Wade Nelson

Car wouldn't restart the next day, cold. Not getting any spark. How would you diagnose the ignition module, lacking an oscilloscope? What would you start by checking?

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...

More information. The '91 MR2 has a digital fuel injection system but a very early one; it lacks OBD-2, so no codes are available. It also uses an early style Kamann (vortex) air flow meter rather than a more modern MAF - mass airflow sensor. It has an old-style distributor and ignitor, similar to the 280ZX, plug wires, etc. (Not the more modern coil-on-plug). Tip: It was running flawlessly prior to the no-start episode(s), and even AFTER the first one. What would that allow you to rule out as a cause?

How would you diagnose a failed crank angle sensor OTHER than by the expensive technique of "throwing parts at it?"

The fastest way to determine if it is a lack of fuel is to pull a hose off and add faux fuel (starting fluid). I gave it a big bolt of starting fluid and it still would not crank. No point in going to all the effort of checking the fuel pump or pressure given that it's LIKELY an ignition related problem.

There is no spark. Please proceed.

THIS CAR IS FIXED! Here's something they do on another auto repair site I frequent; one for professional technicians. An online quiz to help sharpen your diagnosis skills. I'll present a vehicle with a problem, and you suggest the course of diagnosis you would take. Keep it in mind --- THIS CAR IS FIXED! I know what's wrong with it! If you suggest a particular diagnostic step I'll tell you what you would or would NOT have gotten as results. Or I'll tell you that particular diagnostic step would not bring you closer to solving the problem. Anyone can chime in at any time and guess at the underlying problem. Ok, the vehicle is a 1991 Toyota MR-2. It's a no-start. That is, it cranks, but does not start. Background. Vehicle has been running perfectly and reliably for years. Two days ago I went to start it up in the grocery store parking lot and I had to crank it 4-5 times instead of the instantaneous starting I'm used to. After I got it home and went to restart it later, it would crank endlessly but not start. I had fueled it up that same morning, which may or may NOT be relevant. What would be your first step to diagnose this no-start? Battery is good, it cranks just fine, it just doesn't start. Good luck! What would be your first diagnostic step?

Between the "MAF" air/fuel measuring unit and the intake manifold (where the throttle butterfly is located) there's usually a connection for a PCV hose, a big 3/4" hose you can pull off and spritz starting fluid in there. Or you can simply loosen that "snorkel" and spritz in around the edges of it. Nothin' personal Andy, but you don't sound very mechanically inclined. From your post I really couldn't tell if you had a starting problem, a cranking problem, or both. Is now the right time to learn or should you find someone with a bit of diagnosis experience to help you out? I did most of my learning by watching others. Getting (often wrong or confusing) directions on the Internet and then trying to execute has GOT to be the hardest possible way to learn.

I recommend you start by DIAGNOSING why it won't start and run. Get a can of starting fluid or brake cleaner (anything flammable) and spritz some into the intake, or have someone else do so while you crank her over. If you can start and keep it running it's a fuel problem. If that doesn't help, then it's time to begin diagnosing an ignition problem, pull a plug wire and see if you have spark. If faux fuel doesn't help, AND you have spark, you might next pull a plug and make sure you have compression. Put your thumb over the hole or put a compression gauge on it. If it won't CRANK and your battery is known good try runing a wire from the battery to the starter solenoid input, in essence, hotwire the starter and see if it cranks. I'm wondering if you perhaps have a worn out ignition switch.

I run the Ad Blocker Plus extension to Chrome / Mozilla. I don't see 98% of all ads. I even create my own filters (child's play --- click the ABP icon, then highlight the offending item...) and block the other 2% on some sites.

Hmm from what little chemistry I remember I'm not sure I'd want to add salt to the mix. Any idea what benefit adding it has? I'd especially want to dip only the tips of the wires into the witch's brew so NONE Of the salt could wick its way up inside the insulation to start an entire NEW generation of corrosion. Perhaps substitute tin or zinc or some other "sacrificial" metal for the sodium chloride? What about using CLR instead of vinegar? I've had absolutely AMAZING results with CLR on rusted lawnmower parts, carbs, gas tanks, ... greatest stuff ever invented! Remember using "Navel Jelly" and a wire brush? My belly button is STILL sore!! W

Huntsville Alabama, off Brandywine Lane near Mt Gap Elementary school. Gray 280Z covered in bird poop and tree sap. Cracking paint / bondo. This one looks ready to become a parts donor.

I realize this is a zombie thread. Even so, were I to encounter this problem, first thing I'd do would be to disconnect the alternator entirely. Run strictly on battery. Rule the alternator in/out as the source of problems.

