JakeWard Posted January 28, 2017 Report Share Posted January 28, 2017 So first it's a 72 521 with a stock L16 32/36 and original distributor. Driving along just fine then it'll fall on it's face like it has no spark, let out a backfire, I pull over, and it keeps idling. Soon as I try to drive away, it does the same thing over and over. Anyone have something like this happen? I can't seem to replicate it on demand just inconveniently in traffic. Quote Link to comment
flatcat19 Posted January 28, 2017 Report Share Posted January 28, 2017 Since it's backfiring, you have fuel. Suck, squish, bang, blow. Quote Link to comment
sebpv Posted January 28, 2017 Report Share Posted January 28, 2017 check you spark plugs maybe. Check the gap and the current state Quote Link to comment
datzenmike Posted January 28, 2017 Report Share Posted January 28, 2017 So first it's a 72 521 with a stock L16 32/36 and original distributor. Driving along just fine then it'll fall on it's face like it has no spark, let out a backfire, I pull over, and it keeps idling. Soon as I try to drive away, it does the same thing over and over. Anyone have something like this happen? I can't seem to replicate it on demand just inconveniently in traffic. Backfire out the exhaust????????? Well you can get the same thing by turning the ignition off and then on again. The engine keeps turning pushing unburned gas and air into the exhaust. When spark is resumed all the gas in the pipe explodes. This tells me that you have an interruption of your ignition spark... could be badly worn points, any loose wire on the primary side of the coil or to the points. Start by checking every wire connection. A loose connection is hard to find, engine and driving vibration opens and closes the connection. Idle the engine and wiggle the wires. Backfire out the carburetor????????? This is almost always caused by an overly lean mixture. Remove the spark plugs and look at them. Lean mixtures will over heat the plugs and clean them, the porcelain will be very light in color or even extremely white . A proper mixture will be a tan color and a rich mixture will be very dark and even sooty black. Lean conditions can be from too small a jet or something clogging the jet. 2 Quote Link to comment
DanielC Posted January 28, 2017 Report Share Posted January 28, 2017 There is no filter on the fuel pick up pipe in the gas tank. Crud in the tank can collect around the pick up pipe, and clog it. When you slow down, or let the engine idle, there is not an much demand for fuel, and the crud can drift away from the pick up pipe. A quick check of this problem is to blow air back through the fuel line toward the gas tank, and see if the problem goes away temporary. Quote Link to comment
JakeWard Posted January 29, 2017 Author Report Share Posted January 29, 2017 I just swapped the fuel filter because it was cheap and had a bit of junk in it. There's a bit of fraying on one of the braided dealios inside the distributor. Related? I don't know https://flic.kr/p/R4qmdh Quote Link to comment
kelowg Posted January 29, 2017 Report Share Posted January 29, 2017 Well it sure as hell cant help. Clogged line/pickup and or loose connections most likely Quote Link to comment
tr8er Posted January 29, 2017 Report Share Posted January 29, 2017 Backfire out the carburetor????????? This is almost always caused by an overly lean mixture. Remove the spark plugs and look at them. Lean mixtures will over heat the plugs and clean them, the porcelain will be very light in color or even extremely white . A proper mixture will be a tan color and a rich mixture will be very dark and even sooty black. Lean conditions can be from too small a jet or something clogging the jet. My guess Quote Link to comment
datzenmike Posted January 29, 2017 Report Share Posted January 29, 2017 So Jake... backfire out the exhaust or the carb???? Help us narrow this down some. Quote Link to comment
JakeWard Posted January 29, 2017 Author Report Share Posted January 29, 2017 Backfiring out the exhaust. Quote Link to comment
datzenmike Posted January 29, 2017 Report Share Posted January 29, 2017 Then look at the primary side wiring of the distributor including the points, coil and ballast resistor. Make sure the distributor is securely grounded to the engine. Are the points in good condition and gaped about 0.022"? Quote Link to comment
Jersey Posted January 29, 2017 Report Share Posted January 29, 2017 I drove one of my 620s to the dump one day and it ran awesome. The next day I go to start it and nothing! It would turn over: But would not fire. It took me a while to figure it out, it was the wire inside the distributor that ran to the 2nd set of points, it had a very small nick in it and was grounding out against the inside of the distributor. I replaced it and it fired right up and ran great. Quote Link to comment
