Help with Diagnosis

[WJR]

Quad sat for like half a year. I went to ride, it was difficult to start, and after riding a short distance, quad worked OK, but not really screaming, a little boggy. Parked it. Went to ride a little the following day, still hard to start, then when it did go, it was gutless. First I changed the gas, that didn't really help. Then, after reading through a bunch of pages on here, I gutted the quick connects, thinking fuel flow issue. I cycled the pump, really good flow. But, now quad won't start at all. So, I figured maybe the injectors are clogged--tapped on them, no help. Took them out and let them spray, both worked. Put those back, now I am thinking either pump or pressure regulator. So, I cleaned the pump terminals, made sure all was tight, then made a really half-assed gauge to put in fuel line. Cycled pump, pressure never reads above 40 PSI, assuming my gauge is anywhere near accurate. Still doesn't start, or it starts and goes like 10 revs and dies. So, now I partially clamp off fuel return line to get pressure in fuel line to 60-65 psi, everything sounds great, revs well, snappy, etc. I could get the pressure up to like 90 or so tightening the clamp on the fuel line, so it seems like the the pump is OK, but I don't know how these pumps act. So, I think its the pressure regulator or the fuel pump. I'm trying to avoid buying both. Anyone have any thoughts?
Thanks,
WJR

[Canniboomer]

It's probably not the pump, and the pressure regulator is working. Rail pressure is 43.5 psi, so a reading of 40 is in the normal range.
I would suspect the return fittings at the tank are causing restriction, or a clogging fuel filter or suction side restriction, or the injectors partially clogging, or the idle screw set too low.
Clamping the return line will put excess strain on the pump. Ideally, there should be no restriction before the filter, and after the pressure regulator. You can also pulse some air backwards into the suction line -- to help unclog the in-tank clunker/strainer.

[WJR]

Thanks for your reply.

I guess it must be an injector, or the wire connection to one. Fuel flows freely, cleaned the inflow strainer, good outflow stream inside of tank, good flow through new filter. Bike will sometimes idle now. Fuel reads 41 ish psi while idling. Now, if I touch the throttle, it dies. If I partially clamp off the return line to raise rail pressure to 80, i can rev it. Ill guess one clogged injector, and as I increase the rail pressure, the one that works puts out, more or less, proportionally more fuel, so at 80psi, its injecting enough to let it rev.

I'll follow up when I get new injectors on.

[WJR]

While I was checking the injector pulses, I noticed that with the pump side injector unplugged it made no difference. So, I took it out, and forced some gum and varnish remover backwards through it a few times with a syringe, let it sit a bit, then reinstalled it, and it fired and revved great. Makes me wonder if the injectors are a little gummy yet, though. Maybe time to replace them.

Thanks again.

[rayspeed]

I would just run a tank with some good injector cleaner like techron thru it at their full recomended strength which would only be a quarter of the bottle or so. But I am cheap...