Fuel Filter Question

[KenM]

O.K, let's say your tooling along and your fuel filter gets clogged. Engine stops. So you change the filter, fill it up with diesel before screwing it back on. Doesn't the engine suck all the fuel out of the feed line before it stops running? So after replacing the fuel filter will the engine suck fuel back up the feed line to the engine, or would one have to manually pump at the engine cracking each injector to get fuel back to each injector? Just bought a 1984 34 Mainship and want to be prepared for what ever gremlins may happen. So... i.e... what is the procedure to replace a clogged fuel filter.
Thanks in advance.

 

[HiDHo]

Yes to all, you will have to bleed out the air. Buy a fuel filter vacuum gage it will give you a warning that the filter element is getting dirty.

 

[mbevins]

Yes , you'll probably need to reprime the system. I installed a quick disconnect into the filter cap. Hook up a priming pump and problem solved.
Some guys have small electric pumps permently plumbed in for the same situation.

 

[Ski in NC]

Try it dockside. Repriming is a good skill to know.

Turn fuel valve off at filter supply. Let engine run in neutral at 1000rpm til it dies. Open fuel valve and see what it takes to get it restarted. That will simulate a clogged filter.

Harder challenge is an air loading. Like what happens when you run out of fuel. Supply is not restricted, it is just air. Crack loose cap on racor and let engine run til it dies. The refill filter, pump primer, open bleed screws on secondary and inj pump. bleed it and get it going.

Good to know what it takes to get going again if things go badly on the fuel side.

 

[ranger58sb]

Try it dockside. Repriming is a good skill to know.

Excellent!

Ken, FWIW, when we change filter during normal service, we have to reprime... but generally not all the way to the injectors.

After a stoppage like you describe, I'd most likely to have to crack the injectors, too.

But learning your engine at the dock is MUCH better than learning in rough seas!



I've seen vacuum gauges for primary fuel filters (e.g., Racors) but I've not ever noticed anything like that for spin-on secondary fuel filters.

-Chris

 

[Lou_tribal]

As I will change my filter for the first time next spring I also have a question. My filter is higher than my engine pump. By this I mean that the fuel line is going down from the filter to the pump. Also its model is a spin on cartridge with clear bowl below for water. Logically, as it is higher than pump, air won't go down the line when removing the filter. So changing the filter than filling it till fuel leaks by the bleed screw at the top of the filter head should be enough and I should not need to bleed the whole fuel system. Am I right to think so?
Ski you know my engine setup is a bit particular so I would like to avoid screwing up everything

 

[RT Firefly]

Greetings,
We still don't know WHAT engine Mr. KM has in his vessel. Filter change procedure may be slightly different depending on the engine. Yes, it's all basically the same but with subtle differences I suspect.

 

[sunchaser]

O.K, let's say your tooling along and your fuel filter gets clogged. Engine stops. .

Prevention is the key.

Insure your tanks are clean while at the dock. Several TF members have posted on this action, particularly Flywright and Alaska Seaduction. PM them for tips.

As suggested, get vacuum gauges installed. Generally, you should never see vacuum with our low HP small fuel flow engines. And bleeding the engine should not be required if changing the primary only. If you do see vacuum increasing, something is probably haywire. Don't wait, find the problem while at the dock.

Learn how to bleed your system while at the dock. Change your filters before they become clogged, both primary and on engine.

Only fill up at reputable high volume fuel stations.

Did I mention prevention is important?

 

[Capt.Bill11]

The likelyhood of the filter getting completely clogged so fast that you get no warning before shut down is slim.

In most cases you can tell something is wrong by the way the engine is running.

And no, the engine will not necessarily suck the lines dry with a clogged filter. With a clogged filter there can still be fuel in the lines but the pump just can't move it do to the high vacuum created by the clogged filter.

Pull the clogged filter out, replace it with a clean one, and off you go.

 

[Bay Pelican]

If you are paying the slightest attention to the sound of your engine(s) and to the rpm gauges you will catch a clogged fuel filter long before it shuts the engine down.

I and many others have installed in line electric fuel pumps which can serve as a priming pump.

If you do a lot of cruising a duel Racor system is ideal, allowing you to switch filters underway without any hesitation.

 

[Max Simmons]

Not sure if this has been mentioned before, but the p/o of my boat painted the heads of all the bleed screws so they're easy to identify.

 

[CaptTom]

Not sure if this has been mentioned before, but the p/o of my boat painted the heads of all the bleed screws so they're easy to identify.

Now THAT is a good idea. I have to go back to the manual to remember which two bolt heads to crack on my injector pump.

FWIW, my engine manual says you only need to crack 2-3 injectors, no need to do all six of them. I tried it and it worked. Still makes me nervous though.

 

[bayview]

What Bill said,

Usually not necessary to bleed all injectors just the furthest one from the pump. A clogged filter will often show up as reduced power but run fine at low power because some fuel is getting through. Unusual to suddenly shut down without notice.

