Fuel filter/pump question

[Dale Genther]

I'm currently restoring a 1952 Chris Craft Utility and in the proces of removing and documenting what remains of the old systems I discovered something I'm not familiar with. There is a spin on type fuel filter located near the fuel tank. It is mounted below the level of the tank. It has two inlets and two outlets. The fuel tank feeds into one of the two inlets, the other is plugged. One of the outlets feeds directly to the fuel pump on the engine. The engine is a recent 360 cu.in Chrysler with velvet drive gear. The other outlet goes to a small 12 VDC fuel pump. The outlet from this pump tee's into the line leading from the first outlet to the engine. There is a check valve located in the line between where the pump tee's in and the fuel filter. This check is oriented so that the fuel cannot feed back into the filter. The fuel pump is wired into the bilge blower switch so that it runs whenever the blower is turned on. I'm assuming that this small pump is to "prime" fuel to the engine whenever the engine is about to be started. Does this sound right and has anyone evere seen an installation like this?

[Gary E]

You do not mention shut off valves, are there any?

I can not imagine a pump needed to do anything other than maybe fill the new empty fuel filter but since you say there is a check valve to prevent that, this setup sounds very wrong to me.

Often a fuel/water separator is used in the fuel line mounted near the reduction gears for ease of service. Shut off valves should be used so you dont spill fuel in the bilge. If a filter is needed, use one of the inline filters mounted after the engines fuel pump and very near the carb.

As for that pump starting every time the blower runs...YIKES !! I would 86 that pump and spin on filter PRONTO.

[Dale Genther]

Gary, there is a "secondary" fuel filter of the in-line type mounted near the carb. There are shutoff valves on the fuel tank outlet and on the inlet to the engine. I assumed the spinon filter was to catch the "big chunks" and any water, and the secondary was to catch the small particles. Just as I have on my sailboat diesel. Don't you think a primary/seconary filter arrangement is the best way to go?

[Gary E]

What you are calling "primary filter" should be a water separator, and it should allow draining without removing the filter. THis so that if you have to do it in rough water you can easily hold a can under it to drain the water.

Look in the Racor line of filters etc to see the current setup.

Sounds like you have the correct fuel filter near the carb.

look here...
http://www.parker.com/racor/gas.html

[ 12-07-2005, 12:13 PM: Message edited by: Gary E ]

[sdowney717]

sounds like someone wanted to fill the carbs with an electric pump for ease in starting. Engines that sit long enough will have a dry float bowl and the engine will have to crank and crank waiting for the mechanical pump to fill the bowl.
I actually installed something similar.
I might perhaps put the on switch on a push button or a separate switch from the blower.
What make of electric pump is used?

[pcford]

I'm do runabout restoration....

The "spin-on" filter is likely what we call a "Mercruiser filter." It's an inexpensive water-separating filter. +/- $25. They are good; usually put one on boats I do. They are aftermarket, of course.

The glass bowl next to the mechanical fuel pump is probably original.

Electrical fuel pumps on a boat are madness...you should go out right now and take it off.

[Peter Malcolm Jardine]

The comments about the dry carb is correct. When my CC cruiser sits for a week or two, there is a longgggg line that needs to be filled with gas... and the mechanical pump takes time to fill it. That said, throw the electric pump away, and just make sure your fuel pump is recent. It's not a big deal.

[Old Bingey]

I was glad to see the instant response about the electric fuel pump. That's real dangerous.

The best way to fill the float bowl is a little hand powered mechanical pump (an outboard motor squeeze bulb works fine) feeding the engine driven fuel pump.

Another thing: It is best to have the fuel filter on the suction side of the fuel pump particularly if you use those spin on filters so if the "O" ring doesn't seal right, the pressure won't make it leak gasoline into the engine room... better to suck a little air into the filter.

Oddly enough, you want to do it the other way around on a Diesel boat because the fuel is so thick sometimes that you can't suck it through the filter and have to pump it... just a strainer ahead of the pump is all you want on a Diesel engine. The best thing is clean fuel and a clean tank.

[Paulyboy]

What about installing a one way valve near the fuel tank to keep the line charged? You'll find these on almost all cars nowadays as an improvement in both emissions and reliability. The quicker an engine starts, the better off for emissions and the sooner oil pressure builds up to correct levels. And while we're on the subject of emissions, do marine engines have to meet emissions standards anywhere?

[Peter Malcolm Jardine]

My 1964 283's probably don't meet them. ;)

[ 12-12-2005, 04:23 PM: Message edited by: Peter Malcolm Jardine ]

[Dale Genther]

sdowney717 - You are correct, the spin on filter is a Mercruiser (Quicksilver). Ther is no glass bowl next to the fuel pump. The engine fuel pump is an OEM Chrysler with a small in-line filter. The electric fuel pump is an AC model EP425 6442339.

Old Bingey - The spin on filter is on the suction side of the electric pump and the small in-line filter is on the suction side of the engine fuel pump. Which means it is on the pressure side of the electric pump.

I think I'm going to put it back in the way it was (with the electric pump), just remove the wiring from it until I see how the boat starts after ir sits a while. I only started the engine onece, over a year ago, before I took it out and turned the boat over for a new bottom and a lot of new planking. I have the boat turned righside up now and have installed the engine back in it. Right now the engine is the only thing in the boat as I'm in the process of totally rebuilding the interior. I'm hoping to get it in the water this summer.

