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Dan
Dan, ASE Certified Technician
Category: Car
Satisfied Customers: 1307
Experience:  Dealer Auto Technician
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I have a 2008 Suzuki SX4. 2.0, automatic with 125k miles.

Customer Question

I have a 2008 Suzuki SX4. 2.0, automatic with 125k miles. The car will crank but not start. The only way the car will start is to disconnect the crankshaft sensor. It will start and run ok but will not go over 4ooo rpm's. Also the tach works every other time I start the car. Please help
Submitted: 5 months ago.
Category: Car
Expert:  rpmdiag replied 5 months ago.

Hi, I’m Ron and I can help you.
I have been in the auto repair business with my own shops since 1975 and also teach automotive repair. I am confident we can resolve your problem together. Please understand that I don't know your skill level. In most cases when you have a problem with the way the vehicle performs, specialized tooling is required to acquire computer data/information or engine testing results. We didn’t build these complicated vehicles; we just diagnose and fix them. Also understand that I can't see, smell, hear, or touch the vehicle either, so it may take a few replies to get to satisfactory results. I am also going to direct you with the fastest, easiest and most common things to check first. Please be patient and permit me to do what I do best.
I also try to give all of the information you may need, expecting a “positive rating” in return. I will also continue assisting you after you have rated me, if necessary. If there is any reason I cannot get a positive rating, please let me know why “in advance”, so I can go another direction for you. I am sorry you’re having this problem; I’ll help you through it.

Something is wrong with the timing of the reluctor wheel and the CRANK sensor, this is why it runs when you disconnect it, it is sending an incorrect signal to the computer when it's connected.

Thanks, Ron

Customer: replied 5 months ago.
The reluctor wheel is new.
Customer: replied 5 months ago.
Same issue with both reluctors
Expert:  rpmdiag replied 5 months ago.

Okay, then it's possible we have slipped timing belt/chain.

Either that, or the PCM can be bad, BUT I would run some tests with the scan tool at this point, running and KOEO.

Thanks again, and please don't forget to rate me and keep this link in case you need me again later on.

Ron

Customer: replied 5 months ago.
Timing chains are new, tried 3 different ECU's. This model only uses crank sensor for rpm's not timing.
Expert:  rpmdiag replied 5 months ago.

I've heard this complaint many times, and it's always been a timing issue. something has to have slipped out of time somewhere. Wish I was there to help you, we'd find it.

Thanks, Ron

Customer: replied 5 months ago.
I am confident the engine is in time. I cannot figure this out. i'm thinking I need a Suzuki tech.
Expert:  rpmdiag replied 5 months ago.

I'll opt out for you. Thanks, Ron

Expert:  Dan replied 5 months ago.

You need to plug everything in and clear the codes with a scan tool. Try to start it and see which code comes up. You need a scan tool to make sure you have cam to crank sensor correlation.

Customer: replied 5 months ago.
No codes come up confirmed or pending. Thats what's fustrating.
Expert:  Dan replied 5 months ago.

Do you have a scan tool capable of reading live data?

Customer: replied 5 months ago.
Expert:  Dan replied 5 months ago.

Check to see if you are getting an rpm signal on the scan tool while cranking engine.

Customer: replied 5 months ago.
sometimes. not always
Expert:  Dan replied 5 months ago.

Sounds like you may have an intermittent wiring issue. Check connectors at crank sensor and pcm look for corrosion. Look for any broken or pinched wiring. You may have to hook this up to an oscilloscope to find the problem.

Customer: replied 5 months ago.
I have ohmed out all wiring from crank and came sensors. I have even ran new wires from crank sensor to ecm. Terminals look good.
Expert:  Dan replied 5 months ago.

You need to look in the scan tool and see if you have a cam to crank sensor correlation, it should say yes or no.

Expert:  Dan replied 5 months ago.

If you can unplug one sensor and it runs, they are out of sync, the ecm will prevent the engine from starting. This is a safety feature in the ecm to prevent valve damage. if the timing is actually off.

Customer: replied 5 months ago.
I replaced the crankshaft in the engine. I reinstalled the reluctor wheel on new crankshaft. There is nothing to index the reluctor to crank. I read online at several places that it doesn't matter on this vehicle where its at. How would ecu know its out of time. Timing has been checked 3 times and is correct.
Customer: replied 5 months ago.
it will not run with cam sensor disconnected and crank connected.
Expert:  Dan replied 5 months ago.

it used pulse width to determine the crank position and compares it to cam pulse signal. if they are out of sync it will not start. I would double check that reluctor on the crank shaft. I would not listen to those sites, it definately has a key way and matters about the indexing.

Customer: replied 5 months ago.
It has no keyway or match marks. I called the shop that turned the crank and they verified. The reluctor is internal and engine must be removed to check. Engine must be pulled out to access the crank sensor as well. I agree with what you say if there were a way to correctly index the reluctor. Any other ideas?
Customer: replied 5 months ago.
if timing was off wouldnt it show a code for crank or cam sensor?
Expert:  Dan replied 5 months ago.

if you unplug ckp and it runs good, no misfires, then your mechanical valve timing should be ok, when you unplug the ckp the ecm uses a base timing value to fire the coils.

Customer: replied 5 months ago.
It runs fine but will not rev past 4k rpm's.
Expert:  Dan replied 5 months ago.

if you plug in ckp and engine stalls, the correlation in off, then your reluctors on the cam or crank are off.

Customer: replied 5 months ago.
Can I bypass it somwhow?
Expert:  Dan replied 5 months ago.

I don't think you can bypass, you need those ckp and cmp values in the ecm for it to run properly.

Customer: replied 5 months ago.
Well I'm stuck then. Don't know what to do.

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