Fuel pressure issue

[jedclampit]

Set pressure to 7 ~7.5#, reset float levels.

Fuel filter near header is just bad plumbing. Metal housings/frame mount will conduct heat to fuel very well.

Your leaving something on the table not running a return line system.

[TWISTER]

Jed,
We tried the pressure at 7.5 lbs and it dropped to 4. The fuel filter is mounted on the right side upper frame rail. I have ran it there for 8 years now and never an issue. I'm not saying its the best spot, I'm just saying that has been a constant without issue.

I do need to clear up something though. After talking to my driver tonight he told me that the needle on the gauge bounces back and forth from 9-6,9-6,9-6 not the way I originally understood it to be doing. He said it was just like bouncing a ball. Don't know if this changes anyone's thought pattern but just wanted to clear this up.

[jedclampit]

You need more volume to maintain the pressure. Why you lack the volume could be pump,restriction or vapor lock.

Not a fan of this mag, nor did I read the entire article, but you may find some useful info.

http://www.circletrack.com/enginetech/ctrp_1301_tech_engine_under_pressure/viewall.html

[Brian Gray]

i had problems with the filter near the header untill i ran a return with regulator on the return . also some regulators have an internal bleed look at the valve and see if it has a bypass . i was told by braswell 5 - 7 lbs on gas max. obviously if your maintaing pressure you have volume i'd check the regulator.

[hucktyson]

If your running a cv2508 / spin brand pump that is supposed to use a dead head style regulator. They don't produce enough volume to use a by pass regulator like gray is describing. The ideal situation would see you running a DSR belt driven pump off the back
Of your power steering with a bypass regulator because unlike the CV it won't run out of fuel at sustained high rpm . If you run 5 psi with a pushrod style cv pump like Brian suggests your going to melt pistons on a big hammer down track. With a pump like that you should have 7- 7.25 psi and with a dead head style regulator is your pressure is jumping around you have something wrong. I ran that set up for years and it was flawless. Although I was running a CV/Spin deadhead regulator not a Holley .

[TALON75]

Hmm, my cv pump does just fine with a return regulator. I used to run non regulated with a 9psi spring, no problems there either. What regulator are you using? Have you checked or replaced the line running to the guage?

[FlatTire]

I had a fuel hose fitting that had a pin hole leak causing the fuel pressure to drop when the float bowls ran out of fuel. The only way I found that leak was by opening up the dipstick cap on my fuel tank and pressuring up the fuel system with shop air. Just turn your shop air pressure down before you do this.

Maybe you could get this thing on a chassis dyno. You could measure the air-fuel ratio to see what's really going on. You might call your carburetor builder and pick his brain too.

[TWISTER]

Thanks for all the help everyone. I have been talking to my carb man(stealth) for 3-4 weeks about this as well as my engine builder(vic hill). The conclusion we have come to is to replace or rebuild my pump and replace the regulator with a better quality one. The regulator I am replacing it with has a place to mount a gauge on it. That way i can see if there is a descrepancy from that point to my gauge in the car. Also going to pressure test as much of my system as possible to check for a leak. In the off season we are going to convert over to the DSR pump on back of oil pump with return line system. Seems "no one" is having a problem there.

Talon, the line to my gauge is one piece that I have not replaced. Going to do that though. It seemed that the issue was being caused on the suction side of the pump but at this stage of the game who knows.
Again thanks to everyone for their input. I will let everyone know what I find so that it may possibly help someone else out in the future.

[powerslide]

http://www.youtube.com/watch?v=Kl2pa7pmES4

This is a big problem on dodge diesel trucks when you install a pressure gauge. Put a shutoff valve between the gauge and the fuel pressure line and adjust it so when you start the car it takes a brief moment for the pressure to come up. Search water hammer effects and you will find more solutions. I'm betting more cars do this but most drivers arent staring at the gauge, long as it runs, the plugs look good and the idiot light doesnt come on we dont care much.

[powerslide]

We had a car once that had a gauge screwed right into the fuel log. It would jump around like you describe at idle. If possible move the input where the gauge reads pressure further from the pump

[jasjenh]

I just went through the same problem on my brothers modified. it was the regulator. we run the same style regulator on a dead head system. we went through the whole system and even rebuilt the regulator twice before we found the area where the ball on the diaphragm seats was not sealing properly. I checked it by seating the diaphragm by hand and putting liquid in there and watching if it leaked past the ball. I fixed it by using valve grinding compound and lightly reseating the ball. It has more stable pressure now, then when the regulator was new. Everyone told us it was on the suction side to. good luck these types of problems suck

[fairlanechris70]

Had a similiar problem this year. one fitting on the fuel line wasn't completely snugged up and was sucking air.