Homer Posted December 3, 2007 Share Posted December 3, 2007 Could be the fuel pump speed control computer having a spazz unless you have run a bypass or have the 12v mod. Lyndon. Aside from the Walbro the rest of the pump system is stock. Is the fuel pump speed control part of the relay system in the boot? The main ECU is a Power FC. Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 3, 2007 Share Posted December 3, 2007 You install the diagnostic bridge and run the fuel system for a while, see if the pressure changes. if you can see the pressure change you should hear the pump whine change as well (you may have to expose the pump cover for this, i.e. take out the carpet and spare wheel). Now you can hear the fuel pump whine change pitch as you change the fuel pressure. I can't recall which way it goes so do it a few times to get the feel of it. Now if the fuel pressure changes while under observation, the pump will either change pitch like you upped the pressure or like you lowered it. If it's the same behaviour, it's the FPR. If it's the opposite behaviour, it's the pump... -Ian Quote Link to comment Share on other sites More sharing options...
Homer Posted December 3, 2007 Share Posted December 3, 2007 You install the diagnostic bridge and run the fuel system for a while, see if the pressure changes. if you can see the pressure change you should hear the pump whine change as well (you may have to expose the pump cover for this, i.e. take out the carpet and spare wheel). Now you can hear the fuel pump whine change pitch as you change the fuel pressure. I can't recall which way it goes so do it a few times to get the feel of it. Now if the fuel pressure changes while under observation, the pump will either change pitch like you upped the pressure or like you lowered it. If it's the same behaviour, it's the FPR. If it's the opposite behaviour, it's the pump... -Ian Thanks Ian. I tried this, the whine from the pump changes when the nut on the fpr is adjusted (and the fuel pressure adjusted up and down). The pump has always been a bit on the noisy side so no need to remove anything to hear it. Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 4, 2007 Author Share Posted December 4, 2007 Thanks to everyone for your advice. I've been continuing to investigate by bridging the diagnostic ports and checking the pressure before and after every journey. Interestingly, the static fuel pressure doesn't appear to fluctuate at all under observation, at least not over the duration of 10 minutes or so. But if I leave it overnight, or if I drive the car, you can guarantee that the static pressure will have changed. (I foolishly allowed the driver's door to close this morning while I was checking the fuel pressure, and the exceedingly annoying Sigma alarm then locked me out. With no spare key, it was a job for the AA...) Quote Link to comment Share on other sites More sharing options...
dandan Posted December 4, 2007 Share Posted December 4, 2007 But if I leave it overnight, or if I drive the car, you can guarantee that the static pressure will have changed. Does it change from a cold start if you leave the car to warm up with bonnet closed? or Does it change after a hard run (hot) when left to cool down idling with the bonnet open? Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 4, 2007 Author Share Posted December 4, 2007 I'm not really sure, as I've been measuring the static pressure with the engine off. But I was also coming to the conclusion that temperature might be a factor. Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 4, 2007 Share Posted December 4, 2007 In that case you can monitor it as things cool down? Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 4, 2007 Author Share Posted December 4, 2007 I just checked the static pressure after 20 mins of driving and it was reading 30. (Bear in mind it was set to 40.) But over about 10 minutes of observation, the pressure did steadily rise! So maybe it is a temperature thing? What would cause that? I've tried pinching the vacuum hoses attached, and that doesn't seem to make any difference. I don't know if it should. Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 4, 2007 Author Share Posted December 4, 2007 Maybe I lied. I checked 20 mins later and the pressure hadn't risen at all. It was holding at 33. So I upped it to 40. But within 5 minutes (with the fuel pump running) it had edged up to 43. I'm not even sure if it's safe to drive now. It's misfiring all over the place... One minute the AFR is reading 10, and 10 minutes later it's so lean it's off the scale and misfiring. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 4, 2007 Share Posted December 4, 2007 You should check the FP with vac / pressure line DISCONNECTED. Vac fluctuations due to an engine fault could cause pressure variations. Personally I think you should fit a proper FPR, like the stock one, or a Bosch one, and give that pile of *rap the old floatation test Quote Link to comment Share on other sites More sharing options...
