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Early Sprint Fuel Pump
http://forum.triumphdolomite.co.uk/viewtopic.php?f=4&t=35420
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Author:  James R [ Tue Nov 19, 2019 4:18 pm ]
Post subject:  Early Sprint Fuel Pump

Hi.

I am looking for some advice/knowledge in respect of an early short arm fuel pump for my 74 Sprint please.... I have read the many threads on the subject of pumps etc on the forum but still find myself unsure of an after market products suitability......

So original pump is an AC Delco (pic called resize 154419 attached) with a 46mm measurement from housing flange to top outer of arm/lever. With the many differing arm shapes and sizes, I have found at Robsport a short arm version (rare in itself i believe) with a 50mm measurement from flange to top outer of arm/lever (see pic 2). One thing of note is that on the arm of the AC Delco unit i have the number 7990048 stamped on it but other threads seem to suggest it should be 7990047... not sure of the significance of this....

Anyhow my question is how critical will 4mm be? My assumption is that this shouldn't be an issue at all, but would appreciate any input from individuals more experienced in this area than I as to whether this pump is a suitable replacement, and that it will be OK for the car.

Thanks in advance for any assistance...

James

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Robsport Fuel Pump 19.11.19.JPG
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Author:  Carledo [ Tue Nov 19, 2019 11:27 pm ]
Post subject:  Re: Early Sprint Fuel Pump

MY opinion - and it is just that - is that I wouldn't fit that pump on my car!

Not only is the length different but the height of the end of the arm, relative to the pump body is also different, possibly by more than 4mm, it's difficult to tell! This could result in the arm dropping below the jackshaft and breaking, incorrect function of the pump stroke and early failure because of one or more of these. Or the 2 errors might cancel each other out!

So I have to ask you, "Do you feel lucky?"

Steve

Author:  cleverusername [ Tue Nov 19, 2019 11:56 pm ]
Post subject:  Re: Early Sprint Fuel Pump

Can I clarify something, did Robsport sell the pump as being suitable for a Sprint?

If so, you should probably contact them and ask whether the different in dimensions matters.

Author:  James R [ Wed Nov 20, 2019 11:52 am ]
Post subject:  Re: Early Sprint Fuel Pump

Thanks Gents.

No i dont feel lucky Steve... Not a luck person as it goes...! :shock:

This really provides a bit of a unwanted conundrum , because in doing some serious googling, of all the available pumps whether they are to be fitted with spacer or not, you get no consistency in pump arm shape, or dimensions… Really a lottery..

I decided to check the Rimmer’s product that they would provide if you order part 312167, and what you would actually receive is a longer arm version with the measurement being 65mm (body to end of arm). So with a 13mm spacer that’s 52mm, 6mm longer than my old AC Delco unit, and 2 mm longer than the Robsport.. Absolutely nuts…

Robsport to be fair said that they use these on Sprint’s but they do, where possible, advise their customers to convert them to electric fuel pumps, using their product FUE401 which is a pump they fit to Stag’s as well. I had hoped to keep away from an electric one due to the apparent struggles these seem to bring with getting pump pressure correct etc, but I am now wandering if this is the lesser of the 2 evil’s. I really don’t want broken metal in the engine if I can avoid it, but had wanted to maintain the standard set up….

I don’t suppose anyone might have a working original AC Delco unit hiding somewhere?? I know the answer to that, in that I have more chance of spotting Lord Lucan Riding Red Rum!!!

Thanks for your input Gents. Appreciate it !!

Author:  dursley92 [ Wed Nov 20, 2019 5:29 pm ]
Post subject:  Re: Early Sprint Fuel Pump

Couple of pictures I have kept from this and other forums just to muddy the waters.

