Diesel purge

I am going to do a diesel purge on my '87 300sdl this weekend. Should I do it before I change the fuel filters or after? I am thinking before so I do not trash the new filters.
I am getting a little engine shake after I let off the accelerator at stops and I think (hope) it may be a dirty injector. Acceleration is fine, mileage is ok 25-30mpg. I have not done a purge since I bought the car over a year ago. If it is not a dirty injector any suggetions?

When I change the fuel filter, I always fill the new filter with diesel purge (rather than pumping diesel fuel into it). The old filter shouldn't affect the passage of the diesel purge (which is "pure"). I guess I would do the regular purge cycle first; then fill the new filter with diesel purge and start it up again.

Ron Dwelle

[CJ]

I run diesel purge drectly from the bottle while shutting off the fuel supply. I then fill the new filter with the remaing diesel purge.

Here is a link that may help you out.

http://www.mindspring.com/~houlihan/merc/purge.htm

[Ken300D]

A new fuel filter will hold just about all of a can of diesel purge. It is nearly as effective to do a purge this way as it is to disconnect the fuel lines and run purge from a bottle.

And much easier.

Ken300D

[QUOTE]Originally posted by Ken300D
[B]A new fuel filter will hold just about all of a can of diesel purge. It is nearly as effective to do a purge this way as it is to disconnect the fuel lines and run purge from a bottle.


However, if you just fill the fuel filter, most of the diesel purge will run back into the tank through the fuel return line. The IP pumps much more fuel than is used, so the excess returns to the tank. When diluted in the tank, the diesel purge doesn't do as much good.

Ron Dwelle

[benchracer]

I'm with Ron on this one, Ken. I've used the Purge both ways. Filling the filter just allows the Purge to run back to the tank where it's diluted by the fuel. I think you'll really notice the results when you run it directly from the bottle with the overflow going back into the bottle. There really is not much extra work involved at all.

[Ken300D]

I see. Well, I thought the return line to the tank was mostly to provide a return path for those little injector return hoses. Did not know that there was an additional return generated by the fuel system pump.

So, there's no way to tell without measuring, but doing diesel purge in the filter might be half as effective as using the "jar and hoses" approach - maybe less.

Ken300D

[Billybob]

If these are the small black hoses attached to the fuel filter and looping from injector to injector ending with a short plugged hose then “return lines” is a misnomer. These lines carry filter fuel under pressure to the upper portion of the injectors. This fuel apparently acts as a lubricant to the upper workings of the injectors. Fuel is under pressure coming from the fuel filter while the engine is running.

I'm no expert by far in fact I am merely an observant fool who disconnected the line from the fuel filter banjo fitting leading to the first injector on my running engine and watched as finely filtered diesel continued to squirt from the filter fitting as I tried to replace the small black line onto the fitting under pressure.

[QUOTE]Originally posted by Ken300D
[B]I see. So, there's no way to tell without measuring, but doing diesel purge in the filter might be half as effective as using the "jar and hoses" approach - maybe less.

I don't know how to measure it, but I think it's a lot more than half. If you run the return line into a jar with Diesel Purge, the engine will keep recycling it in and burning it. I've never timed it, but I would guess the engine will run at least 15 minutes on one can of diesel purge while it is recycling (enging running at idle). That suggests that recycling the Diesel Purge is 15x as effective as pumping it directly back into the fuel tank.

[benchracer]

[QUOTE]Originally posted by dweller
[B]

Originally posted by Ken300D
I've never timed it, but I would guess the engine will run at least 15 minutes on one can of diesel purge while it is recycling (enging running at idle).

I timed it, although not precisely. It took longer than 20 minutes and I occasionally increased the engine rpm. I shut the engine down before it sucked air and had enough Purge left in the jar to swig a mouthful.

[ajb]

I just did this last weekend, and it did take about 15-20min with varying engine speeds. I was also surprised by the amount of Purge being returned to the jar by the return line. The "jar" method seemed to be a better way to make sure your injectors were really clean & removing & replacing the hoses was not really a big deal.
Best of all I was impressed how much smoother & responsive the motor in my 240 ran.

Aivars

[can-do]

Greetings All,

After running purge several times, and differently each time I have come to the conclusion that you need to change the spin on filter first, prime it with fresh fuel. Remove the fuel line going to the fuel tank as well as the filter return line. Run your purge from a jar. If you fill the filter with the purge it just saturates the filter and not all is used during the process, and if you leave the old filter in place before purging, you simply end up throwing half your purge away after the process when you change out filters.

Just my observation,

Charles