Starts and runs for 3 seconds

Check the fuel pressure and comeback with the pressure readings here is a guide to help

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Can I ask if the security light is flashing? That will cause this as well.

Please run down this guide and report back

Cheers

I'll get a guage and check it tomorrow. I did check the spark plugs today (they are new ) - black soot on all of them, one of them was gaped too small - reset the gap on all of them. Now the engine will run for exactly 4 seconds. Before regaping the plugs it would run for exactly 3 seconds. Took off the fuel rail with all four injectors - they all have a very nice spray. Bypassed fuel relay to keep the pump running - engine still dies at 4 seconds. Will check pressure next.

Try to replace the plugs with new because fouled plugs will not work also it could be a plugged catalytic converter. Here is a guide to confirm the issue.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Checked fuel pressure today. Pressure coming out of the pump: 75psi, pressure at the rail is 49 or 50psi - with or with out the vacuum hose plugged into the manifold port.

That sounds okay, did you ever see if the security light was on?

Ok, so the regulator should be keeping the pressure at 37. I'll try and find a new one on Monday. As I understand this, the fuel pressure is too high at the injectors and they are spraying too much fuel into the manifold making the sensors send crazy signals to the computer - then the computer is shutting everything down? And all this stuff takes exactly 3 seconds? (I did get it up to 4 seconds - but now it is back at 3).

Installed new regulator yesterday, pressure at the rail was 43psi - engine would not start. Re-installed original regulator, pressure: 50psi - engine will not start.
It has spark, and it sounds like it will run, but when let the key off of the start position - engine stops.

Sounds like ignition circuit at ignition switch is open-No power to the igniton system- Check the ignition failure sensor on rear of cylinder head.

Did start today, ran for 3 seconds, one or two times it ran for 4 seconds. Will only actualy start and run 1 in 6 tries.
Checked the wires to the shut off switch:

Pink/Black is 12v with Key ON
Orange has 12v also with the Key On - voltage stays at 12 while the engine is running for 3 seconds - and stays at 12v while/and after the engine dies.
White has .10 with Key ON and 1.5-3v when it does run.
Black is Ground at all times.

Was just thinking, what are the odds that the new crank sensor is a bad one?

Its possible I get bad parts all the time.

What numbers should I be looking for?

If I put the Red lead from my volt meter to the Black wire on the cranksensor. And the Black lead from my meter on the Blue wire from the sensor I have a resistance of 6.88.
There is NO continuity to the Red wire on the sensor, and NO continuity between the Blue and Black wires on the sensor if I reverse the leads from the meter.

I've check for the resistances/ohms for the CPS no reference on it-try researching it. See below

Can't find specs anywhere? Maybe they are not ment to be tested? - Only replaced?
I ordered a new computer for the car, it should be here tomorrow. We'll see if that fixes anything.

Just got the new computer today. I installed it in the car but it didn't fix anything. The engine still does exactly the same thing. I'm going to replace the crank sensor again, maybe that other one is a bad one out of the box......

Hi itsallgood,

I am not sure about the EFI system used in this model, but a faulty MAP/MASS/Air Flow sensor would also cause such a problem. Air leaks in between these sensors are also possible causes.

Hi!
Airflow meter was my first guess also, back when I first started playing with this thing. If I remember correctly, if I unpluged the electrical connector on the sensor, the engine would not even start. If I left the electric connector attached but took the whole assembly off of the rubber intake hose, it would start but still only run for the 3 seconds. I did check voltages going to the connector - and I concluded that was not the problem, and started looking somewhere else.
MAP sensor - that is one that I have not checked yet. Do you know the procedure?
I have concluded that the Fuel pressure regulator is bad - 50 psi at the rail, with the pump running, vacuum attached or not - pressure drops to 5psi as soon as the fuel pump stops. Will also replace the fuel rail - the center part where the small o ring seats is not round and it lookd that might be the reason for the pressure drop.
Also found that one of the coils is arking to the valve cover - under the boot - as it sits on top of the plug.
Was thinking that maybe the arking coil is tripping the missfire sensor and shutting the whole thing off?

Hi itsallgood,

If it uses Air Flow, then there is no MAP.

What you mentioned about the coil is also possible.

High fuel pressure can also be due to clogged or pinched return hose apart from a defective fuel pressure regulator.

So today I just got my order from the dealer (to the tune of $575 )..... I got a fuel rail, a fuel regulator, both coils and wires, ignition sensor, and MAP sensor. I installed it all on the engine and started it up. Guess what?.....nothing new - it ran for exactly 3 seconds and died!

