Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
My car's suffering the symptoms of a bad check valve in the fuel pump, its a Honda crx 88-91, the problem is it means removing the tank to complete the job. The car wants to stall on a cold start 1st time of the day starting. I plugged in a fuel pressure tester awhile ago, and noticed rest pressure was dropping, since then I've installed reconditioned fuel injectors, and a new fuel filter, and a different fuel pressure regulator. Still continues to do this. My LM1 wideband, it shows that its going leaner as the throttle increases. It hesitates off idle like a throttle position sensor, but I used an oscilloscope on the TPS, and its calibrated properly also.
I just looked on the internet and theres an M12 1.25 banjo bolt check valve, do you think this would be worth a try?
Thanks Noah, I read that the pump has to work overtime so I think I know what your saying, maybe its a weak pump too? I'll see how it goes I ordered the bolt from America, first trade deal lol, probably take 2 weeks to get to me. I don't know if I should install it closer to the rail or before the fuel filter, I suppose nearer the rail would keep the pressure more than the other way.
Cheers Andy, you can access the fuel pump power and ground under the seat theres a plate, or on the 88-91 you have to drop the tank, but in England its a rust zone, my friend said the thread on the pipe might be screwed up, there is a plastic plate covering it though. The other way is to chop a hole inside the car, but you have to cut the return line and join it again to remove the pump. Garagebuilthondas in the U.S does a great video on it, its not a tough job but by the look of the strap bolts, it will be more of a battle
If the idle valve drops the revs below 750rpm to around 400rpm, could the check valve issue cause it to surge at idle? That's whats going on too, its like the crank slows down, and the idle control valve kicks in and revs go to around 1250, then sometimes back to 750 then to 400, I've tried 2 idle control valves as I had them anyway, Im thinking whatever causing it to dip, then the fuel pressures dropping off too at 400, thats my guess anyway, but I don't know if thats even possible with the car running. Still waiting for the banjo bolt check valve. I might fit the walbro fuel pump next week, theres an issue with that too, the Honda pumps are much bigger, I've read people have to fill the tank up more, I'm hoping to position the walbro at the bottom so its in the correct place, but mite have to extend wires not sure..
Well the news is I fit the one way valve/check valve banjo bolt today, its instant throttle now... zero hesitation, but it seemed to want to go to stall after being left for hours in the cold will know more tomorrow, so its not fuel pressure related, unless its fuel volume related. The car starts up on the button now, no hesitation whatsoever, and seems to have picked up some low end power, all good through the rev range, but I think the stalling thing is another issue
