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Hi,

does anyone know what the normal outlet pressure should be from the fuel pump?

I am still plagued by the front carb overflowing occasionally. I had the Grose jets fitted but changed it at the weekend for a normal needle jet. Thought it had fixed the problem but after a ten mile run last night it had a constant stream of fuel out of the overflow. Float is fine, and needle jet seals under its own weight when you turn the lid upside down and blow through the inlet pipe.

I am thinking now that the pattern part replacement pump may have too strong a spring fitted and it is forcing the valves off their seats.

I have ordered a fuel pressure gauge to test the delivery pressure, which I am thinking only needs to be quite low, but not sure exactly what.

Thanks, Ralph.

 

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Hi Ralph,

I don't know, I would look at the workshop manual.

My Idea: are the needle valves both the same and do they have the same bore.

I've been told there are different sizes of bore out there.

Wider bore = more force on the floater opening the valve

Ciao, Marco

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16 minutes ago, Z320 said:

Hi Ralph,

I don't know, I would look at the workshop manual.

My Idea: are the needle valves both the same and do they have the same bore.

I've been told there are different sizes of bore out there.

Wider bore = more force on the floater opening the valve

Ciao, Marco

Quite correct Marco, although they look the same, those for smaller engines ( Mini etc) have a bore of 0.070", whereas the TR fitment should be 0.096", however the replacements now, sold under the part number WZX1101A  or VZX1101 depending where you get them from, seem to be universal and come in a kit with different float chamber gaskets to suit several different carbs and are listed as suitable for H & HS carbs from H2 to H6, so I assume they must have standardised on the larger size?, I will soon know as I have ordered a pair from TRGB.

Ralph

I hadn`t thought of looking in the manual, but have just done so and was surprised to find the pump pressure was given, at only 1.25 to 2.5 lbs/sq.in

It will be interesting to see what the pattern pump is delivering when I get my tester later in the week.

Edited by Ralph Whitaker
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The pump should deliver between 1.5 to 3.5 psi - no more. 

According to the Burlen (SU) catalogue the correct needle valve is listed as VZX1101 which has a spring-loaded aluminium bodied needle with Delrin tip and 0.096 bore.   The alternative is a WZX1102 which is the same size but without spring loading and with a heavier brass bodied needle.   

http://sucarb.co.uk/float-chambers-spares/needle-valve-kits/standard-needle-valves.html

The WZX1101a appears to be a Unipart after-market part and is not listed in the Burlen book. 

 

Afterthought  - I understand it is possible to accidentally install the fuel pump so the lever arm is below instead of above the camshaft.....???

Edited by RobH
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You can reduce the pressure by shimming the pump away from the engine block.

Stuart.

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That will reduce the maximum fuel flow rate Stuart but I don't believe it will change the pressure, will it ?  

As I understand it, the fuel pressure is set by the spring inside the pump which returns the diaphragm to the rest position. The arm merely lowers the diaphragm, to suck in more petrol, so spacing the pump means less volume is sucked in.  Until the fuel above the diaphragm is used up, the lever arm isn't moving the diaphragm.  If the fuel is being used up quickly, the diaphragm is pulled down more often/further to increase the flow. 

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The best solution would be to change the spring, but spacing the pump away will reduce the amount the spring is compressed, so dropping the max pressure.

Bob

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This membrane pump is genius!

The pump pressure is caused / limited by the spring inside and the size of the membrane, not by the revs and not by the stroke. This is why it is not possible to regulate the pressure by shimming the pump. You can test this when the engine is running on tickover and when you have a primer lever!

 

Pull the primer lever gently and you feel how you lift it “empty”, up to a very late point when you feel something working inside the pump. This is the internal pump lever, automatically lifted up by the membrane and only moved by the highest top of the cam – because the max. pressure is reached.

If you shim the pump you get to exactly the same point (same pressure).

Edited by Z320
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One float champer is leak, one is OK.

So I would guess the problem is not the pump but one of the float chambers?

Ralph,

did you check both floaters are the same and both are sealed (not petrol inside), same weight?

