Switching from mechanical fuel pump to electric??
 

I'm looking at adding an electric fuel pump to my carb 454mag. After I install the electric pump, should the mechanical pump be removed from the sea water pump assembly or can I leave it on there in case I should need to go back to it? Or will it be damaged without any fuel running through the mechanical pump?

Re: Switching from mechanical fuel pump to electric??
 

it will be damaged,due to dead heading. remove it and block off the opening with a block off plate. if using an electric make sure you use a oil pressure hop switch on the ground side of the electrical circuit for the pump, and use relay to power the pump as to cut down on any excessively high draws in the bilge.

Re: Switching from mechanical fuel pump to electric??
 

i run both in parallel, so if one pukes im still good to go home

Re: Switching from mechanical fuel pump to electric??
 

I wouldn't bother swapping to a electric. It's been prooven on this board that electric pumps don't survive in a marine application.

Re: Switching from mechanical fuel pump to electric??
 

I was wondering why you would want to switch ?
I have Electric Back-ups on a Press. Switch but woulodnt want them instead of a Mech

Re: Switching from mechanical fuel pump to electric??
 

Run them both,,, Put a tee in the line before the Mech pump and then put a Reg before the Carb ,,, You will have the best of both worlds and not have to remove the Mech pump,,, Like said be for ,,,, run the Elec of the Oil pressure ,, or ,, I have seen them hooked up to the Tach ,,, so they come on at 2500 rpm,, or when ever you want..

RHC

Re: Switching from mechanical fuel pump to electric??
 

Do it the way RHC said to but use a MSD rpm activated switch with a adjustable low rpm module.

Re: Switching from mechanical fuel pump to electric??
 

Don't need it....why do it?

Re: Switching from mechanical fuel pump to electric??
 

ditto!!!!

Re: Switching from mechanical fuel pump to electric??
 

My boat came with electrics and mechanicals, in parallel. I have not had to use the electrics at all. 750 hp each @ 5500rpm. Never saw a drop in fuel pressure since I've had it.

Re: Switching from mechanical fuel pump to electric??
 

Thanks everyone! I like the idea of running both pumps in line as stated.

Basically, I'm tired of having to pump the hell out of the throttle everytime we go out. Figure by putting an electric pump in line, will get fuel to the motor quicker for ease of starting.

I keep hearing that the electric pumps aren't reliable, yet all the newer motors are factory with electric fuel pumps... is it just the after market pumps that don't hold up???

Thanks again!!!!

Re: Switching from mechanical fuel pump to electric??
 

Why would you have to pump the throttle, carb leaking down?

Re: Switching from mechanical fuel pump to electric??
 

I have to pump the throttle on each motor about 10+ times to get them to fire over. I don't know squat about carbs and if they are leaking down or not. What causes them to leak down? If they are, is there a fix I can perform?

Re: Switching from mechanical fuel pump to electric??
 

What kind of carb. I had the same problem with Edelbrock carb. Switched to a Barry Grant SEA DEMON and love it. No choke and it starts at the click of the key :D

Re: Switching from mechanical fuel pump to electric??
 

Not sure of the carb, they are 1994 454 mags if that helps.

Re: Switching from mechanical fuel pump to electric??
 

possibly not the carb, for stock applications there is an anti-siphon valve in the pick-up tube in the tank. it causes alot of issues like the one your having you may want to check it. it will allow the fuel to drain back to the tank if is not working. as far as electric, as stated, they are in fact reliable , thus mercury uses them on all their stuff. it is just to find the right one and not cheap either. additionally the install with propper ground's and excite triggered relays are just as important.

Re: Switching from mechanical fuel pump to electric??
 

How do you get into the fuel tank to check an anti siphon valve? I have a cover in the floor over the fuel senders, other than that, I can't see any part of the fuel tanks. I have two tanks. Any way to test to see if it's working? Put another one in line between the tank and the fuel filter/separator? The problem is with both engines, neither is easy to start. Once started, they start without any issue the rest of the day.

Re: Switching from mechanical fuel pump to electric??
 

You most likely have a Carter (Mfg. by Webber) carb. They are notorious for this problem. I tried everything and ended up with a Holley similar to the one they put on the 500hp's. I had 502 mags that did the very same thing and that cured it. Those are 800cfm so, that might be a little big for your 454.

