TR2/3/3A empty float bowls - TR3 with twin SU H6 carbs

[eschneider]

Ugh. This car is killing me. I've been through the carbs twice, replaced the needle and seats 3 times, and rebuilt the fuel pump once. I have all brand new fuel lines (including the metal lines from the tank, with fresh compression ferrules) and clean gas. Clear fuel filter, no yukkies.

Pump is pumping gas to the carbs. I have 1.5 PSI of pressure (manual says 1-3 lbs) Lines are clear - no restrictions. (NEW) Needles keep sticking, both float bowls are empty. I tried the gros-jets, then viton/nylon needles, and now the solid brass needles.

Any ideas, other than an exorcism?

 

[DougF]

Are your floats hanging up? Are they adjusted properly and allowing fuel past your needles?
If adjustment doesn't work, try installing the original seats and needles.

 

[Monkeywrench]

Check the floats. Check the forked plate that rides on top of the float. Take it out and look for ANY signs of corrosion or a rough spot where it rides on the float. This could be causing the float to hang up.

 

[piman]

Hello Eschneider,

I think that you have the float chambers with a banjo bolt overflow line connected at the top of the chamber lid. The lower gasket\seal to the banjo is an unusual shape, it is circular with three scallops at 120 degrees apart on the ID.
I think that if you have the wrong gasket then the chamber doesn't breathe properly and this may be your problem.
I can't describe the shape any better but if you have good manual it may well have a diagram?

Alec

 

[Dave Russell]

Hi Alec,
You have a good point. On SU's with a banjo float bowl vent, this scalloped gasket needs to be between the float bowl top & the banjo. Between the banjo top & it's hold down bolt should be a non scalloped metal gasket.

Float bowls that do not use a banjo vent have slots cut into the top of the bowl under the bolt head seat. This type requires a metal breather cover between the bowl top slots & the bolt head. These covers are often lost or omitted.
D

 

[eschneider]

Hi all,

thanks for the input.

as fot the banjo bolts - no, they have nipples with push-on rubber lines, and a seperate vent.

as for the float adjustment, yes, I did set the float level, the forked float lever is straight, and all surfaces are smooth and clean.

I'm going to check the camshaft pump lobe for wear. maybe it's a low-volume problem?

 

[DNK]

Is 1.5 Enough pressure?

 

[Don Elliott]

Remove the tops of the float bowls and pour in some gas and watch what happens. If it drains down somewhere, you know the problemm is after the float bowls. Is it wet with dripping gas on the inner fender below the carbs ? I would think you have enough pressure at 1.5 psi. While the tops are off the float bowls, and with all the sparkplug leads off, crank over the engine and see if it pumps fresh gas up to the float bowls. Did you or someone recently have the fuel pump out ? Maybe the fuel pump was re-installed with the lever that runs on the lobe of the cam on the wrong side of the cam.

 

[PeterK]

Whoaaa doggies,

If you have an active gas leak, don't crank the car with the spark plug leads off or you risk igniting the gas vapors. Instead, just remove the coil wire from the distributor and coil.

Another way to check the fuel pump is to install a clear filter after the pump and watch so see if it pulses fuel.

 

[fad64b]

I am very interested in hearing what the solution will be, I have a friend with an MGA and the float bowl needle always sticks shut on the rear carb and inhibits the car from starting mostly after the car has sat for a week or two

 

[eschneider]

>Remove the tops of the float bowls and pour in some gas and >watch what happens. If it drains down somewhere, you know >the problemm is after the float bowls. Is it wet with >dripping gas on the inner fender below the carbs ?

no drainage, but this is the only way the car will run - to manually pour gas into the float bowls. Runs great till it runs out of gas. Even after the needle and seat seem to be moving freely, no gas is getting into the bowls.


>crank over the engine and see if it pumps fresh gas up to >the float bowls.

Yes, that was my first test. I pulled the supply line off the first carb and checked to make sure the pump was supplying fuel to the carbs and doin its job - got good pulses of fuel into a platic bottle. Volume seems OK. That is where I measured the pressure, too.

I guess I'll try needle and seat again. 4 times seems excessive.....

