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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8578
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsubishi Galant ES: Why would the signal from the crankshaft

Customer Question

Why would the signal from the crankshaft position sensor make the fans engage but the car won't start ?
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.

Hi,

I'm not sure what you mean... the crank position sensor doesn't have any relationship with the fans at all.

It sounds like you've done a whole pile of repairs to this car...What exactly happened, from the beginning?

Customer: replied 1 year ago.
My son drove it home and hours later it wouldn't start and cranked slowly I assume the timing belt slipped. But also couldn't hear a fuel pump so I started there after that didn't change anything I read in my import book that the crankshaft position sensor controls fuel and spark so that's where I am not spark and relay on pump clicks off when it won't start
Customer: replied 1 year ago.
The fans come on when I turn the engine over with a ratchet like the signal is going to them
Expert:  Doug replied 1 year ago.

Thanks. That is correct with regard to the crank shaft sensor... it is step one for fuel (both injector pulse and pump operation) and spark.
The fan operation when you turn the engine by hand is a bit unusual, there really isn't any reason it should be doing that under normal circumstances.

You didn't put an aftermarket crank or cam sensor on this engine did you? They cause lots of weird electrical problems.

Also when turning by hand, you are feeling normal compression (heavy resistance about twice per turn) right?

Customer: replied 1 year ago.
Yeah compression seems to be fine,I have tried 3 different sensors with no change
Customer: replied 1 year ago.
Should I put the original sensor back on and see what happens?
Expert:  Doug replied 1 year ago.

If they were aftermarket sensors.... yes, put the genuine sensors back on for now. The aftermarket crank sensors are worse than 50/50 odds of working, and the aftermarket cam sensors are about 1 in 20 that work.... having aftermarket of either in there is going to make things more difficult to diagnose.

Get the original stuff in there for me and see what it does (in case anything has changed), and if not we will start fresh with some voltage checks etc.

Customer: replied 1 year ago.
Same result no change have put both senses back in turn mower with the ratchet and it does the same exact thing
Customer: replied 1 year ago.
Motor sorry
Expert:  Doug replied 1 year ago.

No problem.

With the original sensors in, please unplug the crank sensor and with the key on measure voltage between ground and each pin. You should have one pin with 5V and one pin with 12V.

Once confirmed, plug the sensor back in and back probe the 5V wire. In this state, rotate the engine slowly by hand and report the voltage behavior as you turn the engine slowly.

Customer: replied 1 year ago.
Ok with key on probing signal wire and rotating engine it reads 4.93 _ 0.38 and repeated over
Customer: replied 1 year ago.
pretty much 5-0
Expert:  Doug replied 1 year ago.

Great, that is what we wanted.

So lets go back and double check there is no spark while cranking, and then check the fuel injector pulse while cranking (a noid light is best).

Customer: replied 1 year ago.
How do I check the fuel injector pulse?
Expert:  Doug replied 1 year ago.

Unplug one of the injectors and connect preferably a noid light across the two connector pins, or in its absence a regular test light is OK for just a quick test. When you crank the engine, the light should flash.

Customer: replied 1 year ago.
No pulse from injector. There is a 12 volt constant when grounded from the battery
Customer: replied 1 year ago.
On one side
Expert:  Doug replied 1 year ago.

Thanks... and spark?

Customer: replied 1 year ago.
No spark, but it does read 12volt on one pin with key on
Expert:  Doug replied 1 year ago.

Thanks.

Nothing has happened to they key right? Do we have a second key we can try for comparison?

Nothing has changed with the computer either?

Customer: replied 1 year ago.
Just have the one key and as far as I know the computer never got touched
Customer: replied 1 year ago.
I know the relay and fuse were all checked and replaced a few
Expert:  Doug replied 1 year ago.

Thanks.

My concern here is that losing spark and fuel pulse is usually going to be either crank sensor or immobilizer related. If the computer and key have not had anything happen to them the immobilizer is rather unlikely though. It is starting to look like you will need a new crank sensor, just a Mitsubishi one.

Do you have access to a scan tool we can use to see what the computer is seeing for engine RPM while cranking?

Customer: replied 1 year ago.
The rev meter usually jumps a little while cranking but in this case nothing which makes me say crankshaft sensor but don't know
Expert:  Doug replied 1 year ago.

Yeah that is another decent indication too.

Just to be clear, of the different sensors you tried you never tried a Mitsubishi one right, just aftermarket?

Customer: replied 1 year ago.
Correct
Customer: replied 1 year ago.
K I'll go grab one
Customer: replied 1 year ago.
Could that be causing the weird fans issues?
Customer: replied 1 year ago.
Would a temperature sensor cause a no start?
Expert:  Doug replied 1 year ago.

I'm not real sure on that... I haven't seen that specifically before, that is somewhat unusual. There isn't any real connection between the two except the computer of course, which we don't want to really consider that until we're out of ideas.

The temp sensor would cause over fueling if it were reading out of spec, but it would not cause no spark.

Customer: replied 1 year ago.
The sensor I'm looking at has a Mitsubishi emblem on it but duralast box tho
Expert:  Doug replied 1 year ago.

Yeah that's the worst one.
You have to get them from a dealership.... all the aftermarket ones are chinese knock offs, they have the logo on them because they just cast molds from the original.

Customer: replied 1 year ago.
K I'll be back in a bit
Expert:  Doug replied 1 year ago.

ok

Customer: replied 1 year ago.
Why would the original sensor and the new sensor react in the same manner?
Customer: replied 1 year ago.
If it was malfunctioning?
Expert:  Doug replied 1 year ago.

Don't know... which is why I asked about if we had a scan tool to see what the computer was seeing.

Customer: replied 1 year ago.
I got the sensor and same result
Expert:  Doug replied 1 year ago.