Bob

Re: Switching from mechanical fuel pump to electric??
 

Either the fuel pump or the carb has a internal leak. If you fix the leak, you'll fix the starting problem. Adding the electric pump will only crutch the problem.

Re: Switching from mechanical fuel pump to electric??
 

Actually adding an electric pump most likely won't help your problem at all since the electric pump will need to be hooked up to an oil pressure switch it won't put out any pressure until you've got oil pressure. You most likely have a bad diaphragm in the fuel pump, or your carburetors are leaking down and need to be rebuilt. You may want to take the carbs off, have them cleaned install a kit in them and try it again.

Another thought would be cranking the engine over for a 20 seconds or so before pumping the throttle this will get fuel into the engine, and make sure you have oil everywhere. Now pump the throttle 2 or 3 times, and try her.

Re: Switching from mechanical fuel pump to electric??
 

You say "1994 454 mags" is this happening on both engines?

Re: Switching from mechanical fuel pump to electric??
 

That is correct, it is happening on both motors. When they are cold, we have to pump the hell out of them to get them started, hate hearing them crank and crank until we finally get a sputter and finally startup. Once running, they are perfect for the rest of the day. No other complaint other than starting the dammed things....

Re: Switching from mechanical fuel pump to electric??
 

Bad accelerator pumps? Is the choke working? The carb has fuel in at start-up. Needs absolutely no fuel presure to start an engine. So, either you are somehow loosing fuel out of your fuel bowls, or you have a bad accelerator pump. What carbs you got?

Do this - with the engine off, remove the flame arrestor. Open the choke. Look down the carburetor. Have someone move the throttle to full throttle. As it moves, you should see gas squirt in. If not - you have a bad accelerator pump. Have someone go through the carb. Or your carb has lost its fuel. In either case - have a knowledgable person rebuild the carbs.

Re: Switching from mechanical fuel pump to electric??
 

I had gen 6 502 in my 357 kamma boat which had electric pumps that i had nothing but a head aches and problems with,at wide open throttle,the motors would lean out so fast from lack of fuel pressure the valve seats would even fall out from the heat and distroyed the engines(one at a time,rebuild one,the other would blow)could never get it right with hundreds of dollars spent on pumps alone!As far as running 2 inline,tryed that also,didnt work,caused more of a restriction,when one pump would fail,the other had to now pull or push fuel threw a blockage which created a lack of fuel to the carbs and blew motors!Best thing to do is stay with what the motor is designed to use and fix the carbs other wise it could be trouble!Stay with OEM, GOOD LUCK! Try this,put a vacum guage on the motors while cranking and idleing,if the vacum isnt that great your problem could be the motors arent pulling enough fuel air mixture to create a good explosion until the motor is almost flood with fuel!Do they smell rich when they fire and run rich until they warm up?IF week vacum shows on guage,do a leakdown test next!! GOOD LUCK AGAIN!!

Re: Switching from mechanical fuel pump to electric??
 

Thanks everyone! Great insights!

Engines don't seem to be loading up with too much fuel at any time. After reading all this, I'm going to hold on the electric fuel pumps and go over the tips of checking my current carbs and start getting an education on how they work and if they are working correctly. Then resolve any issues I might have there and evaluate the situation again.

Re: Switching from mechanical fuel pump to electric??
 

what is the cost of a new carb, like the demon mentioned? Looking at the rebuild kits, they are about 100-130 bucks. If I put the extra money out for a new carb, would I be gaining anything over the stock carb? I have to get out to the boat and see what kind of carb I have, I'm assuming it's the weber, but don't know for sure.

How do I check to see if the electric chokes are working? If I turn the key just one click, should I see the carb being choked at that time or do I have to watch the carb at the time the motor starts to crank?

Re: Switching from mechanical fuel pump to electric??
 

Sea Demons are $500+ each on Ebay. A guy in WI sells them by the hundreds. The price of your Rebuild Kits seem high. Take the tag off the carb and cross ref at a auto store.
Get a good marine book. If this is happening on both carbs, I think you have other issues. I also had a prob like this with stock carb years ago. I always shot starter fluid down the carb if it sat more than a week. I also do not like the engine turning over for minutes before it roars to life :D

Re: Switching from mechanical fuel pump to electric??
 

