2000 Chevy Tracker will not hot restart

Tracker runs perfectly, until it is shut off after a long highway run. Then it will not hot restart. Turns over fine, but no start. If you wait 20 min or so, it starts up and runs fine again. No error codes. It was due for new plugs and plug wires, so I replaced these. When it next stopped, I pulled a plug and put a spark tester on it. No spark. A bad coil pack was suggested to me, so I replaced both coils. No change. The crankshaft position sensor tested fine cold, but was just outside spec for resistance between the two terminals when hot, so I replaced it. No change. My understanding is that a camshaft position sensor if bad will not prevent the car from starting, it will just start slowly, but I will check spec on that sensor next. Any ideas? I’m thinking a fault in the computer

That sound like the problem you are having

Nope. I have a SOHC engine, and have replaced the drive belt recently as per maintenance schedules.

Possible, but unlikely. You seem to be on the right path so far in your diagnosis. I’d have guessed it was the crank position sensor. I expect your are correct that a faulty cam sensor wouldn’t prevent starting. One thing is certain, the engine won’t start if there’s no spark. A faulty ignition module is where I’d look next, especially check to make sure it is getting its power supply. Ignition modules can definitely be heat sensitive according to the reports we get here. You’ve checked for diagnostic codes, right?

I’m not exactly sure what you mean by “ignition module”. The 2000 Chevy Tracker 1.6L has two coils and signals from the powertrain control module fire them directly I believe. I have replaced both coils (and all 4 wires) as this was identified as a potential problem early on, but this had no effect.

I am currently checking out the camshaft position sensor. My manual has voltage input specs for the terminals of the sensor, and this checks out fine cold. I need to check out hot next, but that seems to me to perhaps be checking the output for the powertrain control module(main computer), not directly the camshaft sensor. . .

And yes, there are no error codes when plugged in and checked.

The car now will idle for about 15 min before it stalls out and needs to cool down for 15 or 20 before it will restart. I checked the input voltage for the camshaft position sensor when hot and the car would not start, and the voltage was within spec.

Does it abruptly stop (like spark problem) or does it act like its running out of gas?

As noted above, it stalls out, pretty much immediately, and when checked, there is no spark until it cools.

I’m taking your word that when this is occurring that there is no spark. Crank position sensor been checked?

As noted above, crank sensor checked, was outside specs, and replaced.

Sorry about that, missed it (all the talk of cam position sensor).

You are right from what I can tell. There’s no separate ignition module for this engine design. That circuit function must be part of the powertrain control module (engine computer).

So there’s no spark at any of the spark plugs when it is hot and won’t start? hmm … that’s a very big clue, means the no-hot-start is a problem somewhere in the ignition system, and not the fuel system. To get a spark you need

  • proper battery voltage
  • battery voltage getting to everywhere it needs to go in the computerized ignition system
  • computer properly senses engine rotation from crank position sensor signal
  • computer outputs “spark” command to the coil circuitry
  • coils produce the spark and it goes to the spark plug
  • engine is properly grounded to the chassis, which is properly grounded to battery negative

So there’s something wrong somewhere in that list. It might pay to take your tracker to a shop that has the Chevy scan tool. they can figure out what’s wrong, and from that diagnosis you can decide to replace the faulty part yourself if you like. They’ll have the test equipment needed to make a quick diagnosis. If you want to do the diagnosis yourself, start by making sure all the circuity involved with the crank sensor and the spark generation has proper power and ground. A faulty ground or a cracked fuse could cause something like this.

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Working my way through it. It has been to factory shop and there are no error codes and they replaced a bunch of stuff that had absolutely nothing to do with the problem and of course did not fix the problem. So a no go on the factory shop, as well as another pro shop that had no idea. . .

Whatever the problem is, it has to be related to heat buildup making a part fail. It doesn’t do it at all in the (Alaskan) winter, it takes a long highway run in spring to make it fail and need to cool for 15 - 20 min before it will restart, and with our unprecedented heat wave in Alaska right now, it was stall and not run until cooled if it idles for 10 - 15 min.

Here’s some ideas: Plastic electrical connectors change dimension w/temperature, and that could cause a break in a needed electrical pathway w/temperature. Rusted ground connections can change their resistance w/temperature. Fuses – especially if they have a small crack – can fail with temperature. Transistors – especially the power transistors ( presumably located on the PCM) that fire the coils – can fail w/temperature. Semiconductor sensors, resistors, and small pick-up coils can fail w/temperature. Alarm systems that shut-off the ignition system if a problem is detected can fail w/temperature. Batteries and alternators can fail w/temperature. Fuel pumps can fail w/temperature, but this doesn’t seem to be a fuel problem so far. Any aftermarket product connected to the electrical system should be considered a prime suspect.

A shop should be able to figure this out w/out much difficulty if they can test it while it won’t start and has no spark. That’s not the same thing as saying it will be easy to fix once diagnosed, but it is an important first step. A diy’er has access to a heat gun or hair dryer and ice cubes, so that’s a way to quickly modify the temperature of suspect components for testing purposes. There’s also a product that sprays extremely cold air from a can, often used in electronic labs to discover heat related component failures.

Thanks. There are no aftermarket products or accessories on this car and no alarms. All fuses appear clean and in good condition with no dirt or corrosion, and there is absolutely no corrosion on any connections that I have checked, they are very clean and shiny. I’ve checked most if not all of the plastic connectors in the ignition system, and all appear in good condition, tight, and with no corrosion or dirt contaminating them. I have added clean electrical grease to some to ensure good connections. It cannot be a fuel system problem as it is the spark that fails as tested and comes back when the engine cools. It also cannot be a battery problem, as the car turns over just fine when hot, it just will not fire and run. . .
Again, the only thing I am left with in my mind, is the actual Powertrain Control Module (main computer) which has something malfunctioning. This could also explain why it is not showing error codes as well I think. Unfortunately, so far I cannot find any new replacement PCMs anywhere in Alaska or the lower 48 states where I have looked so far.

It could be that replacing the PCM will fix the problem, but then again it might be something else. If I had this problem I want to do some more diagnosis before replacing the PCM. Without the manufacture’s scan tool it will probably be necessary for your shop to have access to a diagnostic tool such as this.

It’s priced reasonably, $23. (I have no experience w/this product btw, I have a conventional tube o-scope)

OK, got it figured out. After pro shops being stumped and not being able to figure it out, I read several shop manuals, and did more online research, and went through every test for every component in the engine control systems myself. Everything was within specs for all of the inputs and outputs of the PCM, so I went back and put old components back in the car that worked when cold and it turned out the camshaft position sensor which I replaced because it was just outside specs when hot tested, was bad new from the factory, as was the second one I got. Three new camshaft sensors later, the car runs perfectly again. Sheesh! Sometimes if ya want something done right, ya just have to do it yourself!

Thanks to everyone for all the suggestions!