I'm going to CONCUR with Captain Obvious. Grounding needs to occur in a STAR or a TREE pattern, with the "trunk" of the tree connected to the battery minus post. If you went in and added ADDITIONAL grounds in the fashion you suggested, you would most likely create a "GROUND LOOP", that is a circular pathway whereby electrons could chose from multiple paths to get back to "ground." You want to avoid ground loops at all costs. Thats why all grounds are done in "star" or "tree" patterns, so there is one AND ONLY ONE path back to "ground." Ground loops make nice AM radios, both broadcast and receivers. They'll make your existing, in-dash radio whine. They'll cause EXQUISITE feedback in guitar amplifiers. They make the ECM misread sensors. There's very litte in terms of circuit malfunctions that a ground loop cannot cause. In THEORY, wires have no resistance. In reality a 1000' spool of 14 AWG wire has about 6 ohms. That's small, but significant. When you flow 100mA of current through 6 ohms you get .6V of voltage DROP. That's more than enough to make headlights dim, or make the ECM misread sensors, and consequently, inject the wrong amount of fuel. Give electrons TWO ways to get back to "ground" and you get a differential current, some flowing down one path, some flowing down another. And that's where all the fun begins. So what you want to do is clean up and FIX the original, factory grounding scheme on your vehilce rather than adding additional grounds. Sure, take out a 14 awg wire and replace it with a 12 or a 10 for a better, less resistance ground path. Clean up body grounds, add star washers. Take ring terminals and buff them with sandpaper or steel wool before snugging them down. There's a lot more to this than I can explain in a short blog post, but I've given you the basics. One (and only one) path to ground, clean connections, fat wires.

Grind the paint off, use a star washer, bolt it down tight, THEN hit the whole assembly with a little spray paint to prevent future corrosion. The contact points (ring terminal against washer, washer against body) need to be bare (shiny) metal to bare metal; simply relying on the threads of the screw to conduct adequate current (with minimal resistance) is inadequate IN MY EXPERIENCE, which is substantial.

If I had to guess what was wrong with your Z, BEFORE having read all this thread, I'd immediately suspect a grounding problem. I would make sure your ground from your battery to your chassis is good. And unbolt, clean your main engine ground as well. Your problem SEEMS to come when your body, touching the fender, grounds the EFI harness. That suggests the EFI harness is not correctly grounded, via either the chassis ground, or the ring terminals discussed in this thread. I cannot count how many times I've removed chassis grounds and found them bolted to paint. You take an angle grinder (wheel of death!) and remove the paint, add a star washer, THEN bolt them back down. Body shops are the absolute worst about this since the lowest paid flunky is the guy re-attaching all the taillamps, ground connections, etc. In my "X" years of auto electrical experience, "weird" behavior has almost INVARIABLY been caused by poor or non-existent grounding. So that's the place you start. My other #1 lesson is don't INSPECT grounds, disassemble and clean them. You really can't see what's underneath in most cases.

Sorry Cappy, but I think you're wrong. There's at least one ring terminal ground in the FI harness, at least on my ZX. Kinda hard to see in Mgood's pictures, it goes underneath the hold-down strap that holds the EFI harness stable (circled) Do you see it now? And my, my, my. What I wouldn't give to have an engine bay as clean and shiny as that! Wowzer! Wade

You might consider buying a parts car. If it runs AT ALL you could probably sell the engine/block to someone else. Then there are tons of zx doo-dads people desperately need. Of course you have to consider the added cost of the divorce if you start parting Z's out in the back yard.

Some guy out there transplanted a V-12 Jag motor into a Z car. I'd like to own that one. Short of that I'd like a really nice Z with a Chevy 350 transplant, tastefully done. A Z that hauls axx. Finished, running, not a work in progress. Prefer with working AC.

I bought one new in 1985 (black bumpers, wing) and drove it 18 years and 180,000 miles. Fantastic little car. Best cockpit design and seats ever. 27-31mpg and fun, fun, fun.

Salvage yard?

Huntsville Alabama, behind Taziki's Greek restaurant / Publix Grocery, Carl T. Jones and Whitesburg. Silver / Gun metal 240Z, metal flake paint, custom wheels, minor nick on front nose surface rusted. Overall a very good candidate for restoration, interior rough, door handle sitting in ashtray. Appears to be dd.

