SUPER Complicated problem! Need Master Mechanic!

[DRIVEN]

I'm leaning toward defective regulator.

After it's been running for a while and the pressure begins to drop, what happens if you simply take a pair of pliers and restrict the return hose? If you can get back up to your original (cold) psi then you know the pump isn't your issue. If psi stays low then you know it isn't the regulator.

BTW, excellent write-up on your question. Very specific with clear pics to boot.

 

[fleming442]

What wire did you tap into to trigger the relays (HotWire kit)? Should be the pink/ignition circuit. Anything else would be suspect. Does the pump run with the key on? Have you run full fuel flow into a jug?
EDIT: I think I see the problem. The pink wire you are using at the rear is probably the fuel sender lead. That is definitely not going to work. It should be tapped off the 10ga. pink at the ignition switch (as in- if you didn't run a wire, you need to). I'm talking about the lead with the old, rubber insulated spade connector; what's going on there?

 

[lsxsierra]

my guess would be regulator. the pump looks like a fuel injected pump. higher pressure than carb. they make different regulators for that. ones that take high pressure pumps and drops the fuel pressure down for carb. I had one on my previous car. and they make a regular carbureted fuel pressure regulator that works with a regular fuel pump of low pressure like on side of block. can not use the regular carbureted fuel pressure regulator with the high pressure pump. will eventually ruin the regulator or burn up the pump.

 

[TURNA]

Liquid filled pressure gauge???

They are not accurate once they get hot.

Get a non liquid filled one and see what it reads.

 

[1bad79]

Do I just saw this thread I have almost the same set up in my cutlass but with a quadrajet and my regulator/ fuel pressure does the exact same thing but my engine runs fine and after investigating it I never found the reason it runs fine so f*ck it I said and have been driving ever since

 

[1bad79]

Liquid filled pressure gauge???

They are not accurate once they get hot.

Get a non liquid filled one and see what it reads.

I also have a liquid filled gauge it never occurred to me to try a non liquid filled one

 

[RGBody87]

What wire did you tap into to trigger the relays (HotWire kit)? Should be the pink/ignition circuit. Anything else would be suspect. Does the pump run with the key on? Have you run full fuel flow into a jug?
EDIT: I think I see the problem. The pink wire you are using at the rear is probably the fuel sender lead. That is definitely not going to work. It should be tapped off the 10ga. pink at the ignition switch (as in- if you didn't run a wire, you need to). I'm talking about the lead with the old, rubber insulated spade connector; what's going on there?

I ordered the Pink and Black striped wire that GM uses in the car to make it look more original.. (for no real purpose) and ran it directly to the fuse box under the dash where it has the IGN (Ignition tap). I read the factory manual and that wire is hot once the key goes past accessory mode and will apply pressure while turning key and in run position at 12V which is what I need to kick the "hotwire kit" relay to the ON position. It has been working so far and the fuel pump has been allowed to free flow in the past so I could see the amount of fuel dumped in free flow mode and to clear the new lines with new fuel.

 

[RGBody87]

my guess would be regulator. the pump looks like a fuel injected pump. higher pressure than carb. they make different regulators for that. ones that take high pressure pumps and drops the fuel pressure down for carb. I had one on my previous car. and they make a regular carbureted fuel pressure regulator that works with a regular fuel pump of low pressure like on side of block. can not use the regular carbureted fuel pressure regulator with the high pressure pump. will eventually ruin the regulator or burn up the pump.

Thank you,
I've contacted holly and made holley aware of exactly what pump and what regulator I chose. I've already replaced the regulator once with the same one because we thought the wrong spring may have been installed. It pressurizes correctly at start up or when turning the key to the ON initially. After a while of running the engine the pressure drops off. I have not - however - run just the fuel system for 5-10 minutes alone. Maybe I can see if it's only a problem when the engine compartment and exhaust tubes are hot.....

 

[RGBody87]

Liquid filled pressure gauge???

They are not accurate once they get hot.

Get a non liquid filled one and see what it reads.

Yes Sir.
I'll see if I can put together some kind of Tap or pressure gauge kit to accurately read once the car has been running. Part of me has suspected the liquid in the gauge affecting the reading in HOT or COLD applications. Another thing I will have to try and test this weekend.

 

[RGBody87]

Liquid filled pressure gauge???

They are not accurate once they get hot.

Get a non liquid filled one and see what it reads.

Turna, Check this out.....

"Indeed, an "oil filled" gauge is tougher and more durable than a "dry" gauge, with the oil protecting the precision internals from shock and vibration, which explains why fewer and fewer dry gauges are offered for performance engines today. And there's no arguing that a liquid filled gauge looks like a higher quality instrument. Unfortunately, there's a hidden "gotcha" that users of this type of gauge experience, a reported lack of accuracy, or consistency, is common. In fact "oil filled" fuel pressure gauges do exhibit seemingly random pressure swings from 1-9 PSI. This is a fuel pressure "yellow-flag" for EFI engines running 40-60 PSI of fuel pressure, and a "black-flag" for carbureted engines running as little as 2-10 PSI. "

Source - https://www.verociousmotorsports.com/Articles/VM-Articles-Fuel-Pressure-Gauges-Liquid-Filled-vs-Dry