83 Cold Start Issues

[Classic83owner]

Hi everyone, I'm new to this site and I'd like to ask if anyone has a flow chart for diagnosing a cold start problem. The FSM and Chilton's both tell you how to test the cold start injector and all that but nowhere can I find a diagnostic flow chart. I've even looked through ALLDATA at work and all it gives you is specific tests. I really hate the idea of hit-and-miss diagnostics.

The car will start right up but will only idle until it warms up. You can play with the accelerator and get it to rev but it cuts out and misses really bad. What also seems strange is even though I know the cold start injector is not working, I can smell rich exhaust. Runs great when fully warmed up but you can smell it's running rich even then. I do know the cold start injector is good. I bought the car without a motor and now it's all together I.m trying to work out all the bugs. Any help ya'll can give me would be greatly appreciated.

[Zed Head]

You said that it starts cold but will only idle until warm. So "cold start" doesn't seem to be the problem. Cold running is the problem. The cold start injector only operates when the key is turned to Start.

Add more details. Did you install an 83 engine? Did you re-install all of the hardware, including emissions equipment or did you leave some things off? Are you using all 1983 intake, exhaust, AFM, etc. or did you use parts from the new engine?

By 1983 Nissan had a lot of things interconnected for emissions and mileage. If one thing doesn't work right, sometimes it affects other things also.

[Classic83owner]

Quite right you are about the problem. That's why I used the word "issues" as it only has problems when cold. DETAILS: 79 block and head, AFM year is unknown but it came from the same person I got the engine from but he has several Z's so who knows? It does test out good and works normal from what I can tell all else is factory equipment. Cylinder head temp sensor relocated to the thermostat housing. The only things I done away with is the EGR and I bypassed the TVV as it was broken. Neither of these should cause the problem at hand. As I said, it seems strange that it seems to run rich at all times. I forgot to mention that the "sensor" light is on which I understand to be for the 02 sensor so that could be a major factor on this car. I'm a mechanic by trade but I don't know nothing about these cars or the antique systems they use. I specialize in steering and suspension anyway.

I believe I probably have some loose electrical connections, etc. I did have to fix a rats nest of wiring inside the passenger front fender where the horn relay is. I could have more issues like this else where. (Luckily the wires were chewed through away from the connectors so it was a simple fix with some wire, solder, and shring tubing.) So all said and done, I'm trying to find a flow chart for diagnosing the cold running problem and I guess I could use any advise on the "sensor" light even though I haven't even looked for information on fixing that bug yet. I really hate the idea of hit and miss diagnosis. Now days I can go on ALLDATA and find flow charts for problems like these but I guess they didn't think of that back then.

[Zed Head]

Even in 1983 the system was still primitive. An earlier FSM might be helpful, like 81. The later FSMs seem to be written for use with an electronic tester which nobody has anymore, if they ever had one to begin with.

The ZX EFI systems are more complicated than the early Z's. You might start another thread with a more descriptive title. Cold start issues are boring, and that's not your problem anyway.

[Wade Nelson]

I've never seen a flow chart for diagnosing a cold running problem, sorry.

Why don't we start with a few basics, do a little DIAGNOSIS work and see where it leads you.

First thing is to determine if it's running lean or rich when it's cold. Either one could cause it not to rev.

I'd do that by adding faux fuel --- starting fluid, brake cleaner spray, any flammable aerosol fluid. If you have a helper rev it up while you spritz it with loads of starting fluid, and it revs easily, you know you're running lean, very lean.

If that were the case, the first thing I'd check would be the coolant temperature circuit, which TELLS the ECM that it's a cold start, and causes it to greatly enrich the mixture, sometimes 200% or more for the first 30 seconds, and then maybe 150% until it hits a certain temperature.

There should be a spec showing you what the resistance of that sensor is at different temperatures in the FSM. You could check it AT the sensor, inspect the wiring, and perhaps check it @ the ECM pins to make sure the signal got there correctly.

Since you've had an engine swap, when I hear that a sensor isn't reading correctly, my FIRST thought is that the engine and/or body grounding strap is missing, so the ECM is working off a different "ground" than the sensor is. Result: Incorrect readings.

You say you KNOW the colad start injector is not working? How do you KNOW that? How did you test it?

On the earlier Z's the CSI only injects while cranking, but who knows on later Z's. Maybe it's used for enrichment as well. Any reason not to fix or replace it?

You can smell rich exhaust. That can't be a good sign on a 1983, as I would ASSUME you have a catalytic converter which should all but eliminate any fuel smells and/or black smoke exhaust. If it hasn't been melted by a rich mixture by now, well perhaps you removed itg.

Some of the AFM's -- air fuel meters --- have an air temperature sensor in them as well, used by the ECM to adjust the mixture. I seem to recall there was a major CHANGE in this feature in the later models, as the Kent-Moore EFI tester warned you could destroy the AFM by hooking it up to the wrong model.

So you need to obtain a matching AFM for the ECM you are using, and/or get schematics for both the donor car and yours and compare the wiring. I believe, I seem to recall, there was a PIN change on the later AFM's.

Welcome to the nightmarish hell of engine swap incompatibilities...

[Classic83owner]

Thanks to everyone who's been following this thread. Although I didn't get exactly what I wanted I did get a lot of useful information. (I'd like a million dollars too but oh well). Just to answer some questions and clear up other points.... I know the CSI is good cause I tested all the injectors during the intake swap from 79 to factory 83. I've connected a DVOM to the CSI connector and get nothing during cranking or start-up. I've got a 3-2-1 header with 02 sensor mounted at the collector and no cat.

I've come to the conclusion that even though I hate the idea of hit and miss diagnostics, I'm just gonna have to break out the electrical diagrams and start testing everything. On the bright side, I did find a "inspection procedure foe EFI" that I had overlooked in the FSM which should be a good place to start.

Again thanks everyone. I'll keep you posted on progress when I get time to work on it.