[Old Bingey]

Just don't leave that electric pump switched on or hook it up to the ignition switch so it comes on automatically. One thing that can happen is that a little piece of trash can make the needle and seat leak and the electric pump will flood the manifold and just keep on pumping. It has been a long time since I worked on gasoline boats but it seems like somebody told me that electric fuel pumps are illegal now. I do know that some people on this island were standing on the beach watching the sunset and saw their boat blow up. The bottom half of it is still on the bottom of the bay. I salvaged the shafts and wheels. It isn't good to have anything but real trustworthy plumbing on the pressure side of any pump pumping gasoline below decks in a boat.

[wyndham]

Being a die hard sailor I know little or nothing of power boats but I do know that electrcity and gasoline do not mix. I would abandon the elctric fuel pump yesterday if not sooner.

[seo]

Electric pumps are used in many modern gasoline boat engines. Necessary because the current NFPA fuel system rules require an "anti-siphon" valve if the fuel tank is located above the carburetor.
(The object of this rule is to prevent fuel from siphoning past a stuck float bowl needle valve and filling the engine with gasoline by pouring it down the carburetor.)
The anti-siphon valve can be an electric solenoid valve like Cummins uses to shut off its K series engine. Much more common is a little in-line valve with a spring-loaded ball valve. The suction of a fuel pump is enough to suck the valve open and allow fuel through. When the pump is off, the spring pushes the ball into its seat, and prevents siphoning.
Some manufacturers have quit using the old-fashioned diaphragm fuel-transfer pump that drives off the camshaft. The problem is that it's hard to seal the pump drive "flipper" from the crankbase of the engine. So it's possible that if you get a pinhole in the diaphragm the pump can fill the crankbase of the engine with gasoline. Then when you start the engine the gasoline gets hot, vaporizes, and explodes.
Crankbase explosions are colorful events, featuring pieces of cast-iron block flying like shrapnel. I used to work on tugs with Fairbanks OP engines that were prone to these. They had big spring-loaded doors on some of the inspection plates that would in theory blow open and prevent the explosion from shattering the engine. Very reassuring. They were also prone to stack fires, but that's another story.
The typical UL approved DC electric fuel pump is a solenoid "clicker" pump. Stewart Warner used to make the best, under the "Conelac" name.
Before freaking out about the pump, reflect for a moment that almost every car with fuel injection has a DC electric pump INSIDE THE FUEL TANK! The first one of these I saw was on a 1974 Volvo with Bosch fuel injection. A properly designed and installed electric pump is not a huge hazard.
For what it's worth, an outboard motor bulb priming pump is not usually NFPA approved for use in an enclosed space (It's not type A compliant for flame resistance). There are special rules for open boats, which they comply with.
NFPA (National Fire Protection Association) is a standard-setting group with great experience, lots of technical expertise, and access to statistics on what causes fires. All fire safety codes including UL and US Coast Guard and standard building codes are based on NFPA standards. My own opinion is that if you ignore their rules because you think you know more than they do, you are conclusively proving how little you know.

[seo]

I wonder if the "check valve" you mention in the fuel line is in fact an anti-siphon valve, which is an odd check valve in reverse.
The "dry line" problem is interesting. Why would the fuel line be dry after the boat has sat for a week? It's not that the fuel evaporated, because it needs somewhere to evaporate to. (An open pan of gasoline will evaporate. A closed-top container with a small vent hole will evaporate very very slowly. A sealed container won't evaporate at all.
(Long explanation here of Reid vapor pressure. blah, blah, blah.)
Assuming that the fuel tank is vented, there's no positive pressure on the system from the tank. If the tank is very low in the boat (Below the engine) there could be negative (back siphon) pressure trying to suck the fuel lines back into the tank. The float bowl needle valve and diaphragm pump check valve might not be proof against this relentless suction. Even a tiny leak would eventually allow all the fuel to siphon back into the tank. The event might be seemingly random, depending on how full the float bowl was, or where the pump diaphragm was, or how full the fuel tank was at the moment you shut the engine down.
A way to find out if this is the problem is to shut off the fuel valves when you leave the boat. If it starts right up after a week with valves shut, but has to crank a while after a week with valves left open, it indicates that the system is siphoning back to the tank.

When installing a fuel system, remember that every part of the system BELOW the level of fuel in the tank is under pressure (caused by the siphoning phenomenom) Doesn't matter how high the riser loop is. Unless the riser is vented, any line below the fuel tank level is under pressure.
IF I had a boat arranged the way you describe, I'd want three things: 1) Electric pump above the tank level (it's a positive displacement pump, after all) 2) Pump to be UL approved for marine gasoline service. 3) All wiring to be really well done. crimped connectors, heat-shrink sealing, proper fuse protection (If it's a 5 amp pump, don't put it on a 20 amp circuit breaker...)
One reasonable approach would be to put a switch on the panel to turn the pump on for priming. Wiring it with the blower isn't crazy, as long as the fuse isn't too big to protect either device. It would also be reasonable to figure that this pump was designed to run constantly for fuel supply. If the pump's delivery is adequate to supply the engine's burn rate you might consider bypassing the mechanical pump (On an older engine this pump does not comply with current standards) and going straight from the electric pump to the carburetor. That's what the pump is designed for.
I have been told (but don't know for sure) that the way that those Quicksilver spin-on filters work is that the filter element material is sensitive to water. If water collects in the filter bottom to a depth that it contacts the filter element, the element swells up and shuts off flow. I've always wondered if this was true.)
seo