Rochester float bowl fuel too high.

[83lee]

1966 Series IIa

I've recently purchased and overhauled a Rochester B and have a continual problem with the fuel in the bowl getting so high, after a few minutes of running, that it kills the engine and runs out over the manifolds.



I've triple checked all my work...float settings (hanging and upside down). The float valve and seat are new and look fine. I've shaken the float after being submerged...no fuel in it, and have held it under looking for bubbles. The only thing I can't check is the width between floats, as I don't have (nor know where to get) a gauge for that, but they seem to fit fine in their place.

Also I have a new fuel pump...if that makes any difference...

Really stumped here. Any ideas?


(I've got a Zenith all lapped and ready to go, but need to locate a "90 degree thing" and the bellcrank/linkage stuff.)

[greenmeanie]

What height did you set the floats at? If you have them set at the smallest engine size on the ovehaul shart you should be good. The other thing is that the floats or needle could be sticking. Repair procedure #1 applies at that point - take the air filter off and hit it hard with something.

[kevkon]

What type is the new fuel pump?

[83lee]

Float Level 1 9/16"

Float Drop 1 3/4"


Fuel pump is a non-genuine with sediment bowl.

[TeriAnn]

I've recently purchased and overhauled a Rochester B and have a continual problem with the fuel in the bowl getting so high, after a few minutes of running, that it kills the engine and runs out over the manifolds.

If everything is set up OK you have one of two problems. One the float valve not closing or not clossing with enough force (float partially filled or otherwise too heavy/not buoyant enough) or two too much fuel pressure. These carbs are low pressure. 3 lbs pressure is about right.

This assumes the carb is set up correctly including the vacuum passage at the bottom of the carb being open to the pressure at the base of the carb (thick bottom gasket with slit to open path between hole in base and bottom of carb throat). This helps set fuel level in the bowl.

More information about carb set up can be found on one of my web pages:

http://www.expeditionlandrover.info/landRoverFAQ/FAQ_rochester.htm

[83lee]

I just changed out the new float valve and have put back in the old one (just in case), and I'll drive it later today to try it.

Pretty sure the floats are holding air, but I just read the way to check them is to immerse in hot water. Hmmm. OK I'll try that later.

I did cut the gasket to allow that lower port to get vacuum, and I dremel-ground a nice slot in the 1/2 " plastic spacer as well.


3 PSI out of the fuel pump. How do I check that? Inexpensive gauge from Grainger or ACE teed-in just before the carb?

Thanks for the website link, Teri Ann. I've been referring to that often, and of course find it very useful. That's where I got the float settings.

[83lee]

Update

Spent hours today changing the float level. No difference at any setting...still overflows.

I got a gauge and checked the fuel pressure, 6 psi at all rpm's. Is that excessive?

One thing that may shed some light...I was able to get it to run nicely when parked, but after driving up the street and back, it began that overflow routine. The engine dies and I quickly pop the bonnet and see a gusher of fuel running down the carb onto the hot manifolds. Scary.


So to sum up, pretty sure it is not the float valve (tried two of them) and not a leak in the floats (checked this five times). I suppose it could be the floats or hinge hanging up somewhere... or some strange siphoning action happening that I have no understanding of...or, that 6 psi out of the fuel pump being too much???

Any last thoughts anybody?


I'm about ready to chuck it and start working on those Zenith parts.

[kevkon]

I'd say 6psi is too high for that float and valve.

[gudjeon]

Any tiny bit of dirt/rust/crud getting on the needle and seat will turn it into Niagara Falls.

[83lee]

And a waterfall it was too!!

It's really clean. The needle valves have the viton (high tech rubber) tip. I just installed a new inline fuel filter a few months ago.


Getting back to that 6 psi...

How much pressure would a Genuine fuel pump put out (vs. non-genuine)?

Is it just the Rochester that doesn't like it, or all the others too?

Is a pressure regulator the next step?

-Thanks.

[kevkon]

That's a good question. I'll check the big book. Mine is a genuine and it puts out about 1.5 to 2.5 psi which is about all the Weber can handle.

[daveb]

6 psi is way too much. Is this an electric pump? Whatever, get rid of it and fit a proper one before you have a fire. A pressure regulator will work too.

[TeriAnn]

3 PSI at idle & no less than 2 PSI at 3000 RPM will work best on any of the LR compatible carbs. That's the normal range of the stock AC pump.

[kevkon]

According to the big black book the range for a genuine AC 2 1/4 fuel pump is 1.5 to 2.5 psi. You are overpowering that float/needle assembly. You can get a Holley low pressure regulator or get another pump.

[83lee]

OK, thanks for looking that up, and to all for the advise.

Pretty sure the pump is AC. I'll get the number off of it later...maybe it's the wrong pump??

I've got a Holly 12-804 pressure regulator coming in this afternoon which I'll install and hopefully be able to get the rig home. Then I'll see about getting the right pump.


A bit disappointed with the Rochester for having a 1/4 inch hole cast in the top of the carb. The fuel just pours out there when you have float or pressure problems like I'm having. Don't think I've seen that on other carbs.