Hyundai Forums banner

1 - 20 of 165 Posts

·
Registered
Joined
·
169 Posts
Discussion Starter #1
Hi Folks. My '98 Accent was running fine until about 3 weeks ago. The first symptoms were stumbling badly on startup (sounded like it was only running on 1 or 2 cylinders) then would catch after about 3 seconds and run fine. It did this intermittently for 3 times then quit altogether and won't start at all. The timing belt is good and all the cranking leaves a strong fuel smell up front so I think the pump is okay. I'm suspecting either the crank or camshaft position sensors. My question - is there a way to test these sensors to see if they are functioning ok? I don't want to just start replacing parts without some indication that one is faulty. Thank you.
 

·
Registered
Joined
·
3,960 Posts
You can go on youtube to get the answer about how to test cam and/or crank sensors.

I believe that Hyundai uses the cam sensor
(in correlation with the crank sensor) to determine the position of the piston
and the cycle that the cylinder is in
all to be able to set up spark timing..start up
After that it just uses the crank sensor, the cam is not used but still monitored
 

·
Registered
Joined
·
169 Posts
Discussion Starter #4
Ok, I took off the crank and camshaft sensors and did some resistance probing. The crankshaft sensor measures 0.85 K Ohm between the center pin and one of the end pins. The camshaft sensor measures 3.04 M Ohms between the center pin and one of the end pins on the 4M scale of my multimeter with the black lead on the center pin. However when I switch to the 40M setting the reading jumps to 22 M Ohms, which doesn't make sense to me. Also when I switch the red and black leads (i.e., red lead now on the center pin) I intermittently get readings that cycle between 2M Ohms and 36 M Ohms then the meter goes to 0.L after a while (on the 40M scale). So I'm suspecting a bad camshaft sensor. Does anyone know if the 0.85 K Ohm reading for the crank sensor is within spec? Thanks all for any input.
 

·
Registered
Joined
·
12,412 Posts
Your crank sensor resistance sounds about right, and measuring the resistance of a cam sensor isn't a valid test. That's why the guy in the video never attempted it.

You didn't need to remove the crank sensor to test it. The easiest way to test it is to monitor the fuel pump power supply then just crank the engine. If the PCM switches the pump power on DURING CRANK the crank sensor must be working. The pump wouldn't switch on otherwise.
The cam sensor is tested by monitoring the voltage on the signal wire, then move a ferrous metal past the face of the sensor. The signal voltage should switch between 5/12V and 0V when the metal is moved past the face of the sensor.
 

·
Registered
Joined
·
169 Posts
Discussion Starter #6
I did the cam sensor test as per the video. I first disconnected the sensor from the connector and checked the output from 3 terminals with the ignition switch on. One outer terminal was ground, the other outer terminal had 12 volts on it. Then I plugged the cam sensor back in with some paper clips in-between so I could attach the voltmeter leads. With the ignition on the center signal terminal has 5 volts on it. When I wave a wrench by it it goes close to 0 volts however I have to be within about 1/16" to get the signal voltage to change. Does 1/16" sound correct? I also notice that the sensor probe was covered in oil when I removed it. Would the oil affect any results?

Now on go the crank sensor. I disconnected the connector to see what was on each of the 3 terminals. One outer terminal and the center terminal both have 1.5V on them. The other outer terminal is ground. I'm puzzled by the 1.5V on both of these input terminals with the sensor disconnected. Does that sound right? I did not continue to test the crank sensor plugged back in pending an opinion on that 1.5V result. Thanks once again.
 

·
Registered
Joined
·
12,412 Posts
Does 1/16" sound correct?
Yeah, sounds OK to me. I also notice that the sensor probe was covered in oil when I removed it.

rreitz said:
Would the oil affect any results?
No.

rreitz said:
I'm puzzled by the 1.5V on both of these input terminals with the sensor disconnected. Does that sound right?
Who knows. I've never seen published figures for what the open circuit voltage of a crank sensor circuit should be because it's not normally how the crank sensor is tested.
 

·
Registered
Joined
·
169 Posts
Discussion Starter #8
Ok, back to the crank sensor then based on monitoring the fuel power supply - where is the best place to tap into the fuel pump power supply? I remember that when the car died for good there was a strong fuel smell in the engine compartment after constant cranking and no start. I just assumed it was supplying fuel to the cylinders. I'm not sure where to tap into the fuel power circuit. As always, thanks for all the tips (all the way from the UK!)
 

