Unkel Kunkel Posted December 4, 2021 Report Share Posted December 4, 2021 Spitfire Mk1V.. Engine burst into life today after many years of slumber.. A sort of, “ It lives, Igor! , it Lives !”, moment But petrol pouring out of both SUs carbs have been overhauled - new floats and needle valves. Stopped and blew out valves in case of “ debris” /rubber slivvers etc affecting needle valves = same. Found an ancient “Command” gauge - checked fuel pump pressure = approx. 7psi. Isn’t this a bit high ? The pump is new ( Powertune from J Paddocks) pressure regulator needed? Return it - but wonder if they all like this now? So Considering -regulator Take the spring out of the old one? Appreciate your views and advice Andrew Link to comment Share on other sites More sharing options...
NonMember Posted December 4, 2021 Report Share Posted December 4, 2021 Yes, that's WWAAAAYYY high. The book figure is 1.5 to 2.5PSI. A lot of reproduction pumps are set for too high pressure. Send it back for a refund, it's not fit for purpose. Link to comment Share on other sites More sharing options...
Unkel Kunkel Posted December 5, 2021 Author Report Share Posted December 5, 2021 Thanks - I have now found a reference in the official “Repair Operations Manual” where it states : “2.5 to 3.5 psi “ - a lot less, as you say. Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 5, 2021 Report Share Posted December 5, 2021 exactly which pump do you have a plastic insulator or not mkIV should have no spacer and short arm pump as mix and no match can attribute to too high or too low pressures depends on the pump arm and spacer or not Pete Link to comment Share on other sites More sharing options...
Unkel Kunkel Posted December 5, 2021 Author Report Share Posted December 5, 2021 1 hour ago, Pete Lewis said: exactly which pump do you have a plastic insulator or not mkIV should have no spacer and short arm pump as mix and no match can attribute to too high or too low pressures depends on the pump arm and spacer or not Pete Hi Pete , The original pump is as fitted in 1973 - no spacer , straight, short lever one like this: The replacement is this : which is listed on the receipt also as RKC1624. It terms of the arm it looks just the same size and angle. No spacer, just a paper gasket.It went on easily. The manual suggests adding paper gaskets to reduce pressure. The pressure would seem to be determined by the spring under the diaphragm which as the pump lever comes off the heel of the cam the spring is free to return the diaphragm upwards and pump outwards. So it would seem spacing , by limiting the travel of the diaphragm downwards would also reduce the “return stroke volume” that the spring is able to deliver - so the volume - and pressure would be lower. Return it - or are they all like this. Pressure regulator . Canabalise the old one for the main spring? I appreciate your views and advice Andrew Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 5, 2021 Report Share Posted December 5, 2021 many have used the old spring if its able to swap without wrecking it ans yes spacing would reduce the pull on the spring but thats going to take a lot of faffing about with a trial and error to get a result its really just blasted annoying this stuff is made with no respect for the basic specification i cant think of any carb that has ever been designed to work with 7psi its just nuts a regulator would solve it but why should we have too ??? its just not fit for purpose then where else do you go JP are generally reputable its ying yong foo junk we are plagued with a number of electric units do specify the output pressure/volume so you have some idea of what you are getting but the old spring is the simplest solution if thats the way you wish to go Pete Link to comment Share on other sites More sharing options...
johny Posted December 5, 2021 Report Share Posted December 5, 2021 Certainly, after confirming the reading, let JP know as its only by constantly complaining that we might get an improvement.... Link to comment Share on other sites More sharing options...
Steve P Posted December 5, 2021 Report Share Posted December 5, 2021 That`s why a lot of people (including me with my 1500 Herald) went electric,small 2.5 PSi pump in the boot,no more flooding or leaks,modern parts,it seems wherever they come from,are crap. Steve Link to comment Share on other sites More sharing options...
johny Posted December 5, 2021 Report Share Posted December 5, 2021 Its strange as I got a replacement mechanical pump for my Vitesse from the same supplier and its been fine (although Ive never checked its output pressure). Obviously not the same model pump but probably from the same manufacturer... Link to comment Share on other sites More sharing options...
Unkel Kunkel Posted December 5, 2021 Author Report Share Posted December 5, 2021 Thanks everyone. I will inform Paddocks and see how they respond. I should say I have used them for years and hold them in high regard.At the very least they need to be made aware there may be issues at least on some pumps regarding pressure being twice the upper specified limit. However, I suspect that they all have a similar problem.To preserve their good name they may have take it up with their suppliers. Maybe these things are just too cheap.. Out of curiosity, I’ll take the spring out of the old pump and compare it Depending on response from JP may swap it over. In any event, I have already ordered a Malpassi Filter King… Link to comment Share on other sites More sharing options...
