Electric fuel pump

[pweems1973]

Hello. I am new to RVs. I have a 1987 Pace Arrow. I am having trouble with the fuel pump system. When I have the electric fuel pump connected, it is sending too much fuel to the carburetor and floods out. Is there a relay or a pressure switch that tells the electric fuel pump to kick on and off? If so, where us it located?

 

[DonTom]

Hello. I am new to RVs. I have a 1987 Pace Arrow. I am having trouble with the fuel pump system. When I have the electric fuel pump connected, it is sending too much fuel to the carburetor and floods out. Is there a relay or a pressure switch that tells the electric fuel pump to kick on and off? If so, where us it located?

Welcome!

Is it a stock fuel pump? Have you checked its PSI with a fuel pump gauge?

If that checks okay, you could have a carb float problem. See below how the gas flow stops when the float closes the float needle and prevents more gas from entering the carb. This is more likely your problem than the fuel pump.

Just a small grain of sand (or whatever) at the float needle seat will cause the carb to overflow even with a perfectly good fuel pump:



-Don- Reno, NV

 

[pweems1973]

The fuel pump came from factory. The carburetor that was on it was flooding so I bought a new carburetor. The new one is doing the same thing.
The electric pump is sending too much fuel. Is it supposed to have a relay or a pressure switch to tell it to kick off?

 

[Kirk]

What chassis do you have?

 

[DonTom]

The fuel pump came from factory. The carburetor that was on it was flooding so I bought a new carburetor. The new one is doing the same thing.
The electric pump is sending too much fuel. Is it supposed to have a relay or a pressure switch to tell it to kick off?

The fuel pump should automatically stop when the carb is full. While there probably is a fuel pump relay, that is just for the current of the fuel pump.

I am going to guess that your replacement carb has the same problem.

These days such is not uncommon. Not many know how to correctly work on carbs these days.

Such has also happened to me in the past, where the replacement carb was also bad with the same problem and the third one had a different problem but the 4th one worked perfectly. A 1984 Chevy Van 305 CID, in this case.

I assume you purchased a rebuilt carb as that is most likely all that is available.

IMO, around 50% of the rebuilt carbs these days don't work correctly. A very common problem.

-Don- Reno, NV

 

[DonTom]

BTW, I would like to make that one a poll.

How many here have replaced a carb and got a bad one? Any others for two bad ones in a row?

And how many have replaced a carb where it worked out perfectly?

Of the rebuilt carbs--new ones don't count.

-Don- Reno, NV

 

[CharlesinGA]

No the fuel pump doesn't shut off, but there is a return to the tank, and excess fuel simply goes back to the tank. This happens at a regulator. You don't want to dead end the pump, so you bypass it and regulate the pressure to the carb. Speed shops and performance places sell regulators. Holley makes them, many other companies do also. Summit Racing would be a good source. I deal with Summit alot because they have a huge retail store attached to a giant warehouse and they are about 50 miles from me.

You do, as Don noted, need to check the pressure at or near the carb inlet. I seem to recall that 4 to 6 psi would be suitable but don't take that for the gospel and do some research. I have a vac and fuel pump gauge from the 1950's that my dad had, I've only used it to measure fuel pressure once or twice, usually vacuum instead.

Charles

 

[Mark_K5LXP]

How many here have replaced a carb and got a bad one?

I always rebuilt the one I had. Even if the linkage or butterfly bushings are shot the only thing that would make me want to trash it would be corrosion or damage. Since they came off a mostly running car/motorcycle they're intact, just need a soak in the dip tank, a BJ with compressed air, new set of gaskets, rubber bits and back to the races.

Wonder what a replacement carb costs these days compared to a throttle body refit kit. I would think finding a carb with all the right flappers and dingalings to match what OEM you have would be a challenge.

Mark B.
Albuquerque, NM

 

[DonTom]

I always rebuilt the one I had.

That is probably the best way, based on the high percentage of badly rebuilt carbs I have purchased over the years.

But I have only rebuilt motorcycle carbs.

-Don- Reno, NV

 

[Tulecreeper]

That is probably the best way, based on the high percentage of badly rebuilt carbs I have purchased over the years.

But I have only rebuilt motorcycle carbs.

-Don- Reno, NV

I've done both and found that a carburetor is a carburetor...2-barrel, 4-barrel, just a different number of parts that do the same thing.

 

[DonTom]

I've done both and found that a carburetor is a carburetor...2-barrel, 4-barrel, just a different number of parts that do the same thing.

Yeah, I realize that. I am not sure why I never tried to rebuild a cage carb. But with the motorcycles, I have no choice.

I like to assume the professionals could do the job correctly on cage vehicles. But my experiences there prove the opposite. I no longer have any cages with carbs and most likely never will. But if I did, I had it with rebuilt carbs and would do it myself next time as long as I could buy the carb rebuild kit somewhere.

One thing for sure is that I could not do a worse job than the rebuilds I have purchased over the years. OTOH, I wonder what they do wrong--and why they don't work correctly--and how I could prevent the same mistakes.

-Don- Reno, NV