Attention: TDR Forum Junkies 
Hey guys,
I've got more problems [verymad].I have had my fuel system apart multiple times recently and every time I get it back together the fuel pressure is doing something different. At first I attributed this to air in the system, but I have checked it over and bled the air and found no leaks. I also recently took two 300+ mile trips with no change from start to finish. I would think if it was air it would work its way out in that time. It also makes no difference if the fuel tank is full or not. Right now i am getting about 20 psi idle, which I would be happy with, however, maintaining 65 mph on the highway it drops as low as 13 psi! I could be wrong but i don’t think there should be that much fluctuation. Especially considering thats not even WOT, only about 15 psi of boost at 65 mph. The even bigger mystery is that just the other day I had the fuel system apart and put it back together and I had 22 psi at idle and only dropped to about 18 psi on the highway. It was great! Right after that the truck developed a leak in the water drain valve on the filter housing and i took it apart to replace it. When i put it back together and bled the air it wouldn’t maintain pressure. Since then i made the 2 long trips i mentioned earlier with no change. On the second trip i also had a “Dead Pedal” incident. I don’t think that is related but I'm not sure. I was doing about 55 with the cruise on and suddenly i lost power. I downshifted after a few seconds and suddenly the pedal worked again but i had a check engine light. I pulled over and pulled a P0121 code, which, i believe, is low voltage at the throttle position sensor. I don’t think these two things are related unless my ECM is going bad and so not putting out enough voltage to TPS and the FASS lift pump causing it to not maintain pressure very well. I don't think the gauge is the issue because it is mechanical. Fuel goes from the shrader valve on the vp44 to an isolator to the gauge. I have read the blue chip vp44 diagnostics on the dead pedal and I don't know for sure if the pedal was totally dead or just had a dead spot. I didn't know to check and i was on the highway when it happened. However, i don't think it could be a bad vp44 because it is less than two years old and is US remanufactured. So my questions are, should i replace the APPS? I can get one from Geno's for about $160. I don't want to spend money I don't need to obviously. Could a bad ECM possibly be causing these issues? Is there any way to test voltage to the lift pump to see if thats causing it to not keep pressure up? Could the FASS just be worn out? it is about 10 years old....I also have a big line kit and fittings from vulcan on the way to replace all the Banjo bolts from the inlet side of the fuel filter to the vp44 just incase it is sucking air somewhere.
Any input or ideas will be greatly appreciated!!
I've got more problems [verymad].I have had my fuel system apart multiple times recently and every time I get it back together the fuel pressure is doing something different. At first I attributed this to air in the system, but I have checked it over and bled the air and found no leaks. I also recently took two 300+ mile trips with no change from start to finish. I would think if it was air it would work its way out in that time. It also makes no difference if the fuel tank is full or not. Right now i am getting about 20 psi idle, which I would be happy with, however, maintaining 65 mph on the highway it drops as low as 13 psi! I could be wrong but i don’t think there should be that much fluctuation. Especially considering thats not even WOT, only about 15 psi of boost at 65 mph. The even bigger mystery is that just the other day I had the fuel system apart and put it back together and I had 22 psi at idle and only dropped to about 18 psi on the highway. It was great! Right after that the truck developed a leak in the water drain valve on the filter housing and i took it apart to replace it. When i put it back together and bled the air it wouldn’t maintain pressure. Since then i made the 2 long trips i mentioned earlier with no change. On the second trip i also had a “Dead Pedal” incident. I don’t think that is related but I'm not sure. I was doing about 55 with the cruise on and suddenly i lost power. I downshifted after a few seconds and suddenly the pedal worked again but i had a check engine light. I pulled over and pulled a P0121 code, which, i believe, is low voltage at the throttle position sensor. I don’t think these two things are related unless my ECM is going bad and so not putting out enough voltage to TPS and the FASS lift pump causing it to not maintain pressure very well. I don't think the gauge is the issue because it is mechanical. Fuel goes from the shrader valve on the vp44 to an isolator to the gauge. I have read the blue chip vp44 diagnostics on the dead pedal and I don't know for sure if the pedal was totally dead or just had a dead spot. I didn't know to check and i was on the highway when it happened. However, i don't think it could be a bad vp44 because it is less than two years old and is US remanufactured. So my questions are, should i replace the APPS? I can get one from Geno's for about $160. I don't want to spend money I don't need to obviously. Could a bad ECM possibly be causing these issues? Is there any way to test voltage to the lift pump to see if thats causing it to not keep pressure up? Could the FASS just be worn out? it is about 10 years old....I also have a big line kit and fittings from vulcan on the way to replace all the Banjo bolts from the inlet side of the fuel filter to the vp44 just incase it is sucking air somewhere.
Any input or ideas will be greatly appreciated!!
