Help replacing fuel check valve on 3406e

thank it a high dust situations it a log truck would the return lines need replacing also

 

The other prolem with that old of an e model is if the lines due collapse and deteriorate the rubber will plug the check valves in the fuel primer pump and also allow fuel to drain back to the tanks, or prevent flow thru the hand primer pump. It has a push/pull function and each check valve is installed opposite each other to allow that process. Pull the hand primer pump off and look to see if the rubber flapper in the valves appear to be seated. If not replace the hand primer pump.

 

had the check valve off is the spring behind the ball supposed to be weak are strong the small one on the return line spring seems strong the other one spring seems week and real easy to mash in

 

I have never noticed them to be weak. If they are bad the pressure will fluctuate and pressure drop off to zero as soon as the engine is shutoff.

 

replaced check valve and its still loosing power

 

Put a short peace of clear fuel line just before the fuel pump to check for bubbles.

I got a two foot peace of clear plastic line at the local hardware store and got ends crimped on it, worked great to find my air leak .

It started out as the truck would lose prime over the weekend and slowly got worse until it would lose prime setting overnight and finally after a few hours, put the clear line in and you could see LOTS of air getting sucked through the line, turned out the line going into filter vacuum gauge had a small hole in it.

 

K-Whopper: It sounds like you have deeper problems, tough to troubleshoot from Kuwait. One of the simplest checks for that problem is to run a bypass pickup line from the tank to the fuel block where you replaced that check valve, drop the line down in your tank and secure and take for a road test. If it runs OK then your problem can be a cracked pickup tube, debris in tank, malfunctioning tank vent or if it has a vented cap.

If that does not help, then run a hose from the return side of that block and put it into a bucket. Run the engine and check for bubbles. Be careful becasue that engine will fill a five gallon bucket up in a hurry. If there is a lot of bubbles (heavy air flow) which you will get a heavy flow of fuel, you can have an injector o-ring that is cut or leaking and causing the same problrm.

Sometimes if the return line of check valves if the truck has dual tank returns become plugged they will hold air back into the engine. Finding a problem such as this unles qualified and experienced can be time consuming. Good Luck..