06 Hyundai Elantra cranks without starting. Has spark.

[No country for new cars]

Posting for my brother's car. 06 Elantra, 199,xxx miles, automatic. Recently had it stalling at lower speeds. Tried replacing the filter in the pump, which didn't fix it. Only 2 codes popped up, P0304 and P0453, neither of which I've known to prevent starting. About to try plugs, since it really needs new ones anyway.

With key on and engine off, you can hear the pump priming. You can hear the pump trying to send fuel while the other person tries starting. Iirc, that rules out the CKP.

So far, we've ruled out the timing belt (still there, still mounted properly and it spins when the engine is cranked) and the pump itself. Removed plugs and cranked, all of which had spark, although it was weak. Not sure if i smelled any gas from the engine while the plugs were out and the engine was cranking.

I'm about to head over there and remove the fuel rail, leaving the injectors attached to see if fuel sprays out. Either that, or I'll look for a stethoscope when i stop for plugs.

I'm starting to think it may be the fuel pressure regulator. If it is, at least it's easy to get to. Under the rear seat, attached to the fuel pump.

 

[yodog]

Have you checked the battery? It could be right on the fence between a life state of functional operation and death and despair.

 

[HankHill]

Does your Hyundai have a crank position sensor? In my experience with other brands of older vehicles with your symptoms have had a bad crank position sensor. Never touched a Hyundai before thought. If it does have a CPS and its cheap and easy to access, I'd just give it a try.

Maybe someone can post about using a scanner with live function, that allows you to see what is going on?

 

[No country for new cars]

Does your Hyundai have a crank position sensor? In my experience with other brands of older vehicles with your symptoms have had a bad crank position sensor. Never touched a Hyundai before thought. If it does have a CPS and its cheap and easy to access, I'd just give it a try.

Maybe someone can post about using a scanner with live function, that allows you to see what is going on?

The reason I'm thinking it isn't the CKP is because i can hear the fuel pump running while he cranks the engine

 

[No country for new cars]

Have you checked the battery? It could be right on the fence between a life state of functional operation and death and despair.

Battery is good. Just to be certain, I'll try jumping it when the new plugs are in

 

[JMJNet]

For battery, you need to load test them to make sure it has the amp to start the car.
This is a neccessary requirement.

 

[FowVay]

you need to check the fuel pressure at the rail along with the camshaft/crankshaft position sensor function. Start with the basics.

 

[HankHill]

I'm not sure if on Hyundai's if the pump is supposed to run during the entire cranking of the engine, I would say maybe yes, can't find that info using search. No info on any cars really..

Are you thinking that since the the pump was running during the crank that fuel must be injecting into the cylinders?

There is a procedure on an Hyundai forum to test if the engine is getting fuel. It involves removing an intake hose and checking that there is a fuel odor. This is used to see if the engine is getting fuel.

There was a post by a mechanic that took 2006 Elantra with 200k on it, with a no start condition. His immediate diagnosis was either fuel pump or CPS, 50/50 probability. Stated failure of either component was either on or off, no symptoms, it would just not run. He could hear the pump running, and checked pressure at the rail. He then replaced the CPS and it started. He also warned that you should always use an OE senor, aftermarket sensors have lasted a very short time. For whatever reason he had no concern about spark, didn't check at all.

In your situation with no start, spark, its either the fuel pump or CPS. Since the pump is operating, the experienced diagnosis is then a CPS.

Still sticking by my diagnosis of the CPS. Hope you get it running soon!

 

[HankHill]

you need to check the fuel pressure at the rail along with the camshaft/crankshaft position sensor function. Start with the basics.

How do you test the CPS and the CamSP sensor? Can you see the functions of in a live feed on a scanner? I do agree now that the pressure should be tested, it was mentioned as a diagnosis test, I failed to include it however. Sorry OP!

 

[Nukeman7]

The reason I'm thinking it isn't the CKP is because i can hear the fuel pump running while he cranks the engine

I don't that you can rule out the Crankshaft Position Sensor (CPS) just because you can hear the fuel pump is running. A faulty CPS typically results in coordinating the ignition spark signal and injector spray at the wrong time which could mimic your symptoms. Also, I would not be 100% convinced that the fuel is getting to the cylinders just because you hear the pump running. I would try a simple test by spraying carburetor cleaner into the air intake for ~10 seconds and immediately seeing if it fires up and runs for several seconds. If it does, you have confirmed compression, timing, and ignition are OK, thereby, narrowing down the issue to fuel delivery. If it doesn't fire up, you have essentially verified it is not a fuel delivery problem.

 

[No country for new cars]

Update: used a stethoscope to listen for injector pulse and all 4 injectors were pulsing. Also changed all plugs. They were in horrible condition. The gap should be .044 but it was .081 on cylinder 4, which would explain the P0304. Replaced them all with new OE type, gapped properly. Gave it a shot of ether and it started, then ran for a moment, as long as he kept feathering the gas pedal. As soon as he stopped hitting the gas, it died.

I'm almost 100% convinced that it's the regulator now.

 

[No country for new cars]

Not focused properly, but they are in order, 1 thru 4 left to right

 

[mk378]

Could be an air leak. Unmetered air (leak is after the MAF sensor) will make idling and starting very lean. When you open the throttle the total volume of air increases and the leak is insignificant.

Rotted / detached PCV and brake booster hoses will do this. Also check the big air pipe between the MAF and throttle body, they can get chewed by mice.

 

[No country for new cars]

Could be an air leak. Unmetered air (leak is after the MAF sensor) will make idling and starting very lean. When you open the throttle the total volume of air increases and the leak is insignificant.

Rotted / detached PCV and brake booster hoses will do this. Also check the big air pipe between the MAF and throttle body, they can get chewed by mice.

Checked all of those hoses. Old, obviously, but not cracked or dryrotted.

 

[HankHill]

The fuel pressure regulator, right?

 

[Chris142]

Just because the fuel pump makes noise don't mean it's making enough pressure

 

[Jump1]

Don't know how to for sure verify crank position sensor, but if car has a tach they usually feed from it. While cranking see if tach moves some. If yes it's not a guaranteed verification it's good but likely a quick check. IF it stays at 0 I'd suspect it's bad and then google how to really check it.

 

[HankHill]

Don't know how to for sure verify crank position sensor, but if car has a tach they usually feed from it. While cranking see if tach moves some. If yes it's not a guaranteed verification it's good but likely a quick check. IF it stays at 0 I'd suspect it's bad and then google how to really check it.

His injectors are working so the crank sensor is good.

 

[Chris142]

Give it a tablespoon of fuel down the throat. See if it fires.

 

[No country for new cars]

Give it a tablespoon of fuel down the throat. See if it fires.

Gave it a shot of ether to start. It started, and as long as he kept his foot on the gas, it would run. Died right after letting off the pedal