Was looking at the intake manifold - can't see exactly, but it almost looks like there is NO gasket between the intake manifold and the head? Seems to me that there should be one?

Get this, I replaced the intake gasket, it did have one, but it didn't look like it was sealed in there.
Then I tried starting it up - would not start?
Everything was plugged in - but now if I unplug the the MAF the engine will start and run - not for exactly 3 sesonds like before - but for 4 or 5 seconds - a couple times it ran for 6 seconds.
So now, MAF pluged in - engine will not start.
MAF unpluged - engines runs for 4 to 6 seconds.

Hi itsallgood,

Did you try using another MAF ?
Also check the TPS voltage with ignition on.

Hi KHLow2008,

A friend of mine had a 2001 Santa Fe in his shop last weekend just for a tune up. He said I could use it as a test vehicle - but the guy was coming to pick it up in about an hour - so I had to have it put back together real quick.

I did get to swap my MAF into that car - that engine would not start with my MAF installed, however that engine did run just fine without its own MAF installed - which tells me that my MAF is bad - but I also reasoned that MY engine should also run (same as the other one) without a MAF installed, and it does not, which caused me to reason that there was still another problem somewhere.

I wanted to install that MAF in my car, but I did't have the chance due to that fact that the owner was coming to get his car.

I agree that I need a new MAF, but I want to make sure that I find the real problem before I go and give the dealer my right arm again.

I'll go check the TPS readings now......

TPS has 3 wires going to it:
With the key ON;
Green - Ground
Red - 5V
Orange - .77V at idle to 4.38V wide open

i would like to chime in wiht a note, sometmes the fuel pump will prime with the initial key on which will bring your fuel pressure to the specs to get it to start, but if the computer doesnt recive or process the signal from the Camshaft sensor the pump wont turn on again, and the three seconds could cause it to run just untill it has ran low fuel pressure thus die.

Me and ken, administrator, were talking and we came up with the conclusion here for you to try.

disconnect alternator,
check out the battery leads, the computer gets power through it, tighten them down and clean them. and disconnect the exhaust piping from the manifolds and turn it over, it will be loud but hopefully it runs.

get back.

Hello gentlemen, I appreciate your concern, thank you!

As you suggested, I disconnected the alternator and started it up – the engine ran for exactly 5 seconds.
The battery is brand new, and the terminals have been cleaned to the metal, they have a solid connection to the battery.
I disconnected the exhaust pipe from the CAT at the bottom of the engine – it ran for 5 seconds. Then I took the exhaust manifold off of the head and started it up. It sounded like one of my neighbors cars that he drives on the weekends……sorry that’s another story. Anyway, the engine started, but still the same thing – it only ran for five seconds.
When I started working on this car last month it ran for exactly 3 seconds every time. Now, after I’ve replaced as many parts as I have, it has a variable run time (4 to 6 seconds, most of the time it is exactly 5 seconds).
My conclusion is that it must have a problem with one of the sensors that is absolutely necessary for the computer to keep the engine running? Those being the CPS, CAM, MAP, or Ignition Failure sensor (all are new, CPS is the second new one). As far as I know if there were a problem with any of the other sensors, the engine would run poorly – but it should still run.

Unhook all the sensors besides the CAM and CRANK shaft sensors and see if it will start up and run that way.

Get back to me with the results.

also i assume there is no codes being stored in the engines computer?

after the sensors try this also tip via ken.

disconnect 1 fuel injector at a time and crank the engine does it run any longer? same?

I went and bought a scan tool this morning.
It does have code 0340 - CAM sensor.
......That was my first guess, and the very first sensor that I replaced when the problem started (just beacuse it was the easiest one to get to, and the probability seemed to be in my favor to replace it).
I'm looking for a way that I can test this one before I go and order another one?
There is a key on the end of the cam (for the CAM sensor to read) - I thought maybe it was broken, or loose or something - but it'is tight, it's not broken, and it only mounts to the shaft in one position.

will she start and run without the cam sensor hooked up?

try hooking a meter up with t-pins and have someone crank it, is it throwing a reference? if its changing in its pulse then the key ring that it reads off of is good and chances are its a faulty sensor or theres damage in its wiring harness.

also it will have to go thorugh a relearn procedure when replaced, same with your crank shaft sensor. dont forget that

keep posted.