Ciao, Marco

Edited by Z320
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22 hours ago, RobH said:

 

The WZX1101a appears to be a Unipart after-market part and is not listed in the Burlen book. 

 

The Unipart ones I have seen for sale all start with GSU........, and quote compatible with WZX1101/VZX1101. The original part number was AUC8170 for just the needle and jet, but it is now packaged as a "kit" with 4 different float chamber gaskets which is probably why the change of part number.

 Moss,  Rimmers, and TRGB all use WZX1101 (A), but Burlen use VZX1101 as you say. I assume the VZX denotes Viton tipped, however academic as they don`t have them.

I hunted all over for these as everyone is out of stock, TRGB however came through with stock, but presumably not Viton tipped as they were WZX1101

Ralph

Edited by Ralph Whitaker
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18 hours ago, Z320 said:

One float champer is leak, one is OK.

So I would guess the problem is not the pump but one of the float chambers?

Ralph,

did you check both floaters are the same and both are sealed (not petrol inside), same weight?

Ciao, Marco

Marco,

there is no petrol inside the float, but I have not checked that they are the same weight, I have nothing that I can weigh them on that will be accurate. I ought to swap the jets and the floats and see if the problem moves to the back carb.

Ralph

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Hi Ralph,

I checked both of my float valves not long time ago,

both are 0.096” bore, a drill 2.5 mm did not fit through, a drill 2.4 mm did.

They have been delivered on a standard order, body is plastic, not brass.

It’s a good idea to swap valves an floaters and see what happens.

I don’t know how the fuel hoses are connected on the float chambers on H6.

On HS6 this can also be leak because of week hoses or “unlucky” clips,

while it looks like there is an overflow from the chambers.

Perhaps a photo could help?

Ciao, Marco  

Edited by Z320
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OK, so received my fuel pressure gauge, and tested my pump, which maxed out at 5 1/2 psi as can be seen below.

Not huge, but more than twice the pressure given in the workshop manual ( 1 1/4 to 2 1/2 psi).

I`m ordering an in line pressure regulator so I can drop it down to 2 psi.

Ralph

20210728_125256.jpg

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Ralph,

I have had a similar problem with my Webers.

The mechanic had changed the electric pump from small Facet to Red Facet, added a  Fuel King fuel pressure regulator and set it, supposedly using a gauge. The carbs spat, the engine backfired, flooded carbs, stalling. The TR ran well only at high revs. I first asked a carb specialist who said to set at 2.5 psi. He sold me a gauge. Hasn't arrived.

But meantime, I thought I would give it a go myself, even though I have zero confidence! But I refitted the old regulator that has a numbered dial 0-5 and bypassed the new one. Set it at 2.5, same problems, no change. Checked TerriAnn's Weber page (in Bonanza Collection that also has SU technical informattion and advice, by the way), and she says 1.5-3 psi. I set it to 1.5 psi.

Problem solved. Now sounds "sweet", says my wife who happened to be around when I was testing.

As they say here in Cork: "How bad?" (Which means: "What a good thing!" Or similar).

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Hi Ralph,

good you found out, 

but you now arrange and agree with a wrong replacement pump.

Please complain by the suplier who sold you, tell them the hole story and demand your money back.

Perhaps he reacts and sells not more of the problem pumps to others.

Ciao, Marco

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David,

interesting you had a similar problem. Mine too ran fine when the engine was working, fast cruising etc, but started acting up when I slowed down for junctions, or tried to potter through villages, and if I stopped at traffic lights or junctions I had to keep the revs up or it sputtered and stalled. Not every time, but too often for comfort. While ever the fuel being delivered was being used it was OK, but when supply exceeded demand it played up.

Marco,

I bought the pump a couple of years ago, a pattern part of ebay, and I think that is all you can get now. I will be looking out for an original AC unit to re build, but as the pump works well otherwise I will tame it with a regulator in line. I do have another very similar looking AC pump that has a different mounting flange, and I think it came off a Land-Rover. I thought about using the spring out of that, but don`t know what poundage it is so decided to leave it as is.