It might help if you understood how alternator lights work. When you turn the ignition on, there's 12V on one side of the bulb (battery voltage), and since there's nothing coming out of the alternator (yet), there's zero volts on the other side. So the bulb glows. Once you start the engine, there's 12V on both sides of the bulb, so it goes out. Now that's not 100% true. There's 13.8V or so coming out of the alternator, and since the alternator is tied directly to the battery (in most cases), the battery voltage ALSO rises to 13.8, so the lamp goes out. While your engine is running, if your alternator bulb glows dimly, that means you have a voltage DROP. Instead of having 13.8 on both sides of the bulb, you may have 13.8 on one side and 13.0 on the other side. Just enough to make it glow, dimly. So how did it get that way? You'll have to get a schematic, and see how voltage gets to both sides of the bulb. Does it come through the ignition switch on one side? If so, the contacts in the ignition switch may be corroded, worn, dirty. If the alternator light is mounted to a circuit board, the power/grounds to that circuit board may be corroded / weak. What you really need to do is a voltage drop TEST! Start by measuring the voltage across the battery terminals with the engine running. If the alternator's good, it should read 13.8 or thereabouts. Now, leave the black test lead on the battery terminal, and hook the red test lead to each side of your alternator light, in turn. Let's say one side reads 13.75 volts. That's "good enough!" Nothing wrong with THAT side. (A minor voltage drop of .05V isn't significant on a car this old) But the other side reads 12.5 volts. Something's wrong. YOu've got a voltage DROP on THAT side of the wiring. You've got to trace that wire back, through whatever switches, fuses, splices, relays, whatever path it takes all the way back to either the alternator or battery + terminal. Find the bad connection and repair it. Testing alternators on the vehicle is tricky. It's a lot easier to take them off, take them down to NAPA or Autozone or wherever and put them on their tester. Usually a diode fails, one out of three, so instead of a 60Amp alternator being CAPABLE of putting out 60A, it's only capable of putting out 40A. I don't know what kind of tester your guy used, but it obviously had a problem correctly testing a new alternator, on-car. In general, however, here's how I test vehicle elctrical systems. I start by checking battery voltage. 12.5-12.6 is 100% charged. Anything above 12.6 is just "surface charge" and can be ignored. A battery that is 12.3 is 50% discharged. Surprised? No, it's not 6V, but 12.3. Then I start the vehicle up. With my meter still on the battery the voltage should rise to at least 13.5 Volts, indicating the alternator is running. Then I turn on every power accessory the vehicle has, fans, AC, defroster, wipers, headlamps... The voltage should stay steady at 13.5 or so. If it drops, the alternator isn't putting out sufficient current. Time to get it checked. The first thing you should do on EVERY electrical repair is remove and clean the battery terminals, the main engine ground, chassis ground -- which you'll often find mounted on top of paint instead of shiny metal. Unless you have good power feeds and grounds, nothing else you do will produce clear results. Just inspecting them doesn't work. Too often there's corrosion where you can't see it and it'll stop a car dead, prevent it from charging properly, yada yada. Hope this helps.

What's missing here is an understanding of the purpose of a ballast resistor. Allow me to explain. When the vehicle is being cranked, the battery voltage may drop down as low as 9.6 volts. At that voltage the coil needs every bit of available voltage to make a "good enough" spark to start the engine. So typically the coil is wired directly to the starter, so when the starter is engaged, the coil gets full battery voltage. Scenario #2: You're motoring down the highway and the alternator is putting out 13.8V or so. The same coil that BARELY puts out a spark at 9.6V is now putting out 60,000V or more with an input of 13.8 V. Perhaps even higher, 100,000V. That's way more than your plugs NEED, and it's way more than the insulation on the plug wires, cap, etc. are designed for. So when you're NOT cranking, simply running, instead of running the coil directly off the battery, the juice for it comes THROUGH a ballast resistor, which will knock it down to 10V or so. This comes through the ignition switch, or any ignition-hot circuit, into the ballast resistor, and on to the coil. So you typically have TWO wires going to the coil, one from the starter circuit, and the other from the ballast resistor. So I had a coil fail on a Subaru, I went and bought some ginormous yellow mega-sparky coil, wired it in without a ballast resistor and what happened? It ran great. For awhile. I pulled the plugs out some 3000 miles later and the electrodes were nearly gone. Evaporated. MIA. The 100-200K volts that super coil was putting out simply obliterated them. My guess is if I'd put my hand anywhere NEAR any of the spark plug wires I'd have gotten a good jolt as well. So I went to the auto parts store and asked them for a generic (Ford) ballast resistor, and wired it in. No more evaporating electrodes! SOME coils have dual inputs, with an internal ballast resistor on one side. Or so I'm told, as I haven't run into one yet. Don't confuse + and - inputs with "dual +" inputs as are most common. The points in an older car switch the 12v ignition voltage to the coil on and off. Without a ballast resistor they'll be switching a lot more current, and wear out a lot faster --- basically plating one point over onto the other. Electronic ignition simply replaces points with a switching transistor. It won't last as long either if you're switching full voltage to a coil. Most electronic ignitions use a different coil, and, because they're electronic, they can automatically adjust the dwell (the % of time the coil is powered up) to produce a better spark at lower voltages and a less intense one at higher voltages. So you see coils, like the one in my 280ZX? 4-Runner?? , that is stamped "For electronic ignition" Hope this helps you understand what's going on and how to wire things correctly.

Carry a can of starting fluid with you. Next time it dies give it a spritz and see if it will start. First thing you've got to do is CONFIRM whether the problem is fuel or ignition related.