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Chris (aka-Moose)
Chris (aka-Moose), Technician
Category: Car
Satisfied Customers: 894
Experience:  16 years of experience
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2005 hyundai sonata: driving down..checked timing belt..wont start

Customer Question

i have a 2005 hyundai sonata witha 2.4 liter engine was driving down the road and the car just died. checked timing belt its ok, checked fuel pump it seemed weak so i replaced it not it still wont start can spray with starting fluid and it will run any suggestions?
Submitted: 4 years ago.
Category: Car
Expert:  Auto Go replied 4 years ago.
we need to check to see if the car has injector pulse and if it does we need to check power to the fuel pump. have you checked the fuel pressure and verified it to be low? if so what was your pressure reading?

do you have any noid lights for checking injector pulse?
Customer: replied 4 years ago.
i dont have to check actual fuel psi, nor do i have a set of noid lights but i can get some. also i noticed that the fuel gauge isnt working either. power to the fuel pump isnt a problem its running.
Expert:  Auto Go replied 4 years ago.
if the pump is running we need to check the injector pulse. since it will run on spray, that means spark is good, timing is good, and compression is sufficient to run the engine. you say the pump is running so I will ASSUME fuel pressure is ok (even though we should NEVER ASSUME ANYTHING!!!!!)

if you can get ahold of those noid lights I would. you could use a test light i suppose, but it's dangerous and you could damage the drivers in the computer.

one thing you can do it test for power at an injector. with the key on, one wire should have power all the time. the other wire the PCM pulses to ground to turn on and off the injector. do you have power?
Customer: replied 4 years ago.
yes i have checked power to the injectors before i replaced the fuel pump it had like 9.5v. i dont know exactly what kind of voltage it needs to pulse the injectors.
Expert:  Auto Go replied 4 years ago.
ok. it should be the same as battery voltage. I'd assume the battery voltage is a bit low as I'm sure you've been cranking the starter. that's ok. as long as it will still crank.

it seems like there is no injector pulse. ill do some research real quick and see if I can find a solution. it's difficult because you do have spark, just no injector pulse. if you had neither spark nor injector pulse it would be easier. ill post back as soon as I have more info.
Customer: replied 4 years ago.
ok, it will be tommorrow before i can get ahold of the noid lights but i will check it. if its like a ford i know it needs 12v to pulse the injectors.
Expert:  Auto Go replied 4 years ago.
as long as the voltage on the injectors matches the battery volts you should be ok. you can try putting a battery charger on it to boost the voltage but I don't think it will help
Expert:  Auto Go replied 4 years ago.
also monitor the voltage on the middle black wire of the cam position sensor. this is about the only thing other than a computer malfunction that can keep the injectors from firing only and not kill spark. it should switch from 0 to 5 volts as the engine is cranked. a regular volt meter may not be fast enough to accurately show the voltage change and a lab scope may be required. what I would expect to see is possibly 2.5 volts on a voltmeter (a volt meter reads averages and the average of 0 and 5 is 2.5. you can turn the engine over by hand and look for the voltage to change. If you have turned the crank 3 times and the voltage stays at either 5 or 0, then the cam sensor is bad. I'm really leaning in that direction. the cam sensor is located in the end of the cyliner head above the transmisson.

give this a try and let me know
Customer: replied 4 years ago.
Checked injectors for noid have nothing, checked cam sensor have nothing, power and ground good replaced sensor car still has no noid.
Expert:  Auto Go replied 4 years ago.
did your cam sensor signal straighten out when you replaced it?
Customer: replied 4 years ago.
nope it did the exact same as it did with the old sensor. could the crank sensor cause this problem
Expert:  Auto Go replied 4 years ago.
if the crank sensor was dead u would have no spark either. im researchung
Customer: replied 4 years ago.
so what else do you think it could be? I have a feeling that something is going wrong with the pcm
Expert:  Auto Go replied 4 years ago.
we need to find out why we dont' have a signal on the cam sensor. the PCM uses the cam sensor for injector sync. It uses the crank sensor to determine the position of the crank for spark. the PCM knows where the crank is using the crank sensor and will fire the plugs on both the compression and exhaust stroke. however, it only wants to fire the injectors on the the intake stroke, not the power stroke and if it can't determine what stroke the piston is on (uses the cam sensor for this) it dosen't know when to fire the injector. that is the problem we have.

technically you need to have a lab scope to test the CMP (cam sensor) but I doubt one is available to you.

I'm sorry Ive been slow to respond, I've been having internet issues and have been responding through my cell phone,but I'm up and running so now I can really work on the problem. give me a bit I'll be back.
Expert:  Auto Go replied 4 years ago.
ok do this. unplug the cam sensor. turn the key on. one wire should have battery voltage. one wire should have 5 volts. the 3rd wire should be ground. make sure you have all 3 of these items. let me know.
Customer: replied 4 years ago.
already checked that one has 12v the other has like 4.75v and the third is ground
Expert:  Auto Go replied 4 years ago.
ok. when you plug the connector back in, back probe the wire that had the 5 volts or 4.75 on it. key on what do you get. if it's 0, or 5 volts or there abouts and it never changes as you manually rotate the engine and you already replaced the sensor, then there is a problem with the camshaft reluctor wheel such as the cam is broken off at the end or whatever the sensor picks up that is attached to the camshaft has broken or fallen off. that's the only plausable solution.

check the sensor as I have stated. I know you already did this, but we have to be absolutely sure. it makes no sense that there is no signal on the middle wire of the CMP if all 3 wires check out with it unplugged. It almost has to have an alternating 0 to 5 volt signal on the middle wire as you rotate the engine. if those wires check out. it's unlikely there is mechanical damage inside the engine. not impossible, but unlikely. it should only change once every 2 crank revolutions. turn it SLOWLY by hand so if it decides to start, it won't
Customer: replied 4 years ago.
ok ill try that and let you know what i find.
Expert:  Auto Go replied 4 years ago.

graphic

this is what the voltage should look like on the CMP 5 volt wire as you rotate the crankshaft. just something I dug up while I wait for you to get back to me. we shall get to the bottom of this!

Expert:  Auto Go replied 4 years ago.

also measure the resistance of the coolant temp sensor. at 68 degrees you should have 2300 to 2600 ohms. the colder it gets, the more resistance you have. the warmer it gets, the less resistance you have. the computer uses the sensor to determine how much fuel to give the engine when its cold, cold engines require more fuel. Ive seen them flood out when the sensor shorts (low resistance = cold engine (-40 degrees) and engine overfuels) but I haven't seen them cut fuel completely for an open circuit sensor. If it sees open circuit, it should default to a base strategy and go ahead and run. its a long shot, but we need to rule it out.

 

one more thing, does it try to start then stall like a couple seconds later, or does it just crank and not even attepmt to run?

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