Inline fuel pump pressure problems walbro 255

[hubdawg]

2004 5.3 LS with truck intake showing 52 lbs at the shrader valve on the fuel rail. Truck won’t run pops and crackles. Looks like I need 58+ lbs according to the web. I tested pressure at the engine side of the pump still 52. Then I disconnected behind the pump and ran a hose into a full gas can. Still...52lbs. Shouldn’t this be pumping way more than that and be regulated at the regulator on the fuel rail. I have the return line back to the stock tank. I replaced the pump with a brand new one and exact same results. Any ideas? It’s an inline pump with a single fuel filter ahead of it and the fuel filter is clean

[Lonnies Performance]

If you have a regulator on the rail it will control the pressure... not the pump.
It should be 58psi.

To be clear, the regulator on the rail should have a return line on it. Is this the case?
If so, blocking off the return line will show a pressure spike of what the pump is capable of.

Also the vehicle should run ok with 52psi pressure, as the ECM is capable of compensating this lowered pressure which equates to approx an 8% lean condition.
Once in closed loop the fuel trims should learn & correct the error. The pressure should be corrected, but I would not entirely blame the pressure on your current poor running.

[hubdawg]

So if I understand what you’re saying if I block off the little 1/8 or 1/4 inch line from the pressure regulator that goes to the intake I’ll see a spike in pressure. When I had the pressure gauge right in front of the pump it was still 52. The power brake booster port out of the back of the intake is missing that red ring but the o ring seal seems good. The his motor and tranny were swapped from a good running donor so I don’t know what has changed when I transplanted

[Lonnies Performance]

The little line is typically a reference pressure to the intake. It controls pressure based on intake vacuum.
This can raise pressure if you disconnect it to the order of 1 psi for every inch of vacuum the engine produces.
For example 12" vacuum lowers the pressure approx. 6psi.
Not all factory regulators are referenced to intake vacuum.
Disconnect it & post your results.

A return line I was referring to, goes back to the fuel tank from the regulator or fuel rail.

It would help if you posted a picture of what the regulator looks like.

[hubdawg]

[showdog75]

I'd be looking at the coils. Should run ok at 52 psi.

[Lonnies Performance]

That vacuum line shown is what pulls the pressure down at idle. If you disconnect it, I'bet the pressure returns to 58.

Get it running & check your codes to get an idea of what may be causing the issue.
Too many unknowns to make an intelligent diagnosis at this time.

[hubdawg]

Found a crack in one of the studs used for mounting the engine cover on the intake. Must have cracked it with a chain when I swapped engine/tranny install. This made for a huge vacuum leak and very erratic readings. Got a new used intake coming to put on this weekend. Once installed I'll check everything again. Thanks for the help