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Dr. Hamman
Dr. Hamman, Technician
Category: Classic Car
Satisfied Customers: 6286
Experience:  I have 30 years experience repairing, restoring, and customizing cars, and pickup trucks.
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Datsun 1983 720 pick up. 2.2 carburated. Z22 motor loses

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Datsun 1983 720 pick up. 2.2 carburated. Z22 motor loses power and stalls, sometimes. Other times wont quit. Always starts. Always idles from a cold start, but sometimes starts and idles for only 5 seconds, over and over after its warm. Wait an hour, might start and run fine and wont quit. Or might start and stall again. Idles very smoothly at 1000 rpm, nice running without hesitation. Drovel 9000 miles previous to problem with no problems.
Checked fuel pressure/filter/pump
Checked float level.
checked float 'bowl' for dirt, perfectly clean. sprayed a bit of carb cleaner in there for good measure.
Checked air filter
Changed worn cap and rotor, no change in symptoms
Plug wires are within spec for resistance
2 coil system, swapped coils, no chage in symptoms
changed plugs, gapped.
Checked for vacume leaks
Haven't visually checked condition of spark, but when it runs it runs great. Always starts.

Hi, I will do my best to assist you. When you are finished please click on accept. I don't get paid unless you do. I don't know if you are a pro or a novice so we may have to fine tune the answer. I only know as much about your problem as you have told me in your post, so my answer will be based on what you have posted. Feel free to add any additional info you feel is needed.

Ok, I carefully looked at everything you have done, and it looks like this problem has put you through the mill so to speak. There is one problem that these trucks had that matches your symptoms perfectly, and that is a failing ignition module. There is also another problem that comes to mind, and that is a bad electrical connection in the ignition system. So I would start off by meticulously checking, cleaning, and crimping the connectors in the ignition system until they make firm contact when they are plugged in. I also recommend soldering the crimp on connector to the wires they are connected to. This eliminates the possibility that there is a loss of connection in the crimp itself. I have seen this loss of connection in the crimp hundreds of times on vehicles, and this can be one of the most difficult problems to diagnose that you can run into. Soldering the crimp on connectors can be done without removing the connectors from the wires in most cases. The solder flows onto both the wire and the connector, and creates perfect continuity, regardless if the connection had conductivity issues before.

I would also hook a test light up to the positive side of the ignition coil. Set it up where you can see it while you run the engine. What we want to see is if the light goes out when the engine dies. If the light going out does coincide with the engine dying then the ignition is loosing power, and that would mean wiring or ignition switch failure. Odds are the ignition module will be the problem. If the module has the normal mode of failure it will quite possibly test as good, because internal heat is what triggers them to shut down when they fail. Good luck, and Thanks for using Just Answer.

I hope this helps, 100% satisfaction is my goal. If the answer is not clear, please reply and I will assist you more. When you're satisfied, click on accept. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.
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Customer: replied 7 years ago.

Hey Doc, still working on the Datsun 720 Truckl problem, just doing a bit more research on the ignition module. By the way I had already priced these out and found that the module is like 246.00 cheapest but an entire distributor, including module is only 136.00, although my professional mechanic friend reminded me of the old mechanic wisdom that new parts are often bad and not to get too discouraged if the first one doesnt work. Anyway, in my research I came across this post which has a very neat little piece of info at the end. Perhaps I'll try this little trick before purchasing the new unit. Enjoy.

'81 Datsun 200 SX which would sometimes start severely missing and running very poorly, almost undriveable. It never would do it when I could check it out, always out on the freeways, usually at highway speeds. It would clear up as quickly and it occurred, usually after about 30 seconds of running extremely rough.

Timing was ok, fuel pressure ok, new fuel injectors, new cap, rotor, wires and plugs. Both coils ok, new condensers, O2 sensor ok, no vacuum leaks, no leakage air, no temperature problems, no smoke, nothing apparently to trigger the problem. It would just be running perfectly down the road and suddenly out of the blue, start running ragged for a short time and then straighten out and run perfectly again. Sometimes for several months at a time.

Suspected computer, but could not be sure. Finally it did it once in the driveway. I immediately clamped a timing light on the secondary coil wires and found that the intake side plugs weren't firing. Traced it down to the ignition control module in the distributor which has 2 outputs, one output for each coil, and the output for the intake side coil was intermittent. Since the intake plugs are more important that the exhaust side plugs, when they would quit firing at high speed, the engine could hardly run. However the engine could idle perfectly on the exhaust plugs.

Since both plugs in each cylinder fire at the same time, I simply switched coil wires to allow the good side of the ignition module to control the intake plugs. It ran perfectly again with no intermittent problem as before. I went and ordered a new ignition module and kept the old one as a spare. The new module was $170.00. Copied from Bob Hewitts automotive repair page.

It is always tough to spend the money on a part when you are not sure. RockAuto parts had a close out sale on these for $43.99, I will include a link below. It was for the KEMPARTS Part # XXXXX they had others, but this one was on sale. Look under 1983 NISSAN 720 PICKUP 2.2L 2187cc L4 2BBL (M) [Z22] SOHC : Ignition : Ignition Control Module

Link Module sale