 

[Lepke]

Bleeding issue depends on the engine make. Detroit non issue.
Ideal setup is 2 primary filters with valves so 1 filter can be changed while running.
On my boat one filter is new and waiting, the other carries the fuel load. My vacuum gauge shows Zero when the filter is new. I change at 7", but I use 2 micron primaries. A 30 micron would probably change at 2 or 3.
Also an aux electric fuel pump will make bleeding easier. Mounted between the vacuum gauge and the lift pump. The lift pump will pull thru the aux pump ok. And should your lift pump fail the aux pump can take over. One like the picture is less than $20 inc shipping on ebay.

 

[mgdavis]

I've done this a couple of times, which I'm not proud to admit, by sucking the mud off the bottom of the tank.

In my experience the fuel lines will not go dry and require a complete prime. What happens instead is that the fluid remains in the line between the Racor and engine when a vacuum is pulled, starving the engine of fuel. There is no air available, so no air is introduced into the line. After changing the Racor filter some extra cranking will be required, but I have not had to crack open fittings and bleed manually. This is with a Perkins T6.3544.

 

[Jetstream]

As I will change my filter for the first time next spring I also have a question. My filter is higher than my engine pump. By this I mean that the fuel line is going down from the filter to the pump. Also its model is a spin on cartridge with clear bowl below for water. Logically, as it is higher than pump, air won't go down the line when removing the filter. So changing the filter than filling it till fuel leaks by the bleed screw at the top of the filter head should be enough and I should not need to bleed the whole fuel system. Am I right to think so?
Ski you know my engine setup is a bit particular so I would like to avoid screwing up everything

Yes Lou you are correct. It depends a bit on the engines as some are more susceptible to air locks than others but as a general rule if you just prime your filter after changing it you should be fine. That's how I do ours (6BTA) and generally have no problems,

Brett

 

[Wxx3]

Try it dockside. Repriming is a good skill to know.

Turn fuel valve off at filter supply. Let engine run in neutral at 1000rpm til it dies. Open fuel valve and see what it takes to get it restarted. That will simulate a clogged filter.

Harder challenge is an air loading. Like what happens when you run out of fuel. Supply is not restricted, it is just air. Crack loose cap on racor and let engine run til it dies. The refill filter, pump primer, open bleed screws on secondary and inj pump. bleed it and get it going.

Good to know what it takes to get going again if things go badly on the fuel side.

Ski,

Wonderful advice.
I wish I would have thought of it. But weirdly, any significant problems in getting the Lehman restarted always seemed to occur at dock.

Also, in spite of all of my fuel shenanigans, I've never had to crack open injector tubes. But I think that's a function of the SP135 and injector pump.

Richard

 

[Wxx3]

Bleeding issue depends on the engine make. Detroit non issue.
Ideal setup is 2 primary filters with valves so 1 filter can be changed while running.
On my boat one filter is new and waiting, the other carries the fuel load. My vacuum gauge shows Zero when the filter is new. I change at 7", but I use 2 micron primaries. A 30 micron would probably change at 2 or 3.
Also an aux electric fuel pump will make bleeding easier. Mounted between the vacuum gauge and the lift pump. The lift pump will pull thru the aux pump ok. And should your lift pump fail the aux pump can take over. One like the picture is less than $20 inc shipping on ebay.

Yes. This is also exactly what I did. However I was leary of putting pump in line, making the lift pump suck harder, so I made a loop/bypass.

Think main line from fuel tank to Racors, with a loop between Racors and Fuel Tank, as I wanted to prime Racors also, as needed.


I put the extra valves, V2, V3 in because I did not want to introduce another source of air/leaks if not needed.

But I have also run the eingine with both valves open and it runs fine.
However, if priming, with only valve 2 open, the fuel just makes a little loop and primes nothing, therefore V1 must be closed for priming.

Best mod I ever made, as it makes life much easier and faster.

Richard

 

[Wxx3]

See Picture of what I describe above
Red handle is main gravity line from tank.
blue handle valves are bypass, both are usually closed, only open when priming and then Red is closed.

 

[sunchaser]

See Picture of what I describe above
Red handle is main gravity line from tank.
blue handle valves are bypass, both are usually closed, only open when priming and then Red is closed.

IMHO this is the textbook and correct way to install an auxiliary fuel pump or squeeze bulb primer. Good job.

 

[smitty477]

"My vacuum gauge shows Zero when the filter is new. I change at 7", but I use 2 micron primaries. A 30 micron would probably change at 2 or 3."


Interesting as the opposite would be true in any case I have seen. If I had utilized a 2 mic primary (lower than recommended) I would change it at a lower vac reading as they plug very fast and will move from the lower vac reading to a too high vac reading (12" in my case) very quickly.
On the other hand when I use the 30 or 10 mic primaries the amount of use (fuel processed) between the lower vac readings and too high takes much longer. Therefore I would naturally wait longer when changing the 30 mic vs the 2 mic filters.
In any case if/when I was worried about filter capacity or filter life I put a bulk fuel filter before the primary with an additional vac gage there - that adds all kinds of capacity and life to any of your chosen filters down line.

 

[Bay Pelican]

Similar to what I have on Bay Pelican. Two feeds to the engines, one gravity, one through the pump. Either can be shut off.

