I am wondering what the average purge time is on an Older Mercedes diesel. I know these engines return a lot of fuel but I am not sure how much fuel the IP has in it? How long should I wait after the clear filter directly before the lift pump and IP is completly filled with diesel? I would rather purge extra diesel back to the veg tank than start a cold car with some veg still in the IP and injector lines, But dont want to purge that much (i'm cheap!)
Thanks in advance for any responses...

it depends on your systems design. how many valves do you have, 2 or 3?

also note, what really matters is # of engine revolutions. purge time can be as little as 7 seconds @ highway speed.

on the 3 valve frybrid kit, the valves are *after* all of the filters, so you dont need to fill the filters for purging. the frybrid style loop also brings fuel in from the diesel tank and returns it to the veg tank on purge. not filling any filters, my purge time is set conservatively to 20 seconds @ 1100 rpm.

to be sure, i usually purge about a mile from my end destination when the weather is below 70 degrees.

greasecar type kits that dont have a return to the veg tank usually purge about 30-45 seconds.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I always error on the side of caution with this one. I timed how long it took to purge out the veg oil in my 240 at idle it takes a couple minutes. So I have mine set to close at 2 1/2 minutes. But I'd rather run a little extra diesel to make sure I've purged out the VO. Running at much of a speed you're going to purge a lot faster.

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