Quote:
Originally Posted by Ancient Benz Guy
I have tried unplugging the ELR with the engine both cold and warmed up. In both cases the idle speed drops to about 480 RPM but the engine keeps running. Runs quite smoothly at the low RPM. It also starts right up with it unplugged. When it is plugged back in the engine revs up a little beyond the normal idle speed (by ear) then returns to about 590 as read on the tach. While in there I did notice some fuel weeping around the hose that goes from the fuel warmer thermostat to the lift pump. I will fix this, but surely that can’t be the cause? Or can it? Should I put in a new lift pump just in case?
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I’d argue that your base idle is a bit low. Unplugged test idle speed shoukd be 570.
If the thermostat is doing something funky, including letting air in, then you could well have issues. Do you see bubbles in any of the clear tubing?
I’d be inclined to look into your base fuel pressure and flow before condemning the lift pump…. But I’d also be considering refreshing the seals in it regardless with those miles on it..