GAS LEAK UNDER PLENUM

Rongold

Member
Hi all,

My 2014 MKS (3.7L standard engine) has developed a gas leak under the plenum at the rear bank of cylinders. There is always a fuel smell, but I don't see any puddles. If I put my nose at the passenger end of the plenum towards the rear, I can smell it. I can see the one injector at the passenger end of the fuel rail, and it is dry, so that leaves either one of the other 2 injectors under the plenum, their upper O-rings, or the rail itself. Unfortunately, you cannot see under there from either end of the engine. The car has 19,000 miles and is out of warranty. Being a former auto repair shop owner, I have repaired many cars with this problem, so doing the job is no big thing for me. I am just wondering what is the most common failure for this car with this problem---A cracked injector, a leaking upper O-ring, or a porous or cracked fuel rail ??? Has anyone else had this problem, and what exactly was leaking ??? Thanks in advance for your thoughts.


RON
 

Rongold

Member
Well, I see there were a lot of lookers, but no posters with advice. I tackled the job today. In my prime, this job would have taken me 2-3 hours, but now with old age (73) and arthritis, it took me 6 hours. I removed the plenum, took a very good look at the injectors that were at the rear of the engine, and saw no evidence of a fuel leak. I then removed the fuel rail. I had purchased a used rail with 6 injectors on Ebay last week that came off of a 2015 Taurus. I DID NOT use the injectors, but I swapped in the later rail, and moved the original front injectors to the rear and the original rear injectors to the front with all new O-rings on all 6 of them. This way I would be able to see if one of the rear injectors was possibly porous and leaking as the original rear ones are now totally visible in the front. If you remember in my post above, you CANNOT see cylinder #2 injector or cylinder #3 injector with the plenum in place. I then reassembled everything and started the engine. I don't see anything nor do I smell anything now. Either the old rail was porous or 1 of the upper O-rings on the injectors was leaking. I did a little searching and found out that Ford replaced the original part number for the rail (AT4Z-9F792-A) with (GT4Z-9F792-A). Maybe my original rail was the old design (possibly porous), and the replacement is the newer design. Both rails had the same engineering number (AT4E-9F797-GA) on them, but the original rail's date code was 13121 (year 13 day of year 121) and the newer one was dated 15162 (year 15, day of year 162). Maybe the later rail was the newer part number. Whatever it was, my PROBLEM IS SOLVED !!!

RON
 
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