tjs Posted June 7, 2022 Report Share Posted June 7, 2022 Yet another fuel pump question. Firstly, here is the issue: As you can see its a prestige kit. Been working fine and relatively quiet for 7+yrs. After this weekend replacing all rubber lines with Cohline 100% ethanol proof lines (top DIN standard), and a new Sytec paper filter, I am getting an excessively noisy pump. The bores on the rubber lines ar 9.5+mm. The PRV is working (if i pinch the line, pump load increases and note changes). But i cannot get rid of this buzz. Don't think its line resonance. PRV is not the diaphragm type. Any ideas? Car seemingly drives fine but sounds like its starving a bit at high rpm and Torque. Essentially, nothing on the setup jas changed. Wondering if the new sytec filter is too restrictive, but being Motorsport rated i doubt it... Regards Alex Quote Link to post Share on other sites
barkerwilliams Posted June 7, 2022 Report Share Posted June 7, 2022 Is the suction side of the pump, tank fitting, tank air vent, stop tap (if you have one) all clear. If you take the supply line off the pump does fuel run freely? Alan Quote Link to post Share on other sites
Waldi Posted June 7, 2022 Report Share Posted June 7, 2022 Likely cavitation. If you have replaced the suction filter for a different type, it may have more resistance thus create a lower pump inlet pressure. ”Motor sport rated” means little in this respect. Maybe better to buy a filter from Prestige. Cheers, Waldi Quote Link to post Share on other sites
tjs Posted June 7, 2022 Author Report Share Posted June 7, 2022 (edited) Alan, going to try that now - but won't running it dry cause bigger issues? Waldi - its a high flow rated element "for up to 3.5l engines" but yes, if it's not meeting the flow rate requirement of the pi and prv...who knows. I'll try and run it without the element and see what happens. Edited June 7, 2022 by tjs Quote Link to post Share on other sites
Mike C Posted June 7, 2022 Report Share Posted June 7, 2022 New elbow on the pump suction causing uneven flow into the pump body? I always like to have 5 X pipe diameters of straight pipe into any pump suction to even out the flow. Quote Link to post Share on other sites
astontr6 Posted June 8, 2022 Report Share Posted June 8, 2022 13 hours ago, tjs said: Yet another fuel pump question. Firstly, here is the issue: As you can see its a prestige kit. Been working fine and relatively quiet for 7+yrs. After this weekend replacing all rubber lines with Cohline 100% ethanol proof lines (top DIN standard), and a new Sytec paper filter, I am getting an excessively noisy pump. The bores on the rubber lines ar 9.5+mm. The PRV is working (if i pinch the line, pump load increases and note changes). But i cannot get rid of this buzz. Don't think its line resonance. PRV is not the diaphragm type. Any ideas? Car seemingly drives fine but sounds like its starving a bit at high rpm and Torque. Essentially, nothing on the setup jas changed. Wondering if the new sytec filter is too restrictive, but being Motorsport rated i doubt it... Regards Alex I have only ever used Bosch Type filters because of their low resistance. If you do the blow test on one you will see what I mean. Your Sytec filter is probably meant to be on the pressure side of the pump? It is difficult to tell from your picture. I was always told that one must have a low resistance filter on the input side. Bruce, Quote Link to post Share on other sites
Waldi Posted June 8, 2022 Report Share Posted June 8, 2022 As Bruce says, on the pressure side the differential pressure across a filter is not so important. 0.05 bar or so on the pressure side would not matter (at all). But on the inlet side of our cars, the static pressure (made by fuel height from fuel above the pump inlet) is very low. 50 cm of fuel column equals only around 0.04bar(!). This shows why a low pressure drop in the linlet section (nozzles, pipe and filter)) is important. Waldi Quote Link to post Share on other sites
Schnippel Posted June 8, 2022 Report Share Posted June 8, 2022 Hello , an example for pump units 0 580 464 126 for original or electronic systems on TR 5/6. Quiet because there are no bottlenecks and tight corners. As recommended by Bosch. System pressure valve comes from the hydraulics. für orig. PI Hawe Many greetings Ralf Quote Link to post Share on other sites
