RedZ85 Posted May 1, 2006 Share Posted May 1, 2006 ...AND I STILL HAVE FUEL PRESSURE PROBLEMS!!! Ok, i redid my entire fuel system and have all kinds of pictures for a write up im working on...however, it still doesnt work correctly. My fuel pressure goes from the set pressure of 7 PSI to about 2 PSI after about 15 min of driving. Could i be experiencing vapor lock? Here are some pics of the proximities of my 1/2 aluminum fuel line and the steal braided hose to the exhaust. The drivers side header and the steal braded fuel lines in the engine compartment. You can see the aluminum tubing with the AN fittings and the exhaust to the left. On the far right you can see the fuel pressure regulator. Its a Mallory return style regulator thats recomended for the Mallory COMP 110 pump which i am using. YES, the vacuum port is pluged. Here is my setup. Could i be experiencing vapor lock?? Do i need some sort of heat shielding?? My engine compartment does get really hot, but the problem persists even if i have the hood up. Also, i notice that me fuel pump make excessive noise (sounds like a Holley pump) after i drve for a little while (10 min or so). When i power off the pump momentaraly, then re-power the pump, the noise is gone. Thanks Quote Link to comment Share on other sites More sharing options...
Mike C Posted May 1, 2006 Share Posted May 1, 2006 How does it run with the gas cap off or open? Quote Link to comment Share on other sites More sharing options...
RedZ85 Posted May 1, 2006 Author Share Posted May 1, 2006 How does it run with the gas cap off or open? It runs exacty the same unfortunatly. Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 1, 2006 Share Posted May 1, 2006 Have you checked the filter to see if it's plugged? I had a boat load of crud come out of my tank after running it for a few days last year. I had just gotten it running and had to replace the filter after about 50 miles. Since then it's been fine but acted in a similar manner, would run fine for the first few minutes and then crappy until the system was shut down. I have a high pressure high flow pump for the LT1 but it showed the same behavior. Wheelman Quote Link to comment Share on other sites More sharing options...
Paz8 Posted May 1, 2006 Share Posted May 1, 2006 Maybe the noise from the pump is caused by the pump sucking air, fuel pick-up in tank?? Or the pump is bad or has some dirt in the gear rotors, just my $.02 Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted May 1, 2006 Share Posted May 1, 2006 Sounds exactly like what Pete Paraska went through with his Z. In his case, it was the gas tank liner coming loose and blocking the fuel inlet. If you have a piece of debris floating around your tank, it will run until the piece gets sucked up onto the inlet. Turning the pump off lets the debris float away, then gives you some good run time before it eventualy finds its way back to the inlet and blocks the fuel flow again. A blocked fuel line would also make the pump noisey. Quote Link to comment Share on other sites More sharing options...
DaleMX Posted May 1, 2006 Share Posted May 1, 2006 My tank is full of crud too. When I first installed the new lines I had to change the filter within 5 minutes of running. I flushed it out by running the pump into a 5 gallon container and installed a new filter, but it still plugs up about every 3-500 miles of driving. Quote Link to comment Share on other sites More sharing options...
Lason Posted May 1, 2006 Share Posted May 1, 2006 could be a bad pump too. I have seen a lot of holleys do the same thing. From what I can tell the pumps motor gets hot and the fuel pressure drops due to the pump not being able to keep up. Oh yeah, watch that reg. Had one a few years ago just explode while I was tuning my carb. The top just shot off of it and shot gas all over me and my motor. Ill never use mallory crap again even though I did like their pumps. Quote Link to comment Share on other sites More sharing options...
RedZ85 Posted May 1, 2006 Author Share Posted May 1, 2006 was taken down to a radiator shop where it was boiled out, rust treated and then sealed before i put it back in the car with the new fuel setup. Also i had new 1/2 lines for the outlet/return installed. If there was some debris in the tank, it wouldnt be able to clog 1/2 in line. If i have the engine off and the pump on, i get constant fuel pressure, so i believe that the engine heat is causing my problems. When i turn the pump off then on again, the noise goes away but my pressure is still low. Could it be the gauge giving a faulty reading due to the heat? Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted May 1, 2006 Share Posted May 1, 2006 Yes, you could be experiencing vapor lock. A return style system is good, but the pump and the engine compartment heat is raising the temp of the fuel in the tank since it's circulating through the hot engine bay area. Also, with the return style, where is the return located? It must come into the tank from the top front of the tank and the pickup must be a the bottom rear of the tank. I have both plumbed on the rear of the tank and I get aeration and a loss of fuel pressure when the tank gets less than half full. Going to have to replumb the return to the top front of the tank facing down. Quote Link to comment Share on other sites More sharing options...
