Does this point gap look right to you?

[ddezso]

I am clearly a novice mechanic. Within the past 6 months my veteran Z mechanic installed, balanced and synched new ZTherapy carbs, valve lash adjustment, timing, new points - the works - and it was running like a dream.

Recently the car has started having mild backfiring when I take it out of gear and the RPM's drop as I coast to a stop - or any time I rev it then release throttle quickly.

I went to the local car show (my mechanic friend is usually there) and since this is a symptom of misfiring we popped the distributor cap and the points were touching which I guess happens over time.

To make a long story longer I adjusted the points which is easy but it is not solving the problem. I've tried all sorts of gaps with no improvement. Plugs are fairly new, plug wires are pretty new, I checked the timing and the marks line up.

Please check out the picture and see if that tells you anything and please advise if you know other obvious things that I am missing.

Thanks..!

[Arne]

Don't worry about the points, it's not ignition related unless your spark is so weak that it's not completely igniting and burning the intake charge.

I'm geussing you have the emissions equipment on the car and hooked up? If so, some (or maybe all) of this may be fairly normal. The air pump and associated fittings are designed to inject fresh air (oxygen) into the hot exhaust to continue the combustion process and reduce unburnt fuel. When you back off and coast, or or release the throttle quickly (called "drop throttle" condition in emissions parlance) there is a quick burst of unburnt fuel as the carbs don't respond instantly. The mixture is rather rich for a split second. All that unburnt fuel is hot, add oxygen and the that extra fuel burns rather violently - it pops in the exhaust. I recall lots of early '70s cars doing that when I was young. And sure enough, my '71 does it as well.

Now if you don't have operating emissions gear on the car, I'd suspect an exhaust leak (allowing fresh air to be sucked into the exhaust), a slightly rich mixture, or a combination of the two.

[Mike]

Point gap looks kinda small. I also see pitting where the point seized together. You should replace the points. Get new ones at Napa or directly from Nissan. Don't buy cheap points. While you're at it, get a new distributor cap & rotor (from Nissan preferably).

I'm not saying this will fix your problem, but, I believe you should always start with a good set of points and a new cap/rotor. They are cheap (less than $20 for all). These things corrode and can become pitted causing resistance.

-- Mike

[brushie1320022]

It does sound like an exhaust sucking in the air...But what do I know...

[ddezso]

Don't worry about the points, it's not ignition related unless your spark is so weak that it's not completely igniting and burning the intake charge.

I'm geussing you have the emissions equipment on the car and hooked up? If so, some (or maybe all) of this may be fairly normal. The air pump and associated fittings are designed to inject fresh air (oxygen) into the hot exhaust to continue the combustion process and reduce unburnt fuel. When you back off and coast, or or release the throttle quickly (called "drop throttle" condition in emissions parlance) there is a quick burst of unburnt fuel as the carbs don't respond instantly. The mixture is rather rich for a split second. All that unburnt fuel is hot, add oxygen and the that extra fuel burns rather violently - it pops in the exhaust. I recall lots of early '70s cars doing that when I was young. And sure enough, my '71 does it as well.

Now if you don't have operating emissions gear on the car, I'd suspect an exhaust leak (allowing fresh air to be sucked into the exhaust), a slightly rich mixture, or a combination of the two.

Thanks Arne. The emissions equipment is not on the car and hooked up. I'll start with new points, cap, and rotor and go from there.

2 questions:

Where would you go to get the best possible parts for this, local dealership?

Also - I know there is supposed to be a wee bit of grease along the shaft that the point deal rides along - what type of grease do I use?

Thanks...

[sblake01]

1) Local Nissan dealership or somerwhere like http://nissanparts.cc

2) Dielectric grease.

[Victor Laury]

What are Points? Is that something from the stone age before Nissan EI?

[Arne]

What are Points? Is that something from the stone age before Nissan EI?

Nothing wrong with well maintained points for a daily driver, as long as you are willing to take care of them. (And I kinda LIKE fiddling with stuff like that. Takes me back to my youth.) While I do have a ZX ignition on the shelf in my garage, both of my cars are currently running quite well on original points-type ignitions.

Drove the red 240Z to work this morning - the points worked fine.

[Mike]

Points are horrible. They are always pitting and bouncing unevenly off the cam at high RPM. Similar to the covered wagon, they were a good idea at the time.

You can buy the whole get-up at Motorsport. FYI, they also sell a drop-in electronic pick up system that will replace the points. But, I'm not sure if you're at that stage just yet. Start with the new points and then work your way up the ladder later.

[Arne]

Points are horrible....

Well, I agree in principal, but maybe horrible is too strong. I totally agree that modern electronic ignitions are better than points in most every way. But I'm old enough to remember when points were all we had - so I had to learn to deal with them. And they will do the job.

Also consider that the modern ignitions aren't perfect either. I've heard lots of problems with Pertronix, tach issues with several kinds, and they are generally all-or-nothing. They either work or they don't, if you don't have spare parts you can't limp home with a dead EI. Ask beandip about what you do when your Nissan E12-80 module dies abruptly while cruising in 105 degree heat on I-5. And finally, one of the often touted advantages is steady and stable timing - which will not be the case if the distributor shaft bushings are worn, as is the case in many old Nissan dizzies these days.

I guess my main point in this thread (which I didn't express well) is that first, the ignition system is not likely to be the cause of the small pops in the exhaust; and second, you shouldn't worry about converting from points to EI until you are satisfied the car is tuned well with the points. Introducing a completely new system when you're trying to fix a problem is a sure way to get even more messed up.

[beandip]

Ask beandip about what you do when your Nissan E12-80 module dies abruptly while cruising in 105 degree heat on I-5. And finally, one of the often touted advantages is steady and stable timing - which will not be the case if the distributor shaft bushings are worn, as is the case in many old Nissan dizzies these days.

I ]

It was a fuel pump not the module. However in trying to figure what was wrong , I did change the module . I had just found one at the bone yard and it is so simple to change , I tried that. When this didn't fix the problem and I was about to have a heat stroke , we just had the Z put on a flat bed. Good ole Hagerty . the vary first mod I did on my Z was a ZX ignition . That was in 2000 and have never been sorry . Knock on wood ! Gary

[EScanlon]

That point gap looks to be about 1/8" of an inch on this monitor! LOL

Then again, since people are using their monitors for all sorts of :stupid: things, I did adjust the CONTRAST and they don't look scorched at all!

(It's amazing what you can do with the different controls on your monitor, you can even make BLACK look GRAY! Which means I'm going to have to be "VEWY VEWY CARE-FUL when I use it to match paint colors to send to my printer!!!)

J/K

E