Contour Enthusiasts Group Archives Forums General Troubleshooting Where is this check valve everyone tells me to check?

Where is the fuel pressure check valve that everyone says might be stuck open cuasing my hard starts after i changed my fuel filter? I know there is one on the fuel rail, that one is fine.

Also, would that fuel rail valve spit fuel out if an injector was leaking?

If i can check that fuel pressure check valve and diagnose a leaky injector that would really help me get more sleep. :p

Hi,

The check valve that "I" referred to when I replied earlier, is in the gas tank and sits on top of the fuel pump sump. The only way to access it is to remove the fuel tank or cut a hole in the back seat floorpan to access it through the top. The check valves in the tank and injectors should maintain fuel pressure on the rail for at least an hour after shutting down the engine hot or cold...shouldn't matter. To check if this is happening properly, you would have to buy an expensive fuel pressure gauge. A crude method would be to push in the schrader valve on the rail after an hour(HOT)and observe what comes out and in what quantity. You should be VERY CAREFUL because when you do this, you are creating an EXTREMELY EXPLOSIVE VAPOR CLOUD! Use some rags to "contain" the vapor and don't create a cloud. You should get a rather constant spray of fuel for about 5-10 seconds. It should be fuel and a bit of air...1-2 seconds worth towards the end of the spray. If you get a lot of air then you have experienced what is termed "Vapor Lock", the fuel gets so hot that it vaporizes, in the rail mostly, and increases pressure a bit pushing the fuel back down the fuel line pressurizing every fuel component in its path. This big pocket of air unfortunately is sitting at the injectors and will cause longer crank times to allow the injectors to "inject" this useless air while they wait for the liquid fuel to return. When an extended period of time elapses the engine and fuel will cool, the fuel will condense back to a liquid and a "normal" start will occur. I see you are in Texas, so I would guess this is what you are experiencing.

...Ed

thank's a lot, but its not vapor lock becuase if i let the car sit overnight, it will not start up unless i "prime" it without cranking it. However, it starts up without a problem 15 minutes after driving 30 miles at 60 mph (which i did today). So its not vapor lock, it has to be the pump check valve or an injector not holding pressure. Any way to narow it down between those two?

Hi,

Not sure how accurate this would be but, you could try isolating the two by pinching off the fuel filter (engine side) line after shutdown, let the car sit for several hours and then, while still pinched remove the tank side tube to the filter. I would think you should get some amount of spray if pressure is still present. Then while still disconnected, release the pinched line and see if you again get some spray. Again, I don't know if this would tell you anything accurately and I would be very careful "pinching" the fuel line as they are very rigid and may crack and become permanently deformed afterwards. A much more involved and likely more accurate method would be to make a test rig utilizing two pressure gauges separated by a shutoff valve. On either end of the valves install nipples similar to what the filter has, install the test fixture in place of the filter, start up the engine, rev up once or twice, shut down and go close the shutoff valve. Sit and watch the pressure gauges to see which one loses pressure first and fastest. I'm sure that eventually (days) both will lose all pressure. I also don't have any idea just how much and how long they should hold.

Sorry I can't give you an easier way...maybe someone else can help. I don't think OBD software could do any kind of isolating of pressures...maybe though at the dealer?

...Ed