"theoretical" fuel system bleed question

[Ken Heyman]

When I replaced my R24S Racor filter, my fuel system did not depressurize. After screwing on the new filter (per methods discussed in this forum) my pump still ticks rhythmically. Is there sufficient pressure downstream (engine side) of the pump? I haven't filled the plastic bowl as of yet with diesel fuel. I know I can do this manually or by using the electric pump(have to crack the bleed on the engine). Still I thought the system would have lost pressure by virtue of the filter change. Last year after removing my fuel tank and reinstalling after cleaning, there was still pressure in the system and in fact it didn't require bleeding. As there was a bit of fuel coming from the nut on the engine filter,the system may have"self bled" before I tightened the nut. I have not opted to keep the bleed nut open a 1/4 turn as some have done to create a self bleeding system.
Magic?

Thanks in advance,

Ken

[Stu Jackson]

"Magic" is a great answer -- quit while you're ahead!   

It sounds like the fuel lines from the Racor to the injectors have remained full and you just haven't, for some reason or other, gotten any air into the system.  That happened to me one time, and I wish it would again!

Think of the fuel lines as a FULL cup or glass with the fuel filter sitting on the top of the lip of the cup:  you're replacing the fuel filter, which is at the top -- this isn't removing any fluid from down below (in the glass).  If you fill the Racor filter by gravity from the tank (opening the vent on the Racor housing) or by pouring diesel into the bowl, you may not get any air into the system and never have to bleed at the secondary filter.

Good work!  Actually I think you've found the trick:  I don't fill the bowl, I use the electric pump to do that, so I'm actually introducing air into the system.  I'll try your way the next time, should save a lot of work.

[Ron Hill]

Ken : I believe that with the loose (bleed) nut on the top of your engine fuel filter bracket, you had a self bleed system until the fuel started to come out. 
It's so simple to fill the Racor w/bowl with fuel or as I do fuel additive/injector cleaner, why not?  Then open and close the bleed valve a few times and start the engine.  That insures that the absolute minimum of air is introduced into the fuel system.  Why let air into the system so you have to bleed it out?????  I've NEVER had an engine quit or even hiccup!!   

[David Sanner]

Ron does filling the filter & bowl with and injector cleaner do some sort
of power wash on the injectors & cylinders?  Have you ever noticed any
difference imediately after doing this?

Does the engine run rough at all will that stuff is worked through the system?

Thanks

[Stu Jackson]

Ken

Thanks so much.  You wrote: "I haven't filled the plastic bowl as of yet with diesel fuel. I know I can do this manually or by using the electric pump(have to crack the bleed on the engine). Still I thought the system would have lost pressure by virtue of the filter change."

I changed my fuel filter today, and used your method.

This is for our M25, 3 cylinder, 21 hp engine - a real original!

Drain filter bowl from under bowl knob into trustworthy container, after turning off fuel valve under the port locker.

Remove filter and sediment bowl.  Remember to install a fuel shutoff at the bloody pump/filter location under the head sink!

Carefully contain and dispose of fluids.

No need to open vent nut (13mm) on Racor filter housing.

Replace with new filter and bowl with new rubber gaskets provided with new filter.

Hand torque only is required to both remove and reinstall, an oil filter handle doesn't fit and isn't required to seal the gaskets.

Open fuel valve from tank.  Don't forget to do this!!!

I turned on the key and then opened the knurled knob.  Perhaps should have done in reverse order.

About one minute of fast fuel filter clicking, closed and then opened knob, still fast clicking, open knob all the way, slowed down, closed knob speeded up again, but within less than another minute it slowed to the regular click after I closed the knob.  

I didn't have to deal with that crazy nut on top of the secondary diesel filter housing on the starboard side of the engine.  unless I change that secondary engine mounted filter
Thanks again.

PS - Went to an auto store to look at fuel system/injector cleaners recommended by Ron to fill the filter and bowl before starting the engine.  I didn't find anything specific for diesel engines, so went as described above.  I understand Ron's concept.  Any specific recommendations on the injector cleaner to use?

