Diesel Purge - bypass the fuel filter or not?

[shortbus]

There are 2 tutorials in the how-to. One specifically cautions *not* to bypass the fuel filter, and the other shows the car's fuel filter bypassed but a cheap inline filter used on the supply line from the DP container to the pump. Which is best? If I don't bypass the car's fuel filter, should I drain and prime the filter with DP (or replace and prime with DP) prior to doing the purge? Wouldn't there be a filter full of diesel diluting the DP if I didn't? I have a replacement fuel filter on hand, but if I prime it with DP and then run the purge, I'll have very little DP left in the can - might draw air? What about priming the new filter with Diesel Kleen and then running the full can of DP (diluted with Diesel Kleen) through the new filter 'til the DP's gone? Unfortunately I only have the one can of DP on hand...

 

[Lex4TDI4Life]

1. Bypass the filter and run it straight from the can. It's not like they stuff they put in there was pumped out of a neglected truck stop tank.

2. You dont need to run the whole can to see the benefits. Stop well short of getting air into the system

 

[Rickstah]

Update...yeah, what Lex said

Hey Shortbus. One can will do wonders for your injectors if they need cleaning. You don't need to worry about running through your fuel filter, it's a little more tedious to do it that way, besides. I've done the Purge procedure multiple times without using a filter, but once I built the little device that had a filter and a return capability, it was just too easy. The only other concern with a fuel filter is if your vehicle pushes fuel through the fuel filter when it is unhooked. Mine doesn't, so it is easy peasy. Check my sig for a simple how-to using the DP, or there are numerous videos and such all over the web.

The virtue of having some type of filter on the fuel going to the injector pump is obvious...a bug could fall in, or some crud could get in the open can, you never can tell. Like I said, I've done it without filtering, but it is smarter to filter it. I'll never go back to the old way, simply because now the contraption I made is always ready to be used.

About starting your car after you have your fuel filter unhooked. I've never had to prime the fuel filter after just having the lines unhooked. This wouldn't be the worst time to replace your filter, though, if it needs it. Just get a mighty-vac, then prime your fuel filter by drawing fuel up through it with the vac, then button it up and start it up. No worries ...lots of how-tos for that, also. Good luck.

 

[jimbote]

Gonna point out the obvious here....if you're not using a filter and pulling straight from the can and returning to the can where is the crap going that your trying to purge? ...
right back where it started, in your fuel system! ...
use a filter!

 

[Rickstah]

Good point, another reason to use an inline filter. Is the returned fuel picked up after it goes through the injectors or before?

 

[DeafBug]

Gonna point out the obvious here....if you're not using a filter and pulling straight from the can and returning to the can where is the crap going that your trying to purge? ...
right back where it started, in your fuel system! ...
use a filter!

I completely understand what you are saying. My question is "Shouldn't the fuel in the fuel lines between the pump and filter been already filtered. So that means all the fuel in the pump and the lines from the pump and the injectors and back to the filter is already filtered." So what crap are you talking about and I don't mean the fuel, just what needs to be filtered?

I have used DP a lot on many cars I work on and no one has told me the ill-effects on the pump afterwards or later. Just take the lines off and run it from the can like Lex said. The fuel that is already in the pump is not DP, so what! At least the mixture is strong, at least 50%. Don't try to run the whole can as you will get air. Run like 3/4 of the can, then dump the rest in the tank.

 

[Rickstah]

Hey Deaf, not speaking for jimbote, but his point may be that if you run just a couple of hoses into the DP can, one of them is the return, and it is possible the DP has dissolved some deposits that may go back into the can of DP, to likely be sucked back into the injector pump. My question about that was...is the return fuel picked up and sent back before it goes into the injectors, in which case there would be no deposits coming back?

Currently looking for a process flow of the fuel

 

[BobnOH]

.................. My question about that was...is the return fuel picked up and sent back before it goes into the injectors, in which case there would be no deposits coming back?

yes, the pump takes in way more than it needs at idle. Once the fuel injects there is no fuel recovery

 

[Rickstah]

Thanks, Bob...so maybe we don't get the dissolved particulates or whatever after all on the return trip.

 

[jimbote]

Good point, another reason to use an inline filter. Is the returned fuel picked up after it goes through the injectors or before?

on a VE pump there if fuel returning from the injectors and fuel returning from the pump....the return fuel from the injectors goes back to the pump @ the banjo fitting but I dont think it reenters the pump body...it only enters the banjo where it combines with the return stream from the pump....I may be incorrect but I believe the return flow/pressure from the pump won't allow backflow