Image

Image

Author:  Carledo [ Wed Nov 20, 2019 9:40 pm ]
Post subject:  Re: Early Sprint Fuel Pump

You have to bear in mind that the operating stroke length, ie the distance the arm moves to work the pump, is less than 10mm governed by the eccentric (it's not really a cam) on the jackshaft. So movement at the tip of the arm is less than 10mm also, if 4mm of that is already used up in fitting preload, that's a pretty big deal! And may be a clue as to why this style of aftermarket pump tends to have a short and troubled lifespan.

I honestly don't know what the cure is, if you want to keep a stock mechanical pump, serviceable used original ones are pretty much gone now and the quality of available replacements seems too poor generally to make their use a viable long term solution. Which only leaves the electric option. This is not SO bad, so long as you come to terms with the idea that you will need some kind of pressure control device with most aftermarket electric pumps.

It seems silly to suggest it, but if you can FIND an original, points style SU electric pump from a Morris Minor and fit it in the correct (long "suck" short "blow") underbonnet position, it will almost certainly have enough power to run a twin 1.75" Sprint even though the original Moggy fitment was a single 1.25" carb. The reason I know this is that I used just such pump to run the 3x1.5" SU carbs on a 2.5 litre MKII Zodiac I once owned. Despite dire warnings from folk who thought they knew better, this worked fine over several years of hard use and didn't need a pressure regulator either! Nor did it result in high rev fuel starvation as the prophets of doom predicted! It also helped improve cold starting as you could prime the carbs simply by switching the ignition on! Then when the clicking slowed down, crank it over! A concealed switch in the power feed to the pump also makes a handy extra thiefproofing device!

Thinking about it, a (short suck, long blow) MGB pump in the boot would work even better as the engine capacity and carb size is a much closer match.

Steve

Author:  dursley92 [ Thu Nov 21, 2019 2:54 pm ]
Post subject:  Re: Early Sprint Fuel Pump

I use one of these for my Sprint engine and it seems to work fine, low pressure so no regulator reqd.

https://www.ebay.co.uk/itm/Facet-Electr ... 2798198053

Image

Author:  James R [ Thu Nov 21, 2019 5:18 pm ]
Post subject:  Re: Early Sprint Fuel Pump

Steve/Russ – Thank you!

Having read what you have kindly advised, I spoke to SU carbs today about the electric SU fuel pump options available as they are the manufacturer and carburetor specialists after all….

They recommend for the Sprint with standard HS6 set up an AZX1307 pump, which is listed as a high pressure pump on their website. It’s a 12 volt unit with a minimum flow of 15 gallons per hour, and a 2.73/3.8 lb/in2 pressure rate and with this I would not need a regulator. So it seems more of a low pressure one and they also said it is mounted in the boot so fits the short suck, long blow method Steve mentions….

http://sucarb.co.uk/su-fuel-pumps-spare ... -kits.html

Looking at the Facet Russ has this is 1.5 to 4 PSI with a flow rate of 25 gallons an hour, so my simple logic is telling me that the SU is another possible option that I could use without a regulator..

Being quite a novice in such matters, is this sound advice from the SU Carb company on the use of this Part and would it work do you think. Just after your very valued opinions gents…. Thank you!

Author:  MIG Wielder [ Thu Nov 21, 2019 5:23 pm ]
Post subject:  Re: Early Sprint Fuel Pump

Quote:
MY opinion - and it is just that - is that I wouldn't fit that pump on my car!

Not only is the length different but the height of the end of the arm, relative to the pump body is also different, possibly by more than 4mm, it's difficult to tell! This could result in the arm dropping below the jackshaft and breaking, incorrect function of the pump stroke and early failure because of one or more of these. Or the 2 errors might cancel each other out!
Steve
I see what Steve means. I have an old 1850 A.C. pump and the wear mark on the face of the operating arm is quite high up. I've highlighted the top and bottom parts of the wear and projected the lowest part of the wear ridge onto the pump face.
Just out of interest I've also measured the lift on the jackshaft cam . It comes out as just 4.2mm.
Tony.

Attachments:
ac RA1 fuel pump.jpg
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