JakeWard Posted January 29, 2017 Author Report Share Posted January 29, 2017 Not to throw more parts at a problem, I have an incoming matchbox dizzy lined up from a trade but it's used and may not work (seems unlikely) I need to check the gap, and replace that frayed wire on the inside of the cap. Quote Link to comment
datzenmike Posted January 29, 2017 Report Share Posted January 29, 2017 Yes, start with the obvious (possible) causes first. Occam's razor...... the simplest explanation is usually the right one. Quote Link to comment
JakeWard Posted January 31, 2017 Author Report Share Posted January 31, 2017 So I was going to ask what to call that part, but randomly stumbled on it. Which ignition condenser is which? Or are they interchangeable? There's a JA500 and a JA503 Quote Link to comment
datzenmike Posted February 1, 2017 Report Share Posted February 1, 2017 I would imagine they are all pretty much the same. The condenser (also called a capacitor) reduces point arc when they open. Quote Link to comment
JakeWard Posted February 4, 2017 Author Report Share Posted February 4, 2017 Ended up with a matchbox dizzy in a trade. Tossing it on tomorrow if it's not dumping rain. Quote Link to comment
datzenmike Posted February 4, 2017 Report Share Posted February 4, 2017 In Cali.... it's only rain. You can run your stock coil IF you keep your ballast resistor. This will only convert to a pointless ignition. If you want the full effect of higher voltage you will need a one ohm 12 volt coil. Any '78 and up coil will do for this. If you try to use your points coil for this the matchbox will draw too much power through it and over heat and burn it up. A points coil is only able to handle less than 8 volts. This is why there is a ballast to drop the voltage. Quote Link to comment
JakeWard Posted February 4, 2017 Author Report Share Posted February 4, 2017 So just snag a duralast coil from Autozone? Or is the junkyard Nissan OEM better? Quote Link to comment
datzenmike Posted February 4, 2017 Report Share Posted February 4, 2017 Can't go wrong with a Nissan coil. They were designed for this. (likely cheaper too) ALWAYS trust the stock parts above any other when possible. Quote Link to comment
JakeWard Posted February 6, 2017 Author Report Share Posted February 6, 2017 Can you tell me what I did wrong here? Truck wouldn't start in the range that the timing plate allowed. Do I have the plate on upside down? Wrong pedestal? https://www.flickr.com/gp/78177498@N05/6d6562 https://www.flickr.com/gp/78177498@N05/YK930R Quote Link to comment
datzenmike Posted February 6, 2017 Report Share Posted February 6, 2017 Do you have spark at the coil???? If yes.... check the timing while turning the engine over with the starter. Quote Link to comment
JakeWard Posted February 6, 2017 Author Report Share Posted February 6, 2017 Oh it's started now. I took out both bolts in an attempt to mess with it until it started. I just have no way to secure it in its spot because both bolts can't go back in. Quote Link to comment
datzenmike Posted February 6, 2017 Report Share Posted February 6, 2017 It's OK this can be adjusted back into the adjustment range. Put that plate on the distributor properly so that both screws are holding it. Adjust roughly into the middle of the adjustment range. Set carefully to TDC using the timing scale and notch on the crank pulley and see where the rotor is pointing on the cap above it. Where is the closest plug wire?... clockwise or counter clockwise??? Determine if you need the rotor turned clockwise or counter clockwise to get the rotor under any of the plug wires on the cap. Lift the distributor out and look down, you probably will see this. (bottom picture) It's the top of the crank driven oil pump and distributor drive spindle. Take note of it's position. Unbolt the oil pump and lower it and the spindle (expect oil drips) turn and re-install it one tooth (clockwise or counter clockwise it's up to you) When the distributor is put back in it will have moved the rotor 9 degrees forward or back. Nine degrees closer to one of the plug wires. Just keep trying until the rotor is under a plug wire. Once you have it, this becomes the new No. 1 plug lead. The firing order is 1342 (counter clockwise) so if it needs changing, move all the plug wires around on the cap You should now be within the adjustment range on the distributor. 1 Quote Link to comment
JakeWard Posted March 22, 2017 Author Report Share Posted March 22, 2017 Ended up replacing the 2 condensers for 13 bucks, and away I went. Quote Link to comment
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