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Electric fuel pump conversion


Bryce18parker

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I want to transition to a electric fuel pump in my 89 sunsetter. 

Any schematics for setting it up with a relay, oil pressure switch and bypass?

Thanks in advance everyone!

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  • 3 weeks later...

I did! But having issues!!

Wired it though an oil pressure switch.

I cant get it to draw fuel from the tank. If I set a 5gallon gas can in the back of the boat and drop the line in it will draw from the can.

Couple thoughts: 

1. Pump is not strong enough to pull through the anti siphon valve or the vavle is clog or bad. I checked vavle and it seems ok

2. Fuel pump is mounted to high in relation to the tank. So it might have an easier time if I mount it lower maybe, or will only run with a mostly full tank. Would also explain why it would run off a full 5 gallon tank and wont run off it's own quarter full tank.

 

Any other ideas??

 

 

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6 hours ago, MadMan said:

An air leak anywhere going to the tank could cause it.

I thought about this point but it didnt make sense to me since it will draw just fine from a 5gallon can that is open.

Am I missing somethin?

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8 minutes ago, Eagleboy99 said:

And the original mech pump pulled fine from the tank?

Yes it did, pulled just fine. Would have stuck with it but the new motor isnt drilled for a mech pump.

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5 minutes ago, Eagleboy99 said:

Ahh...  new motor.  That adds another dimension. Have you considered using an in-tank pump?  Lot sof them made for SBCs of your era.

I have not considered an in tank pump. Any links on a good one or two. I dont think a new motor should make a difference.  Using the same carb and all. Just the rotating assembly is new

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1 hour ago, Eagleboy99 said:

Airtex, Moeller, etc.  You will likely have to modify your tank though.  You might want to tallk to Paul at Bakes; Vince and SkiDIM; and Ron at skiboatpartsonline.  

Seems like a complicated fix for fuel delivery, modifying the tank and such. 

Any validity to my theory of the pump being mounted to high?

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IMHO, no.  But I'm not a fuel pump expert.  Have you compared the GPH on your old mechanical to the one you got to others?  Since the PSI will all be in the same range, maybe some have more deliverability?

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Messed with it a bit today.

Bypassed the anti siphon and unbolted the pump and lowered. It started pumping just fine.

Raised the pump by hand and held it while powering the pump and it still pumped so I returned it to the original location. Started the boat and it ran one bowl of fuel then died. Pump was no longer drawing fuel. Lowered the pump again and it worked fine.

I guess electric pumps are better at pushing than pulling is what I have been reading.

Maybe with the pump lower it will be able to draw past the anti siphon valve, maybe not. I'll sort that out next.

 

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21 minutes ago, Bryce18parker said:

electric pumps are better at pushing than pulling is what I have been reading.

There are literally tens of thousands of inboards with a motor mounted (not in-tank) pump, athough everyone is doing in-tank now.  Those motor ones work fine, but I bet it is because they are much higher pressure.

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1 hour ago, Bryce18parker said:

I guess electric pumps are better at pushing than pulling is what I have been reading.

Most fluid pumps are that way.  A perfect vacuum is ~14.7 PSI, which isn't really that much.  The output side can have much higher pressure. 

Keep in mind that pumps are rated by their flow at a specific pressure.  Asking it for more pressure will reduce the flow, to the point that it will have zero flow at a maximum pressure.  Asking it to pull fluid is the same as asking for more pressure. 

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21 minutes ago, justgary said:

Most fluid pumps are that way.  A perfect vacuum is ~14.7 PSI, which isn't really that much.  The output side can have much higher pressure. 

Keep in mind that pumps are rated by their flow at a specific pressure.  Asking it for more pressure will reduce the flow, to the point that it will have zero flow at a maximum pressure.  Asking it to pull fluid is the same as asking for more pressure. 

I like your point!! I guess this pump just isnt enough then. I'll have to look I to some other options if this one cant make it happen. Lake test some time this week and I'll know!

 

Thanks!

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Just for kicks, check your fuel hose.  I have had a terrible time with alcohol fuel and hoses.  The hose looks great on the outside, but has chunks coming loose on the inside.  I had one off of a riding mower that you could blow through easily from engine to tank, but not from tank to engine.  Stumped me for quite a while.  Rather than just turn the hose around, I swapped it out for a new one.

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15 hours ago, justgary said:

Just for kicks, check your fuel hose.  I have had a terrible time with alcohol fuel and hoses.  The hose looks great on the outside, but has chunks coming loose on the inside.  I had one off of a riding mower that you could blow through easily from engine to tank, but not from tank to engine.  Stumped me for quite a while.  Rather than just turn the hose around, I swapped it out for a new one.

New fuel line on the way too! Want to eliminate all the stupid little things and just make it over all better. I really think it was mounted to high. 

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@Bryce18parker - I have and for the same reason, the hole was not drilled for the fuel pump rod.  The pump I used is an GM F car (Camaro) electric fuel pump (9 psi unit), I don't have the number handy right now.  It is working great,  it sucks my tank to empty, I installed the pump along the gunnel just below the floor.  Note - my system is different than yours but I do use the standard vent and anti siphon valve with no issues, my tank is slightly lower than the pump itself so the pump is probably 4-6" above a low fuel level.  I installed new fuel lines and it does suck the fuel but pressurizes the water separator.  

A friends boat had an incredible time getting his pump to prime after he ran it out of fuel, so some good points on making sure all the hose connections are tight on the suction side of the pump. 

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