I just had my injectors cleaned and decided to hook up my pressure gauge when I put em back in. Car started up, no fuel leaks, and read only 24psi with vac line connected. I unplugged it and it went up to 33psi.

I thought it should be 43 to 45psi? Does this point to a bad regulator or a bad pump?

The pressure held steady while running. Also holding at 20psi after shutting the engine off.

B18C
Walbro 255
Benen fuel rail
-8 or -6 fuel lines
e85
FIC 1000's
Oem FPR


Here is the reading vac line connected




And disconnected

 

Tonight I tried something else, crimping off the return line with the pump running. Sure enough, it would go up to 50+ psi if I completely shut off the return. Which tells me the pump is capable of putting out enough pressure.

This leads me to believe I need an FPR? Am I on the right track here?

 

The regulator may be a problem, but that is likely not your ONLY problem. With a Walbro 255, the internal bypass in the pump doesn't begin to open until 73 psi... so if you clamp off the return line, you should see AT LEAST 72 psi... and likely closer to 90 psi. A "High Pressure" Walbro 255 should peg your gauge at 100 psi.

Assuming your gauge readings are accurate... something is weak on the delivery side. The fact that the FPR does in fact alter the fuel pressure 8-10 psi from static to vacuum conditions would suggest that it may be functioning just fine.

 

Thanks, that is good to know.

It is worth noting then that when I crimped the line I could hear the pump straining significantly when it went to 50psi, as if it was slowing down. Should this not be happening?

Also the gauge is brand new and supposed to read within 2%, but it is definitely a cheap gauge. Should I hook it up straight to the pump and see what happens?

Thanks

 

Clogged fuel filter?

 

Fuel filter is new, has maybe 100 miles on it.

 

Use a different gauge to verify the gauge is reading correctly

 

Alright I will verify the gauge reading is accurate. I was also thinking I might drive around with the gauge connected, the hose reaches out the hood by my wiper so the gauge sits right at the windshield where I could read it. I was thinking if while driving under load, I could see if the fuel pressure does drop when the fuel demand is higher indicating the pump is unable to keep up. It should also then correlate with the studder I am experiencing.

Or, is it just a really, really bad idea to drive around with the gauge connected??

 

Just an update, I was about to drive the car today and while letting it warm up, I looked carefully underneath with a light and noticed there is a gas leak. It is coming from almost the middle of the car, somewhat towards the back as far as I can tell. It's tough to say exactly with the car so low. I'll get it up in the air later and check it out.

I don't know if this leak is enough to cause the low pressure, it was just a steady drip. Upon idling for a couple minutes, it maybe leaked a few ounces of gas.

I'll update when I find where the problem is.

 

Probably a rusty fuel line.

 

Looks like all of the lines have been replaced with a large diameter rubber-type hose. Appears the leak is most likely coming from the connection points at the end of the hose up by the tank, then is running down and dripping under the middle of the car.

So I guess whether the pump is the problem or not, I'll be lowering the tank. Might as well replace the pump while I'm at it.

 

a small leak like that should have absolutely zero impact of fuel pressure.
my guess is the gauge is wrong. as said above, get a completely different gauge (different brand), preferably an actual fuel pressure test kit, and compare readings. fuel pressure test kits can be bought at most parts stores for around $30.

 

It was a bad gauge. I stopped by my mechanic's shop and borrowed his gauge, it read right around 42-43psi.

Thanks for the suggestions!