All great suggestions so far. I would like to ask, if this problem just started, or has it been acting this way since you got it? (sorry if this has already been ask.)
As to the possible exhaust restriction, here is a fairly easy test, (once you get that engine cover off), that will show a severely restricted exhaust system:
I would install two gauges, (the two birds with one stone (test) thing)
These are no load tests
and can be done by one person. I suggest running both (no load) vacuum and fuel pressure, tests at the same time.
1. A manifold vacuum gauge.
2. A fuel rail pressure gauge.
Start the engine with the trans in N and slowly accelerate the engine (over about 10 seconds) from idle to over 3500 rpm. The vacuum gauge should go to a maximum reading (20"hg +) and stay there. If the gauge climbs to a high reading and then starts to drop as the engine speed continues to increase, you have excessive exhaust restriction. An exhaust restricted enough to cause this type gauge action will cause a significant power loss.
Fuel pressure test:
Running a fuel pressure test with out a significant load on the engine is not a totally valid fuel pressure test. But, if the fuel pressure is very low with no load on the engine or, as was stated earlier 'drops to zero as soon as the engine is shut off' this indicates a serious fuel delivery problem. If the fuel pressure holds steady during the following vacuum test then a loaded test on fuel pressure needs to be done. (see below)
Accelerate the engine several times to confirm results.
I have to agree that the problem sounds more like a fuel delivery problem.
If a problem does not show up during the no load test
, run the loaded fuel pressure test
. You will need to drive the coach so you need two
people to do this, please do not try to drive and watch the gauge.
Loaded fuel pressure test
= [takes 2 people]
1st person driving up a long hill, (if possible a hill that has shown the power loss), the engine needs to be in a hard pull for 30 seconds or longer,
the 2nd person watching the fuel pressure gauge. If the fuel pressure drops during the loaded test then the search starts for the cause. That cause, could be a plugged something (filter or Pump 'sock')
or maybe a mashed fuel line. There could be a dent in the metal fuel line or even somewhere along a rubber line there could be a bent retaining clip compressing the fuel line and causing an excessive restriction to the fuel.
If the fuel pressure holds during a load test, then your power problem is not fuel delivery.
NOTE: if the vacuum gauge is still connected during the loaded test. The vacuum gauge will normally be on zero during a hard pull. If there is an exhaust restriction that did not show up earlier, the vacuum gauge may
start to read a slight (1-2"hg positive [1/2 to 1psi]) pressure.
hope this helps,