·
Registered
Joined
·
12,412 Posts
I don't think your car has a pump check connector, so the easiest place to monitor the pump supply will be right at the fuel tank connector under the rear seat.
On top of the tank module there are 4 wires and a 4 terminal connector. The yellow wire on the tank module is the fuel pump power supply...see below.

The smell of fuel in the engine bay kinda suggests your crank sensor is working. The sensor might not be the cause of your non start. I guess we'll find out soon enough.


 

Attachments

·
Registered
Joined
·
169 Posts
Discussion Starter #10
That fuel pump top cover looks way to pristine for a 1990's Accent! Mine looks rusty brown and old ... I put both sensors back in and cancelled my order to RockAuto until I can come to a better conclusion. I will see if I can monitor the voltage on the yellow connector if there is a bare spot where I can attach a clip - but I suspect the wire will be totally covered from connector to terminal mount. Another way would be to crank and then pull a couple of the plugs to see if they are wet. I did pull them out this AM to see if there were any clues and they were coated with what smelled like unburnt fuel so I cleaned them and put them back in. However the car has been sitting for 4 days so I will crank and look at them right after if I can't find a convenient tap into the fuel tank connector. Thanks again for the interest.
 

·
Registered
Joined
·
12,412 Posts
Just follow the yellow wire from the tank module to the harness connector, then use a paper clip or sewing needle to back probe the yellow wire connector terminal. You can then connect your meter or test light to the back probe.
 

·
Registered
Joined
·
3,960 Posts
What happened to testing for spark and injector pulse for a crank, no start condition?
If both are missing then crank sensor can be suspect
If only one then crank sensor is probably working

Don't mind me.
Continue to work with Autospark.
I am just looking for a quicker way to find out what is wrong.
 

·
Registered
Joined
·
12,412 Posts
What happened to testing for spark and injector pulse for a crank, no start condition?
Nothing happened to it. You just never suggested it in your earlier post.
Had you suggested that there was a way to test the sensors with them still attached to the engine the OP might not have gone ahead and removed them.
 

·
Registered
Joined
·
169 Posts
Discussion Starter #14
What happened to testing for spark and injector pulse for a crank, no start condition?
If both are missing then crank sensor can be suspect
If only one then crank sensor is probably working

Don't mind me.
Continue to work with Autospark.
I am just looking for a quicker way to find out what is wrong.
All are welcome!! All the original sensors are back in so I'm starting from scratch. I think we concluded that cam sensor is working. I'm still not so sure about the crank sensor although it has a reasonable ohm reading. I went out and cranked it over. I hear one chug from probably one cylinder firing then nothing; just cranks after that. I immediately pulled the plugs and they are wet with gas so I'm assuming the fuel pump is energized. What is the test for 'spark and injector pulse for a crank'?
 

·
Registered
Joined
·
3,960 Posts
If the crank sensor isn't working then the ECU won't send out a spark signal to fire coils and no signal for injectors to fire
If you have one or the other then the crank sensor should be working

The cam sensor is the one used to time the firing of the spark plugs
After the engine starts then the ECU uses the crank sensor to time spark
Cam sensor is not used but is monitored

If you had an oscilloscope then you could actually see the signal from the cam sensor to see if it was good
You could also do timing with it to see when the spark is firing. See relative compression. etc
But, most of us don't have an oscilloscope.
However, wet plugs usually means there is no spark.
And the injectors are working

Not sure if you use coil with spark plug wires or coil over plugs.
If they were coil over plugs then hard to see all the coils going bad at the same time
Other wise, need to see if the coils are getting 12 volts, ground and the signal to fire

Personally, would ask Autospark what to do next.
 

·
Registered
Joined
·
169 Posts
Discussion Starter #16
Here is what is known to this point. Plugs are wet with gas so fuel pump is getting signal to do its thing. I guess that means crank sensor is working. I get one chug when turning over then nothing other than cranking so there is at least one spark going off. I don't quite understand your explanation above: "The cam sensor is the one used to time the firing of the spark plugs" "After the engine starts then the ECU uses the crank sensor to time spark" So which is it - is the cam sensor used to time the firing of the plugs or is the crank sensor used to time the plugs? Or did you mean that the cam sensor is used for the timing at initial start and then the crank sensor takes over after the engine starts. I have a 4 prong coil on the right side of the engine with the plug wires going to each cylinder. I think that means coil with spark plug wires versus coil over plugs if that is what you are describing above. I will check coil pack tonight to see if it is getting the 12 volts as you suggested along with ground. Not sure how to check if it is getting signal to fire. Thanks for the input.
 

