Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Sign in to follow this  
powbmps

Fuel pump wiring question

Recommended Posts

powbmps

The replacement block I am using requires me to convert from a mechanical to an electrical fuel pump. Just trying to figure out if I'm wiring these two wires correctly. Instructions (are lousy) say that one wire needs to go to the ignition switch and one needs to go to the starter solenoid. I have both of them hooked to the starter relay. One on the side from the ignition and one on the side to the starter solenoid.

Does this make sense?

20151201_182241.jpg

Share this post


Link to post
grandude

So where does the pump get ground? Is there a 3rd wire? Is this a Merc? What brand fuel pump?

Share this post


Link to post
oldjeep

I don't think that'll work. Pretty sure that The wire from the ignition switch needs to be hot in the run position, not just the start position.

Edited by oldjeep

Share this post


Link to post
powbmps

Sorry for the lack of detail. It's a 350 5.7 Vortec Gen+ motor. I believe it is a Carter(?) fuel pump. Pump has two connections, one grounded to the block and the other to the oil pressure safety switch. The two wires I am wondering about come from the oil pressure safety switch. The diagram that came with the pump is vague (at least to me). One goes to the starter solenoid and the other goes to the ignition-starter switch. I Googled some images/diagrams but just got myself more confused.

Pump.jpg

Share this post


Link to post
malibuparadise

Sorry for the lack of detail. It's a 350 5.7 Vortec Gen+ motor. I believe it is a Carter(?) fuel pump. Pump has two connections, one grounded to the block and the other to the oil pressure safety switch. The two wires I am wondering about come from the oil pressure safety switch. The diagram that came with the pump is vague (at least to me). One goes to the starter solenoid and the other goes to the ignition-starter switch. I Googled some images/diagrams but just got myself more confused.

Pump.jpg

Note the Carter's elec. terminals (posts) are on the BOTTOM of the fuel pump and mine were rinky-dinky press fit caps....The pump is mounted with rubber bushings on top but it still vibrates and they loosened up a couple times, so I went with a Holley Marine elec. fuel pump.

Share this post


Link to post
GreenMan

The drawing is difficult to see in detail but I'll assume the terminals on the oil pressure safety switch are:

P for Pump

S for Starter

I for Ignition.

When oil pressure is low, P is connected to S

When oil pressure is high, P is connected to I

The objective is that fuel cannot be pumping under the hood while while the engine is not running, regardless of the ignition switch being on or not.

If the engine is stopped (low oil pressure) and ignition is on (not 'start' or cranking) there is no power at S therefore no power going to P. Fuel pump does not run.

When cranking (key in start position) the starter solenoid is energised and power runs from the now 'hot' terminal S to terminal P and runs the pump.

Either during cranking/starting or shortly after, oil pressure is established and the safety switch transfers and I is now connected to P and maintains the pump.

If the engine stalls or whatever, oil pressure decays and the switch transfers so S is again connected to P. S is dead due not cranking so the power to the pump is interrupted.

S can connect directly to the starter solenoid wire.

I has to connect to something that is only hot with Ignition on.

I would not advise running terminal I directly from the ignition switch as the pump is a fairly high current draw device. The result may be either or both a burned out ignition switch and low voltage at the pump. Needs to be fed via a local relay. You may need to add a relay for this purpose or there may be a convenient relay on the engine that energises with ignition on?

Hope it helps!

Regards, Stephen.

Share this post


Link to post
powbmps

Perfect Stephen. This is the basic explanation I have been looking for. Thank you!!!

The drawing is difficult to see in detail but I'll assume the terminals on the oil pressure safety switch are:

P for Pump

S for Starter

I for Ignition.

When oil pressure is low, P is connected to S

When oil pressure is high, P is connected to I

The objective is that fuel cannot be pumping under the hood while while the engine is not running, regardless of the ignition switch being on or not.

If the engine is stopped (low oil pressure) and ignition is on (not 'start' or cranking) there is no power at S therefore no power going to P. Fuel pump does not run.

When cranking (key in start position) the starter solenoid is energised and power runs from the now 'hot' terminal S to terminal P and runs the pump.

Either during cranking/starting or shortly after, oil pressure is established and the safety switch transfers and I is now connected to P and maintains the pump.

If the engine stalls or whatever, oil pressure decays and the switch transfers so S is again connected to P. S is dead due not cranking so the power to the pump is interrupted.

S can connect directly to the starter solenoid wire.

I has to connect to something that is only hot with Ignition on.

I would not advise running terminal I directly from the ignition switch as the pump is a fairly high current draw device. The result may be either or both a burned out ignition switch and low voltage at the pump. Needs to be fed via a local relay. You may need to add a relay for this purpose or there may be a convenient relay on the engine that energises with ignition on?

Hope it helps!

Regards, Stephen.

Share this post


Link to post
GreenMan

Perfect Stephen. This is the basic explanation I have been looking for. Thank you!!!

No worries! :)

Share this post


Link to post
powbmps

So the yellow wire (S) in my photo above is attached to the same post as the wire that goes directly to the solenoid, so I am assuming that it is okay where it is?

Share this post


Link to post
GreenMan

Yep!

(I'll assume it goes to the small terminal on the starter solenoid and not the large, main stud with the battery cable).

Share this post


Link to post
powbmps

Yes. Now I just need to figure out where to connect the (I) wire. There is an unused wire coming from the wiring harness and a note on the engine diagram that says "may be used for an accessory. LOAD MUST NOT EXCEED 5 AMPS." According to Carter info, the pump draws 4.5 amps. Maybe this would be a good line to use?