Two weeks ago the engine was running (for 3 seconds) with all the sensors plugged in. Last week the MAF died (engine would not start with MAF plugged in).....I unplugged it and kept looking for another problem. Yesterday, after I hooked up the scanner and got the code. The engine would not start.....as of right now, both the MAF and CAM must be unplugged to start the engine (runs for 4 seconds)...... The online Hyundai manual says that the CAM sensor should have a 12v supply (checked it - it is there, and it is good) it should also have a ground supply (checked that also - it is good) and lastly the signal feed to the computer should send an on (5v)/off (0v) signal to the computer. I'm only getting a .10v signal coming from the sensor. Three weeks ago, I did have a 5v signal coming from the sensor - but the engine was still only running for that same 3 seconds?
I'm just going to through a new sensor in there first, and if that doesn't get the thing running, I'll pull out the computer again and see if that signal wire from the CAM to the ECM is clear.
...Was just reading that the ECU does have a 4 second time limit to get a signal from CAM!...The manual doesn't say exactly what the ECU will do if it does not get a signal....I'm going to guess that it SHUTS the engine off if it doesn't get the signal??

For what its worth, my other car is a 2001 Elantra - no MAF on this car, and I unplugged the CAM sensor just to see what would happen. Well it runs just fine! Like as if it doesn't need that sensor at all!

NO! You are replacing a bunch of things when you don't know if it is the problem or not! You either have a vacuum leak, a problem with timing or your injectors are not properly firing. If you are able to initially start the car then your CPS is fine, at least for the moment. Remove the ducting to the throttle body, buy a bottle of carburator cleaner and have an assisstant crank the engine while you give the car artificial gas and tell me how long it runs (keep it running with the throttle partially open). If you have a fuel pump reset button then follow the steps to reset this just to be sure.

if the engien doesnt pick up a reference code from the cam sensor then it goes into loop mode and the computer uses crank shaft sensor information and guesses when to inject fuel. it will still run if its unplugged.
however if the faulty one is plugged in, it will supply a reference but it could be completely opposite, and thus shutting down the engine.


now back to the p0340 code. Camshaft Position Sensor Circuit Malfunction.

Either the cam sensor has failed, or the crank shaft sensor has failed.

Pcm is no good, or not installed properly.

may be a shorted or open circuit in its wiring harness.

How about you not make the guy go out and spend $400 on a buch of computer equipment when he can't get the car to start and run. If he was experiencing stalling or a rough idle then that would be different, however a car that runs for 3 seconds is starved for one of 3 things, fuel, spark or vacuum. Why don't you guys start with things that are intuitive, inexpensive and that MAKE SENSE first before you start telling someone to start replacing expensive components that you have no clue on how to test. Nobody even bothered to ask the guy if he used an OBD II tester to see if it threw codes at him.

i havnt told him to go out and buy anything if you read.

you say its starved of three things, well if that was so, what do you think controls the three things, ignition, fuel, air? you think a magical little man under the hood controls those? time to be real here.

secondly he posted what code was wrong, and it just so happens to be a CAM sensor code, one of the things he thought was wrong and what we are working on now. Only the proper scanner would hook up and read, you cant stick a OBD II reader on a pre obd vehicle or vice versa.

thirdly you suggested in a previous topic to check for a vaccum leak, well if it was a vaccum leak, it would not keep dieing out at the same time. and that if you are able to start the car the CPS is fine. If that isnt the biggest load ive ever heard. what if it is telling a cylinder to fire that is no where near to the right one, say fires on cylinder 3 that is on the exhaust stroke instead of cylinder #1 on the compression stroke.

and you also suggest cleaning the throttle body! theres no way in heck it would be that plugged up that the vehicle wouldnt run!


and lastly how would a vaccum leak or dirty throttle body cause the MAF sensor and cam sensor to be unplugged before the vehicle will attempt to start?

all sounds electrical to me.

so please get the facts straight before complaining about others.

To merlin boy:

My point was to check things that were obvious and simple first before dashing into blamming the ECU. A vacuum leak, fuel or basic timing issue is much easier on the wallet to fix than an ECU.

Ok so the guy went out there an timed his running engine with a stop watch?

Ya thanks I am a computer engineer and I understand how the system works.
The computer is pre-programed with the firing order. IT DOSENT JUST CHANGE THE FIRING ORDER HOWEVER IT WANTS TO. The CPS sensor is a hall effect sensor which is signaled to fire by a rotating magnetic ring on the flywheel or the crankshaft front balancer. This causes the breaking current to the ignition coil pack. THE ENGINE WOULD NOT FIRE IF IT FAILED!

The fuel pump is always under pressure if the ignition is on! If it isn't then your fuel pump is failing.