·
Registered
Joined
·
3,960 Posts
So which is it - is the cam sensor used to time the firing of the plugs or is the crank sensor used to time the plugs? Or did you mean that the cam sensor is used for the timing at initial start and then the crank sensor takes over after the engine starts.
It is a four stroke engine
Which means there is two revolutions per cycle
The crank shaft sensor revolves twice
and doesn't know which part of the cycle it is in
The cam revolves once and does know which part of the cycle it is in
So timing of the spark starts with using the cam sensor to start the engine
and then using the crank shaft sensor to keep the engine running

The ECU uses the crank shaft sensor for timing the spark plugs after the engine is started.
The ECU also uses the crank shaft sensor to know that the engine is running
And so timing the firing of the injectors or injector pulse.
Having one or the other means the crank sensor is sending a signal to the ECU.

You have a coil pack. Check for 12 volts and ground.
As far as I know, Hyundai uses a waste spark system.
Meaning is that of the four cylinders, there two pairs of cylinders that are direct opposite.
One is in compression ready to fire and the other is in exhaust
The coils are paired so they fire at the same time

We have a crank no start. Plugs are wet.
Meaning we have no spark.
Need to check coils and see if there is a signal from the ECU to coils to fire.
Here is where @AUTOSPARK shines. Electrical.
 

·
Registered
Joined
·
12,412 Posts
did you mean that the cam sensor is used for the timing at initial start and then the crank sensor takes over after the engine starts.
Yes, that's what he meant.
When you crank the engine over to start the engine computer (PCM) calculates the spark and injector timing using both the cam & crank sensor signals.
On an engine like yours with fixed camshaft timing, once the spark/injector timing has been calculated and the engine has started the cam signal is no longer required and is pretty much ignored by the PCM until the next start.

rreitz said:
I have a 4 prong coil on the right side of the engine with the plug wires going to each cylinder. I think that means coil with spark plug wires versus coil over plugs
Correct.

rreitz said:
I will check coil pack tonight to see if it is getting the 12 volts as you suggested along with ground.
I think the X3 Accent coil has a 3 terminal connector. If you disconnect the coil, switch the ignition on, then measure the voltage on each of the three terminals of the harness connector you should have one with 12V. That will be the coil power supply terminal. The other two terminals are the ground trigger signals that come from the PCM. The way you test the trigger signal is by connecting a 12V bulb between power supply terminal and one of the trigger terminals. Crank the engine over for 5~6 seconds while watching the bulb and you should see it flash. It wont be very bright though because the trigger signal pulse is very short, so it might be a good idea to have someone else turn the key to crank the engine while you keep an eye on the bulb. Once you have checked one trigger terminal on the connector, move the bulb to the other and crank again.
 

·
Registered
Joined
·
169 Posts
Discussion Starter #19
Next step. Disconnected the 3 wirer connector at the coil. The end terminal with black wire/blue stripe has 12V with ignition on. The center and other end terminal have close to 0V. Stuck 3 stretched out paper clips into each terminal slot and alligator clipped one end of a 12V lamp tester (which I found in my tool box but never knew it had a use) to the 12V terminal. On the pointy end of the lamp tester I attached long wire I made a while back that has alligator clips on each end. The other end of the wire was clipped onto the center terminal. With the long wires attached as described I was able to move the lamp part out of the engine bay onto the fender so I could see what was going on (no one here to help). Cranked the engine and the lamp flashed while cranking. Moved the wire that was on the center terminal to the other end terminal and cranked the engine and the lamp also flashed while cranking. So we appear to have tested the crank sensor, the cam sensor and the signal from the PCM. What would be the test for the coil since we're running out of things to test? In addition to the 4 wire terminals coming out of the top of the coil there is a little rectangular box attached to the side that has a fat black wire coming out of the coil pack to it. Is there a ohm test that can be done? This is getting exciting now.
 

·
Registered
Joined
·
12,412 Posts
Is there a ohm test that can be done?
Yes, but personally I would just attach a spare spark plug to the end of the HT leads (wires) then crank the engine over and see if the plug sparks.

Attach one of your crock clip leads between the threads of the plug and the engine block to ground the plug.
Disconnect an HT lead from one of the plugs fitted to the engine and attach it to the top of the spare plug you just grounded.
Only disconnect one HT lead from the engine. Leave the other 3 attached to their plugs.
Now crank the engine over and see if a spark is produced at the plug electrode.
It's a quick/simple test so you might as well repeat the procedure for the remaining 3 leads just to be sure they're all producing a spark.
If you get a good spark from each I think it's safe to assume the coils are good so you could probably skip the Ohms test.
 
1 - 20 of 165 Posts
Top