kylestt Posted December 4, 2007 Share Posted December 4, 2007 I'm not really sure, as I've been measuring the static pressure with the engine off. But I was also coming to the conclusion that temperature might be a factor. So am i reading this properly, the fuel pressure numbers that are listed in this thread are read with the engine not running? As Chris mentioned, it needs to be done with the motor running and the vacuum line disconnected for an accurate reading. Then with the vacuum line disconnected and the engine running, make the proper adjustments, set it, and put the vacuum line back on and go have fun Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 5, 2007 Author Share Posted December 5, 2007 So am i reading this properly, the fuel pressure numbers that are listed in this thread are read with the engine not running? Yeah, I was advised this was the 'accurate' way to check the static pressure. I don't really know what the vacuum line does and I didn't realise you could check fuel pressure with this disconnected. We're talking about the 3mm (ID) hose that is attached to the engine, right? I worry about detaching things from the engine and then starting up, as I don't really know what I'm doing!! While annoying, I was at least calm in the knowledge that the problem could be one of fuel pump, fuel filter or FPR. Now Chris says it could be an engine fault. My week has just got worse. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted December 5, 2007 Share Posted December 5, 2007 Just a thought, can't remember but is the FPR normally connected to the vacuum/pressure damper on the plenum? could be faulty and causing the problem? never taken one apart so i don't know. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 5, 2007 Share Posted December 5, 2007 If you get fluctuation when you check at different times with the small hose diconnected and plugged at the engine side, engine not running then it's not engine related. If with the hose disconnected and only with the engine running do you see fluctuations it could be alternator (voltage) related. It's probably the FPR itself though. I never cease to be amazed why people rip perfectly good stock parts off, and fit less reliable and durable ones! Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 5, 2007 Share Posted December 5, 2007 Because sometimes we junk the stock fuel rail as well I'll class something as junk once I've seen them go wrong enough times, like the FSE valve. As the Aeromotive has been running fine on many a car for a few years now I'm inclined to think it's OK unless you know any diffferent regarding the reliability...? -Ian Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 5, 2007 Share Posted December 5, 2007 I have 2 knackered ones here, off other cars, similar problem, unable to hold a steady pressure. Quote Link to comment Share on other sites More sharing options...
b_have Posted December 5, 2007 Share Posted December 5, 2007 Thanks Ian. I tried this, the whine from the pump changes when the nut on the fpr is adjusted (and the fuel pressure adjusted up and down). The pump has always been a bit on the noisy side so no need to remove anything to hear it. I would check the pump first, If its noisy, its likely to have a blocked sock filter. I replace mine annualy and always need to dial in the fpr after. A single Walbro should be almost quiet with a new sock. Quote Link to comment Share on other sites More sharing options...
TLicense Posted December 5, 2007 Share Posted December 5, 2007 I have 2 knackered ones here, off other cars, similar problem, unable to hold a steady pressure. What do you think's gone on them? After all it's only a diaphragm and a spring... Quote Link to comment Share on other sites More sharing options...