I didnt suggest cleaning the throttle body moron. I said give it artificial fuel and see what happens. If the car runs as long as you have fuel and then sputters and dies then you either have a major vacuum leak or fuel issue. If it still dies as you say then it is exclusively a timing issue. IT HELPS NARROW THINGS DOWN AND ELIMINATES OTHER POSSIBILITES!

IF YOU WANT TO BAN ME FINE BUT I HATE PEOPLE WHO DON'T TAKE THE TIME TO ELIMINATE OBVIOUS POSSIBILITIES.

And for the person who's post and car this is: I appologize for the aggrivation. I do not consult or have a team, I do this on my own and I may not be as professional as the master mechanics here, but I hope you take my considerations. If they are completely wrong then my fault.

about the crank shaft sensor, they can fail and give a FALSE READING and since it doesnt show that its faulty and giving no reference the computer will still use the false signal and fire at wrong times!

the fuel pump energizes when the key is turned to the on position to power up and prime up the fuel system so it will start.

when the key is turned to the start position and a ignition signal or pulse if you will, is recieved via the crank or cam sensor then the pump turns on again and the injectors fire, and hopefully the veihcle starts.


with the code he has which is cam sensor issue. as it is, it may be that the pump isnt getting that command to turn back on, or maybe it doesnt want turn on when itstold to causing that initial bit of fuel that was provided to be burned up, and the engine die at the same time because of the same amount of fuel.

im thinking disabling all the other sensors may be working becaus without the MAF sensor hooked up the engine is commanding less FUEL due to less air and that causes it to run for 3 seconds more?

correct me if im wrong.

so itsallgood, that is my theory or what is wrong.

and if you can check out what i listed about the cam sensor and crank sensor in my previous post, and reply back to me, hopefully tellign me the problem is fixed.

ill be waiting.

and with the argument between me and mr airsoftsold, i suppose you can say were a few mechanics with different oppinions, and i guess now you have more things to check.

airsoftsoldrecn9,

I am quite new here so do not know much about how others work so I just watch and if there is anything that I think I can assist, I just go in.

We are here to help others, not to prove that you are superior than others.

Your first post to this question is in bad taste, I must say.
Any suggestion is always welcomed when there is a problem. We learn together too, nobody knows everything.

The person who posted this was doing some repairs and he knows about cars too, just that he was unable to solve the problem.

Btw if you are that smart, why waste time here? There are so many things you could do with your intelligience. :)

Good day.

Note: I agree wuth the theory put forward by blackop555 regarding the sensors. Some sensors will work intermittently even if the reading and resistance might be correct.

As I stated before I was trying to offer "free/ inexpensive" proposals to try first before immediatly jumping to a conclusion on something different; you think the guy is going to come back if he replaces the ECU, cam sensor or his fuel pump and still has a problem?

And no I completely disagree on the fuel pump. The pump will run as long as the ignition is on until the proper fuel pressure is maintained. It has nothing to do with then engine firing or not. If you don't believe me go take an injector out and turn the ignition on. You will drain your tank out of that port, whether the car runs or not.

I made my suggestions. Look at all my posts, I have made possibly 5 out of 50 bad diagnosises. If you want to add this one to it then that is fine, I don't have a problem being wrong.

I looked into the matter further and the cam sensor does indeed specifiy the cylinder to fire, while the crank signal specifies when to fire. I am not sure why Hyundai engineers would bother with a variable timing order. My only guess as to the reason for this would be that if you happened to turned the engine with the CPS out of position you would change the timing. A cam sensor would not allow for this to occur. If I am correct then when the ignition is on and you sweep a magnet passed the CPS sensor at the correct distance a spark plug should fire. IF YOU DO THIS AND IT WORKS THEN YOU NEED TO MOVE THE TIMING BACK TO TDC AND MAKE SURE THE CPS SENSOR WILL FIRE ON THE #1 CYLINDER. My guess is it will not since the cam sensor decides which is the correct cylinder to fire. If you decide to replace then change out the CAM sensor, CPS sensor and then the ECU in that particular order.

Again I appologize for the incorrect diagnosis.

To airsoftsoldrecn9,

I would like to say this about the fuel pump. The fuel pump would operate for a short time when the ignition is switched on to prime the fuel line, then it stops working till the engine is cranked.

Maybe the Hyundai system used over here is different system?

From what I know, for saftey reasons, the fuel pump would not work when the engine is not running except for the initiial priming usage.

Other points are too confusing for me to comment, but from my working experience, I have seen many illogical happenings. Things may test good but they just don't work.