 

[dklawson]

I recently had a similar problem with the Mini. It uses twin HS2 carbs. I found its starting/running problem was a stuck "brand new" float valve on the front carb. I had recently installed Viton tipped valves from VB to replace Grose Jets I suspected were leaking.

I can tell those of you who are curious that a well stuck float valve won't be unseated by even as much as 3 psi (which the Mini runs).

I haven't implemented a permanent fix yet. I ran a thread on the Spridget forum about this a while back asking if anyone had seen (on any cars) something I remembered from my youth. Some car I worked on had a music wire clip that secured the moving needle of the float valve to the float arm. When the float fell the clip pulled the needle off its seat. The clip was still loose enough to allow free motion of the needle in normal operation. Off this forum one person told me that every Briggs & Stratton engine he's worked on had such clips. I'm considering making some for my Mini. So far the Strombergs on the GT6 have never done this... they have their own set of problems usually associated with infrequent use.

 

[martx-5]

Have you tried taking the needle(s) out of the seat and then hooking everything back up on the float bowl(s) to see if they fill up? Maybe the passageway going to the seats are plugged up.

 

[BOXoROCKS]

Good one Art, I thought I was going to die from apoplexy waiting for some one to suggest the obvious.

 

[heliguy]

H6 carbs? When you remove the banjo bolt that holds the fuel line onto the top of the float bowl, there should be a small filter and spring in there..............if filter is clogged..................................

 

[eschneider]

Have you tried taking the needle(s) out of the seat and then hooking everything back up on the float bowl(s) to see if they fill up? Maybe the passageway going to the seats are plugged up.

nope. they are free and clear.

 

[eschneider]

H6 carbs? When you remove the banjo bolt that holds the fuel line onto the top of the float bowl, there should be a small filter and spring in there..............if filter is clogged..................................

no banjos. no screens. no filters. flows freely.

 

[eschneider]

if anyone had seen (on any cars) something I remembered from my youth. Some car I worked on had a music wire clip that secured the moving needle of the float valve to the float arm. When the float fell the clip pulled the needle off its seat. The clip was still loose enough to allow free motion of the needle in normal operation.

you mean like this?

 

[Dave Russell]

if anyone had seen (on any cars) something I remembered from my youth. Some car I worked on had a music wire clip that secured the moving needle of the float valve to the float arm. When the float fell the clip pulled the needle off its seat. The clip was still loose enough to allow free motion of the needle in normal operation.

you mean like this?

These clips are pretty much standard on Japanese motorcycle carbs. Mainly because of the very low (1/2 psi) fuel pressure that is normal on gravity feed carbs. I have found that SU's & such do not feed reliably with very low fuel pressures. Less than 2 to 2 1/2 psi. The needle, seat, & float need to operate very smoothly & friction free to feed at low pressures.

OTOH, pressures much above 3 psi will cause the opposite problem. Not much room for error.
D

 

[eschneider]

Thanks eeryone for your input.....

I think it's fixed, but I've said that before.

I installed a new pump. pressure in previous new pump was 1.5 PSI. Pressure in "just installed" pump reads 6 PSI on one (snap on) pressure guage, 8 PSI on a second (snap on) pressure gauge. Volume is roughly double.

I'm worried that this is high, but it's not blowing the needles off the seats.... yet. I currently have nylon needles with a rubber (viton?) tip, in a brass seat.

Yes, I'm going to rig a catch-can to monitor overflowing.

I'm concerned about the fuel pumps being supplied by moss. The previous pump was brand new, although it had been on the shelf awhile. The new pump is Moss' new pump-primer-lever OE replacement style. The cam lever had disturbing play side-to-side, and the fuel line ports were machined so that the compression fitting would not seal. Not even close. I used the top half of the previous new pump so that the fuel lines could be re-attached. Of course, the jury is still out on 6-8 PSI of pressure. That's high.

This is not a slam, flame, or negative comment towards Moss. I'm relaying a problem that others might be experiencing.

Also, FWIW, the only needle and seat that really stuck (more than a tap on the float bowl) was the gros-jet type. Maybe I got a bad one - but it's worth sharing the experience with others.