Waldi Posted June 8, 2022 Report Share Posted June 8, 2022 Hi Ralf, I run the xx.126 pump as well. It looks like your pressure reducing valve does not have a 3rd connection, so I assume this valve is on a take-off from the pressure side, with a T-piece or similar? Gruesse, Waldi Quote Link to post Share on other sites
CP26309 Posted June 8, 2022 Report Share Posted June 8, 2022 Original Lucas pump works fine on mine for the last 50 years! Quote Link to post Share on other sites
FatJon Posted June 8, 2022 Report Share Posted June 8, 2022 Sounds like cavitation due to low inlet flow. Fill the tank and if it goes away that confirms it. Quote Link to post Share on other sites
barkerwilliams Posted June 8, 2022 Report Share Posted June 8, 2022 (edited) "Alan, going to try that now - but won't running it dry cause bigger issues?" Yes if its "dry" that will be an issue, but what if its only, say, 85% of flow, that would be Ok on part throttle but weak mixture on full throttle. So whether there were other issues it would depend on your driving style and what you expected from the car. Remember the pump is constant speed /output even at tickover it needs to supply enough fuel to meet the pressure and volume (or more) needed by the injectors at fulll throttle, maximum revs. If the required fuel is less than the output the PRV should recycle the excess pumped fuel back to the tank to maintain the pressure. Unfortunately it is difficult to monitor the fuel pressure supplied to the metering unit whilst driving which would indicate a healthy fuel system. Fitting an electronic pressure sender and gauge in the circuit is a little excessive just as a diagnostic tool. Remember that although the pumps have a high pressure output they have little suction to draw fuel yet the flow requirements, which I forget, are about a couple of hundred litres per hour, As the plumbing, particularly the tank connector which is very small bore, condition is vital as anything less than free flowing leads to cavitation as the pump struggles to maintain pressure. Incidently if you check the wiring do not omit to check the earth, which if using the original wiring on the black loom wires terminated on a 3.5mm connector in the boot immediatly adjacent to the near side rear light cluster behind the trim and is not wonderfull for the higher power drawn by Bosch pumps. Alan Edited June 8, 2022 by barkerwilliams Quote Link to post Share on other sites
tjs Posted June 9, 2022 Author Report Share Posted June 9, 2022 Solved now, thanks for suggestions. 1. Filled the tank to increase the head. No change, still loud/sucking air. 2. Removed the tank feed and pre-filter, and was quiet. So removed and inspected the pre-filter. The flat oring seal at the bottom of the can had slipped and was partially covering the outlet hole, probably about 1/4th of the area of the outlet was covered. That was all it took. Re seated and all was fine and quiet! With the much increased flow then got the resonance in the steel braided line you can see in the vid. Solved that by clamping it gently with a piece of foam, and m12 nut as a weight and a zip tie...will make a better solution soon! Cheers all Quote Link to post Share on other sites
RobinC Posted June 9, 2022 Report Share Posted June 9, 2022 It may be worth trying the high flow metal filter element available for the Sytec 'Billet' filter supplied with the Prestige kit. The standard filter is supplied with a paper element ( 55micron ). The high flow metal filter element is a coarse 8 micron filter. Finer particles are dealt with by the Bosch post-pump filter. The high flow element is available here : https://www.merlinmotorsport.co.uk/p/high-flow-metal-filter-element-for-sytec-bullet-filters-bulla02 or here: https://www.fuelpumpsonline.co.uk/sytec-bullet-fuel-filter-replacement-hi-flow-metal-element-bulla02-1919-p.asp Alternatively just google for 'BULLA02 filter element' Cheers, Robin C Quote Link to post Share on other sites
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