PPS - When replacing the secondary engine mounted filter, the nut on the filter bracket will have to be backed off, or in my case removed, to allow the air to get out of that portion of the system.  For that, it is a very wise thing to install a fuel pump shut off toggle switch to minimize the amount of spilled fuel since the slippery diesel makes it hard to replace the screw efficiently and quickly.  I have done that and it makes secondary bleeding much easier.

PPPS - Any injector cleaner will do, works like a charm.  [Nov. 2009]

PPPPS - injector cleaner is never a bad idea, but you can do it without it:  http://c34.org/bbs/index.php/topic,5558.0.html  [Oct. 2010]

[Ron Hill]

Stu : I don't have a jug of the cleaner at home, but as I recall it's "PS Diesel Additive".  I get it at Wall Mart for about $9.50 per jug (2 qt).  It is a "C tane" booster also.  It comes in a grey bottle with black lettering and good for a couple hundred gal of fuel.
Yes, it works as a "injector power wash".  Being an oil base it's not harmful to the injectors and is rapidly diluted by the fuel pump mixing in diesel.  Works for me.      

[Ken Heyman]

Stu/Ron,

Okay, the empirical evidence is in and I think we can call this a plan. I'm always going to "default" to the knurled knob to bleed the system. If not successful, only then will I crack the nut on the engine mounted filter. I'm also going to try the injector "wash"---maybe squeak out a few additional RPM but more importantly avoid a future problem.

Thanks,

Ken

[Ron Hill]

Ken : The engine filter still MAY have to be bled.  It all depends how much fuel drains out of the input/output lines from the filter assembly ( and is replaced by air).
What I do is use 2 needle nose vice grips as "hemostats" and clamp the lines on either side shut.  I put some small plastic hose on the vice grips so it can't damage the fuel hose.  A thought.   

[Stu Jackson]

Ken, I think you're right.  It worked for me thanks to your idea (above).

Ron, I keep putting "install a fuel shut off valve right at the Racor" on my To Do List.

[Stu Jackson]

As a reminder, you should never have to loosen your injectors to bleed the engine.  Only two things: the knurled knob and the nut of the top of the secondary fuel filter bracket.

This came up on another forum, thought I'd repeat it.

For M25-series engines.

[Ron Hill]

FYI, You need to unloose the fuel inlet tube to each injector, if you have removed/replaced the injection pump until the fuel is flowing - then retighten !!

[HBDave]

For the last ten years I've been replacing my fuel filters with great success using the procedure outlined below. I've never had to bleed the system at either of the filters or the injectors.

[Ed. This has the nomenclature of primary and secondary backwards.  The Racor is the primary, the engine mounted filter is the secondary.  Stu, Dec. 2009]

1.   Close fuel shut off valve.   
2.   Slightly loosen Racor secondary filter.
3.   Using a 1 pound coffee can, insert / hold the coffee can over the filter and finish removing filter.
4.   Remove the filter from the boat and discard. (no draining required, etc.)
5.   Insert new Racor filter in coffee can and fill with clean fuel.
6.   Install new Racor filter (Full).
7.   Slightly loosen primary engine filter.
8.   Using a one gallon zip lock bag under / around the engine filter and remove.
9.   Remove the filter from the boat and discard.
10.   Install new engine filter (Empty – You don't want to introduce any contaminates at this filter).
11.   Open fuel shut off valve.
12.   Open fuel bleed valve.
13.   Turn on ignition / key.
14.   Wait for very fast fuel pump ticking to become fast.
15.   Close fuel bleed valve.
16.   Fuel Pump ticking should return to normal.
17.   Start engine and check for leaks.

Note:  The only thing we disagree about is item 10 - I have never been able to bleed the system on our M25 when replacing the engine (secondary) filter WITHOUT removing the bleed screw on the secondary filter housing.  Stu  April 2011