Recurring power loss problem on 1984 300D (runs on WVO, has injection line heaters, in-line heater and auxiliary 12 v. pump before filter):
Power loss is worst/most noticable at high speeds (on freeway) and up long grades. Worst case it got down to 7mph on freeway shoulder.
Weird: If car rests for 20 minutes, gets going fine again for 10-20 miles.
Changed all filters more than once, bled system properly. Still happened.
Poured ATF into tank and directly into spin-on filter. Made marked difference for 20-30 miles, then problem recurs.
Had tank and tank screen cleaned out, thought it must be dirt coming form tank. No change.
Had injectors cleaned. No change.
Thought I found leaking fuel line, was just overflow line.
Asked mechanic to check all fuel lines for leaks drawing air. Factory trained MB mech for over 25 years, says significant air leak would cause car not to start at all. Saw threads here that seem to think otherwise (power loss thread started by tc art). What's the truth?
Any ideas? Could it be the main fuel pump (IP?) Is there a way to check the IP without replacing it? Why would ATF make it temporarily better if it's a failing pump? This is the part that stumps me.
Saw good thread here about power loss related to a misaligned throttle linkage, will check that too. (same, tc art thread)
p.s. hand pump doesn't seem to be leaking.
p.p.s. hand pump on my other MB, the wagon, IS leaking, has experienced occassional power loss, but after running some diesel through it, seems fine again, although still leaking.
p.p.p.s IF I got some bad (hydrogenated) oil in the system (small amount is possible), could clog and cause power loss or blockage in a fuel line I think, but could be "burned out" with diesel (and would have seen more problems in wagon, since both cars use same oil.)
appreciate any help from you guys
thanks so much
Stanya