Electric Fuel pump conversion,,greatest thing

[jeff york]

I have a nicely restored 77 Airstream Argosy Motor home. Its powered by what you might call a hoped up 454 GM motor. In my quest to move toward EFI (electronic fuel injection) I took the first step by replacing my mechanical fuel pump with an electric fuel pump. This was the best upgrade I have done so far. Instead of pumping the gas pedal to the point of not knowing if you are flooding the carb in an effort to prime your carb after sitting several days, Now, I simply turn the key on, listen for the fuel pump, wait a few seconds and then turn the key to start and instantly the engine fires up. Instant fuel pressure means instant starts. If anyone is interested, I can give a few details of the installation and procedures with pictures. I highly recommend this conversion and rate it a 9 on convenience but it can be a little high on the difficulty scale for the novice

[jeff york]

Tonight I finished up the install conversion of the electric fuel pump. I replaced all the flex fuel lines, turned the fuel pressure down to 3.5 PSI, installed new fuel filters and button up the installation. I then allowed the engine to warm up and took it out for a short test drive. I ran it up to 60 mph. What amazes me is not only how easy the engine is to start, but how much more responsive it is on the throttle. I will say again, this is the best upgrade to the motor I have done to make it more reliable. Fast easy starts at the touch of the key. I am now leaning towards the MSD EFI conversion kit. 

[jeff york]

Jerry Cooper said "

Make sure you install a cutout switch on oil pan, so fuel pump cannot flood oil if same malfunctions "

Jerry, I am confused by your comment. With a stock mechanical fuel pump you have a common link that can cause fuel to get into your crankcase, oil pan, oil supply. That common is when the diaphragm in the mechanical pump crack allowing fuel to get past the diaphragm seal and into the oil system by way of the mechanical drive system in the engine block.

In an electric fuel pump system, there is zero physical common between the electric pump and the oil, crankcase systems. Therefore it is not possible to get fuel in the oil systems. If an electric fuel pump fails, you simply lose fuel pressure and therefore fuel to the carb and your engine wont run. What a cutoff switch would be useful is for cutting off the electric fuel pump in the event the engine stops running. This way you stop the potential flow of fuel to a hot engine thats not running. I find that situation rare and extremely unlikely situation or problem because if the engine stops running your electric fuel pump wont cause any harm if you have a pressure regulator on it. Because even if the pump is running and the engine is not, the regulator will prevent fuel from flowing past the needle valve and float in the carb , So, effectively you have  no fuel flow. Now an oil pressure switch can be incorporated as an extra safety measure in the event of the engine stopping.

[jeff york]

What I have learned I hope to help others. First let me say, when working on a fuel system, use every precaution you can. My racing experience taught me that fuel is a lot more explosive then most of us think.

I was experiencing starting problems and that pumping and pumping of the gas pedal if my rig had been setting for more then a few days. It was always a guess between " Did I pump it enough to get it to start or did I flood the carb ? Will my battery last long enough to get my engine to start ? I built a highly modified high compression stroked and bored 454. It taxes my battery and starter and my battery compartment in my Vintage Airstream is not big enough for a serious big deep cycle battery.

I replaced my mechanical fuel pump with a new one. But, could not get the pump to prime so I could not get the engine to start. Since I am working towards installing a EFI system, I thought I would install an electric fuel pump. But, I needed a pump with only a 3 to 7 psi rating. Of course that will not support EFI but will support my Rochester Quad carb. So, I decided in the interest of getting out for the camping season, to install a low pressure Mr Gasket 12 S fuel pump. This is a pump that is installed outside of the fuel tank but must be very close to the tank. Electric pumps are push pumps, factory installed mechanical pumps are pull or "suck" pumps. Big difference.

So, as you can see in my picture, I installed the pump just outside of the saddle tank about mid way back in my motorhome. Because its a saddle tank, I am unable to install the pump at the optimal location which would be near or at the same level as the bottom of the tank. Saddle tanks tend to have a very low bottom. So installing the pump at or near the bottom level would have placed the pump in an area to close to possible damage from rocks from the road, logs or obstructions I could run over while backing into a campsite and so forth. So, I located it on a frame section that allowed it to be below the top of the tank.

