I have a 1996 Buick Regal 3.1. It has a P0300 code. Plugs, wires, module, coils packs, fuel filter have been changed since the SES light came on. Nothing has changed. I took it to my automotive class. The fuel pressure was at 34psi while running, but the specs says it should be 41-47. My instructor told me since the FPR wasn't leaking, my pressure problem was most likely from the fuel pump. Changed the pump with no difference. I've changed all the parts myself, but this is nerve racking. It seems like something small because it runs pretty good, just has a little shutter. Compression test was fine for all cylinders. But cylinder 3 had a lot of misfires when I used the scanner in the misfire menu. The history on this car: came from a tow yard not running. Complete head and valve job was done. After all of this, it still has this problem. What now? Please help.
I forgot to add that all injectors were changed at the time of the post. I have tried checking for vacuum leaks, but not with a smoke machine. I took it to the shop that I used to go to ( before I worked on my own cars), I told the guy everything I did. He didn't want to take it for a diagnostic. Back to the drawing board. Thanks for your reply!
January, 20, 2013 AT 10:44 AM
You don't need a smoke machine use a vacuum gauge this gauge tells you a lot about the engine and also is the fuel pressure within specs?
January, 20, 2013 AT 4:43 PM
I checked the fuel pressure Friday, it was 38 psi. I took the vacuum hose off the for, hit the throttle, it jumped passed 45 to 50 I think. But I've tried leaving the hose off to see if gas comes out. 10 to 15 mins, no gas. I got a hard start, then cut off on Friday. It started, but was stumbling real bad. I got a blinking ses light, then it held. I got home to check the light, which was a p0300. This was after driving 80 miles on the freeway. Some guy told me that the crankshaft sensor or camshaft sensor may be acting up. Said it was where my hard starts we're probably coming from. I hope this info helps
January, 20, 2013 AT 10:17 PM
Sounds like you either have a leaky injector/s or the fuel pump is weak-it has to be on 41-47 psi when you turn key on-also you need to check the engine compression, spark plugs and injectors-also the cam and crank sensor-
May, 12, 2013 AT 8:34 PM
It's been some months now. I took it to another shop. They ran a dyno. Told me the pressure was low(which I already knew) they told me they couldn't go any further until that problem was fixed. I changed it, but no difference.I performed a vacuum test. The needle was bouncing at 12. The book said this could be from a worn or broken valve spring. What do you think?