Walbro inline pump pressure problems HELP!!

[hubdawg]

72 Blazer with 2004 LS 5.3 with truck intake and fuel return line. I'm running a new walbro 255 inline pump with a inline filter in front of it. At the shrader valve on the fuel rail I get 52lbs of pressure when I crank or cycle the key and most say I need at least 58-60lbs. My truck wont run right and pops and crackles when I start it. I disconnected the fuel line on the engine side of the pump and checked pressure there....still 52lbs. Next I disconnected between the stock tank and the the pump and ran a hose directly into a full gas can bypassing the tank.....still 52lbs. Shouldn't this be pumping much more than 52lbs and be regulated at the regulator on the fuel rail. I put in a new Walbro 255 and had same results of pressure. So far I've wasted $120 on a new pump and would like to stop shot gunning parts. Any ideas?

[ls1nova71]

Are you sure it's a genuine Walbro? There are a lot of chinese knock offs out there that are junk. That said, how are you checking for pressure? Disconnecting the lines will not give you an accurate reading because you need the regulator to regulate it, that's how you get pressure. Have you tried unhooking the vacuum hose from the regulator with the engine running to see what it does?

[hubdawg]

Won’t run good enough to pull vacuum line from regulator to intake. The pump it self says walbro on it so I’m convinced it’s real plus the pressure reads exactly like the old one. I have a fuel pressure gauge from orileys hooked via shrader valve port on the fuel line

[hubdawg]

I also used the gauge inline right in front of the pump via an inline t adapter So I was testing the pressure before the regular which was still 52

[hubdawg]

I also used the gauge inline right in front of the pump via an inline t adapter So I was testing the pressure before the regular which was still 52

[ls1nova71]

It should run good enough on 52psi to at least idle it. If it won't even run, then is sounds like you have another problem. Is it a flex fuel engine? If it is, then 52psi is about right.

[hubdawg]

How can you tell if it was a flex fuel engine? Going to try and check all grounds and look for vacuum leaks

[mongocanfly]

did you pull the engine you have from a donor....?
ive heard theres a sticker inside the door frame and a yellow gas cap that are indicators

[Davidf]

Originally Posted by hubdawg

How can you tell if it was a flex fuel engine? Going to try and check all grounds and look for vacuum leaks

I believe the injector connector is more square than rectangular on flex fuel engines. I would think 52# is high enough to let the engine run decently. I would look for vacuum leaks, etc.

Also, I would put the filter on the pressure side of the pump, not the suction side...this could be causing a starvation issue even with a good pressure reading.

[hubdawg]

Have no idea about the sticker it was already transplanted into another vehicle when I bought it. Engine ran great then I put it in my new frame off and now it runs like crap. I’ll try the fuel filter swap and see if it corrects anything

[prodjay10]

how long was it sitting before you started again? Could be a dirty injector
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