Sorry for the delay, I was out on break.
With the sensor ruled out, the injectors and the coils both having 12V supply, and the sensor having 12V and 5V supply, I can't really see any place to go here other than an immobilizer related issue or ecu issue. Either of course would result in crank-no-start conditions. The immobilizer is most concerning here since you are losing both spark and injector pulse. The only things that can cause that under normal situations are the crank sensor failing or the immobilizer not detecting the key correctly. Granted the ecu could fail in that way, it would be rather unusual.
At this point it is going to be necessary to get this vehicle on a scan tool (preferably factory, but professional regardless) so that the engine data can be read while cranking to see if anything appears amiss there, and if on a factory scan tool check the immobilizer for faults and re-program (or attempt to anyway) the key to check for change in behavior afterward.

Customer: replied 1 year ago.
I have a mechanic coming by today and I'll let you know the results
Expert:  Doug replied 1 year ago.

Great, let me know.

Customer: replied 1 year ago.
We scanned the card and there was no code.
Expert:  Doug replied 1 year ago.

What about engine data? MAF reading, RPM reading, TPS reading etc? Reading codes doesn't really help at all. Was this a factory scan tool so we could check the immobilizer status?

Customer: replied 1 year ago.
Let me see
Expert:  Doug replied 1 year ago.

ok

Customer: replied 1 year ago.
Rpm is 125 and crank signal come on
Expert:  Doug replied 1 year ago.

It sounds like the mechanic you have looking at it doesn't really know what to look for. I would strongly recommend getting the vehicle to a professional shop that can do full analysis of what the computer is seeing, scoping the cam/crank signals to see if there is some abnormality being picked up, as well as examining the immobilizer status etc, and if nothing unusual is found then going over ALL inspections already done a second time.

Otherwise if we assume all inspection results are correct and "good" and all things I asked for that were not done were good, then we would have to expect an ecu issue. That is incredibly rare though... poor inspections are far more common than bad ecus.

Customer: replied 1 year ago.
Getting injector pulse now but still no spark
Expert:  Doug replied 1 year ago.

Injector pulse but no spark would be most likely to be wiring, fuse, coil(s), or ecu related.

Those are the only things that can stop spark that would not stop the fuel pulse too.

Customer: replied 1 year ago.
OK new info . I put a new crank sensor in and found a relay that I changed now it is getting fuel pulse and very little spark. But still not starting it pops out of the tail pipe like it tried but won't start could I be 180 out on the cam?
Expert:  Doug replied 1 year ago.

Hi,

Was a genuine Mitsubishi crank sensor used? It is less an issue on the crank sensors, but hall sensors in general Mitsubishi doesn't get along well with aftermarket.

I would double check your timing... there is no 180 off as long as the marks are lined up on the cam and crank, however you need to make sure that the crank gear and crank reluctor did not separate and lose position. The locating pins on the back have a tendency to come out if the crank pulley was real hard to remove.

Customer: replied 1 year ago.
I ordered it from Mitsubishi and how can I tell if it I separated?
Expert:  Doug replied 1 year ago.

That's good on the sensor then, one less variable to consider.

The crank gear usually has a dimple on the face of the tooth that aligns to the mark on the oil pump. This needs to be aligned to the notch in the reluctor plate.

If your crank gear does not have a dimple (aftermarket ones often are missing this), I'd need a photo to see if I can identify the orientation, or of course it could be removed and separated to see if the reluctor is misaligned on the pins.

Customer: replied 1 year ago.
Here is a photo
Expert:  Doug replied 1 year ago.

That looks OK. You're a hair off the timing mark (the mark on the oil pump should be dead centered between the two nibs on either side of the mark on the reluctor), but it shouldn't be an issue.

The roll pin is normally at 3 oclock and the woodruff key at 9 oclock (obscured by the bolt). If you rotated just enough to center that mark the roll pin would be at 9 oclock it looks like, so you should be good to go there.

This engine didn't break a timing belt before did it?

Customer: replied 1 year ago.
It didn't break but was missing 14 teeth in a row.
Customer: replied 1 year ago.
It was definitely slipped when I removed it because I tried to line marks up didn't work
Customer: replied 1 year ago.
It has very weak spark, would that cause a no start?
Expert:  Doug replied 1 year ago.

Thanks.

Before doing anything else, lets do a compression test. 14 teeth is enough to cause valve damage depending on the engine speed when it slipped.

On a four coil system like this there isn't any reason to have weak spark across all four; they share a fuse (which is good or bad only, it won't work partially) so no issue there and the trigger wouldn't likely cause any issue unless the crank sensor was sending a terribly erratic signal and of course that is new. Any other weak spark issue would be all four coils dying at one time which would be impossible odds. They rarely fail to begin with, let alone more than one and all at once. More likely the spark just looks weak because it is turning at ~250 rpm while cranking and system voltage is in the 10-11 V range since the starter is operating. I think pursuing this weak spark theory is not the right course of action.

Lets get a compression test done and see where we stand with internal health.

Customer: replied 1 year ago.
OK I'll do it when I get off work
Expert:  Doug replied 1 year ago.

Sounds good, let me know what you find.

Customer: replied 1 year ago.
No compression on any of the cylinders.
Expert:  Doug replied 1 year ago.

Thanks, ***** ***** explains it.
At this point you can be pretty certain that you bent valves having the timing belt slipped 14 teeth. The only direction going forward from here will be to pull the head and have a machine shop inspect/repair the head as needed. With zero compression you can be certain that more than half the valves are damaged and there is possibility for guide damage as well. Whether you want to have that head repaired or try to source a remanufactured head would be your call at that point.

Expert:  Doug replied 1 year ago.

Please let me know if you need any more help with this or if we can close this ticket out.
Thanks.

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