Adamw Posted March 17 Report Share Posted March 17 Your fuel pressure sensor calibration is wrong, it should be more like 350Kpa, not 3.0. What pressure sensor and regulator do you have? Whenever I find a fuel supply issue I do a quick return flow test to confirm where the issue is - something like below; Use a mityvac or air compressor etc to apply desired boost to the FPR reference. Pull the return line off, hang it in a bucket/bottle. Set the fuel pump prime time to 25sec, store, then power cycle ign. Measure how much fuel you have in the bucket after the 25sec prime. Multiply by 2.4 to get your approx pump flow per minute. For petrol you want a minimum of about 600cc/min per 100HP. Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 18 Author Report Share Posted March 18 It should read bar so that’s what you are seeing in the logs. I’ll adjust it in Link to display correctly but I don’t think too important at the moment. It matches the gauge in the car. It’s a Greddy sensor. The FPR is unknown. No markings or numbers on it that can be found to identify it. Thanks for that return test info. I saw a few people mention it but not the method to do it. I may have found something that is contributing (or the cause?) to it as well. You’ll have to tell me how significant it is. Where the fuel pressure sensor is connected uses a T piece with a 1/8 NPT for the sensor line but then the two connectors for the fuel lines are 6mm ID rather than 8mm ID that the rest of the fuel system uses. Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 18 Report Share Posted March 18 4 hours ago, Japtastic141 said: It should read bar so that’s what you are seeing in the logs. I’ll adjust it in Link to display correctly but I don’t think too important at the moment. You have a fuel pressure problem that you want to solve, so I wouldn't dismiss the sensor calibration straight away, especially when it is obviously out by a factor of at least 100. The units in PC Link are Kpa, not bar. Even if you think it is just a "decimal point" issue, you have 100X less resolution than you should have and the differential fuel pressure calculation wont work with it set as it is. Where did you get the greedy calibration data from? Most Greddy products to use proprietary calibrations and they dont normally make the data available. If it were me I would replace it with a sensor that has known accurate data. AbbeyMS 1 Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 18 Author Report Share Posted March 18 Thanks, Adam. Ok, I'll fix that now. I did note that the readings matched the gauge max memory function in the car and the max that the link recorded. I took some voltage readings at 2.5, 3 and 3.5 bar and extrapolated the rest. Shouldn't that work especially as it looks linear? I'm all for changing old for new when needed but if I can get this setup to work it would save some money and waste of an otherwise good part that's already plumbed in. How about my 8mm-6mm-8mm fuel plumbing? Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 21 Author Report Share Posted March 21 Just replaced the FPR and T piece for an 8mm one but still the same issue so I tried your return fuel test. The fuel flows back nicely when the FPR is at 0 reference but when I apply some pressure from the air compressor to the FPR boost reference port the return flow stops completely. So I believe I've found my issue but why would it be happening? Just a recap for continuity. The pump (along with a direct positive feed from the battery and chassis earth) sock, filter and FPR have been replaced with new items. Quote Link to comment Share on other sites More sharing options...
AbbeyMS Posted March 21 Report Share Posted March 21 do you still have the over pressure valve still plumbed into fuel system after the fuel pump and tank top? Thanks Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 21 Author Report Share Posted March 21 This thing? If so, yes. Quote Link to comment Share on other sites More sharing options...
AbbeyMS Posted March 21 Report Share Posted March 21 6 minutes ago, Japtastic141 said: This thing? If so, yes. throw that in the bin. Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 21 Author Report Share Posted March 21 Doing it now Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 21 Author Report Share Posted March 21 Ok done and that has improved things in that I get return flow now. My results for that are: 4.6 BAR @ 25 seconds = 1150ml returned x 2.4 = 2760cc Based on Adam's post, 450BHP would require a successful test to be above 2700cc so I'm within spec there. I really thought that was going to do it so went out but still the same :( https://drive.google.com/file/d/1LbbTR0FKTtQIc2U49VsjY2upxYsp1HDT/view?usp=sharing You can see the battery voltage does dip by 0.5-0.6v during this. Not sure if that was spotted before and could be causing this? Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 21 Report Share Posted March 21 I notice in one of your pulls when the diff fuel press takes a big dive there is an increase in batt voltage about the same time. No auxes turn off at that point so those events are possibly related. Pump sucking air? Lose connection? You could do a similar static test with FPR pressurised and measure voltage at the pump to confirm how much volt drop you have in the pump supply. Your batt voltage reported by the ECU is quite a bit lower than typical at about 13.0V where as that should be more like 13.8-14.5 so that is not as good as it should be which will be contributing but I dont think is your main issue. For some extra safety in the meantime you could set up a 5D fuel table like below so the a drop in fuel pressure is compensated with increased inj PW. Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 22 Author Report Share Posted March 22 Did you mean decrease? I've only seen decreases in voltage to match the fuel pressure declining. Thanks for the tip on the 5D fuel. I had the fuel pump out yesterday to remove the damper and at the same time checked everything and all looks good. It's a walbro 450lph, pulls 14.1 amps at 13.5v. Just done what you mentioned with the pump set to 5 bar fuel pressure at idle. 13.8v At The Battery 13.4v Link 13.2v Relay Feed In 12.92v Relay Feed Out 12.85v Fuel Pump Connector If I bypass the relay I get the same on road results and the following: 13.04v Feed 12.85v Fuel Pump Connector With the car off the battery reads 12.75v and the exact same voltage when testing in the boot for the feed to the pump. Not sure where to look next... Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 22 Author Report Share Posted March 22 Got the clamp meter and Picoscope out today. 12.5A with no accessories on at idle. With AC, Fans, Rear De-Mister and Headlights on it's around 26A. So it appears that the alternator can provide enough amps although I'm not sure how much higher the amp draw is when driving. Getting around 10A testing the cable at both the battery and fuel pump end. I also ran a new temporary lead direct from the battery to the pump to check if that made any difference but it didn't. This is less than the specs of this pump though. They list 14.1A at 13.5v.... Quote Link to comment Share on other sites More sharing options...
