Truck has not been used a lot in the past year. I pulled it out of the barn to recover a vehicle I got stuck. The area was at the top of a hill. MK ran good but started to loose power halfway up the hill.
Turned around and drove back to barn but made it only halfway. It did seem to run better going down the hill?
I figured it was a bad fuel filter. Replaced the unit that mounts along side the clear bowl separator. Truck runs barely. It starts, idles but will die if I press to much throttle.
It almost sounds like engine is not running on all 8. The muffler flapper is real flappy when at idle. There is no white smoke coming out of exhaust.
Any advice?
Pete
Any luck with this? It sure sounds like a fuel issue. The MK48s I've seen all had ball valves right at the outlet from each tank and the hoses had JIC swivel fittings. Easy to pull the hose off the discharge side, then open the valve to make sure fuel is coming out of tank. If the fuel is bad, it is easy to hook up a short hose to direct the flow into a bucket or 55 gallon drum.
I'd suggest cracking the line where the mechanical fuel pump delivers fuel to the secondary fuel filter- with the engine running it should have about 60 psi and quite a bit of flow. If the engine won't run, you should get some flow from using the hand priming pump located by the fuel filters. If there isn't good flow, the problem is probably in the water separator filter on the suction side of fuel pump or if there is a lot of air bubbles that don't stop there might be an air leak in the suction side hose. On one of our MK48s, the bowl on the separator filter was clear, but the filter element above it was completely plugged up with some weird black stuff. It wasn't gooey, more particulate stuff like carbon black.
Two of the MK48s I got had bad fuel lines (dry rotted & leaking) that ran from the mechanical fuel pump on the front of the engine back to the secondary fuel filter at the passenger side rear of the FPU. They are about 12 feet long and a PITA to change since they are behind panels under the fender and zip tied to other hoses in about 10 places. While I had things torn apart, I also changed the suction side hose that runs from the outlet of the water separator filter up to the mechanical pump.
I bookmarked the fuel pump part of the TM's when I was working on these. In TM 08780B-20 (June 2004 version) fuel section starts Chapter 4 page 665 of 2138; and in the -34 (May 2004 version) page 548 of 2676.
