Electric fuel pump issue.

[bcassedy]

Folks,
I'm at a standstill. The starboard engine on my boat has been plagued with fuel issues:
- water allowed to get into the gas tank. That's been rectified - pumped tank out of all old gas and crud. Old gas to someone who owns a shop and uses it for parts cleaning.

- carburetor issues - corroded. replaced with rebuilt Rochester Quadrajet.

- Fuel pump issues - old mechanical pump failed. Replaced with electrical one (CG approved) from NAPA. Therein lies my current problem. See the attached schematic / steps listing.

The problem is that the engine will start and run - as long as the momentary switch (which completes the ground circuit to the pump is held in place. If it's released AND the Jumper between TS2 and 3 is NOT in place, the pump doesn't run (which would be logical as that jumper's intent is to complete the ground circuit thru the relay and oil pressure switch.
What's driving me nuts is the fact that, with the Jumper in place, the engine NOT running (or being cranked), the pump IS running (ie, somehow the ground circuit is completed.) Obviously, I can't allow this condition to exist - need the pump to activate only with engine running (and not using the momentary switch).

Anyone have any ideas???? I've traced all wires and they go exactly as indicated in the drawing.

Bill

[Busia]

I don't know why you need the relay. I would keep it simple and just power it off of the ignition switch run position. Then when you have the key on you have power to the fuel pump. One place to get this would be the +12 volt wire to the ballast resistor that then goes to the coil.

[seef158]

Or throw the electrical stuff away, buy a replacement mechanical pump. There are mechanical pumps out there that have the boss for the overflow/vent line to the carb, you just have to drill and tap and install a fitting.

[Fastjeff]

Agreed that the mechanic pumps are reliable, but if you want to stay with the e-pump you'll need to trace and test your circuits to make sure the e-pump can run under the momentary (to fill the carb) and normal run conditions. If not, keep checking for 12 volts until you find the problem.

Your circuit--which sure is complicated--looks like it will work.

Jeff

[bcassedy]

Thanks guys.
Busia - I had been advised that there's a requirement to have an oil pressure switch in place so that, if the engine dies AND the ignition switch is on (and it's left on...) the absence of oil pressure (engine stopped) would open the switch, breaking the ground circuit continuity, forcing the pump to stop.

Also, I had the relay in place, had the trouble of the pump running ("frustration, thou art a boat owner!") as soon as I threw the ignition switch to on (not cranking/engine running). Trouble shot that for hours - no luck.
Went to a scenario where (relay is NOT in use...)
a. had 12v pwr from ignition switch (TS6) to the pump.
b. TS2 went to the momentary switch (nothing else connected) and thru that switch, to ground
** At this point, throwing the momentary switch DID cause the pump to run.
c. Connected a wire from TS4 (which had a single wire running to common ground bar behind lower console) to one side of the oil pressure switch.
d. Connected a 2nd wire from TS5 to the other side of the oil pressure switch.
--> At this point, if the ignition is turned on, the pump does NOT run (and shouldn't as there's no ground path yet to the pump's neg lead (TS2)).
e. If I then put the Jumper in place between TS2 and TS4 (thus, in theory, when there's oil pressure, the contacts on OPS close and the ground circuit is then complete). turning on ignition sw (active only [+12v to pump], no cranking/engine not running - no oil pressure) the pump will run.

This is shot of the above with the following caveats...
The relay is shown, but not in use.
The +12v hot wire is on TS1. It was moved to TS6 as noted in 'a.' above.

NOTE - the marine grade rubber fuel line on the outlet side of the pump is replaces with 5/16" double flare copper tubing. Rubber just used for expediency. The inlet side has marine grade rubber hose in place.

--> checking continuity across the oil pressure sw - with the wires connected, shows continuity across the contacts!??? Pull the wires (or only 1 of the wires) off the OPS, that continuity goes away (ie - the switch is in it's normal NO mode - and since there's no oil pressure (engine not running / cranking) that's what you'd expect to see.

Seef158 - I'm at about that point. Thing is that I'd replaced the mechanical pump on starboard about 3 (?) years ago. The amount of run time wasn't very much (boat didn't get used last year at all). Don't know if just sitting can be as detrimental to a pump as long term use?? NAPA used to have the marine version, but no longer available. Crapshoot buying one off ebay. Need to check further.

Jeff - The wires are brand new and I've tested for a short to ground on all of them (except where the wire runs to ground - need to lift those contacts off ground buss bar and then check for short to ground. The wires for the OPS run from the OPS to the fuel pump board at the front of the engine. The fuel pump board is just that, an angled piece of 3/4" plywood where everything is mounted on the schematic. The board is secured to the battery ledge (ie. The mounting surface board is mounted to an angled (think right triangle) board. This board is then affixed to a flat board that's screwed into the battery ledge board.

Fuel pump mounting board.jpg (18.42 KiB) Viewed 22889 times

[Wilfred]

Good luck
I vote for the keep in original/mechanical pump camp

[Fastjeff]

One STRONG caution: I have had (bad) experience with small fuel pumps like that one, and I've found out the hard way that SOME of them do not pump enough flow at the 5 psi or so needed to feed the carb at high throttle settings. In fact, the clunker now on my little boat (60 hp outboard) can't keep up--and that's only a 66 cube motor! Though rated for 9 psi and set at 5.5 psi (via a fuel pressure regulator) the pressure drops into the 2 to 4 psi range at WOT. Not good!

My caution to you is to place a reliable fuel pressure gage (0 to 10 psi) in line at the carb and monitor the fuel pressure at WOT. If it falls to 2 or 3 psi, you'll need a far more capable ($$$) pump or the motor will lean out and drill a piston. I recommend a marine approved, rotary vane pump.

Jeff

[Mherrick]

Too complicated for me.
The 42 year old fuel pump that failed on our boat was replaced with a spare I carry onboard.
If this one lasts half that long, it will probably outlive me.
Like Mr. Brockman before me, I vote mechanical.

[bcassedy]

Wilfred,
I am SERIOUSLY considering doing just that. After 2 months of dealing with the fuel issues, I have gotten frustrated (and shouldn't) with dealing with this. The mechanic I asked to help has recommended going back to the mechanical fuel pump. I've found one online:
https://www.go2marine.com/product/85333 ... -7254.html for 94.32 . NAPA doesn''t carry them anymore, and, they were about the same price. Soooo.... But this will be an 'after the season ends'.

Jeff, I'll keep your comments tucked away, CLOSE. Do not need to any other issues. Happily, we've not pushed Sunset Seeker at WOT more than a couple of times, just to see where WOT RPM's are.

Bill

[Fastjeff]

Just helped a buddy of mine change a mechanical FP on his Mercruiser big block. The fuel and water pumps are combined in one unit, belt driven, with a separate oil sump to lube the fuel pump cam.

Not sure any of y'all (I'm a Southern now) have such a set up, but if you do be sure to maintain the oil level in these little sumps. My buddy didn't know about that and his fuel pump arm was ground away!

Jeff