It's been like 2 months since I bought a walbro 255 fuel pump from summit and installed it. In the last week I have been having a miss. I've changed plugs and wires and still have this miss. I have a fuel gauge hooked up and my FP is bouncingfrom 36-42 off idle. I notice when I shut her off, FP drops withing minutes. I am convinced I may have a faulty pump again, BTW the new one has less than 1k miles. What can i do to figure the FP loss, I hate to have to drop the tank again. Help guys

 

If it turns out you have to swap the pump again, don't bother dropping the tank, just cut the access hole. Much easier.

 

Test the fuel pressure under load; tape it to the windshield and see what the pressure is doing when the miss occurs. Rapid fuel pressure drop off after the engine is off leads to hard starting, not engine miss. And if it takes minutes for the fuel pressure to drop off, I don't consider that to be rapid drop-off.

 

at WOT FP stays dead on at 43 but there is random backfire...@ Idle Fp bounces up and dow, rpm does too From 600-1000 RPMS. Every once in a while when im driving it seems like its running out of gas for like 4 seconds, I then give it gas and it'll go away. Do you think a fuel line is loose or how can i check a faulty fuel pump? When i take vacuum off them regulator there is no leaking gas coming out so i assume the regulator is good.

 

fuel filter?

 

I just put a wix FF last week, still same problem.

 

injectors clogged?

 

The fuel pressure will "bounce" if your MAP is bouncing. I sticky valve might explain spikes in the intake manifold pressure. Put a scanner on it and watch the MAP. By "backfire".... do you mean a burp into the intake manifold, or a pop in the exhaust pipe?

 

Pop in exhaust pipe.....Car does run strong under WOT. I will check injectors late tonight, there fairly new accel 30lb maybe 5k on them.

 

kinda on topic, but my MAP sensor light is comming on and recently my car has died from a stop/light/idle with foot on brake in D. Starting it back up would not start unless i gave it gas..

Could this be the MAP sensor, cause it only comes on at idle and code says low vaccum high voltage.

 

Probably best to start a new thread rather than highjack this one... A radical cam can turn the SES light on for low vacuum.

 

Well mine has stalled a couple times to at idle or when turning...Only dtc was my passenger 02. I do have a hotcam with all bolt-ons if it matters.