Txakura Posted August 17, 2009 Share Posted August 17, 2009 1986 300E (gas) mpfi so I got called to look at a dead Mercedes, but after it sat overnight it fired right up then died again 2 days later it seems like, there is a fuel pressure regulator that is not passing fuel to the distribution manifold there is the inlet from the pump, a line to the fuel distribution block, a small return line and a vacuum line to the air cleaner housing I THINK the return line is for any fuel in the regulator when the throttle is snapped shut or demand for fuel drops off - it has somewhere to go and does not keep the valve in the regulator open I THINK the small 'vacuum line' is actually for any leakage past the spool valve seals, not to move the valve - more of an emissions thing and it creates a small negative pressure on the opposite side of the valve here's the kicker, Mr.Bosch fuel regulator is $900 !!! the next logical step is to check the fuel pressure being supplied to the regulator - if the pump is weak it wouldn't unseat the valve and allow fuel to flow to the manifold - hence no fuel getting past the regulator but it occured to me I have an extra Subaru FI fuel pump... is the world ready for a Mercedes GL Wagon hybrid? Quote Link to comment Share on other sites More sharing options...
muffman Posted August 24, 2009 Share Posted August 24, 2009 I think that the fuel pressure regulator allows fuel to flow back to the tank when there is too much fuel pressure. There should be a feed on the fuel rail from a fuel filter, and that is where the fuel should come in. Fuel pressure regulators normally make your car run really rich when they stop working. I tried the diagnose/replace parts thing for a while on an early 80's volvo, it would be much cheaper to have a mechanic figure out the problem. It is really amazing how much easier stuff with obd/obdII is to diagnose. Quote Link to comment Share on other sites More sharing options...
muffman Posted August 24, 2009 Share Posted August 24, 2009 Oh, does that thing have mechanical fuel injection? Working on that was a nightmare for me. I was thinking the kind of fuel pressure regulator most electronic fuel injection has, the systems are pretty different. Please forgive my pointless rambling. Subarus do have a very bosch-like fuel injection, so the fuel pump might work. Quote Link to comment Share on other sites More sharing options...
Txakura Posted August 27, 2009 Author Share Posted August 27, 2009 we got it, it was a fuel pump relay that (apparently has many functions) was the culprit... the relay was around $300, but I found a re-flashed one from "programa'' for $79 that was very very educational, I am glad my venerable ea82 is still a 'mechanical car' to a large part, and not as crazy with the electronics, relays and such - sure we have a few items but... sort of like an A-10 versus an F-22 both very good at their jobs, just two different ways in going about it Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.