1975 Argosy 454 Chevy Big Block – Replace Mechanical Fuel Pump with Electric Fuel Pump

I am getting ready to bring the “Diskotrek” home.  It’s a fully loaded 1975 Argosy 24′ mobile home that has been sitting for at least five years.  Last weekend I towed it about 10 feet to pull it out of the ruts it was sitting in and to make sure the brakes work (they do!).  All six tires were still holding air and almost at full pressure.  The brake fluid reservoir was almost completely full (I added maybe 4 tablespoons of Dot 3), and pumping the brake definitely moved the fluid in the reservoir.  After pumping the pedal for around a minute, we started to get resistance.  The brakes didn’t work the first time we started rolling, but after a little more pumping, they were good to go (at least at around 3mph!). The only information I have on why it has been sitting so long is that the last time someone tried to get it running, they didn’t want to pony up for a strong enough fuel pump.  That sounds odd (giving up because of a $30 part?!), but it’s all I’ve got to go on, so…

I’ve been researching the fuel pump swap.  These 454 Big Blocks used a mechanical pump (a pump that gets moved by a link to the engine cam).  To start the vehicle, you’re supposed to “prime” the fuel by pumping the gas pedal.  If you pump too much, you’ll flood the engine.  Not only that, but the rod between the pump and the cam shaft often becomes uncoupled or seizes (depending on the style of the year of the motor) so the pump stops, well, pumping.

Some people replace the mechanical pump to keep it stock (which seems to last 3 years or so on average?), so the preferred solution is to replace the mechanical pump with an electric one (or just add it to the line if the mechanical pump is still functioning).  From what I gather, though not absolutely necessary, it’s best to remove the mechanical pump if it fails and cap off the hole, so fuel isn’t being pushed into/through the old, non-functioning pump.  The replacement pump should provide around 5psi and needs to “push” the fuel rather than suck it, so you need to mount the pump as close to the fuel tank as possible, preferably with an inline fuel filter right before the pump (to keep all the rust and other gunk inside your tank from clogging the fuel line or getting to the carburetor).

A lot of people use the Red Holly pump, but at $130, it has much worse reviews than a lot of the $25-$40 pumps I’m seeing online, so I’m not sure the “Holly” premium is worth it.  However, the Carter P4070 gets mentioned a lot, was installed (either by Chevy or Airstream) on newer Airstreams/Argosies to take care of vapor lock issues, has a 72GPH idle flow rate (much higher than I’m seeing from other pumps), and comes highly recommended by a lot of Airforums users.  It’s around $62 delivered, but seems to be worth the little bit extra for something tried and true.

So I pulled both batteries (starting and house) and will put a new starting battery in next weekend along with the new electric fuel pump to see if she starts!

Didn’t see this mentioned in a lot of places, so thought this was worth highlighting…

Airforums user WayneG comments:

A electric fuel pump should be hooked up to run only when the engine is running. To do that it should have a safety interlock that prevents it from pumping unless the ignition switch is on and there is oil pressure. Too many people leave out the oil pressure switch, which is a bad idea. The reason for it is that if you break a fuel line after the electric pump or your carb float sticks open, it will be pouring fuel some place creating a fire hazard. If the engine is not running because of lack of fuel, there will be no oil pressure and the fuel pump will stop pumping. I found this diagram for a fuel pump hookup, there may be better methods.

 

 

 

Links to some of the resources I used for this post:

https://www.airforums.com/forums/f159/454-fuel-pump-85502.html

https://goodoldrvs.ning.com/profiles/blogs/electric-fuel-pump-conversion-greatest-thing

https://www.airforums.com/forums/f159/more-help-please-fuel-pump-question-167580.html

https://www.airforums.com/forums/f311/fuel-pump-question-96380.html

https://www.airforums.com/forums/f159/454-engine-in-argosy-mh-151534.html

https://www.airforums.com/forums/f311/1985-345-fuel-pump-problem-183783.html

https://www.airforums.com/forums/f311/fuel-pump-location-43753.html

https://www.airforums.com/forums/f310/trying-to-start-argosy-after-2-years-90966.html

https://www.airforums.com/forums/f159/454-engine-in-argosy-mh-151534.html

http://theouterlimits.ws/projects/airstream/fuel/index.html

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