unclesam

I have a '79 Class C motorhome on a '78 Chevy G30 chassis with a 400 Sm Block. I would like to replace the mechanical fuel pump with an electronic pump. How do i do this? I've found the fuel pump block off plate and a new electronic in-line fuel pump. But i need to know where to wire it to, and what do i do with the vapor return line that used to go into the fuel pump? If anyone can tell me how to do this i'd really appreciate it.

MT-2500

You are better off to leave it as is.
Inline electrical pumps are not the best deal.
M

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Remember proper testing gives us the answer to many problems.
MT

denisond3

You can probably dispense with the vapor return line that ran from the mechanical pump - if it was really a vapor return. If it was an excess fuel return line however, it had the useful purpose of letting more fuel flow in the lines from the tank and back into the tank - to forestall vapor lock.
You would need to supply electric to the fuel pump from the same circuit that powers the ignition. The only hiccup here is that some cars had two circuits powering the ignition. One was for general running, the 2nd one only for starting. Once you turn on the ignition though, the electric pump would fill the carb - and it wouldnt matter if the pump was shut off while the starter cranked the engine. An electric fuel pump needs a really secure ground connection - for safety.
If the vapor return line or fuel return line is not an issue, you can locate the electric pump wherever you like, such as away from engine heat. I would replace all of the rubber fuel lines on the RV anyway. I would avoid using any rubber fuel lines from the fuel pump to the carburetor though. I dont care for pressurized fuel in ordinary rubber hose - unless it is supported/secured/protected at every point where it will experience vibration or abrasion.
With an RV as old as yours, fuel filters are Vital unless your fuel tanks are made of ABS plastic. I get the in-line plastic kind you can see into, so I can check on how much silt is clogging it. Fram makes them as well as other firms. Its located where I can easily see it by laying under the front bumper - and I can change it in 5 minutes.
I personally like the mechanical fuel pump on my Winnebago. Admittedly there is the problem of starting up when it has been sitting for weeks or months. My solution is to remove the engine cover, the air cleaner, then pour fuel into the float bowl via the vent (its a Holley carb). I get immediate starts! With your vehicle thats probably not feasible. For that reason I might install an electric pump 'in parallel' with the mechanical pump. Running the electric pump with a momentary switch for 20 seconds would fully prime the carburetor, and allow snappy starts. You would need to have the type of electric pump that wont allow much 'backflow' through it, and two "T" fittings, one before the mechanical pump, and one after the mechanical pump.
On my RV I replace the mechanical fuel pump each ten years, and I carry spare fuel filters (note the plural.) With the old tank on your RV, the typical fuel filter can clog up in 50 miles of lumpy interstate, or it may last for 10,000 miles. I even installed a fuel pressure gauge on the dashboard, so I can keep track of the filter 'health'. It gives great peace of mind.
Let us know what you do...