I cut the hard line coming out of the tank and routed soft gas line to the incoming side of the electric pump. I used gradual bends in the rubber gas line to minimize kinks. A gas line should never have a greater then 45 degree bend. I grounded the pump as close to the pump as possible so that the pumps gets adequate power and doesn't over heat. 

What I discovered after installing a "pusher" pump is why my Mechanical "suck" pump would not prime. I had a large external mounted cartridge fuel filter that had loose connections. Those connections on a suck style pump was allowing an air leak in the fuel system. Because it was a suck pump, it didn't leak fuel because the air leak did not allow any pressure to build which would pull the fuel and therefore show the leak. ( I had this issue on my motorcycle several years ago where a crack in the fuel line would not allow the motorcycle to start. It could pull fuel to the carb. But, I didnt recognize this in my motorhomes 454 motor. We want to think of any break in a fuel line to show up as leaking fuel. But, in a suck style factory mechanical pump, it is very possible to have a crack in the line not show up as a leak if that crack is above the level of your fuel tank. So, it was after I installed the electric " push" pump that the leak or loose fittings showed up as fuel leaking. So, if you are having problems starting your engine and you have a mechanically driven pump, you may have cracks in your fuel system that allows air into your fuel system causing a loss of fuel pressure.

Once I tightened up the connections at the leak, my problems were nearly resolved. I also found the rubber line where the hard fuel line at the engine bay turns into a soft line that runs about 18 inches connecting to the remote mounted fuel filter. So that was simply a matter of running a new piece of rubber line from the hard line connection to the remote fuel filter.

Now, when I turn the key to start my 454, its an instant start. No pumping the gas pedal, no wondering if I flooded the carb, didn't pump it enough or if I am going to ware down the battery before I get it to start. It starts with a simple touch of the key. Instantly. By far, this is the best upgrade I have done to my engine to improve its reliability and give me the piece of mind to know, its going to start every time. I highly suggest this if you have the ability to do a semi complex installation on a fuel system. If you cant, I suggest you have a good shop do it for you. Note: I used an inexpensive pump as I intend to install a new EFI system which will require a high pressure pump. But, this gets me camping now. I have about 10 hours in this conversion. Allow for that if you want to do it yourself.

[Jerry Coopere]

Make sure you install a cutout switch on oil pan, so fuel pump cannot flood oil if same malfunctions

Jerry Cooper

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[jeff york]

[Jim Stoltz]

It's not uncommon for the rubber lines that come off the fuel sender to rot on top of the tank. That's what happened to mine. When I replaced the engine I couldn't get it to start, and the generator wouldn't run. I replaced the fuel pump and it still wasn't getting fuel. Finally I cut a hole in the floor so I could replace those rubber lines.

My tank is in the very back. The run from the tank to the fuel pump is probably about 20 feet. This was one of the reasons for vapor lock that GM identified - to small of a line for such a long run. Mine must be a "late" 1984 because all of GMs recommendations described in that manual were done to mine: 1/2" steel line running the full length, electric fuel pump and oil-pressure cut-out switch. However, someone had removed the electric pump a LONG time ago. It must have failed. There was a new one in one of the storage compartments, but it was very old too and didn't work.

[jeff york]

I meant to say some sources say set fuel pressure to 3 psi and some say 5 to 6 psi.

[jeff york]