I'm telling you I've been there done that and changed everything. "IT'S THE CARBS!" They lose their prime after sitting for a week. Starts okay the next day but, crank the heck out of it after sitting for a week. Sound familiar? I tried rebuilding them but, that didn't help. (BTW Napa has a rebuild kit for much less). Tried adjusting the choke but, that's not causing the problem. I've heard of trying some epoxy in the float bowl walls but decided not to screw with it anymore. BTW; I changed everything from the gas tank to adding MSD ignition before I finally got the problem fixed. I BOUGHT NEW CARBS. A 750cfm Holley or Demon will fix it!

You can PM me if you have any questions.

Bob

Re: Switching from mechanical fuel pump to electric??
 

What motor did you put that 750cfm on? Not sure what size I would need for my 454mags?? What did the holley cost you?

Re: Switching from mechanical fuel pump to electric??
 

I bought some used 800 cfm's from stock hp 500's from a guy on OSO. I re-jetted them for my 502 mags. I think the 750 is what you would need. Just call Bary Grant or Holley and they will be able to tell you exactly what you need and prices. You are probably looking at 350. to 500. each, depending on which model you end up with.

If I remember right you will need to change the mounting pattern on the carb spacer. Don't worry the stud mounts are already drilled out for ya.

Bob

Re: Switching from mechanical fuel pump to electric??
 

The problem isn't in his fuel pumps, there is a problem within the carburetors themselves. Changing the pumps won't cure this.

Re: Switching from mechanical fuel pump to electric??
 

Re: Switching from mechanical fuel pump to electric??
 

Re: Switching from mechanical fuel pump to electric??
 

If the fuel pumps are bad,the motors will never start!

Re: Switching from mechanical fuel pump to electric??
 

The only problem he's having is starting after the boat sits for a week. Even without fuel pumps there should be enough fuel left in the carburetors to fire the engines.

Re: Switching from mechanical fuel pump to electric??
 

Listen to what BOB ONEAL is saying, I have the same problem same carb on a built small block. ITS THE CARBS. This Edlebrock model is an old Carter AFB, ya don't see these much anymore. I'll take a Holley or maybe Qjet if I have to, no more AFB's nothing but a hassle. Maybe a REAL good carb guy can make these work but I think they'd be retired by now - this is a '60's Hemi carb and used on a few Buicks.

Re: Switching from mechanical fuel pump to electric??
 

If you don't have alot of money, you can fix the carbs. If anything like a leaky quadrajet, a little devcon fixes 'em right up. You don't even have to take them apart.

But first make sure they are leaking and not just bad accelerator pumps.

Try this - run the engine for a bit. Turn it off. Immediately pull the flame arrestor, open the choke, and have someone pump the throttle while you look down the carb. You should see gas squirting. If not, then defiantely the carbs accelerator pumps are bad and you'll have to rebuild or replace them. If you do see the squirts, but you do not after it sits a few days, then the carb is leaking all its fuel into the manifold. I don't know the Carters, but they probably leak from a drilled passage that is plugged with a pressed in cap. Clean the area and Devcon it up. Fixed for a the cost of a tube of Devcon.

But I am guesing at this point it a leaking plug because you say it runs just fine the rest of the time. No need to rebuld if that's true, just plug the leak.

In either case, you don't have to spemd a lot of money. And a rebuild kit should not be that much money.

Re: Switching from mechanical fuel pump to electric??
 

How does the electric choke work?

The electric choke is simply a heater. Volatge is applied, and as it heats up, it opens the choke butterfly.

a)Pull off the flame arrestor on a cold engine, key off. Move the throttle a bit and the choke should close. If this does not happen, then you definately have a bad choke. If it closes, then

1) Turn ignition on.
2) With you voltmeter set on DC volts, check for battery voltage at the elctrical connection. The red lead on the choke, the black lead to the engine. If you read battery voltgae, you have power to the choke.
3) You can now wait and watch the choke start to open. If it does not, and you still have voltage, carefully touch the choke housing. It should be warm to HOT. If it is, and the choke has yet to start to open, you have a bad choke.
4) If you have voltage, and it opens, you do not have a choke problem.