Ralph

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1 hour ago, Ralph Whitaker said:

 I will be looking out for an original AC unit to re build,

Ralph

I have some original core units for rebuild if you need.

Stuart.

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On 7/29/2021 at 8:10 AM, Ralph Whitaker said:

David,

interesting you had a similar problem. Mine too ran fine when the engine was working, fast cruising etc, but started acting up when I slowed down for junctions, or tried to potter through villages, and if I stopped at traffic lights or junctions I had to keep the revs up or it sputtered and stalled. Not every time, but too often for comfort. While ever the fuel being delivered was being used it was OK, but when supply exceeded demand it played up.

Marco,

I bought the pump a couple of years ago, a pattern part of ebay, and I think that is all you can get now. I will be looking out for an original AC unit to re build, but as the pump works well otherwise I will tame it with a regulator in line. I do have another very similar looking AC pump that has a different mounting flange, and I think it came off a Land-Rover. I thought about using the spring out of that, but don`t know what poundage it is so decided to leave it as is.

Ralph

Ralph, the sooty plug shows what was going on before I reduced the psi. The grey one was the only one I wire brushed as an experiment. It looked like this after going for a drive in stop-start traffic getting out of town and coming back, after a journey on A roads (N roads here). Only slight popping, but very occasionally, so the carburettors may still need de-tuning of some kind is my guess, from being out (set up for competition?) Or maybe it's the timing? The Delco AC mechanical pump does not require a regulator (my 2 didn't have one and ran very well on fixed-needle H6s).

  Best, David

 

20210730_181606.jpg

20210730_181959.jpg

Edited by DavidBee
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Hi David, an original AC pump should not need a regulator, as it will have been fitted with the correct poundage internal spring. These new replacements though seem to be fitted with stronger springs if my experience is anything to go by.

Ralph

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11 hours ago, Ralph Whitaker said:

Hi David, an original AC pump should not need a regulator, as it will have been fitted with the correct poundage internal spring. These new replacements though seem to be fitted with stronger springs if my experience is anything to go by.

Ralph

Yes, I have never heard of a sidescreen TR fitted with an AC Delco mechanical fuel pump needing a regulator. The electric pumps do, because they push out more, I suppose. Advice on the Forum seems to be in favour of reconditioning original mechanical ones which quite a few people have done and you can source an original through this network.

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Fitted the in line pressure regulator yesterday, set at 1.5 psi, and took the car for a short run of about 8 miles.

I have to say it has never run so sweetly.  Consistent tickover at junctions etc, instant pick up and smooth power delivery, and not a hint of flooding from the carbs.

Very pleased so far.

Ralph

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1 hour ago, Ralph Whitaker said:

Fitted the in line pressure regulator yesterday, set at 1.5 psi, and took the car for a short run of about 8 miles.

I have to say it has never run so sweetly.  Consistent tickover at junctions etc, instant pick up and smooth power delivery, and not a hint of flooding from the carbs.

Very pleased so far.

Ralph

Fingers crossed for a great long term RESULT :D

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2 hours ago, Ralph Whitaker said:

Fitted the in line pressure regulator yesterday, set at 1.5 psi, and took the car for a short run of about 8 miles.

I have to say it has never run so sweetly.  Consistent tickover at junctions etc, instant pick up and smooth power delivery, and not a hint of flooding from the carbs.

Very pleased so far.

Ralph

Goes to show: trial and error always works best!

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I had the Webers set at 1.5 psi and the car ran very well on a long spin the other day. Then yesterday at over 2,5000-3,000 rpm engine sounded terrible, fuel starved? No idea. Got off the main road, parked up somewhere safe, reset the fuel pressure regulator dial at 2 psi and engine running went back to normal. I think all the jets, venturi etc are wrong! I have TerriAnn's list of recommended settings and jets etc. for road use, as well as settings for competition, and plan to follow her advice to the letter. Then we will see how the car performs. (The rolling road will be the last resort).

Edited by DavidBee
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