Quote:
Originally Posted by Diesel911
I have used the all Plastic pre/primarly Filters exclusivly and only had a air leak issue when the Hose was hard (looked like the Hose that came with the Car in 1984).
After replacing the Hose with the mentioned 5/16" ID Fuel Hose from the local Auto Parts store I have had no issues for 7 years.
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A new hose sure helps. Did you use the Mercedes fuel hose clamp (with Phillips head) on the 5/16" ID Fuel Hose from the local Auto Parts store? If the auto parts store hose has a smaller o.d. than the Mercedes 8 mm hose, the Mercedes hose clamp may not provide enough clamping force onto the hose/pre-filter because the clamp closes down to a certain diameter and stops there.
The 2 hose connection on the pre-filter is a weak spot for air leaks. Unlike all other fuel hose connections on the rest of the 617 fuel system, the pre-filter connections are the only ones that is smooth, without a barb, which makes having a pliable fuel hose with the correct size hose clamp and a more rigid pre-filter (with the brass sleeve) that much more important. The pre-filter is under suction, the suction increases with engine rpm. If you see no air bubbles at idle, that may not be true at 3000 rpm.
Here's a real long thread on a documented case of pre-filter (primary filter) issues. His symptoms was pinging at idle and at part throttle, sounds of ball bearings in cylinders when cruising down the road. From Oct 2014 to May 2015, he spent a lot of money and time trying different things on his 617 in a Toyota truck, none of which helped. In the end, he replaced the pre-filter (which has been replaced a few times already with the same type pre-filter w/o the brass insert) with a Facor filter, which is metal, and his symptoms went away.
617 weird behavior diagnoses
"........I think my plastic OEM primary filter was leaking air. Someone mentioned that the filters without a metal insert in the plastic hose barb could crush down and allow air in. I'm thinking this is what happened, as I'd gone through multiple filters with the same issue. The Facor is all metal.
I swear it runs smoother and it has better power. I don't trust seat-of-pants dynos, but I'm now able to accelerate in top gear on hills that before I'd either be able to just hold speed or gradually lose speed on..........."
617 weird behavior diagnoses