Unkel Kunkel Posted December 6, 2021 Author Report Share Posted December 6, 2021 Paddocks offered a full refund adding they had not had similar problems reported to them from a large batch of pumps. Meanwhile, I read the manual* again I was a bit doubtful about this working and it sounded a right faff .. - would be worth a try. 2 Flexoid paper gaskets plus a 1.5 mm spacer made from fibre gasket material off cut plus the pump gasket .. I was surprised: the pressure was now down from 7 psi to less than 2 psi. Just the fibre gasket and the usual pump gasket it now gave 3 psi which is in the 2.5-3.5 psi range. I will keep it - (and the old pump in case I need the spring ) It seems we must do a little “tuning “ with gasket / spacers for these pumps to suit our cars needs. and the regulator is now on its way.. * RTFM .. read the f manual Link to comment Share on other sites More sharing options...
johny Posted December 6, 2021 Report Share Posted December 6, 2021 Really good to know however be attentive to the pump spring 'relaxing' with a bit of use and then need spacers removing to get sufficient flow at high demand... Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 6, 2021 Report Share Posted December 6, 2021 looks like there will be a high demand for cornflake packets !!!! pleased a relatively simple idea has fixed the over fuelling whats next ha ! Pete Link to comment Share on other sites More sharing options...
johny Posted December 6, 2021 Report Share Posted December 6, 2021 yes I think over the years theres been quite a bit of time, discussion and money devoted to curing this problem😲 Link to comment Share on other sites More sharing options...
Unkel Kunkel Posted December 6, 2021 Author Report Share Posted December 6, 2021 22 hours ago, Pete Lewis said: looks like there will be a high demand for cornflake packets !!!! pleased a relatively simple idea has fixed the over fuelling whats next ha ! Pete I have a large amount of cardboard from cereal packets - it’s good quality card and has a thousand uses ! ( I was into recycling in the days when it was just called being mean) I used gasket paper off- cuts Link to comment Share on other sites More sharing options...
Gully Posted December 6, 2021 Report Share Posted December 6, 2021 I installed a new fuel pump earlier this year as one of the valves had failed in my old one, but I kept the lower part of the original (casting, spring and previously replaced diaphragm) and simply swapped the tops, which worked fine. A simple way to avoid the pressure issues some encounter. Gully 2 Link to comment Share on other sites More sharing options...
Unkel Kunkel Posted December 18, 2021 Author Report Share Posted December 18, 2021 There seems to be two problems with these Powertune pumps: Problem (1) .Pressure too high iro 7 psi instead of 2.5 -3. Problem ( 2). Very rough -sharp even, shoddy finish to the operating arm that runs on the camshaft. (1). is caused by the spring which pushes the diaphragm upwards after it has been compressed on the cam. Just looking at the “old” spring and one from a new pump they are obviously different. The new spring is slightly longer and thicker gauge. Even allowing some age related change, there is a very obvious difference when you squeeze the springs and a crude test using the kitchen scales shows 3.1 Kg needed to compress the old v 5 Kg for the “new” one. ( 2).The operating arm is made from a stamping but has simply not been “finished” leaving a rough finish is so ragged that I would think it could damage the cam. The rest of the pump seems to be OK. I had lowered the pressure by increasing gasket thickness, but have since removed the pump and swapped over the springs. I worked on the rough operating arm to obtain a smooth finish. Annoyance - These jobs were no big deal deal, but slightly annoying to have to adapt parts which are supposed to be “straight replacements” Safety - It could be argued that a component delivering a pressure so well outside of specification that fuel leakage occurs is safety issue. Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 18, 2021 Report Share Posted December 18, 2021 if the pump output specification was quoted on the box you at least get the chance to avoid it with a pump doubling its spec its just not fit for purpose , especially as they are pumping a hazardous product pete Link to comment Share on other sites More sharing options...
ahebron Posted December 24, 2021 Report Share Posted December 24, 2021 Poor mans fuel injection🙄 I was fiddling with a pair of recalcitrant Amals on a vintage car recently and the only way I could make it run without dying was to wind the fuel pressure up till it would idle. I had removed the original pump from the engine bay and fitted a modern one with an adjustable regulator under the floor behind the seats so I could lean back and adjust the pressure while it was running. Didnt need any throttle to idle at 2000rpm just lots of fuel. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now