Engine Flooded No Start

Answers to the question can a flooded engine cause a no start condition on modern fuel injected vehicles and some possible causes reviewed. Here is a quick story about how often I use to see this happen and how little I see it now.

carburetor Picture

I remember when I was a little kid often my mother would go out to the family car and it would not start. You could hear her cranking the engine for an extended period of time without the engine starting. After a few more tries she would come inside and tell my father the car won’t start.

He would start screaming at her (as we where a dysfunctional family) saying that it was her fault and she flooded the engine. Of course the car I speak of had a carburetor on it and it was possible to flood the engine. In most cases when this happened my dad would go out and hold the accelerator to the floor while cranking and most of the time the engine would fire up.


My mother didn’t understand how she could be flooding the engine. And after the engine was all warmed up she had no problems at all starting it. This was because when the choke is applied on a carburetor there are increased chances of the engine flooding with a crank no start as the result.

On this old carburetor equipped vehicle there were many adjustments that could be made to the choke assembly, such as choke angle and choke pull off which would help increase the amount of air that was allowed to enter the engine cold.

Engine flooded on modern vehicle

fuel injector Picture

The question is can an engine be flooded today to the point where it will not start? The short answer to this question is yes, an engine can still get flooded. But these modern fuel injected vehicles will not flood out unless there is a problem.

I should also mention on most modern vehicles the computer provides a clear flood mode if an engine becomes flooded automatically. This clear flood mode can be entered manually by pressing the gas pedal to the floor while cranking the engine. On a fuel injected vehicle this will turn off the fuel injectors when the engine is not running and after several rotations of the engine the cylinders will be cleared.


Causes of an engine to flood

On modern fuel injected vehicles the right amount of fuel is added to the right amount of air to provide optimal starting regardless of the engine temperature. So how would extra fuel get into the cylinders and cause a flooded engine no start condition.

Picture of cpi injector

I will give you a couple of examples of things that I have seen myself. Back in the early to mid 90s General Motors came out with a fuel injection system known as CPI. This stands for Central Port injection. There was one large fuel injector with little hoses (looked like an octopus) that ran into each cylinder. This setup was most common on the 4.3 L v6 Vortech engine.

The CPI injector was mounted inside of the intake Plenum and could not be seen without removing the upper part of the intake manifold. What would happen is the CPI injector would start to leak and raw fuel would pool up inside the intake manifold. This unmetered raw fuel would be drawn into the combustion chamber and would cause all kinds of problems associated with a flooded engine.


Another situation that can cause an engine to become flooded would be a leaking fuel pressure regulator that is vacuum controlled. This type of fuel metering system was used from the mid 80s to the late 90s on all different kinds of vehicles. When this fuel pressure regulator which had a rubber diaphragm became dry rotted it was possible for a fuel leak to develop. The vacuum line that controlled the fuel pressure regulator could in some cases suck the raw fuel into the intake manifold.

This unmetered raw gas would also cause symptoms that are associated with an engine that is flooded. The case that comes to mind was so severe that the unburned fuel wound up leaking past the piston rings and into the engine crankcase. The first sign that I detected of this problem was that the engine will was way overfilled and smelled like gas.

So even though an engine flooded causing a no start condition is not as common as it used to be back in the days of carbureted vehicles it can still happen. For more information and other problems that can still happen to your car visit the blog for online auto repair.

2 comments

  1. I have a 1987 chevy s10 with the 2.5L 4 tech engine in it, and I am having trouble getting it started in the cold. It acts as if it is flooded, it will turn over freely but will not start. Then after a few attempts you will hear it attempt to start only immediately die. Which to me sounds like a flooded engine. What could be causing this in the cold weather?

  2. MC: In 1987 I think the 2.5L came with TBI. Unusual for a throttle body vehicle to flood to the point of causing a no start (but possible). In 87 the 2.8L came with a vari-jet carburetor. This thing was notorious for cold start problems. The choke angle would have to be set perfectly and special tools were required to do that. So if your 2.5 has a carburetor (its most likely a choke problem). If it’s TBI then cold start enrichment issues or a stuck open injector are possible among other things.

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