Bucking at high rpms - sometimes limps at any load and barely has power to move

[saturnv7890]

Okay so the issue is as described in the title.

At low loads/idle/low rpms, usually its fine but sometimes limps like it's running out of gas.

At high loads/rpms it cuts out like its hitting a rev limiter.


I've put a fuel pressure gauge on, but obviously I can't look it when I'm driving.

Odd behaviour:
At idle, if I blip the trottle quickly, the pressure drops immediately to zero, then gets right back up to just under 3 bar (not quite 3 bar). Maybe the fuel pump is shutting off?

When car is off, I prime the fuel pump, the pressure builds up then drops to zero. I pinched the return line and pressure still goes to zero. This means the fuel pump (walbro 255) does not have a check valve.
Behavior:

https://vimeo.com/69854561

What troubleshooting steps should I take?

[bimm3r82]

With the high loads/rpms hitting the "rev limiter" happened to me when my fuel pressure regulator went out on me..

[saturnv7890]

Is there a definite way of testing if the fpr is bad?

[bloodsnot]

Is there a definite way of testing if the fpr is bad?

Maybe not definite, but you can smell for gas in the vacuum line that comes off of it. You can also try swapping a known working one off of a friend's car to see if it helps.

[saturnv7890]

I sucked on the line going to the fpr and could only get a certain amount of air out before it stopped, so it looks like the diaphragm isn't leaking? But the air inside tasted a lot like gas.

[jlevie]

You can see the gauge while driving by zip tying it to a cowl vent or windshield wiper blade.

Seing the pressure drop near zero when blipping the throttle means an obstruction in the fuel flow path, a bad pump, or interruption of power to the pump.

[saturnv7890]

Ah well I've gotta get myself a barbed tee and some more fuel hose then. Is this something an auto parts store would carry? (the tee)

I just replaced the pump and fuel filter, so the most likely possibility there would be interruption to power to the pump. I'll put some alligator clips and a volt meter on the power supply to the pump. I hear the horn relay fits on the fuel pump relay, is this a good way to test to see if it's the fuel pump relay?


OH! My coils (wasted spark) are powered by +12v from the fuel pump, would this affect the fuel pump power at all?

[EatsHondas]

From the fuel pump itself? Or the live wires that power the pump? I don't know for sure, but it doesn't sound a like a good idea to steal power away from the pump to power anything else.

[saturnv7890]

I believe it's from pin 87 on the relay.

I guess a good idea might be to put in a relay for coil power.

Also, I've come up with a list of connections to check for the fuel pump power supply:
-Fuel pump relay
-C107 (pin 13)
-C190 (pin 2)
-C199 (pin 1)
-G300
-Fuse 11

[saturnv7890]

Check all those connectors and ground, the ground was dirty so I cleaned it till it was shiny again, but now I'm doubting that was the problem.

Video:

https://vimeo.com/70033851

The gauge is fuel pressure, the volt meter is measuring the volts from the output of the fuel pump relay (pin 30) to ground. I blipped the throttle, and the result was an immediate drop in voltage each time. Why??

What should I test from here?