331CI 280z Posted May 1, 2006 Share Posted May 1, 2006 None of the answers are your problem. Your problem is that you have a liquid filled gauge located very close to the intake. The heat from the engine causes an erroneous reading with that setup. If you try a remote mounted gauge, you will get the correct reading. Look in the Barry Grant catalog and it clearly states not to use a liquid filled gauge. Quote Link to comment Share on other sites More sharing options...
RedZ85 Posted May 1, 2006 Author Share Posted May 1, 2006 None of the answers are your problem. Your problem is that you have a liquid filled gauge located very close to the intake. The heat from the engine causes an erroneous reading with that setup. If you try a remote mounted gauge, you will get the correct reading. Look in the Barry Grant catalog and it clearly states not to use a liquid filled gauge. Figures! I will try a remote gauge to see if that solves the problem. Can i just use a non liquid filled gauge in that location?? The 1/2 inch fuel lines in the tank mimic the original plumbing configuration with the return located at the top and the outlet syphin on the bottem. THANKS 331! I think ill get some header wrap and heat shielding for my fuel tubes as well...My engine compartment gets awfuly hot! and that cant be good Quote Link to comment Share on other sites More sharing options...
Turbo Meister Posted May 2, 2006 Share Posted May 2, 2006 You state that you plugged the vacuum line. Where is your vent for atmospheric pressure? If your regulator does not have one the vacuum port must be left open to establish a reference and be the vent. Hanns Quote Link to comment Share on other sites More sharing options...
331CI 280z Posted May 2, 2006 Share Posted May 2, 2006 Cooler fuel is always better. I'm not sure if a non-liquid filled gauge would solve the problem. I mounted my gauge setup to the Mallory regulator, and it is mounted on the firewall. I realize that the closer you put the regulator to the carb the better, but I did not wish to run a fuel pressure gauge with an isolator inside the car. My first setup had a gauge mounted to the fuel line of the Holley 4150 and I received an erroneous reading like you have. It would be at 7 at idle when I first started the car, but would drop when the car was warm. It took me a while to figure out that the gauge setup was the problem. Quote Link to comment Share on other sites More sharing options...
331CI 280z Posted May 2, 2006 Share Posted May 2, 2006 Could you post a pic of the throttle cable setup? I have a Lokar cable, and removed the throttle stop below the pedal, but still haven't been able to get full throttle. I am considering raising the pedal height,and/or cutting off the bracket for the throttle stop off of the floor pan to get more throw on the cable. Quote Link to comment Share on other sites More sharing options...
buZy Posted May 2, 2006 Share Posted May 2, 2006 I run the Mallory COMP 110 pump with NO regulator. It is not need for this particular pump. The pump is a factory set 7 psi. Maybe that is your problem? Just a thought. Brian Quote Link to comment Share on other sites More sharing options...
RedZ85 Posted May 3, 2006 Author Share Posted May 3, 2006 You state that you plugged the vacuum line. Where is your vent for atmospheric pressure? If your regulator does not have one the vacuum port must be left open to establish a reference and be the vent.Hanns Actually the vacuum port NEEDS to be sealed if not in use per the installation instructions. If it is not, the fuel pressure will bounce like crazy. I solved the problem. It seems to be the gauge itself. I replaced the fluid style gauge with a cheap old $13 Mr. Gasket dry gauge. I installed the dry gauge and started the car to set a refrence point. I set it to 7 PSI then turned the car off before it could start to warm up. I then inserted a plug in place of the gauge and drove around for about 30 min or so. Once i returned home, i shut off the fully hot engine (The same environment that caused my liquid gauge to read practcly 0) removed the plug and reinstalled the dry gauge and started the engine up again immediatly. Sure enough, i was still at my refrence point! I was never losing pressure at all, but rather the liquid filled gauge would go from 7 PSI to 0 PSI due to the head of the engine! I left the gauge installed and left the car running for a while and my pressure remained relitivly constant. So now i know...liquid filled gauges are completly false once heat is introduced. I will have a full write up on my fuel system asap. Quote Link to comment Share on other sites More sharing options...
RedZ85 Posted May 3, 2006 Author Share Posted May 3, 2006 I run the Mallory COMP 110 pump with NO regulator. It is not need for this particular pump. The pump is a factory set 7 psi. Maybe that is your problem? Just a thought.Brian I wanted a return system. I heard of issues with just using the bypass in the pump to maintain pressure...plus i like spending money apparently. I was thinking of running the pump alone without a regulator but decided to make my life more complicated and do a full return style system. I am very happy with it and it looks sharp! Quote Link to comment Share on other sites More sharing options...
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