521 backfiring

[jcard]

Sorry in advance for the long post

The last few times I ran my '72 521 it has acted a bit odd. Power was not quite there but wasn't as noticable at freeway speeds( the few times I've taken it on the freeway) as I could feel it more on surface streets. Today on my way into work it started occasionally to buck and then backfired violently ( tailpipe) 2 or 3 times; it was really loud. Since I've been running it nearly daily I have been using middle grade gas as it was pinging a bit under load/ going up a steep grade. I know I needed to look at the timing but I use it relatively little and 'have been meaning to 'get around to it'.

 

It's been some while since I've had to diagnose such a problem so I'd appreciate pointers.

 

The other thing that just started acting up is with normal fluid checks I noticed coolant was low, shortly after topping it off the temp gauge stopped working reliably. I mean it will work for a while then stop, then work for a while then stop.....I checked connectors and it seems ok. I bough a third gauge to install( you guessed it- temp ) to add to the tach and oil pressure gauge I installed earlier this year which have been working great.

 

Other things I noticed around the time that the engine was acting erractic was that the tach ( an electronic type) was swing wildly as if the pulse it was getting was scrambled - It is connected to one side of the coil.

 

So things I'll check:

are valve adjustment( although I'm sure I checked them not that long ago milage wise)

timing

breaker points

dizzy cap

dizzy rotor

sparkers ( although these are new NGKs with less than 1,000 miles )

fuel filter

 

Now I think the carb is running lean, the last time I changed the plugs the ceramic looked pretty light. Not sure how to check micture or if I should even try.

 

This truck has now 159k original miles and as I explained when made my first post my folks were the original owners. I've had some work done to it including new upholstry, carpet, made a mount for a good sound system( kept the OEM radio in dash) and had the brakes gone over.

I just got a new windsheild for the old girl and ( hope) i'm comitted to taking care of her... I don't even bring the engine speed over 4,000....

 

Help!

 

Thanks,

 

Jerry

[DanielC]

Go and do the tune up.  Nissan recommended checking the points every 3,000 miles, and replacing them at 12,000 miles.  Better yet, get a matchbox distributor.

 

A safe redline for a Datsun L-16 is around 7,000 RPM.  A yellow zone, 6,500 to 7,000.  Peak torque on a L-16 is about 3600.  that is around 55 in fourth gear.  The secondary on the carb probably will not even start to open below 2,500.

 

A Datsun engine L-engine is not your fathers Oldsmobile.  It need to, and likes to rev.

[Doctor510]

Check the point gap,  0.020" not pitted!  If pitted, replace and install a NEW condenser. 

[datzenmike]

To backfire out the exhaust you need unburned fuel and air.  One way is for the ignition to momentarily stop or shut off. The fuel and air is pumped out into the exhaust pipe. The ignition starts firing again and the lights this explosive mixture. All it takes is a loose wire or connection anywhere in the ignition system from the ignition switch through the coil and the points. Most likely the points are bad or loose. This will also upset the tach for certain. At 2,000 RPMs fit the ignition is interrupted for only 1/4 of a second all four cylinders would have fired once. That's a lot of gas and air.

[banzai510(hainz)]

ck points and or condensor, Best to get a Point conversion or a Matchbox distributor with the mount and timming playe assembly. (means the whole thing!!!)

 

also a worn out dist bushing will cause this making the carb pop. shaft will wiggle side to side enough to open the points prematurely

 

 

disconnect the tach in case this is cutting out the ignition.

I had 4 Datsun and never ran a tach. I seem to do fine

 

 

why would carb run lean all of the sudden?

 

 

If only the fuel gause is on/off then ck connection in back under the plate.

 

if is the gas and temp then its the volt reg on the dash panel

[datzenmike]

I bought a New Dodge Dart back in '70, it had dual points. When the tach started being slightly erratic, it was time to change them.

[banzai510(hainz)]

dual points are a pain. this will be more noticeable in 3rd gear. thats when the dual points work.

 

I always disconnected the 2nd set of points. thats the side with the smaller capacitor.

 

Get a electronic conversion or Matchbox. Best investment ever

[jcard]

Well new points already made a difference. I won't embarrass myself to describe what the old ones looked like. Eroded doesn't do them justice.

 

I am intrigued though regarding the sold state dizzy replacements. Saw a couple of adverts for these while browsing around for other Datsun 'things'

 

Never having removed one from a L16 engine are they doofus proof or can I get myself into trouble dismounting the dizzy or rather putting it back...?

 

Jerry

[datzenmike]

The distributor, when removed can only go back in, in the same rotor position. However there are several different models of dizzy where the rotor will still be in the same position but the body has been turned slightly so the cap and wires above the rotor have moved too. The best thing is if hunting for a distributor be sure to get the base pedestal... the part that bolts to the timing cover and the plate above it that you loosen and turn the dizzy to set the timing.

 

Often, people just undo the easy adjusting screw and leave the base and plate. Now your dizzy may not mate properly to your base. In other words get everything above the timing cover that it bolts to. Just undo the two 10mm bolts and lift it out..   

 

Be sure to get the matching EI coil. This coil can handle the increased current provided by the EI module and had far higher output than the points coil.

[banzai510(hainz)]

if you points are out again soon that means the wrong coil is in there.

Use the stock made spec coil and the ballast resistor.

 

On 521s most are dual points and the Pertronix kit will not fit.

You have to find a 68-69 Datsun L16 dist and the Pertronix will fit in the stock timming mount.

The later EI Nissan type you need the mount and sit together and a maching coil. Its EZ if you car savy. Most are not but these are EZ cars to work on

olddatsuns.com the tech section has a good write up.

 

 

find a local member that can help you.

I will help a local member if he has all the correct parts and ready to install. But most don't have money and spend it on Wheels and coil over kits only to breakdown again then sell car/truck for cheap

[Oregon_PLG222]

To add my experience to what Datsunmike said, I found that the electronic dizzy I was putting in my 70 521 and my 70 510 fit best at 180 degrees from the original that I pulled out. I just swapped the plug wires accordingly (rotated them around two spaces.)

 

There are some good posts on here about the wiring and other considerations. One post is something like "lose the points"