Fuel Pump Question

[haroldlewis]

I have a 1984 31' 310 Airstream that has been in storage for 3 years which I am getting ready to sell. When I first tried to start it it wasn't getting gas to the carb, once I figured out the problem the engine wasn't getting fuel, I traced the lines back towards the fuel tank and have found 2 fuel pumps, I replaced one and it now starts, I am puzzled as to why there are 2 fuel pumps (the second bypasses the primary pump and has a shut off valve on it, can anyone tell me why?)I don't want to put it up for sale without knowing why.
Thank you Harold
my email is learningvisuals@yahoo.com

[crazeevw]

Possible that second fuel pump may be for genset? I've got electric pump at rear of coach, and engine driven at front.
Thanks, Derek

[ventport]

I would guess it's a back up pump if the first one goes bad. Is it wired up? If so there must be a switch for it somewhere around the dash.

[Silver Goose]

We're only guessing here... Some years back I was comparing notes with a fellow camper. He had a Class A SOB and was telling me the engine wasn't getting enough gas to make it up Raton Pass. A local mechanic installed a 2nd fuel pump and he claims that solved his problem. The PO may have done this for a similar reason, and it sounds like it was plumbed in parallel so he may have installed the cutoff valve to prevent back flow through the 2nd pump when he elected to not use it.

[swebster]

Many of the motorhomes have an electric "booster" pump near the tank which fed through a chassis rail filter into the intake for the engine driven mechanical pump. The electric pump is typically mounted just ahead of the fuel tank and is wired into the ignition (turn the key on and you'll hear it).

Typically symptoms of a bad or failed electric pump are: loss of power going up hills, hard or no starting, loss of power under full throttle.

The fuel filter in-between the electric pump and the mechanical can also wreak havoc in terms of intermittent power, cutouts, etc.

My bet is that the second one is PO add-on perhaps as has been suggested as a back up.

[gunner]

The electric pump was added by either Airstream or the chassis manufacturer to assist with getting fuel from the tank to the mechanical pump. The mechanical pump was not sufficient to meet the fuel requirements during accelleration and climing hills.

[haroldlewis]

Thank all of you for your help!!

[montreal]

Does anyone have any specs on their electric fuel pump. I see that I am missing one!
What is the flow rate or model/make of the ones fitted?
I'm thinking I will need something like a Facet brand pump,an in-line regulator and maybe a fused relay for good measure ??

[Keyair]

Originally Posted by montreal

Does anyone have any specs on their electric fuel pump. I see that I am missing one!
What is the flow rate or model/make of the ones fitted?
I'm thinking I will need something like a Facet brand pump,an in-line regulator and maybe a fused relay for good measure ??

Look in the Classic sticky thread under Chassis Manual, and you will find a specific mention of the vapor lock problem and how to cure it.

Here is how my 84 is setup... I have a switch under the dash that activates the rear pump.

[bkahler]

Originally Posted by Keyair

Look in the Classic sticky thread under Chassis Manual, and you will find a specific mention of the vapor lock problem and how to cure it.

Here is how my 84 is setup... I have a switch under the dash that activates the rear pump.

Steve,

I find it interesting that the 1986 version of the 345 has a slightly different fuel pump mounting arrangement. On the 86 version the pump is mounted in front of the fuel tank hanging down from a cross member. Here is a picture of the mount assembly. Unfortunately I couldn't find a picture of it mounted in place.



Brad

[Keyair]

I like the idea of it being better protected Brad.
Mine hangs below the chassis rail on that rubber flap and it needs a rework... I think I will move it up, and mount it on the rail, on a isloting bushing, so nothing is as vulnerable to say a bit of tire debris on the highway...

[slowmover]

Cushioned ADEL clamps every 6", for starters, on that soft line. Hard line would be better -- mandrel bent for constant internal diameter -- as it also flows better than soft, not just because it is more hardy. It would be hard to find the recommendation of any more than 1-2' feet of soft line total in a fuel supply line. Usually a few junctions at best for the rubber stuff.

Double clamp the ends as well. Keep the gear drives 90-degrees from one another.

It really is best to upgrade this. Rubber line + clamps is just not good practice for fuel systems.

[montreal]

Just fitted my Webcon pump with filter. It fits in side the chassis rail behind the step and battery box which also provides a good place for the relay. Its very neat and near silent (a little too quiet perhaps).
Works well and the engine still runs if it were to fail. I will install a dash waring light to show that it is receiving power.
Cheers all. Runs really nice now