After my 2nd lift pump failure, I had the FASS system installed 8/06/2006. I do not use my truck in the winter months so I have only driven 11k miles since the installation. Last weekend, I was towing my trailer home from Indiana with the cruise on and I noticed a fluctuation in speed. Watching the boost gauge, it would suddenly drop 5-10 lbs of boost, truck would slow, cruise would kick it to hold speed and boost would come back. I turned the cruise off and drove with my foot for awhile and after a minute or so, it did the same thing. This went on for 45 min. or so and I noticed it had kind of smoothed out so I set the cruise again and it was okay for the remaining 2 hrs. I came home and next day read the booklet that came with the system (probably should have done that last fall). Booklet said the fuel filter is usually good for 60k, that was a surprise. Then it said empty the water separator occasionally by loosening the canister and opening the bottom valve. Tried to loosen the canister and it is a smooth design. The only filter wrench I had works on oil filters but would not budge the separator canister. I remembered the young man that installed the system talking to me after I paid the bill, he was an employee not owner/manager. This is a well known Diesel shop in the Midwest and I'm not trashing them but I can only guess the young man doing the work put the muscle to my canister last August. I was able to open the bottom valve and drain some fluid from the water separator but it seemed like just diesel fuel. My question is, does anybody have experience with this system and if so how often do you, drain the separator? change the filter? change the separator. The shop that installed the system is 200 miles from my house or I would drive over and let them deal with it. I have not been back out on the Interstate again since this happened but I'm hoping at this point it was a fuel problem. I had a fuel pressure gauge installed at the same time as the FASS system and it has read 22lbs pressure since day one, occasionally it has been 21-22 but it didn't seem like a problem. I normally do not go WOT but the trans has kicked down a couple times through the mountains and it didn't seem to effect fuel pressure noticeably. During the incident last weekend the fuel pressure gauge was reading 20lbs but never below that. Injector pump is newer than the FASS system.
First, fuel pressure is a little high. Above 20psi you run the risk of harming the Oring on the VP44 inlet. You should be right around 16psi. This could be part of your problem. As to the filters, I don't change the separator at all, just drain it occasionally. I have yet to find water inside. As to the Filter, FASS reccommends about 60k, so I would follow that. If you are not seeing a drop in fuel pressure then the filters are not clogged up. Did it set any codes? Might have to pull those with a downloader or scan tool.
Throttle position sensor The truck has been running fine, although I haven't driven it very much lately and only around town. I had a chance to check the codes today at the Dodge dealer and they said the code indicated (TPS) throttle position sensor. My questions are, is the TPS a plug and play part? Is it the same part for both manual and automatic transmissions? Would you buy a used one for under $100 if you had the chance or bite the bullet and buy new. List at the dealer was over $500, with labor it was over $700 installed. I certainly understand the dangers of using used parts but I'm just looking for the opinion of someone that has experience with this part.
Are you asking about the TPS? @ $700+ new, I would say its worth the risk to get a used on for under 100 and try it out.