Yep!

(I'll assume it goes to the small terminal on the starter solenoid and not the large, main stud with the battery cable).

Wiring.jpg

Edited by powbmps

Share this post


Link to post
MadMan

Note the Carter's elec. terminals (posts) are on the BOTTOM of the fuel pump and mine were rinky-dinky press fit caps....The pump is mounted with rubber bushings on top but it still vibrates and they loosened up a couple times, so I went with a Holley Marine elec. fuel pump.

I had this same problem, fixed it by zip-tying the wire up to the pump.

If you mount the fuel pump close to the fuel tank, so it pushes the fuel most of the way instead of pulling, it will eliminate future vapor lock issues.

Piggy-backing the wires to the starter relay is perfect, it eliminates the need for a separate fuel pump relay (plenty of amps available). You might want to consider an inline fuse to the pump though.

One more thing, some people aren't comfortable relying solely on the oil pressure switch alone to shut of the fuel pump (as in the schematic). It's connected to battery, so the fuel pump would continue to run if the oil pressure switch failed closed, even with ignition off. If your one of these that like the "belt and suspenders" approach you would need to connect it to an ignition switched power source.

Edited by MadMan

Share this post


Link to post
powbmps

If you mount the fuel pump close to the fuel tank, so it pushes the fuel most of the way instead of pulling, it will eliminate future vapor lock issues.

This is where I have it now. Of course it is far away from the fuel tank, higher than the fuel tank and close to the hot engine. The only other option looks to the in the bilge along the stringer. That way I could put it back by the tank and down low away from any heat. I could also use the fuel water separator instead of my little inline filter. However, it will only take a couple inches of water for the electrical connectors to be submerged. I suppose it the pump is working correctly, I would not see that much water in the bilge....

Any thoughts on this?

20151206_115410.jpg20151206_122145.jpg

Edited by powbmps

Share this post


Link to post
powbmps

I spoke with tech support at Carter. Where I have it now is too far from the tank, as they recommend not more than 2'. In the bilge it will go. I'll just need to keep a close eye on how deep the water gets.

Share this post


Link to post
MadMan

I spoke with tech support at Carter. Where I have it now is too far from the tank, as they recommend not more than 2'. In the bilge it will go. I'll just need to keep a close eye on how deep the water gets.

Where is your fuel tank? On my Sunsetter it was standing up, behind the back seat. I mounted the pump between the tank and seat.

Share this post


Link to post
powbmps

Where is your fuel tank? On my Sunsetter it was standing up, behind the back seat. I mounted the pump between the tank and seat.

Sounds like it's in the same location, but I'm not sure if there is enough space.

20151027_100037.jpg

20151030_164033.jpg

Share this post


Link to post
malibuparadise

Your transmission housing is another location that you can mount fuel pump to, i.e., there are bolts that can be removed and then replaced with a bracket, attached via the removed bolt (s), that you can fabricate to mount pump to. I used 1/8" aluminium plate.

The bilge does not seem like a good idea....

Share this post


Link to post
MadMan

Sounds like it's in the same location, but I'm not sure if there is enough space.

Yep, yours is different than mine was. Maybe you could mount it in one of those vent/pockets on the side?? Or you could just run it the way it is. the good (and bad) thing about electric fuel pumps is that they are always pumping at max capacity, even while cranking. This might be enough to overcome vapor lock. The old school mechanical pump is just barely pumping when cranking and is unable to pump out the vapor.

Share this post


Link to post
powbmps

I cannot seem to fit it anywhere else, so I'll give this a try. Still running the fuel/water separator in the stock location as well.

20151212_135658.jpg

Share this post


Link to post
malibuparadise

I cannot seem to fit it anywhere else, so I'll give this a try. Still running the fuel/water separator in the stock location as well.

20151212_135658.jpg

Looks like the terminals are going to get wet since on bottom of pump? Drybilge setup?

Share this post


Link to post
powbmps

So this is the latest version (and probably how it will stay). Used a 2 1/2" fuel pump bracket in place on the bracket that came with the pump to gain some clearance. Before, the connectors were rubbing on the bottom of the boat and now I've got just over 1" clearance. I will see how it works, and if water is an issue, I can put something over the bottom (ie: high tech Styrofoam cup).

Would it be a bad idea to hook up the battery to see if the pump is pumping, or am I better off leaving fuel out of the system over the winter?

20151221_162152.jpg

Edited by powbmps

Share this post


Link to post
Indebound

They say keep the fuel tank ~95% full over winter. With adequate storage stabilizer of course.

Share this post


Link to post
malibuparadise

I would seriously add an in-line fuel pressure age somewhere easy to see (close to carb) since the fuel pump is in the bilge, which I hope stays dry....1" in above is not much with water sloshing back and forth.

The Carter pump is high volume low-pressure (~5 psig) one, so get the corresponding low-range gage.

Share this post


Link to post
powbmps

So I hooked my battery up today so I can check some of my wiring. Pulled the plug wires and turned the key. When it is in the on position, should the fuel pump start pumping and/or should it come on when the starter is cranking? Right now nothing is happening with the key in either position.

Supposed to be 60 here tomorrow, so I am planning on doing some electrical troubleshooting. Was thinking about running a hose to the swimming pool and firing it up if I can get everything working.

Share this post


Link to post
malibuparadise

The engine needs to crank over at least until the oil pressure comes up greater than 5 psig, the oil pressure safety switch should allow power to the fuel pump....I think you need water....

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...