Tim, My mistake. I was just thinking Lucas for everything electrical. It is an SU square body pump that looks like your photo. The SU model number is AUA152EP. Since it was rebuilt with electronic innards, sad to say I don’t know whether it meets original specs or not.
Mike, I wish I had known about your pump rebuild guy in Bremerton. I live in Seattle, a ferry ride away. I bought a rebuilt pump from XKS, paid quite a bit more than you, and did not get any performance stats.
Roger, Rather than try to conduct a science experiment that could end up spraying gasoline all over me (my wife already complains that I smell like gasoline), my plan is to install a pressure regulator, set it at 2 psi and see if that allows the fuel pump to shut off and stops fuel leaks through the jets.
Hello Bob, yes, your caution on spraying gasoline around is appropriate. Always have suitable fire extinguisher ready when using fuel and any ignition source (like electrical).
For the pressure regulator path, here is my experience at these 1 - 3 psi levels for gasoline car engines. There are variations of a type of pressure regulator, see Mr. Gasket type marketed by Holley
It has been my experience multiple times when encountering this type of regulator on other people’s cars that the regulator either did not regulate the pressure or the regulator leaked gasoline to the ground, or both. This has been true even for brand new ones people have asked me to help install when they used a pump with higher pressure than SU carbs were to take. None of these pressure regulators worked (measured fuel pressure in line between regulator and carb, and continuous fuel flow into carbs with engine not running but pump on). Maybe your results will differ from my sample size of about 3, but you should still have a suitable fire extinguisher at hand when trying installing and testing a pressure regulator.
And to avoid putting thoughts too narrowly, try also to identify correct float for the carb. Float geometry and weight both are important.
And needles on the float valves come in a variety of materials and types which have varying response to pressure pulses from pumps. Some pump line pressure can be correct outside the pulse moment or engine vibration contributions but still have the needle valve not staying seated.
Here is the update. I installed a Mr. Gasket fuel regulator and, as Roger described, it seemed to do nothing but cost me money. I turned it down to 1 psi and the fuel pump still clicks slowly after pressurizing the system. I thought I had the floats adjusted so they would not leak yesterday, but turned it on today and one leaked. I had switched the float bowl tops and the leak followed the top. Interesting. I again gave it the blow test and it easily out performed my lungs. Since the fork arm is much longer than normal in H8s, I cut a short tab at the hinge end of the fork and bent it slightly to restrict how far the fork can drop. I increased the fork adjustment slightly to increase the flotation pressure on the needle valve. I then fired it up and all seemed to work well, except the pump which never seems to switch completely off even though there are no visible leaks. I checked all the fittings on both sides of the pump and everything is tight, so I have no idea why the pump won’t shut off when it reaches the correct pressure.
I binged on Joe Curto YouTube videos last night, which says something about the quality of my life. He indicated the T4 brass floats should weigh about 64 grams and mine are 60. I still think I may spring for the Burlen StayUp synthetic floats which are claimed to weigh between 46 and 50 grams. This would have them floating higher than the brass and should make it easier to adjust the float level. I don’t yet have the body on the chassis, so I can’t report on the driveabiliy, but at this point I am content that it sounds good and is not a fire hazard. Let’s hope it stays that way.
The red text is vitally important.
It took my 74yr old Jaguar mechanic to spot the different fuel levels in the bottom, as set by a well known garage in England.
I misquoted the Burlen catalog, which shows H8 (not HD8) carbs. The correct float (original brass I assume) is AUC1182. If it were me, and if I had ANY doubts about the floats, I’d get new ones from Burlen, preferably the improved ones you mentioned.
It is perfectly normal for the pump to click very slowly after the system is pumped up. Just due to backflow through the pump, apparently.
What I have done with smaller H-series SUs is to replace the cork sealing glands with Teflon O-rings. They work GREAT! These were 1/4" diam. jets, but yours may be larger. I have a huge surplus if Teflon O-rings for 1/4" jets, if you are interested.
The float weight is only of secondary importance. As in ships and boats, it’s the float volume, or displacement, that matters. The upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is proportional to the weight of the fluid that the body displaces. (Archimedes’ principle). That’s why your float looked higher in water. The increased density produced a proportional increase in buoyancy.