Its confusing to hear one source state 3 psi max fuel pressure for the 454 and other sources say 3 psi. I thought my fuel line length was a lot shorter then it was because it seemed my saddle tank was close the the engine. But, upon inspection, the fuel line coming out of the tank comes out of the rear of the tank. I bet there is at least 12 feet of line just getting up to the engine bay. I have one last piece of rubber fuel line that I am going up to replace today. Its the flex line that goes from the hard line coming into the engine bay and going to the big fuel filter mounted on the frame. From the big filter I have new line going up to my Rochester carb which also has a paper filter just in front of an mounted to the Rochester quad carb. I am concerned that I have to many filters ( 3) and that it could be restrictive to fuel flow. I had installed a new fuel pump but never could get it to prime. I replaced it because I couldn't get the old mechanical pump to prime. But, upon installing the new electric fuel pump I found the big canister fuel filter mounted on the frame to be leaking. I think the extra pressure of the electric fuel pump exposed why I could not get the mechanical pump to prime, there was an obvious air leak causing the mechanical pump to not build suction. Since the the mechanical pump put out much lower pressure, it may not have leaked or leaked enough fuel for me to see it but leaked enough air to prevent fuel pressure and thus no ability to start the motor off the mechanical pump. I hope all this helps anyone with starting problems or other related fuel system issues. I am going to turn down the fuel pressure to 3.5 psi and see how it performs. I am also going to take some pictures and post them and maybe this will help others. I will say this, starting the motor now is as simple as just hitting the key. Instant fuel pressure has resulted in instant starting.

[Jim Stoltz]

Here's a link to the vapor lock extract from the Chevy Motorhome Chassis Manual:

https://drive.google.com/file/d/0B0QRzZBSwejgQmVLRlE5Y1Y5cXM/view?u...

It describes what GM did through 1985 1/2 to combat vapor lock. They added an electric fuel pump at the tank, but kept the mechanical pump. For whatever reason, in testing the fuel pressure dropped to 0 on the 5-mile hill they were testing on when the mechanical pump was bypassed. Obviously the correct electric pump would avoid this problem. 

I know there's also a version of this document that shows how they installed an anti-drainback valve and return but I can't find it. They did say that with some pumps, no return is necessary. They essentially looped the hose around from the regulator back to the input of the pump so it would circulate rather than pressurize the carb.

According to their study, the Rochester starts to spew fuel at 5-6 PSI. They recommend a max of 3 PSI. 

[jeff york]

Having just installed my electric fuel pump, I have not yet seen any issues with needing a return line to the tank. Tonight I plan to go through some additional tests on the system becuase rain is going to keep me from camping anyway. I have installed a fuel pressure regulator. I currently have it set at 4.5 lbs. I am concerned about having the right pressure setting so as to not have to much pressure pushing fuel past the float needle. I have a mechanic tell me he thinks I should lower the fuel pressure to about 3 psi.

Because I spent so much time money and effort on my 454 custom rebuild, I too was concerned about a split fuel pump diaphragm allowing fuel into the engine crankcase. My engine was balanced blueprinted and built for high performance and the demands it placed on the mechanical fuel pump were far to much. I thought I had a carb problem until a mechanic told me most 454's built like I did mine were not going to run or start right on a mechanical fuel pump. I think he was right. Its now like starting a fuel injected carb. No pumping, no worries about flooding or running the battery down. I am getting double the fuel econ after my rebuild but, the bad side effect is the demands on the battery, starter and fuel system. So, the electric fuel pump seems to have relieved all that stress as I have killed the battery and flooded the engine on a few trips.

I have been looking at several EFI systems. Then a friend had a TBI system he took off of a motor he got out of a 94 GM truck I believe. I got the ECU computer as well. I think all I need to do is get a intake manifold adapter plate. This will play well with my 700R4 four speed overdrive transmission build. Its a bolt on natural. My friend was building a 740 horse 454 so he could not use the stock TBI EFO or the ECU. However, he feels even if I build the 700R4 trans that it wont hold. He says that becuase he blew his 700R4 up. Well yeah, 750 hp.

One of my concerns is that because I have a saddle fuel tank, I could not install the electric fuel pump at or below the bottom of the tank. There is simply nothing below my already low hanging saddle tank in which to mount a fuel pump and I did want to take a chance of knocking a low hanging fuel pump off the vehicle due to what would have been a very low hanging pump. But, I was able to mount it 4 to 6 inches below the top of the fuel tank.

AS far as a return fuel line, I currently don't have one. I don't see how I can put one on since the electric pump has no plumping provision for a return line. But, its a push pump not a pull pump. So, I am not sure I see why I need a return fuel line on a push pump.