Flat spot with edelbrock mpfi conversion - Third Generation F-Body Message Boards

ls1nova · 10-04-2009, 12:14 AM

I have a 1994 tbi blazer that I just completed the edelbrock mpfi conversion. Did the heads cam and chip also. Not sure how to acurately explain this but the engine has a flat spot at 1/4 to 1/2 throttle most of the time. On rare occasions the motor runs stong. No fault codes. Very rarely the engine will actually pop. I am getting very frustrated and not sure were to go. I have a snap on scanner and sensors seem ok to me. I don't think it's the tune, as sometimes it does run strong? Timing is set to 0 degrees with the plug unplugged and the truck in drive. Any help, input, or known sensor readings would be great help. Thanks.

ls1nova · 10-04-2009, 05:49 PM

Worked on this some more today. The fuel rails do not seem to keep pressure. I lent my gauge out so I do not have exact figures. I cycle the key a few times and no pressure at the scrader valve. After I shut the truck off no pressure. It does bubble out while running though. What is the best way to determine whether it is a bad regulator, pump, or injector?

ls1nova · 10-05-2009, 07:19 PM

Took some pressure readings today. Key on=26psi until the pump times out the it immediately goes to zero. Running=26psi. Edelbrock recommends 42-44 with key on and i think 36 running.

ls1nova · 10-06-2009, 11:18 PM

Thanks for all the help. Dropped the tank tonight to find one of the hose clamps loose on the pump and the check valve broke. Anybody have any input on the ac delco ep381 pump. Edelbrock sent me a walbro and I wasn't overly impressed.

ls1nova · 10-07-2009, 11:23 PM

AC delco ep381(25163473) pump from a vortec truck. Fit perfect unlike the POS edelbrock sells. Check valve blew out and got jammed in the sender. Truck runs like a dream now! I am wondering how much more I can gain with a new tune seeing how I am using the supplied edelbrock emissions legal chip. Very happy with the performance none the less.