That’s very true about the pump, very slowly as you say.
When I served my apprenticeship at a carburettor company a very long time ago, Teflon wasn’t available. We used to plump up and lubricate the new cork seals in brake fluid overnight. Untreated, dry new corks would often fail due to people installing them without following this step.
There’s something in that for certain. Are they indentical? Have you removed the needles and seats and tried swapping them over to see if the leak follows that. It could be a poorly manufactured item??
Ask Burlen why there is a needle and seat specifically for H8’s? Can’t hurt.
Mike, While I agree with most of what you say, as a practical matter weight is more than secondarily important. My understanding is that all the T4 floats are the same size and shape. Therefore, the only variable which will affect how much fluid they displace (or how high they float) is weight. A lighter float will sit higher because it will displace less fuel than a heavier one of the same size and shape. As mentioned previously, the original brass floats sit very low in ethanol laced gasoline making them difficult to adjust. On most SUs, setting the float level is not particularly difficult and need not be too precise. Not so with the H8s.
Bob, The jets look like they are about 1/4 inch. Everything is back together now so I can’t check easily. Viart says the jets are .125" but I think that is referring to the inside diameter. It does seem like there would be better materials than cork in the modern age for a critical part. I may take you up on the Teflon O ring offer, and I probably will buy the StayUp floats from Burlen and put the pretty brass ones on a shelf.
Tim, The needle valves are specific to the H8. I pulled them and they are obviously brand new. They work well when I blow into the the top through a short length of fuel hose so I don’t think they are the problem. That led me to think about the fork itself. Because it is longer and the drop to the required float level is deeper, the angles are greater in this setup than other SUs. That is why I notched the hinge end to prevent the fork from dropping more than about 1/8" at the needle valve. This thing is day to day, so I will see if it fires up without leaking tomorrow.
Re: the ticking fuel pump. My experience is with an E-Type and two Austin-Healey 3000s. The pumps in all of those shut off (stopped ticking) when the system was pressurized. I would say this one ticks about every half a second or so after initial startup. That doesn’t seem right.
Bob, you noted earlier that your SU fuel pump is a rebuilt unit. The continuous ticking after the float bowls are full could be due to the rebuilder not addressing the valve discs and valve seats in the pump.
As I noted above, my pump was rebuilt in 2010. The rebuilder, Dave DuBois, provided the sheet below explaining the process. The valves are covered in the first paragraph.
The sheet also notes there are high pressure and low pressure SU pumps. Since all these pumps were designed to work with SU carbs, I suspect the high pressure pumps are not all that ‘high.’ In the case of my pump, the provided specs suggest it’s a low pressure, but high volume pump, and that seems to work very well.
Dave DuBois was a master of the SU pump, but unfortunately he passed away a couple of years ago.
Thanks Mike. One more thing to check. I was intrigued by the idea that there was an SU Pump Guru in Bremerton and did a little research finding that Dave DuBois passed away from cancer not long ago. However, Dave was also a writer and his wisdom and insights are still accessible at http://www.dbraun99.com/Dave%20DuBois/. I found his articles to be well written and informative and printed out a few for future reference. Its a good reminder that what we write may outlast us–for better or for worse.
One factor for whether a high (1.3 psi) or low pressure (0.65 psi) pump is used in an SU system is the vertical pump mounting distance below the float needle valves. Cars with fuel pumps on the firewall at height similar to the carbs may use the low pressure pumps while cars with pumps down on the body frame under the car may use the high pressure pump since approximately an extra 0.5 psi will be needed for the additional vertical lift of fuel to the float chamber.
OK. I am taking a break for a while. The rear carb still has some fuel pooling in the throttle body but it is not dripping onto the floor and gets sucked out immediately on start. After that, the engine seems to run and idle smoothly. The plan is to order the synthetic StayUp floats from Burlen to see if they make a difference. I will probably order VE (leaner) needles as well while I am at it, just to have the option available. I don’t plan to install the needles until the car is on the road and only if needed. That is still many months away. I did verify with Burlen that while it advertises its “new adjustable height StayUp® float,” it is not adjustable at all. The only adjustment point is the fork as has been the case from time immemorial. Thanks everyone for the input. I will report back when the new floats are installed.