AbbeyMS Posted March 22 Report Share Posted March 22 Have you changed the fuel filter? Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 22 Author Report Share Posted March 22 Yes Quote Link to comment Share on other sites More sharing options...
AbbeyMS Posted March 24 Report Share Posted March 24 Had a think , voltage at the pump is low, considerable volt drop from battery to fuel pump. You have run a new wire to the fuel pump from the battery you say , was this direct or via a relay? fuel pump, remind me what make? where did you buy the pump from? Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 24 Author Report Share Posted March 24 Thanks for coming back to it. It does seem so doesn't it being nearly a volt drop. Well, the cable was actually run in Japan. 12AWG. I've checked both ends and the complete run when I've been doing other things in the car with back seats out etc. I bypassed the relay completely the other day and just hooked it up direct but with the same results. I've run a new earth direct to the plug to a tested decent place about 12 inches away. Bought it a few months ago from JDM as I knew there were a lot of fakes on eBay / Amazon etc. Quote Link to comment Share on other sites More sharing options...
AbbeyMS Posted March 24 Report Share Posted March 24 what pump are you using?, save me trawling back through the thread Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 24 Author Report Share Posted March 24 Sorry missed that part! Walbro / Ti Automotive 450lph Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 25 Author Report Share Posted March 25 Ok, bit more to report. I ran a temporary positive lead today directly to the battery. The only one I had around was 10mm2 so a little overkill and not perfect fitting as I didn't have all the connectors I needed as the 10mm was too large, so I believe there will still be some improvements if a new cable is run properly. Old cable 0.7v drop 10mm Cable 0.3v drop @3 Bar 13.9v Battery 13.5v Pump Connector @5 Bar 13.8v Battery 13.3v Pump Connector (old cable was producing 12.9v) Still quite a lot more voltage drop than the calculator reckons but then my test wasn't perfect and I did run it through the relay. Thoughts? Shall I just run a new cable of 6-8mm to see if that resolves it? Or is running such a large cable skewing my results? Quote Link to comment Share on other sites More sharing options...
AbbeyMS Posted March 25 Report Share Posted March 25 Biggest is best for fuel pump control Japtastic141 1 Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 26 Author Report Share Posted March 26 Ran the new cable today. AWG 4 with the appropriate fuse holder and new relay for good measure. Voltage drop and voltage to the pump @ 3 and 5 bar are very similar to the temp 10mm2 cable I tried but still the same on-road results. The return fuel test went fine and the alternator appears to be able to supply the amps the car and pump needs. Could it still be the alternator despite my tests? Other than that I'm really not sure what else there is I can try... Quote Link to comment Share on other sites More sharing options...
David Ferguson Posted March 26 Report Share Posted March 26 Voltage drops are due to current draw. If it's not the fuel pump, then it's some other consumer (coils, injectors, fans, pumps). Use your Picoscope to figure out which one is going up in current as the engine speed increases. Quote Link to comment Share on other sites More sharing options...
Japtastic141 Posted March 27 Author Report Share Posted March 27 Just for my own sanity I moved the FPR boost reference to the rear of the balance tube to use the same as the ECU and wrapped PTFE around the adjustment screw. This made no change. Then I started looking at any high current items I could scope or disable so I disabled the 4WD and ABS as well as pulling most of the relays and fuses that weren't necessary while testing. Still no change. I scoped the pump again and this looks like it's getting the current and voltage it needs and does not dip nearly as much as the ECU voltage so still a mystery why I have the differential fuel pressure.... The ECU is still seeing as low as 12.75v ish when the issue occurs but the fuel pump is only seeing lows of 13.3v Amps increase slightly with increased fuel pressure as you’d expect. The issue is not as pronounced in slower to build RPMs and boost runs. https://drive.google.com/file/d/19L-dyvswf1itpFUykT4HxyCsFmeSISTH/view?usp=sharing https://drive.google.com/file/d/1z3WO-BoKqyAwUJcRv0iRipcx-q0BOcGn/view?usp=sharing Quote Link to comment Share on other sites More sharing options...
AbbeyMS Posted March 28 Report Share Posted March 28 I would be throwing another fuel pump at the car. Thanks Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.