all lights working, and the truck starting with no problem as long as all of the lights were turned off. It did refuse to start immediately when turning on the high beams, however, so there still maybe some kind of electrical issue going on. Again, however, both the battery and coil are only a few weeks old.

Important to note is that, I only gave a cursory glance to my spark plug wires when originally trouble shooting the problem because I assumed that when I had the truck "completely rewired" a few weeks ago, that the electrician had changed the spark plug wires as well. Today, however, I found that this was not the case and that the number one plug cover was cracked and brittle. Perhaps hitting the bump caused it to lose enough conductivity to let the spark escape and stall the truck, and that was the original cause of the stall? Still doesn't explain the parking lights being on with the key off, however.

In any case, I taped up the cracked wire and the truck is running well again. Will replace the wires, dizzy cap and rotor as soon as I can find the parts.

Does anyone have a rational explanation for any of the above?

At least she is running again now, so thanks to all of you, for your input.

Best,

G2L


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