musccoo 82 Report post Posted July 4, 2015 Hi guys, So to make a long story short my car started surging and eventually stopped when I was out the other weekend. Looked on my fuel pressure gauge (in the delivery line before the rail) and pressure was way down at 20psi. So I jumped the fuel pump and to no surprise I didn't hear it go so I swapped it out for a new one this week. Now I've got the new one in when I rev it the pressure drops to low 30's. Thought it was potentially the FPR so put a brand new one of those I had lying around in but no change. It doesn't seem to hold residual pressure for very long after the cars off, I also just quickly did a dead head test by pinching the return line with my fingers (not strong enough?) and my pressure gauge didn't even get to 50psi. I did a fuel volume test too and got more than the specified 875ml in 30s. Heres what it does under load...https://www.youtube.com/watch?v=aom_cxOIPIc&feature=youtu.be Where should I look to next to figure this one out..? Quote Share this post Link to post Share on other sites
musccoo 82 Report post Posted July 4, 2015 (edited) So the first fuel volume test I did above was straight out of the intank pump into a bottle.So heres what I've now done... Plugged a hose into FPR, started the car, and collected fuel into a bottle for 30s, and got a measly maybe 200-300ml. Evidence.... I then undid the fuel feed line into the fuel rail and jumped the fuel pump relay and got about 950ml. I then pinched the feed line while doing the above test again and watched the pressure gauge and it didn't get above 40psi.What does that say...? Edited July 4, 2015 by potatomash Quote Share this post Link to post Share on other sites
_ethrty-Andy_ 2132 Report post Posted July 5, 2015 yeah difference between flow and pressure. much like a battery, can look good all day long, but all turn to custard once there is a load on it. Quote Share this post Link to post Share on other sites
hotwire 352 Report post Posted July 5, 2015 Normal operating fuel pressure (regulator working) is about 38 psi. Vacuum off the regulator -pressure will rise. Flow will be around 2.5 litres per min Quote Share this post Link to post Share on other sites
musccoo 82 Report post Posted July 5, 2015 (edited) yeah difference between flow and pressure. much like a battery, can look good all day long, but all turn to custard once there is a load on it. Would you say this is a normal/good pressure reading? Bottoms off at 34psi and goes through till about 44/45psi https://youtu.be/yxgpKsUlCNg Sent from my HTC One M9 using Tapatalk Edited July 6, 2015 by potatomash Quote Share this post Link to post Share on other sites
musccoo 82 Report post Posted July 9, 2015 Can anyone confirm? I rewired up a fused relay straight to the battery was only getting 10.5v now it's got 13.5v Sent from my HTC One M9 using Tapatalk Quote Share this post Link to post Share on other sites
will 169 Report post Posted July 10, 2015 For starters.. Your system must hold pressure overnight (3 bar). If not, it must be sorted before you fiddle with anything else. Does it? Also, your fused relay is a bodge, if you are only getting 10.5V at the OEM supply, you need to sort out the issue as it will have far reaching consequences, not confined to the pump supply. You need to put your bodge in the bin and fix it properly. Quote Share this post Link to post Share on other sites
musccoo 82 Report post Posted July 10, 2015 Righto. Well I wouldn't say the new power supply Is a bodge it's a good thing so it doesn't fluctuate anyway. But yes I agree I need to find out why the voltage was low in the first place. Not overnight no. Firstly I'd like to eliminate my new pump as being sh*t or not. When the car is running and I pull the gas fuel pressure goes up to 42-44 then drops to about 34-35 then back up to 36-38. Should it do this or Is my pump not putting out enough pressure under load? Sent from my HTC One M9 using Tapatalk Quote Share this post Link to post Share on other sites
