FMU pressure

[jessica2112]

I cannot get my FMU to build more then 55 lbs of pressure. I have two, and rebuilt one of them. One is 8:1 and the other is 10:1 and still the same FP. I tested them, and they do work, but it seems they need to see more then 5 lbs to get a high reading. One did 70, but it was more than 5 lbs to get it to do that. They both can't be bad, one is practically new, off a Mustang that had an sc that was parted out. It got t boned. Larger vac lines maybe?

[2002 v6 camaro uncharged]

I don't remember if you upgraded your fuel pump, so maybe (if you still have your stock fuel pump) it is getting weak our maybe your fuel filter is getting ditry so the pump can't support thr needed fuel pressure. When my fuel pump was going bad my fuel pressure under boost was getting lower and lower the more it started to fail.

[NCState98]

yeah, it sounds like you're at full fuel pump pressure. The FMU is doing its job, but only within the limits of your fuel pump. You're still on the stock pulley right? Impressive to get more than 5lbs.

[Mighty Thor]

If you're sure about the connections and everything, then uncharged is probably correct.

Do you have over 50k on your car? Good idea to change the filter. Also upgrade to a Walbro 255 pump. You can follow Racetronix install which is found at Graysman site.

Just be patient. You're getting close in working out that bug.