dandan Posted December 6, 2007 Share Posted December 6, 2007 Toffee spring? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 6, 2007 Share Posted December 6, 2007 I suspect poorly machined or worn valve seats, I just replaced them with stock or Bosch ones, which never seem to give trouble. Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 8, 2007 Author Share Posted December 8, 2007 Right then... I've replaced the fuel filter and Darryl has kindly fitted me a new Walbro fuel pump. Alas, the FPR is still not holding constant pressure. We last set the static pressure to 40psi, but having just checked it after a long run, it has dropped to 28! That would explain why my AFRs are lean off the scale! While it does seem to fluctuate both ways, I'm now fairly confident that the hotter the car gets, the lower the pressure goes. So now I'm just waiting on a new FPR, which I'm hoping will be the answer to all my woes. Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 23, 2007 Author Share Posted December 23, 2007 Just to keep you all posted.... Over the last few weeks I've replaced the fuel pump, the fuel filter, and the FPR. I did them one at a time, to try and determine that cause of the problem. I was going to put a stock FPR back on, but didn't have the skill to do the swap myself and couldn't find any place that could fit me in the next couple of months, so I bought another Aeromotive unit (and a new gauge). For example, I did give ToyotaGT a call, but they told me they couldn't fit me in for about 8 weeks (that was three weeks ago when I first called) and the price they quoted to put a stock unit on well exceeded the price of a replacement Aeromotive anyway. I didn't want to run the car in this state for two months, so I figured getting a new Aeromotive was the quickest and easiest option. Now all three bits have been swapped, it looks like the problem still remains. I set the static pressure to 40psi, which equates to about 30psi on idle when cold. By the time the car is running hot, the fuel pressure has dropped to 20psi!! I've no idea why this is happening, though Ryan does tell me mine isn't the first car he's seen that does this. It looks like the FPR drops pressure when the air temperature goes up. I'm hoping that this effect is constant and repeatable, in which case the new map should work just fine. But if it's not... Then I totally stumped! Quote Link to comment Share on other sites More sharing options...
Dash Rendar Posted December 26, 2007 Author Share Posted December 26, 2007 *** Please, can somebody help me!! *** Well, it looks like the car is still a mess. When I set out today the fuel pressure on idle was 33psi. An hour later, after driving through a few villages, it had dropped to 16psi and the AFRs were - not surprisingly - lean off the scale. I had pull over and up the FPR pressure 10psi by the road side just to bring the AFRs back on to the scale. I've replaced everything... pump, filter, FPR, gauge and hoses. What the hell is wrong with my car? Can someone explain to me (as my understanding is not great) whether the Aeromotive unit is attached inline after or before the fuel rail. I got the impression from another member that the stock unit sets the pressure before the fuel rail, but that the aftermarket ones fix the pressure after the rail? Or is that not right? If this is the case, could the problem be the fuel rail or the injectors? (It's a stock rail with 800cc injectors.) Some more observations that might help... The Aeromotive FPR was extremely hot to the touch after an hour's driving. Should it be? I can't believe I've had two faulty FPRs. Could it be that I have some sort of 'hot spot' in the engine bay which is causing this? Another strange thing I noticed... When the AFRs were lean off the scale, I could actually smell fuel inside the car! There are no fuel leaks from the FPR itself. If the fuel pressure is right down and the car is burning lean, where can the smell be coming from? Please can someone help. I haven't been able to safely achieve boost on this car since I bought it. I've replaced everything that I've been advised to replace. I'm completely out of money and the car still doesn't work. BTW, I do have a stock FPR on its way. I want to get a fuel pressure gauge fitted inside the cabin, and I'm wondering where it should be plumbed into. I'd like to get it fitted so that it's independent of the the actual FPR that's installed. Is that possible. BTW, Merry Christmas everyone. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted December 26, 2007 Share Posted December 26, 2007 OK rather than go back through the whole thread i want to ask some questions, 1/ Where abouts is the vacuum/pressure feed for the FPR taken from? 2/ Where is the FPR mounted (ie it could be to close to a heat source and this is causing the fluctuation) In answer to your other questions, the FPR should be between the fuel rail and the return, ie at the return end of the fuel rail, as for a remote gauge, you could fit a T piece either just after the FPR or at the other end of the fuel rail, but i would use an electronic gauge, petrol source in the cabin:blink: Quote Link to comment Share on other sites More sharing options...
Wez Posted December 26, 2007 Share Posted December 26, 2007 It does still sounds like a dodgy FPR although highly unlikely its not impossible. I havent read the whole thread but I am guessing you have already measured for constant voltage to the pump, how is the pump wired, are you still using the fuel pump controller? Is it possible to run the pump in diag mode, ie constant 12v? The only things left to affect the fuel pressure from what you have already changed are the fuel pump controller, fuel pump power supply and FPR manifold pressure reference. Quote Link to comment Share on other sites More sharing options...
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