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04 Nissan Sentra 2.5 - won't start & all cylinders are flooded with fuel


The car was running fine, but I pulled it in the garage and the next morning it wouldn’t start. I’m getting fuel, spark, and air. However, I think I’m getting too much fuel. All of the cylinders have fuel sitting in them, about 1/8" deep. It seems to flood in about 5 seconds of trying to start it. At around 8-10 cranks you can smell it. If I pull the fuse to the fuel pump, the car turns over about 5 times and then almost starts, but then it runs out of fuel. I plug the fuse back in and within a few cranks it’s flooded again.

It’s hard to imagine that all 4 injectors have failed at the same time. I’m not sure if it could be a faulty fuel regulator or pump? I disconnected the fuel line by the engine and captured 6-8 ounces of fuel and it looks fine. Any help or suggestions would be appreciated! Figured I would ask before randomly throwing money at it.

Thanks again,

Flooded with what???

Sorry, accidentally hit enter before I was ready to post.

I was going to suggest a faulty coolant temperature sensor, but that’s an awful lot of fuel.

I replaced that earlier today. I figured for $20 it was worth a try. Thanks though.

The car’s computer likely tells the injectors to inject extra fuel on cold starts, and the colder it is, themore fuel is injected. Sometimes the ECM will double or triple pulse the injectors to accomplish this. I expect there’s something wrong w/all that. Are you sure you replace the coolant temp sensor used by the ECM? Cars usually have two, one is for the dash gauge only. You will likely need to get some expertise on how the cold start operation works, all the sensors involved. Have you had the DTC codes read yet? Pending and active. That could provide some clues.

How about the air filter? Have you checked if it is clogged? A clogged air filter can cause extra fuel to be injected. Unlikely, but worth considering. Air leaks could cause something like this. Anything in the cold air intake path to the manifold that has split? An exhaust leak could do this too, esp if it is prior to the O2 sensor.

One more idea, maybe it just flooded for some reason, and now you haven’t been able to get all the gas out. You could try removing the spark plugs and letting it sit for a day or two so all the gas evaporates. I had to do this with a VW RAbbit one time, the fuel system during a test had pumped too much fuel into the cylinders (my fault) and it wouldn’t start no matter what I did, until I removed all the spark plugs and let it sit. Then it started up fine. Best of luck.

I agree with @GeorgeSanJose about letting the fuel evaporate

With all that fuel, the engine can’t build up sufficient compression to start

Sparkplugs must be wet also? Did u change them? My kid flooded car when it was -10f. I changed plugs and got it started but car ran poorly. You pull plugs, disable fuel pump and crank motor to evac cyls? Than what?

All of the cylinders have fuel sitting in them, about 1/8" deep.

How did you determine this? Can you actually see 1/8 inch deep puddles in each cylinder? Is it actually in the spark plug wells? It would take longer than 5 secs. to dump that much fuel in the cylinders unless all the injectors were really, leaking quite bad.

I would advise not starting the engine with diluted oil and if gasoline has been puddled on pistons the oil would be diluted.

A short circuit in the injector wiring from the injectors to the computer or in the computer would hold the injectors open continuously. Check for a short and if there is a short isolate it. An LED circuit tester would speed the diagnosis.,

I can’t see a scenario where all four injectors would find a false ground at the same time and there no be a lot of other problems going on too. If I recall correctly, at initial startup, the fuel pump pressurizes the rail and each injector pulses one, two or three times, all together, depending on temperature. They are not sequential at this time because the engine doesn’t know where it is at until it starts turning and gets signals from the CPK and/or CPS.

So my best guess is that the fuel rail is being over pressurized because the pressure regulator has failed and the excess pressure is somehow holding the fuel injector valve open once it is pulsed. You must have a really good fuel pump. That is assuming that you really do have that much gas in each cylinder.

The other cause would be that either you or someone else has “chipped” this engine. That is the type of car that the ricers like to chip, especially if it is the Spec-V.

Hey all,

The airfilter is good, replaced it a few weeks ago. Last time I unhooked the fuse to the fuel pump and turned it over to use all of the gas in the cylinders, I then took out all of the spark plugs and let it sit over night. Hoping this would dry it out as much as possible. I inspected the exhaust, the connection points in the exhaust and did not notice any holes.

Last time I cleared the fuel out of the cylinders and let it sit for a day, I replaced all the spark plugs. When I get home this evening I am going to crank it with the plugs out and the cylinders dry to see if I can actually see it flooding.

The spark plugs are directly on top of the head and I’m able to shine a flash light down and see the pool sitting in each cylinder. I took a straw and used it as a dipstick for each cylinder. 2 cylinders were about 1/8" and the other 2 were close to double. I can blow into the spark plug hole and see the fluid moving around.

I was leaning towards the pressure regulator but just curious to see what others think.

The car is not throwing any codes either.

Thanks for the responses.

Check the fuel pressure regulator on the end of the fuel rail. Pull the vacuum hose off; if there’s fuel present then the diaphragm is bad - the regulator is shot and its flooding all the cylinders of the engine. Cheap and easy to fix.

How does the car react to a “flood clear” i.e. accelerator held to the floor while cranking? Do the cylinders fill up with raw gas just the same? What is the fuel pump pressure during rail charge and while cranking?

If the cylinders still fill with a ‘flood clear’, use a ‘noid’ to see if the ECM is pulsing the injectors (all of them). If you get a steady light from the ‘noid’ you most likely have a wiring problem or the ECM has headed south.

Hope this helps. Keep us in the loop.

My early 90’s Corolla has all the injectors tied together – electrically, with a wire I mean – it doesn’t pulse each one separately. When one injector is pulsed, they all must pulse. If your Nissan is configured like that – unlikely as newer fuel injection systems tend to pulse the injectors independently – it would be possible I suppose for that line to get grounded or stuck somehow and all the injectors would be constantly spraying fuel. This would be quite unlikely to happen unless the car has been in an accident or rodents have been gnawing on the wires, or some kind of major ECM fault like a broken solder joint.

A clogged air filter will NOT cause flooding in a car with EFI.

I’m thinking along the same lines as others in a couple of respects: 1) a ground problem where the injectors are just basically stuck on, or 2) pressure regulator. As Researcher suggested a noid light will immediately tell you about the power to the injectors, and as Sean mentioned the vacuum line for the regulator will tell you about that - or a fuel pressure gauge.

Unless I miss my guess, this is a 4-banger with vertical cylinders. 1/8" in each cylinder…I’m surprised it didn’t hydrolock. So I’m thinking that the cylinders were wet with fuel, but only as they would be from nonfiring cylinders. 1/8" is probably a slight exaggeration.

I’m thinking it perhaps has no spark. The sudden and catastrophic nature of the failure would suggest perhaps something like the crank position sensor, which if it fails will disable all of the spark plugs at once.

Before going further I’d suggest checking for good spark. Post back with the results.

Offhand, flooded cylinders can be caused by a leaking fuel pressure regulator or the injectors pulsing on too much.

Those issues aside, I agree with mountainbike about a no spark possibly causing this.

Floor the pedal while starting it. Normally, that will clear a flood condition since it doesn’t dump fuel into the cylinders. If, after doing that, you still see fuel in the cylinders, your injectors must still be firing or perhaps are all open. You could always take one injector out and watch it while the car is being started and floored.

It would be hard to believe all injectors have failed all at the same time. If you’re still dumping fuel into the cylinder, it would point to something electrical.