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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8607
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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2004 Montero Sport LS runs fine, now 3 times after parking

Customer Question

2004 Montero Sport LS runs fine, now 3 times after parking and let it sit, it will not restart. Engine cranks, fires off for a few revolutions, then dies. Will crank, but not fire again. Let it sit a couple of days and it will start fine. Fuel filter and fuel pump relay have been replaced. Same symptoms with transmission in neutral. Tried spare ignition key that was rarely used to no avail. 165000 miles, the timing belt was changed at 90000. All other vehicle electrical functions normally, vehicle has the problem currently.
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.


I am assuming that this problem has been ongoing long enough to rule out a bad tank of fuel or water in the otherwise there are really only a few possible expectations here given your symptoms.

The first thing I would want to do is make sure the Service Engine Soon light is working when the problem is occurring. The light needs to do a bulb test at key-on to indicate the computer is powering up... no bulb test, the computer is not powering up and the engine will not run. Then to that end the MFI relay and PCM itself would be your only suspects.

If the light is working as it most likely is, then you would be down to expecting either a crank sensor failure (highly likely), fuel pump or regulator failure (moderately likely), immobilizer issue (moderately likely) or cam sensor failure (not too likely).

From this point you would want to check for spark immediately after the problem occurs. If there is no spark on any coil immediately after the problem occurs, then a crank sensor failure is most likely. When these go bad they give intermittent dead periods and are notable for killing the spark and fuel pump operation. If there is spark but only on one coil or two coils, then we would suspect a cam sensor failure or PTU (power transistor unit... "ignition module" it is sometimes called).

If there is spark immediately after the problem occurs, then we would suspect an immobilizer issue or a fuel pressure issue (be it pump or regulator on the rail related). From here you would want to unplug one or more injectors and use a noid light to see if the PCM is pulsing the injectors on. If it is not, then it is an immobilizer issue nearly without exception and would require a dealer visit to analyze as the immobilizer diagnosis is only possible with a factory scan tool. If there is injector pulse and you have spark on all three coils then you would only suspect a fuel delivery issue at that point, and would want to check fuel pump operation while cranking as well as pressure built; if it works but the pressure is low, then the return line would want to be blocked to see if it returns to normal range; if it does, the regulator is bad and if it doesn't the pump is bad.

Customer: replied 1 year ago.
Engine started normally and runs fine after sitting just 2 hrs this time. If driven daily, we have not had an issue. It only rears up after sitting a couple of days. 2-3 tanks of fuel have been put through it since the first problem 4 weeks ago. The SES light does not come on when starting normally or otherwise. It does have spark briefly or so it seems as the engine fires/runs for 2-3 seconds and dies on the first try when the problem develops. After it dies, it may or may not fire again until after sitting for a 10-15 minutes and then fire/run and die again. It does not fire again until it sits awhile, then it starts right up. It does not stall or run rough in traffic after it starts. I will continue to monitor and check when next issue develops. thx.
Expert:  Doug replied 1 year ago.

You want to make sure that the engine light does turn on.... if the bulb is burnt out of course it is no indication for us, however in normal operation it should bulb test for about 4 seconds whenever you turn the key on from off/resting. If it is not doing this ever, then the bulb is likely burnt out. If it is only not coming on when the problem is present, then that would indicate a PCM or MFI relay issue most likely.

If the engine runs for 2-3 seconds then stalls, this is further indication of an immobilizer issue... the injectors do a batch fire at the crank signal which is enough to run for a second or two then shut off (abruptly, not like a struggling stall) when the injectors are not operating.
Knowing that you are having this behavior, then I would immediately check the spark (again only immediately after the problem is present.... this is NOT a valid check after 10-20 attempted/failed starts as there are conditions where it kills the spark after a certain period of failed starts), and immediately check for injector pulse. Determine if you have one only (if there is spark but no injector pulse) indicating immobilizer related issue or neither present (indicating likely crank sensor problem).