Fuel filter check valve bad. What happens?

[AnotherPerson]

So I had a bad check valve, stuck open. What exactly does this hurt? Its the one on the top of the fuel filter. Return side. I believe I have an issue with the incoming side but I dont want to drop the tank to mess with that one.

 

[wonneber]

So I had a bad check valve, stuck open. What exactly does this hurt? Its the one on the top of the fuel filter. Return side. I believe I have an issue with the incoming side but I dont want to drop the tank to mess with that one.

The check valve (a tee valve sorta) allows diesel fuel to recirculate through the filter and back into the pump until the fuel is warm enough not the gel up in the winter.

If the valve is stuck open I can picture it sucking air backwards from the return side if the fuel in the tank is low.
I wonder if the fuel would drain back to the tank if you parked upwards on a hill.

Its relatively cheap from what I've read and is a know problem with bubbles in the clear fuel tube.

Rich W.

 

[AnotherPerson]

I replaced it. Just wanted to know what happened when it was bad.

Now if only I had a answer to my fan issue.

 

[BobnOH]

This thread has good info on fans-
Check your radiator/condenser fan operation NOW

 

[AnotherPerson]

I know about it. New fan control module. New fuse panel. Power going from box. New fans. Still no low speed. The fuse panel card doesn't even show a fuse 25.

 

[Amine5]

What was the symptoms of a bad check valve that made you think to replace it? I think mine is bad but am not sure, my hpfp make ticking noise but only when warm and my injectors rattles when warm and up hill too , can you help me

 

[94cobra2615]

I know about it. New fan control module. New fuse panel. Power going from box. New fans. Still no low speed. The fuse panel card doesn't even show a fuse 25.

Have you checked the a/c pressure switch by the coolant overflow?

 

[Amine5]

So I had a bad check valve, stuck open. What exactly does this hurt? Its the one on the top of the fuel filter. Return side. I believe I have an issue with the incoming side but I dont want to drop the tank to mess with that one.

What was the symptoms of a bad check valve that made you think to replace it? I think mine is bad but am not sure, my hpfp make ticking noise but only when warm and my injectors rattles when warm and up hill too , can you help me

 

[pruzink]

So I had a bad check valve, stuck open. What exactly does this hurt? Its the one on the top of the fuel filter. Return side. I believe I have an issue with the incoming side but I dont want to drop the tank to mess with that one.

I see that you live in New Orleans. If the 3 way thermostatic valve is stuck in the position where it always sends 100% of the return fuel from the fuel rail back to the tank, I would just leave it that way. I replaced my valve with a "Kerma Widget" about 10 years ago which just plugs the hole to the fuel filter & always sends all of the fuel rail return back to tank. The reason why I did this is because that when I performed the "Diesel Purge" procedure I saw how quickly the fuel rail return got so hot so fast & I just figured that it was more likely to have problems due to fuel that is very hot rather than fuel at the temperature in the fuel tank.

 

[Turtlecharged]

What was the symptoms of a bad check valve that made you think to replace it?

The main reason you would want to replace the filter tee is if it is allowing air into your fuel system.

Check your fuel line for air bubbles, air in your fuel could be causing some of the noises you described.

If you live in a cold climate, you would benefit from the fuel warming aspect of the thermostatic tee. In a warm climate, it is not important to heat the fuel. As long as it is returning fuel to the tank and not leaking fuel or air, you don’t need to worry about it.

The part is fairly inexpensive and isn’t a bad idea to have a spare, just in case.

 

[afterthisnap]

New fan control module.

OEM?

 

[Amine5]

I see that you live in New Orleans. If the 3 way thermostatic valve is stuck in the position where it always sends 100% of the return fuel from the fuel rail back to the tank, I would just leave it that way. I replaced my valve with a "Kerma Widget" about 10 years ago which just plugs the hole to the fuel filter & always sends all of the fuel rail return back to tank. The reason why I did this is because that when I performed the "Diesel Purge" procedure I saw how quickly the fuel rail return got so hot so fast & I just figured that it was more likely to have problems due to fuel that is very hot rather than fuel at the temperature in the fuel tank.

What was the symptoms off warm fuel in your car , in mine i have rattling injector un noisy fuel pump only when warm

 

[pruzink]

What was the symptoms off warm fuel in your car , in mine i have rattling injector un noisy fuel pump only when warm

The only reason that I replaced this part with a Kerma widget is because I thought that these 3 way valves were cheaply made & that it MIGHT fail in the future. When I would do the diesel purge procedure on my car (you run the car off of 100% Diesel Purge for about 30 minutes until you empty the can), even when I started with a cold engine, that fuel return line coming back to that 3 way valve got very hot, very fast, so I just didn't see a big upside to risking the valve failing to the recirculate through the filter position. Even in very cold areas during the winter, the thing you need to worry about is your fuel jelling so I would still prefer to see that hot fuel being returned near the in tank fuel pump.

 

[JETaah]

So I had a bad check valve, stuck open. What exactly does this hurt? Its the one on the top of the fuel filter. Return side. I believe I have an issue with the incoming side but I dont want to drop the tank to mess with that one.

There is no need to drop the tank to get at the fuel pick-up.
Everything to do with drawing and returning fuel is accessible under the rear seat bottom cushion on any MK4 car. Three phillips screws hold the cover that conceals it. The unit comes out by loosening the top ring like a Mason jar. There's more than a couple of YouTube videos on this procedure.

 

[Amine5]

The only reason that I replaced this part with a Kerma widget is because I thought that these 3 way valves were cheaply made & that it MIGHT fail in the future. When I would do the diesel purge procedure on my car (you run the car off of 100% Diesel Purge for about 30 minutes until you empty the can), even when I started with a cold engine, that fuel return line coming back to that 3 way valve got very hot, very fast, so I just didn't see a big upside to risking the valve failing to the recirculate through the filter position. Even in very cold areas during the winter, the thing you need to worry about is your fuel jelling so I would still prefer to see that hot fuel being returned near the in tank fuel pump.

Thanks for your feedback i appreciate, the symptoms i have are , ticking noise only when engine reach operating temperature and rattling when going up hill , so i thought you had the same symptoms. May be having another problem , i can’t figure it out