Fuel Pressure spike

[rodneym]

I went for a drive the other night and I noticed that my fuel PSI gauge jumped from 5.5 to almost 15, then ran like shiz until I cleared its throat. I tapped the gauge thinking it was faulty but it wasn't budging. Then I shut off the pump and it read zero and I turned it on again. I was fine for a minute, then the same thing happened. I wanted to look at the gauge on my fuel log but it was too dark in that area (Note to self: flashlight in the toolbag). I went home carefully. Luckily I was still close.

I've got a Holley Black at the tank and a filter right after it. Then it makes the long trip to the firewall where the regulator is, then to the rear part of the log (from the firewall, not from the front like with a mechanical pump). At first I thought it may be a stuck needle but one out of 4 (dual quads) wouldn't cause that spike, right? So I figured the regulator must be failing. I ordered a replacement diaphram and I'll fix it in the next couple days.

I think that the regulator was failing, causing high pressure in the carbs, blowing the needles and dumping fuel causing the 'almost' stall condition.

How does my diagnosis sound? What am I missing?

[ERA Chas]

Can't think of an alternate-sounds good. Did you get enough fuel to wash down the bores?
How much psi does a Black make unregulated??

[rodneym]

14, so I think that the gauge is accurate.

How does one know when you actually have cylinder wash? Smell the oil? It did not stall but wanted to.

[ERA Chas]

Pull dipstick when cold and smell / feel oil.
Had another thought-but a reach.
Did Tom do anything special to the carbs to make them blow through-capable? Possibly blowing the needle(s) off seat (s) with your 5 to 7psi positive??

[rodneym]

The carbs did get blower work.

You mean blowing the needles off their seat from 5-7psi of fuel pressure?
I'm thinking that the wild swing I saw to 14psi would have done that. BTW, I was was just cruising at around 2,500 RPM when it happened.

[ERA Chas]

No I meant blower boost pressure. Sorry for confusion. Thinking the signal is much stronger drawing fuel and keeping needle/seat apart.
But 2500 RPM is not full boost anyway right?

[rodneym]

No. At 2500 RPM the boost is non existent according to my gauges (when simply cruising on a flat road).

The needle on the MAP gauge is left of 0 (12 o'clock) until about 3,500 RPM or more. The MAP and 2 boost gauges aren't much fun to look at because when they move, you're in pucker mode and you're not looking at the gauges anymore.

The only times I recall seeing the boost needles really move without gunning it is going uphill.

And 'full boost'? I don't think I'll ever see it.

[ERA Chas]

Tape over all those dials and pin it. Shift 200 before the limiter.
That's what you installed the Paxton Twins for...

[Gaz64]

What regulator are you using?

Is it set up as a bypass system or "deadhead" returnless system?

[RICK LAKE]

rodenym I don't know how long or what gas you are using but just lost my FI fuel regulator to the menthol in the fuel. All the rubber hoses are coming part internally.My fuel filter catch all these black partials in the screen. I have a Paxton regulator with vacuum. This problem applies to everyone with 7-10 years on the same fuel system with any rubber hoses. My fuel system lost pressure, Your's went the other way.
The other thing could be a partial of carbon got into the vacuum port to the regulator and gave no signal to control it, or the line is collasping under vacuum or pinched. Hope this helps Good Luck Rick L.

[ACademic]

Originally Posted by rodneym

...I wanted to look at the gauge on my fuel log but it was too dark in that area (Note to self: flashlight in the toolbag).

Rodney, most smart phones emit enough light to double as a flashlight. I have also downloaded an app "LED Torch" that does exactly as it's named. Just sayin'.

Steve

[rodneym]

My system is deadheaded (sp)?

Rick, my engine has the old style superchargers, so I'm not familiar with a Paxton's FPR in my setup. Paxton makes that FPR for high pressure FI, right?

Steve, I have that app on my iPhone. Never thought to use it.