Replacing primer bulb with electric pump??

Dan · 29-07-2010, 09:22 PM

As some will know I'm currently trying to get my bernico ready for the water. Been doing most of it myself and its taking a while but I can see light at the end of the tunnel. I've currently just put a stock old merc powerhead on just to get it on the water and until £ allow for something better. Heres the question, I dont want a primer bulb and have brought a electric fuel pump so whats the best plan,
a) to take of the standard fuel pump on the head and run the pump all the time on a live through ignition?
b) to plum the pump in on a switch and basically just use to to replace the primer bulb ie just to prime prior to starting?

I've looked through a fair few previous threads and posts but am not really sure the best plan of attack, I know a few will say to go with the K.I.S.S theory but I simply do not want to have to use a primer bulb. If its option (a) can someone point me into what I remove/cap and where I connect the new hose.
Cheers
Dan

Jay Smith · 30-07-2010, 03:07 PM

Dan,
I build many lazzer injected engines and people use the low pressure Holley fuel pump in front of the vacume square pump to fill the vapor tank, be careful the motor will not draft through a pump that is shut off. Had a customer prove that just the other day.

Some also "can" the square engine vapor fuel pump all together and just use Holley to supply the vapor tank and the high pressure injector pump..

Cheers,

"Be who you are and say what you feel....
Because those that matter...
don't mind...
And those that mind... don't , Won't or will EVER
matter."

Jay

Dan · 30-07-2010, 03:18 PM

[QUOTE=Jay Smith;186074]Dan,
I build many lazzer injected engines and people use the low pressure Holley fuel pump in front of the vacume square pump to fill the vapor tank, be careful the motor will not draft through a pump that is shut off. Had a customer prove that just the other day.

Some also "can" the square engine vapor fuel pump all together and just use Holley to supply the vapor tank and the high pressure injector pump..

Cheers,

Thanks Jay, so should I leave the pump running all the time on the ignition if fitting in front on the vacuum?
cheers
Dan

Jay Smith · 30-07-2010, 10:24 PM

I do NOT suggest using the key switched HOT purple wire as the total feed for that or any other fuel pump. They ( fuel pumps ) drag way to much voltage I DO suggest using the purple switched hot wire as an exciter for a relay on the positive side of the pump. You can hook directly to the hot side of the battery to a relay and the key switched hot purple can "excite" or operate the relay with little voltage drop in your electrical system.. Also hook the negative direct to the neg. of the battery...

Cheers,

"Be who you are and say what you feel....
Because those that matter...
don't mind...
And those that mind... don't , Won't or will EVER
matter."

Jay

Dan · 30-07-2010, 10:38 PM

[QUOTE=Jay Smith;186113]I do NOT suggest using the key switched HOT purple wire as the total feed for that or any other fuel pump. They ( fuel pumps ) drag way to much voltage I DO suggest using the purple switched hot wire as an exciter for a relay on the positive side of the pump. You can hook directly to the hot side of the battery to a relay and the key switched hot purple can "excite" or operate the relay with little voltage drop in your electrical system.. Also hook the negative direct to the neg. of the battery...

Thanks as always

RossM · 02-08-2010, 06:25 PM

Dan don't use a relay for the fuel pump, there a pain in the arse.
the mutz nuts originally had a relays and after replacing 4 or 5 times we resorted to a switch, they don't like the bumps that you get offshore and they just give up mid journey!

Just run a +ve from the battery to the switch then(switched) back to the pump

Jay Smith · 03-08-2010, 12:27 AM

Ross,

I've NEVER heard or witnessed any problems with failing relays wired as I have described but I guess it may be the duty of the relay attached ,how and or where they are mounted to.

Just curious, if your knocking out relays that quick how do you keep a trim relay system alive in your boat after all it's the same type of system ?

"Be who you are and say what you feel....
Because those that matter...
don't mind...
And those that mind... don't , Won't or will EVER matter
matter."

Jay

RossM · 03-08-2010, 09:10 AM

Jay,

They were mounted to a little bracket next to the trim pumps
In the last couple of years we've only had to replace 2 solenoids(1 trim & 1 starter), however I think that's just down to there age.
I think that the fuel pump relays fail because there always on & when you hit a wave then the relay would briefly spring open & cut the fuel pump, each time it does this it arcs between the contacts & from interrogating one of the broken relays I noticed there was quite bad carbon built up on the contacts after just 1 outing, so bad when the relay was 'excited' it wasn't passing the power through.
We tried various grades of relays ranging from 5 pounds for a 'universal' relay to 60 pounds for a specific fuel pump relay.
I have never had a problems when using relays in cars so thats why I blame the banging from the waves causing the repeated arcing & ultimately the failer of the relay.

Jay Smith · 03-08-2010, 11:04 PM

I see. I'm sure that off shore pounding takes a toll of most anything bolted to the hull !

Makes me have a head ache just thinking about it !

"Be who you are and say what you feel....
Because those that matter...
don't mind...
And those that mind... don't , Won't or will EVER
matter."

Cheers,
Jay

martynwilley · 04-08-2010, 05:42 PM

i run a switched live off the purple to activate a simple 4 pin relay also, has always worked fine for me, i rubber mounted it to the side of my powerhead to try take up some of the vibrations and has never failed me, make sure you go for the sealed relay, they cost a touch more but im my opinion, much betta!