beebeecivic Posted December 24, 2009 Share Posted December 24, 2009 Alright guys, I noticed that when I turned my car off the PSI drops from 26 to zero in less then 10 secs. I can literally hear the gas go back into the tank. My guess is that one of the injectors are stuck. Can some one confirm that? Or is there something else that causes it to do that. Quote Link to comment Share on other sites More sharing options...
SidWell Posted December 25, 2009 Share Posted December 25, 2009 Check your fuel pressure regulator or the fuel pump. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 25, 2009 Author Share Posted December 25, 2009 Check your fuel pressure regulator or the fuel pump. I checked the regulator and it was sort of the cause and the pump is new. Can a leaky intake manifold cause my fuel psi to drop since the regulator is operated by the intake manifold? Quote Link to comment Share on other sites More sharing options...
letitsnow Posted December 25, 2009 Share Posted December 25, 2009 No, the regulator is hooked to the manifold for a vacuum reference only. It can only be a leak, the regulator, the pump, or the injectors. If it's going back to the tank, check the regulator or the pump. Just because it's new doesn't mean it's any good. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 25, 2009 Author Share Posted December 25, 2009 No, the regulator is hooked to the manifold for a vacuum reference only. It can only be a leak, the regulator, the pump, or the injectors. If it's going back to the tank, check the regulator or the pump. Just because it's new doesn't mean it's any good. After searching the millions of post on hybridz I am suspecting the o-rings on the injectors are leaking. I am going to squirt some soap water to see if that's the case. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted December 25, 2009 Share Posted December 25, 2009 Between the injector and the manifold? That won't cause it to lose fuel pressure. Quote Link to comment Share on other sites More sharing options...
pallnet Posted December 25, 2009 Share Posted December 25, 2009 Sir In mostly all electric fuel pumps there is a check valve. This valve is on the outlet side of the fuel pump itself or screwed into the outlet side of the pump and is part of the outlet fitting. It sounds like this is where your problem is. Some pumps require you to change the whole pump if the check valve goes bad and some require you just to change the valve/outlet fitting itself. The stock Z pump has it built into the fitting but good luck finding just the fitting for sale. pallnet Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 25, 2009 Author Share Posted December 25, 2009 SirIn mostly all electric fuel pumps there is a check valve. This valve is on the outlet side of the fuel pump itself or screwed into the outlet side of the pump and is part of the outlet fitting. It sounds like this is where your problem is. Some pumps require you to change the whole pump if the check valve goes bad and some require you just to change the valve/outlet fitting itself. The stock Z pump has it built into the fitting but good luck finding just the fitting for sale. pallnet hey pallnet, the pump is a new Walbro 255. I'll take a look at the pump tomorrow. So the o-ring's are fine? I am out of ideas, I have changed nearly all the vacuum lines and my psi will not build to 36 ; unless I pull the hose from the manifold vac line from the FPR and pinch it, then it will rise. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted December 25, 2009 Share Posted December 25, 2009 When it's idling, the pressure will be less than 36 because the FPR will regulate to 36psi more than the intake pressure. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 25, 2009 Author Share Posted December 25, 2009 When it's idling, the pressure will be less than 36 because the FPR will regulate to 36psi more than the intake pressure. I understand that, I have the gauge from filter to rail , when I hit the throttle the PSI drops to about 20psi, and the intake pops (lean) Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 26, 2009 Author Share Posted December 26, 2009 So I changed back to the old FPR and it held the psi better. But psi is still low. Quote Link to comment Share on other sites More sharing options...
pallnet Posted December 26, 2009 Share Posted December 26, 2009 Wow that new info on your problem. Sound like you have some serious issues. Here are a few things to look at but knowing what year tank you're running would help because on 240Z tanks the pickup tube inside the tank tends to be obstructed if you get a dent in a certain area of the tank, I have seen this a few times. 1) I would put a FPG inline right after the fuel pump. This will tell you where your problem is (Front or rear of car). 2) If it's in the rear of the car (I.E. low pressure reading after the pump) then I would look at the pump, clog in the pickup tube inside the tank of trash in the tank such as rust buildup. Rust buildup will kill that new pump faster then you can imagine. 3) If the problem is in the front such as good reading in the rear but not in the front then you will want to look at the fuel filter. 4) Keep inmind that the FPR can cause the readings to be low in both areas. If you had O-ring issues then your car would run like crap from a vac leak, it would not have an affect on the fuel pressure. If you had a heavily leaking injector or injector set doing so then when you went to start it back up you most likely would either hydro-lock the engine (DOA) or wash down your piston rings and then you would have a serious hard start issue. pallnet Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 26, 2009 Author Share Posted December 26, 2009 Wow that new info on your problem. Sound like you have some serious issues. Here are a few things to look at but knowing what year tank you're running would help because on 240Z tanks the pickup tube inside the tank tends to be obstructed if you get a dent in a certain area of the tank, I have seen this a few times.1) I would put a FPG inline right after the fuel pump. This will tell you where your problem is (Front or rear of car). 2) If it's in the rear of the car (I.E. low pressure reading after the pump) then I would look at the pump, clog in the pickup tube inside the tank of trash in the tank such as rust buildup. Rust buildup will kill that new pump faster then you can imagine. 3) If the problem is in the front such as good reading in the rear but not in the front then you will want to look at the fuel filter. 4) Keep inmind that the FPR can cause the readings to be low in both areas. If you had O-ring issues then your car would run like crap from a vac leak, it would not have an affect on the fuel pressure. If you had a heavily leaking injector or injector set doing so then when you went to start it back up you most likely would either hydro-lock the engine (DOA) or wash down your piston rings and then you would have a serious hard start issue. pallnet hey pallnet thanks for the reply once again. I have a 280z 1. So i jus put the guage between pump and hardline? 2. I thought about dropping my tank and taking a look. 3. And fuel filter I took it out and checked it and everything was clean and clear. As for injectors i did the soap and water trick and nothing seemed to be leaking. thanks agian pallnet Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 28, 2009 Author Share Posted December 28, 2009 So I dropped the tank yesterday and found ton of rust. I guess im going to call a few places to see how much for a boil + seal or POR15. I hope this fixes the problem Quote Link to comment Share on other sites More sharing options...
