Joined: Fri Jun 20 2008, 10:37PM
Location: Sydney Australia
Posts: 221
From the WTF Files!!!!
Q. What is it that goes down the hotter it gets???
A. My bloody fuel pressure!!! :-x :-x :-x :-x
Engine has a 160F thermostat, fan shroud is missing, I know while stationary this is an issue but at 50mph its not a problem.
I had a Holley electric fuel pump installed, with a regulator that was supplied with it. installer even fitted an LPG cut off relay system in the event of fire or crash.
Now when the car gets hot, the car stalls after its been sitting hot i.e. stopping at a servo and filling up...I drive a short distance and the engine just dies...after this happened a couple of times I checked the carby and it was dripping fuel as though it had way too much line pressure? You need to crank and crank and crank the motor to get it to fire again, without touching the throttle.
As the regulator didn't have a gauge, Amazon.com fixed that so I can see for sure the fuel pressure going past 10psi....or so I thought?????
I fitted a phenolic spacer under the carby to stop heat soak, now has a tiny air cleaner to close hood!!
This lessoned the heat soak into the carby a fair bit and the boiling burbling noise in the float bowls stopped.
Now....when I first run the car...I see 6psi line pressure...pretty happy...car is just warming up here in this pic.
Location of the regulator in the engine bay.
Engine is warmed up, thermostat opened, car idling at 800rpm easily (race carby has no choke fitted) line pressure has already dropped 1psi..?
Car has been driven 15mins, parked for 10mins and heat soaked a little, temp gauge shows 200F and fuel line pressure has fallen by 50% to 3psi??? (Oil pressure gauge line was leaking so its not connected)
Car driven back to parking spot, engine now over 215+ F and car stumbling a little off idle at lights...usual ethanol boiling issue I think. Line pressure now closer to 2psi?? WTF is causing this to happen!!!!
Joined: Sat Aug 19 2006, 05:03PM
Location: Ontario, Canada
Posts: 2919
In my experience with fluid-filled fuel pressure gauges, the reading drops as the gauge gets hotter from heat soak. I have to stick my thumbnail under the edge of the rubber plug on the back and "burp" it to equalize the pressure before it reads properly.
However, yours is mounted on the fenderwell, not on top of the engine where mine is, so heat soak may not be as much of an issue. You're also having a real engine problem which may be related to fuel pressure, so my anecdotal advice may not address your gauge reading quandary.
Joined: Wed Nov 17 2010, 03:28PM
Location: florida
Posts: 1311
increase fuel pressure to 9 psi just to see what happens.im not a fan of the holley elec fuel pumps and that style regulator for any real performance.i feel they are not accurate enough so you may be starving your motor.what kind of power are you making?.what carb are you running?the way i look at fuel systems is the money needs to go into the pump because it works way harder than the carb.those holy street pumps don't really hold up.where is pump located? do you have a sump or stock tank? why 2 radiator caps? fuel pressure gauge should be after regulator inline closer to carb for better reading.
Joined: Mon Feb 18 2008, 11:08PM
Location: Tewantin, Queensland, Australia
Posts: 405
I'm in the process (slowly- been too hot and little enthusiasm) of fitting an electric fuel pump to my car. I'm hoping to fit the regulator and the back of the six pack and the return line from there, so it'll have fuel flowing constantly through to help prevent the problem you're having now. Where have you mounted your pump? and do have a return line to tank or is it a "dead-head" regulator?
Joined: Mon Oct 10 2005, 10:24AM
Location: The Netherlands
Posts: 160
dacuda wrote ...
increase fuel pressure to 9 psi just to see what happens....
Not the smartest advice to give IMO. If he's running a Carter or Edelbrock carb, mostlikely at 9 psi the floats will be pushed open and the carb will flood. Maybe even spill enough fuel through the vents on the intake and burn everything down.
I would try to move the fuellines a bit more to the front of the engine bay, away from the engine and exhaust heat. Perhaps use a bit more hardline with some insulation around it and short rubber fuelhoses near the carb, instead of just entire rubber fuel hose from the regulator.
Joined: Wed Nov 17 2010, 03:28PM
Location: florida
Posts: 1311
my point being the gauge is under reading the real pressure.if pressure is dropping off this will tell you if reading is accurate or not.i say 9lbs because that is the limit for a carter or holley .
Joined: Fri Jun 20 2008, 10:37PM
Location: Sydney Australia
Posts: 221
Hey guys...bit of an update.
The gauge is suffering from temp induced pressure effects.
The gauge has a rubber band around the housing that hides a pin, when that pin is pulled up it equalises the pressure to match that of outside, effectively resetting the needle to where it should be, I did this when stinking hot and the needle reset to 6psi.
one problem solved, next one is why it expires and then is hard to start while fuel is leaking from the throttle shaft??
I am installing a pusher thermo fan to keep its temp down, but its weird the fuel line pressurises when engine is off, would the regulator be holding fuel in the line and not letting it bleed back to the tank when pump is off?