motor runs for one minute and then stops

[seattlesailor]

Just did a fuel pump replacement last weekend with Don's kit. Replaced pump, hoses, oil pressure switch. The motor started right away after we finished the work an we ran it for 20 minutes, then sailed and ran it again back to the marina.
Today my friend took the boat and said the motor started right away but stopped after one minute. He said he did not mater if he tried to run it at lower or higher rpm, it always stopped after one minute after every restart.
Could it be water or junk in the fuel tank?
Please let me know what you think.

Thanks Michel

[JOHN COOKSON]

Welcome to the forum. You've come to the right place for all things A4 related.

You are running on one carburetor bowl of fuel. When that runs out the engine quits. It sounds like the OPSS is not working correctly - even though it is new. Bypass or short across the OPSS temporarily and see if the shut downs go away.If this does not cure the shut downs we'll go to the next step.

BTW what oil pressure are you running? Maybe you don't have enough oil pressure to close the OPSS.

TRUE GRIT

[seattlesailor]

John,

Thank you for the quick response, I will try as you suggest to bypass the OPSS. I believe the oil oil pressure is usually around 35 psi.
So if I understand the OPSS is not a high pressure safety but a low pressure safety?

Thanks
Michel

[Al Schober]

Michel,
Yes, the OPSS is a low pressure safety switch. It stops the electrical pump from pumping fuel if the engine stops - just like the mechanical pump. When I need to short my switch and force the electrical pump to run, I just use an adjustable wrench.
Many of us have added a pressure gauge to the carb inlet. You'll need a small gauge (10 or 15 psi, try eBay). Mine has a rear inlet and screws into one leg of a 1/8" NPT tee. The side of the tee has a nipple and goes to the carb inlet. The other leg of the tee has a hose barb for the line to the pump (via the secondary filter).

[BunnyPlanet169]

Given that it worked, and then stopped, I'd be curious to re-crimp/confirm the electrical terminations in the OPSS pump circuit as well.....

[JOHN COOKSON]

Any time you trouble shoot a electrical device it is important to test the device itself and the associated electrical circuit.

So:The next step if shorting across or bypassing the OPSS doesn't end the shut downs is to make sure you are getting 12 volts to the OPSS.

Pull the wire off the OPSS that brings power to the OPSS, turn the key or switch to the run position and see if you can read 12 volts at the end of this wire. Don't leave the key in the run position when the engine isn't running for more than a minute or two or the coil may be heat damaged.

TRUE GRIT

[seattlesailor]

I had a chance to go to the boat today. First thing I did was to check the 5 amps fuse and it was blown. Replaced the fuse and motor runs fine.
Any idea why the fuse will go out? By the way I installed the fuse with the new kit which did not exists with the previous Facet pump.

I bought a bunch of fuses for the next times this happens, Any idea how to prevent this to happen again?

Thanks Michel

[hanleyclifford]

If you are running both ignition and fuel pump thru a 5 amp fuse you are taxing that fuse. Ignition be from 1 to 4 amps, typically, and the pump may want 3 or 4 amps. I like to see ignition on an independent circuit for this and other reasons.

[seattlesailor]

Make sense. Thanks. Curious to see what John Has to say about this. Does he have a 10 AMPS fuse? t I know from one his past posting that this is the set up he has.

[BunnyPlanet169]

If you are running both ignition and fuel pump thru a 5 amp fuse you are taxing that fuse. Ignition be from 1 to 4 amps, typically, and the pump may want 3 or 4 amps. I like to see ignition on an independent circuit for this and other reasons.

Careful. For safety, it makes sense to only power the fuel pump when the ignition is on. For this reason, it's usually powered off coil+. This, plus the OPSS, prevents an energized pump except for when the engine is running.

If the fuse is between coil + and the fuel pump, it's only going to see the load in that branch circuit. It will not see the coil, or E.I., or alternator excite which are also usually powered from coil +.

IIRC the pump draws about 2A, and a 5A fuse comes standard with the MMI kit.

The MMI wiring diagram shows a 20A fuse and a 12AWG wire from the ignition terminal on the starting switch and coil+. Your install may be different, but the 5A fuse in the fuel pump branch circuit is appropriate for these conditions.

http://www.moyermarine.com/forums/showthread.php?t=214&highlight=Wiring+schematic

[ndutton]

Seattle, please confirm the fuse location in the circuit, i.e., protecting the pump only. Without that information the advice is going in a couple of different directions.

If the fuse is protecting the pump only and it ran fine the first day and not the second, carefully follow your wiring and look for damage. Laying across a sharp edge or a hot exhaust pipe is all it takes.

FYI, the published Facet pump current specification is 1.6 amps.

[hanleyclifford]

Careful. For safety, it makes sense to only power the fuel pump when the ignition is on. For this reason, it's usually powered off coil+. This, plus the OPSS, prevents an energized pump except for when the engine is running.

If the fuse is between coil + and the fuel pump, it's only going to see the load in that branch circuit. It will not see the coil, or E.I., or alternator excite which are also usually powered from coil +.

IIRC the pump draws about 2A, and a 5A fuse comes standard with the MMI kit.

The MMI wiring diagram shows a 20A fuse and a 12AWG wire from the ignition terminal on the starting switch and coil+. Your install may be different, but the 5A fuse in the fuel pump branch circuit is appropriate for these conditions.

http://www.moyermarine.com/forums/sh...ring+schematic

Careful is as careful does. The fuel pump should have it's own OPSS. In fact I have three on my boat - the third activates the alternator.

[hanleyclifford]

Make sense. Thanks. Curious to see what John Has to say about this. Does he have a 10 AMPS fuse? t I know from one his past posting that this is the set up he has.

Clearly the 5 amp fuse is not adequate for your installation. To repeat, IMO mixing ignition, pump, alternator on the same circuit is sloppy engineering.

[BunnyPlanet169]

Respectfully, I disagree. IMO, it is perfectly good engineering in having a large, protected wire to coil +, and then short branch circuits from there.

There are a several loads in close physical proximity to coil + that are only normally energized from IGN on the starter key switch. Coil, E.I., fuel pump, alternator excite.

I actually installed a small terminal block next to my coil yesterday for exactly this reason. Too many terminals to hang off the coil+ !

[JOHN COOKSON]

something is probably grounded

Seattle, please confirm the fuse location in the circuit, i.e., protecting the pump only. Without that information the advice is going in a couple of different directions.
If the fuse is protecting the pump only and it ran fine the first day and not the second, carefully follow your wiring and look for damage. Laying across a sharp edge or a hot exhaust pipe is all it takes.
FYI, the published Facet pump current specification is 1.6 amps.

The instructions that came with my new, recently installed Facet fuel pump specified a 3 to 5 amp "automotive type" fuse. If the fuel pump is blowing a 10amp fuse something is the matter. Agree with Neil - something is grounded that shouldn't be grounded. Did you check the fuel pump lead to ground? Maybe the fuel pump has a short of some kind in it.
IMO each major circuit or device should be individually fuse protected.

TRUE GRIT