pallnet Posted December 28, 2009 Share Posted December 28, 2009 Sir It sounds like you found your problem. That new pump on the car needs to be removed and back flushed so that you can try to save it. Clean out all of the fuel lines and hoses on the car. Do this by disconnecting them in places so that you can blow high grade fuel then pressureized air through sections to clean out the rust. pallnet Quote Link to comment Share on other sites More sharing options...
rags Posted December 28, 2009 Share Posted December 28, 2009 I understand that, I have the gauge from filter to rail , when I hit the throttle the PSI drops to about 20psi, and the intake pops (lean) Since you found the tank to be full of rust and your gauge is after the filter, I'm sure the filter is clogged causing the low pressure situation. As Pallnet suggests, drop tank, boil, blow out the fuel lines and pump, and change the filter and you should be back in business. Joe Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 28, 2009 Author Share Posted December 28, 2009 Since you found the tank to be full of rust and your gauge is after the filter, I'm sure the filter is clogged causing the low pressure situation. As Pallnet suggests, drop tank, boil, blow out the fuel lines and pump, and change the filter and you should be back in business. Joe I hope this is the last thing I have to do (fuel system wise) . I have ran out of ideas! haha.. thanks again guys! -bee Quote Link to comment Share on other sites More sharing options...
Daeron Posted December 29, 2009 Share Posted December 29, 2009 3. And fuel filter I took it out and checked it and everything was clean and clear. Since you found the tank to be full of rust and your gauge is after the filter, I'm sure the filter is clogged causing the low pressure situation. Joe Not to bash on you, beebee, but this illustrates a point that cannot be emphasized enough. Fuel filters, at least OE filters on old fuel injected cars with high pressure systems, CANNOT be judged by a simple visual inspection. Unless you are backflushing it with some clear gasoline with some additives, you will frequently see BAD filters flow through pretty clean. I have seen filters that made me think "Well, that can't really be problematic, can it?" and re-installed, only to replace later because they sure were no good. The fact that the filter has been filtering large amounts of particulate matter out for XX hours is one good reason to replace it, and Joe's point brings up another good reason. Chances are a presssure gauge placed inline between pump output and filter inlet would show good pressure, and your nice looking newish fuel filter is the obstruction point. Change the filter; its got crap in it and you want to finish this job and say "I know all that stuff is clean and clear." Fuel system gremlins aren't the ones to ignore... Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 30, 2009 Author Share Posted December 30, 2009 Not to bash on you, beebee, but this illustrates a point that cannot be emphasized enough. Fuel filters, at least OE filters on old fuel injected cars with high pressure systems, CANNOT be judged by a simple visual inspection. Unless you are backflushing it with some clear gasoline with some additives, you will frequently see BAD filters flow through pretty clean. I have seen filters that made me think "Well, that can't really be problematic, can it?" and re-installed, only to replace later because they sure were no good. The fact that the filter has been filtering large amounts of particulate matter out for XX hours is one good reason to replace it, and Joe's point brings up another good reason. Chances are a presssure gauge placed inline between pump output and filter inlet would show good pressure, and your nice looking newish fuel filter is the obstruction point. Change the filter; its got crap in it and you want to finish this job and say "I know all that stuff is clean and clear." Fuel system gremlins aren't the ones to ignore... Your not bashing at all, were all here to learna dn its always great to get advice. After the clean tank I am going to clean my lines, replace the filter and finally clean the pump. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 31, 2009 Share Posted December 31, 2009 PLEASE take your injectors out and have them reverse flushed if this is a turbo application. Even fine particulates can bypass the filter and lodge in the small screens of the injector inlet. This can cause the car to run lean under high load. I have seen one instance where the fuel filter exploded internally, and the FILTER ELEMENT FIBERS clogged the inlets to the injectors. Was not a problem till above 3500rpm when the stock ECU went from one pulse mode to another and they couldn't flow any more. Rusty tanks kill pumps. Keep your fingers crossed. If you have stock injector hold in scheme, a total new set of big and small injector o-rings costs like $4 at Auto Zone, take em out try to get them reverse flush cleaned, stick some new hoses on them (fuel injection hose only) and put them in with new o-rings. It will give you peace of mind you won't have leak issues down the road from those then! Good Luck! Quote Link to comment Share on other sites More sharing options...
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