convert from mechanical to electric fuel pump?

[QuackDuckDuddle]

Hey.. I have 88 omc 4.3L cobra. Just wondering if anyone knows if I can convert from a mechanical to an electric fuel pump. I having issues with one of my fuel pump mounting holes, and am probably going to have to have some welding work done in order to make the mechanical pump work.. I was thinking that I could just as easily block off the hole where the mech. pump used to live and use an electric inline or in tank pump.. any ideas or advice? Thanks.

 

[Don S]

Re: convert from mechanical to electric fuel pump?

Sure, you can change it, but you will have to put in an oil pressure switch to control when the pump runs. Not difficult, just necessary for safety.

 

[dlplost]

Re: convert from mechanical to electric fuel pump?

yes it will work, just make sure you get the proper pressure range pump, and power it from the Ignition switch.
I've used an inline 4-6 psi pump on an old 140 mercruiser before, was still working on that motor last i knew.

 

[dlplost]

Re: convert from mechanical to electric fuel pump?

Sure, you can change it, but you will have to put in an oil pressure switch to control when the pump runs. Not difficult, just necessary for safety.

Oil press switch will prevent the pump from running untill you have oil pressure. if no fuel in the carb it wont start untill you get oil press built up, then wait for fuel to the carb...better have a good batt.

Chevy had this setup on some motors years ago but discontinued it cause it was burning up the starters as you had to crank the motor till you got oil press before it would start.

 

[chiefalen]

Re: convert from mechanical to electric fuel pump?

Yes you can just wire it to the ignition key. I believe your pump puts out between 4-6 pounds of pressure so get one the same output.

 

[Don S]

Re: convert from mechanical to electric fuel pump?

Oil press switch will prevent the pump from running untill you have oil pressure. if no fuel in the carb it wont start untill you get oil press built up, then wait for fuel to the carb...better have a good batt.

That is why you have a second feed that supplies power to the fuel pump from the hot start terminal on the starter.

 

[Don S]

Re: convert from mechanical to electric fuel pump?

 

[dlplost]

Re: convert from mechanical to electric fuel pump?

yes that would definatly work..

 

[Don S]

Re: convert from mechanical to electric fuel pump?

That's why Mercruiser has been using it on carbed engines since 96 or 97.

 

[Silvertip]

Re: convert from mechanical to electric fuel pump?

Call me curious, but if you currently have issues with one of the bolt holes, how do plan to install a block-off plate securely? If it's not secure enough for a pump, it's probably not secure enough for the plate.

Diplost: You said "Chevy had this setup on some motors years ago but discontinued it cause it was burning up the starters as you had to crank the motor till you got oil press before it would start." That's nonsense. The moment you turned the key to the run position the fuel pump starts and even if you don't turn to the START position, the pump runs for 5 seconds to pressurize the fuel system. It then shuts off if you don't start the engine. When you turn the key to start, the system is pressurized and the engine starts. The oil pressure switch transfers power to the pump when the engine is running. The same principle needs to be used on a boat with an electric pump. Any situation where a fuel leak occurs even if the engine quits, means the pump stays running and you pump fuel on a nasty fire. Prolonged cranking on any FI car was due to a bad pressure regulator or leaky injectors that would allow the system to take longer to pressurize. Leaky injectors caused flooding so the excess cranking was not due to fuel pump but due to other engine problems. That whole scenario was true for nearly all FI cars.

 

[QuackDuckDuddle]

Re: convert from mechanical to electric fuel pump?

Thanks for the info guys. I think Im going to try to fix my mounting problem with the mechanical pump. If this fails I will go electric.

One question while I have your ear. The reason I ran into this issue is Im in the final stages of my repower and I tried to start the engine for the first time, but wasnt getting any fuel. I pulled the "out line" on the pump to see if I was getting anything. Nothing. I pulled off the fuel pump took it apart, blew it out and cleaned the inside, hoping that would help, then I snapped a bolt trying to get it back in.. (I know im an idiot). Anyhow, my question is, is there anyway for me to test this fuel pump while I have it out? I tried to push down on the arm with the spring, but man is it hard to do. I had it in a vice w/ a c clamp and was able to compress it a little, but thats it. Any suggestions?

 

[bruceb58]

Re: convert from mechanical to electric fuel pump?

Yes you can just wire it to the ignition key. I believe your pump puts out between 4-6 pounds of pressure so get one the same output.

You still need to run it through an oil pressure switch.

 

[dlplost]

Re: convert from mechanical to electric fuel pump?

the Chevy was a little different, but same principal. the computer didn't turn on the ignition untill it saw acceptable oil pressure.
You HAD to crank the motor until you had oil pressure before it would start, allways. If you were driving and the oil press was too low (low on oil), the computer watched the speedometer, and when you stopped, it shut the motor off. It would NOT restart untill it had oil pressure, thereby leaving you sitting in an intersection blocking traffic.