How do I bleed air from the fuel system?

I am having trouble bleeding air from the fuel system after change of filters. I only have a small pamphlet on the Perkins 4-108. It only references two places on the mechanical pump. One is oblivious the other isn’t. Do you have any information that would assist me?. THANKS Dave (s/v #145, Saw-Whet)

a. Hi Dave, Having had a Yanmar, Vetus and now a Beta ( Kubota ) engines, so I don’t see why it would not work on a Perkins.. I installed a hand primer pump ( a squeeze bulb ) type, BEFORE the first fuel filter in the system. After a filter change, I just hand prime the fuel lines until I hear the fuel returning to the tank, and THAT IS IT. Works like a charm and eliminates the ” bowl filling ” thing and the clean up. This scheme will do nothing if you have air after the fuel pump or in the Hi press. lines to injectors. I hope this helps Regards, Frank Bryant, s/v #186, Visitant

b. The Perkins is easily bled with the starboard side manual fuel pump. If necessary, unscrew the coupling on the right. G & B Stuurop, (s/v Octopus I), Menorca, Spain

c. On any fuel system that you are having trouble bleeding, you should check the fuel pickup tube in the fuel tank. Years ago it was common practice to put a screen on the end of the pickup tube. This screen is subject to plugging and should be removed, as it is more hazard than help. Second, check the gaskets on you fuel filters. If you have a Racor primary fuel filter, the O-ring in the T-handle that hold down the lid can leak air if not properly installed. Finally, make sure that the diaphragm in your lift pump (the fuel pump on the engine) is not leaking, as it could allow air into the fuel, and worse, diesel into your engine oil. Hope this helps, regards [Opua, New Zealand] , Harry Hungate, (s/v Cormorant)

d. Hi, I don’t own a Perkins so I don’t have direct experience…….but I did see this discussion. It would lead me to look for a plug where a return line could be connected. See the link. It sounds like ““Rainsail”” successfully bled his injector system by removing the plug filling an inlet for an unused return line. Pete Bowes

e. Good day Dave Shaw, My wife and I purchased our Corbin 39′ in June 1989 and moved aboard in May 1990. S/V MALLARD was fitted with a Perkins 4-108 and we inherited two good maintenance manuals and a parts description manual. Regrettably the engine had been poorly maintained by the two previous owners; we spent $3,000USD on repairs in Salem, Mass in September 1990; the engine gave out completely as we neared Daytona Beach, Florida in November 1990. It proved to be cheaper to purchase a new Perkins 4-108 than to have the old one (with only 1,900 hrs) repaired. By the time we sold the boat in Kingston, ON in July of this year, the engine was still going strong after almost 7,000 hours; it started at first try on launching, after 10 months on the hard. The new owners have reached Long Island Sound by now, after going down the St Lawrence and down the coast of the Maritime Provinces; they have had no problems with the engine whatsoever. Long preamble to say that, from December 1990 until July 2004, we lived aboard on average 50 weeks out of every year and gained a great deal of “hands-on” experience with our Perkins 4-108. We changed the fuel injector pump and tips on several occasions, as well as the starter motor, etc. The mechanic who installed our Perkins in December 1990 showed us an efficient, effective and easy way to bleed the engine; you will not find these steps described in any manual; you normally have to be a member of the “mechanics fraternity” to be clued-in on these procedures. The operation requires 2 individuals.

STEP 1: Armed with a commercial type blue absorbent paper towel, you crack open, with a 5/16″ wrench, the small screw on the side of the LUCAS fuel injector pump. One person activates by hand the small lever pump in the fuel line; the other ensures that all the air has been purged out of the fuel injector pump and waits until a clear jet of diesel, completely free of air bubbles emerges from the pump. Stop pumping and tighten the screw. By this time, the fuel injector pump is full of diesel yet the fuel has not travelled up the copper tubing to the 4 Injector Tips/Atomizers.

STEP 2: Crack open all 4 nuts (5/8″ wrench) holding the copper fuel lines to the Injector Tips/Atomizers; the mechanic did it by loosening only 2 of the 4 but this procedure never worked well for us. One person works the starter while the one with the wrench watches closely for fuel leaking out where the copper tubing joins the atomizers; as soon as fuel starts flowing, usually at cylinder 1 first, finger OFF the starter button and tighten nut in question. Same procedure for the 3 other cylinders; it takes less starter time with each subsequent atomizer; the engine often starts running by the time the 3rd nut has been tightened. The small manual that comes with the engine leads one to believe that, once all the air has been purged from the Injector pump, you are ready to start the engine. This was never the case for us since, as mentioned earlier, you cannot achieve enough fuel pressure with the small hand lever pump to get the diesel all the way up to the atomizers.

Hope the above will prove to be of some assistance. Guy Comeau, ex-owner of S/V #075, MALLARD, now sailing south under new name of s/v #075, NOVA STAR.