back fires/hesitates under boost


New Member
Aug 28, 2003
Here is what I got! about a week ago my car started back firing and sputtering on anything above 10# of boost. I have walbro 307 and 42.5# injectors with reds 93 and I am running 18# boost. now I was wondering about the fuel press because I can't get it above 40 psi vacume line off or not. Is this normal? Pulled plugs out looked like car was running lean. since then in the last few days I can't even drive the car out of the drive way. Now it Idles like crap and starts to miss and back fire when give it any gas at all. Pulled plugs out today and they are fouling. Now I don't have a scan tool yet and my check engine light is not installed, which I just found out today! Any help at all with my problem will be greatly appreciated.
The question I would really like some input on is, does 40 psi sound like max fuel pressure with my pump and injector set up?
You should be able to adjust it higher then 40 psi line off.Start with the simple things first.Change your fuel filter,if that doesn't help check the regulator.Is your gauge permananly under the hood or can you put it under the wiper to watch it while driving.While under boost your fuel pressure should raise 1 psi for every lb of boost showing on your boost gauge.Don't boost it up too much if your fuel preesure isn't rising with your boost. :eek:
Its mounted under the hood. Changed the filter a few days ago when the problem first started, I think the pump might be going bad it isn't as loud as it used to be and as soon as I cut the car off my fuel press drops off line right away. Now the car barely runs so I have to figure out my other problem. I thought the press was low, thanks.