I just did a Diesel Purge on my car- it effectively got rid of the annoying engine ping I've been complaining about lately- very happy about that. However, it appears that I've somehow created a fuel leak by doing this procedure.

As my car did not have an in-line fuel filter ahead of the main one, part of the procedure was to install one- other wise I had no suction hose to put into the Diesel Purge can. So, I cut the clear plastic line leading to the hand primer pump (attached to the main filter housing in my case) and spliced in an in-line filter using 5/16" rubber hose. With this filter removed I now had a suction point for the Purge.

After sticking the suction and return hoses into the can, I started the car and there was a great spout of Diesel fuel coming up from the hose I had cut. I shut her down real quick. I assume this would have come from the "lift pump" ???

Anyway, I stuck a drill bit into this line to plug it, cranked the starter without pre-glowing, so it wouldn't start, and immediately the drill bit was blown out under the fuel pressure. So, I stuck in the next size up drill bit, and tied it to the dipstick tube, so that if it blew out, it wouldn't hit the fan. This time, it didn't blow out, and I successfully started the engine and ran through the can of Purge as per the instructions. (I even turned on the air conditioning to give the engine a bit of load- thought that would make for a better purge).

After putting everything back together, it seems I now have a fuel leak. It is dripping off the very back of the engine, like 1 drip per second, while the engine's running. With the engine off, no drip. I took the car for a long drive, to make sure all my gush of fuel had evaporated, but the drip is persisting.

So, my question- did I perhaps blow a seal on the lift pump (if that's the right name for it) by plugging it's outlet with the drill bit? That's all I can think of, because everything's staying dry around my in-line filter addition. I don't even know where the lift pump is on my engne- everything is so crowded on the IP side of my engine, I could not see where this fuel line even goes, looking from above. So where do I have to look to even find the thing?

Dave M.

1976 300D

You were supposed to feed the Diesel purge into the lift pump.....and the return hose into this also....I hope you didn't cut the line between the lift pump and the canister filter like I thought you said.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Yep- that's exactly what I did!

DM

I did my homework and followed this procedure http://www.mindspring.com/~houlihan/merc/purge.htm

The problem was, like I said, my car was not equipped with the plastic inline filter. But now it is. In other words, I had to create "Point B" in his photo to give me a supply line. I also plugged the line that normally goes into the filter, as instructed- using a tight fitting drill bit, thus plugging the output of the lift pump. Now it appears my lift pump may be leaking, except I don't know where the damn thing is located- would I find it by crawling under the car and looking up? Roughly where?

Dave M.

1976 300D

Dave, just a thought. You are not leaking from the hand primer pump are you? If you used it to prime up system after purging it might have given up the ghost and started leaking a little.

I climbed under the car to see what's what, because the fuel was running to the back of the engine then to the ground, with everything above where I spliced in the plastic filter nice and dry. I found the leak- and also the lift pump of course- not visible from above. Anyway, I had ruptured the plastic line coming out of the lift pump. These get very brittle with age it would seem, so it split open while I was working the new rubber fuel hose down onto it. Easily fixed with more rubber hose, and the pump itself survived the ordeal.

Conclusion for other first time purgers- there is no risk to the lift pump by plugging that line while running Diesel Purge, as instructed in the link above. That is the part I was worried about. Just make sure it is very securely plugged.

Back in the saddle again--- and thanks for the tip!

Dave