 

[KenM]

Original Poster... so what I've done is to install a vacuum gauge to the primary and installed a "cross over" from the genny fuel filter, so if under way the vacuum gauge goes up (it now reads "0") I can simply open the cross over valve and get home to change the filter. I will soon be changing the very old primary with a new complete filter housing with a "see through" bowl and a vent that works. Also installed a squeeze bulb and valves to get the air out of the system when changing filters. Feel a lot more confident about the whole mess.

 

[boan400]

Hi
Interesting to here your experience, smitty477. I also stick with 2 mic as primary (and 8 on the engine)but dont have any gauge jet, its on the list.
I try to keep the fuel clean as possible in the tanks with a fuel polishing pump(less than 2 mic).
In my world i believe that the engine will wear out earlier with big filters. Tell me I'm wrong.

 

[ranger58sb]

In my world i believe that the engine will wear out earlier with big filters. Tell me I'm wrong.

Don't know about right or wrong.

Our engine maker specifies 30 and 10, for our engine model. For me, a manufacturer's specifications often trumps right or wrong.

-Chris

 

[sunchaser]

Chris

You need to stop reading the book and go with the dock talkers. I saw a lady last week pumping 92 octane into her Suburban. Swore it ran better. She seemed nice enough so I didn't argue.

 

[ranger58sb]

Chris

You need to stop reading the book and go with the dock talkers. I saw a lady last week pumping 92 octane into her Suburban. Swore it ran better. She seemed nice enough so I didn't argue.

I'd be happy to do that if the dock folks are willing to ante up repair bucks if something goes wrong and their recommendations (e.g., incorrect filter specs according to manufacturer, whatever) is found to be the cause.

Oddly they usually seem to quiet down a bit after hearing that.

Well... except for the guys who start every sentence with "Trust me..." or "I guarantee..." Nothing slows them down.



-Chris

 

[Heron]

In my world i believe that the engine will wear out earlier with big filters. Tell me I'm wrong.

I'm a big fan of progressive filtering as others have mentioned.
I have a Huge 27 Micron Fleetguard, first in line, followed by a 10 micron Racor, followed by a 2 micron engine mounted filter.
The fleetguard catches most all the crap and water, passing along pretty clean fuel to the remaining filters downstream. My filter maintenance is negligible and rarely needed now once the system was freshened up after purchase 2 years ago..

When I bought the boat, the primary fleetguard had not been changed in 5 years and 300 hours. The boat had some asphaltine issues from sitting as you can see below, but still flowed fuel and ran perfectly. In those years, the Previous owner would have likely gone broke replacing Racor elements if that was the only filter in the system. This will give you an idea of a big filters capability. After seeing this, my fear of a clogged filter underway is ZERO, but I put a small Walbro in-line pump in place to prime the system Just in case if a filter change is necessary underway..

 

[boatpoker]

Did I miss where the OP told us what kind of engine he's talking about ?

Some are self bleeding(my Mitsubishi), some bleed very easily (my Perkins) with a bleed screw at the injector and some are a bear and do need the injectors cracked (my Volvo, my 3208).

What engine ?

 

[cyfarkas]

Years ago I repowered a Chris craft gas sport fisher to Yanmar 6lp's and a Mase generator. Serious issue was the water alarm was miswired on the secondary such that in a heavy sea, and probably because the tanks were insufficiently cleaned, water entered the brand new engine and blew up the injection pump on the port engine. $10k repair which thankfully was paid by the dealer and insurance.



Months later, the genny quits. I call Mase in the south and the rep is an older raspy voiced smoking ex-Jersey-ite. He hears me out and sez.. it's always the fuel. So I explain that I can start the engine fine but it conks minutes later. He repeats, “it's always the fuel. This continues for several exchanges. He gets a bit excited and yells “ it's the fuel, always the fuel!. Guess what. It was the fuel, I had a pinhole in the hose that sucked tiny air till it conked. Re-priming is all it took to start.



Never forgot Joe. On my new to me MT with single Lehman, after a blessed honeymoon, the Lehman quit at the most inopportune times. Once during a bridge opening with a 6 knot tide current. Did I mention a turn and rocks ahead. Do you know what what happens when you emergency deploy an all chain rode anchor. The explosion shakes the bowels. Remembering Joe, I later started tracing from the source tanks. Dropped a stick into the tank to find the engineering on the boat called for the pickup tubes to only drop half way down the tank. No doubt to avoid the gunk on the bottom. Guess they didn't trust Racors then, let alone dual setups. Longer pickups and not a bump since.



Yes I'm a single engine guy now. But I watch the fuel with an ADD disorder. I installed an in-line priming pump although priming the Lehman is easy. Just not easy enough when you're under a bridge. Plus a dyi polishing subsystem If the boat hasn't been run, a digital timer pumps 2 hours twice a day, one tank at a time, alternating weekly. Nice and slow, the gentle rocking helping the process along. I'm in NY, in the water for the winter, and when I hear the pump start, I know what time it is.



Microns aside, you can't be too skinny or have overly cleaned diesel fuel. The engine purrs, no smoke. A recent valve adjust showed all clean. The piece of mind is enriching.

It's always the fuel my friends.