jmon92conv

OK, in the search for why my car dies when I reach the stop at the end of an exit ramp, I checked the fuel pressure. while trying this, I noticed that when the valve filled up with fuel, air bubbled up through a leaking valve stem. Is this normal, and if not, can I just replace the valve stem like a tire? Is there a special replacement that will withstand fuel. Also the pressure leaks down from 40 to 0 in just a few hours. Could this be related to the valve, and COULD it PLEASE fix the dying problem? This is driving me nuts.

Jeremy

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92 Z conv
5-spd B&M shifter
home-made ram air, air foil, headers, no cat, TB bypass, kevlar pads, slotted rotors, BMR panhard, alston SFC
when it warms up Edelbrock STB maybe springs

I ROCK

You might have a bad regulator like me. Mine's been stalling lately and I haven't been able to start it back up after a manifold install. have someone start the car, then pinch the fuel return line while watching a guage (hopefully you have one or can borrow/rent/buy one). If the pressure increases when the line is pinched - bad regulator. Don't let the pressure get over 60 psi though.

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89 Iroc-Z LB9 305 TPI auto 2.73 posi:
3" Dynomax "cat" back,K&N filters, TB bypass, 3" pipe in place of cat, cleaned and flow-matched injectors, 180' thermo, mild ignition mods, synthetic oil, kicker sound system, soon to attempt engine swap...

jmon92conv

Thanks rock, I will try that this afternoon.

Jeremy

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92 Z conv
5-spd B&M shifter
home-made ram air, air foil, headers, no cat, TB bypass, kevlar pads, slotted rotors, BMR panhard, alston SFC
when it warms up Edelbrock STB maybe springs

87Z-ya

iTrader: (1)

Thats wrong. If you pinch the return line no matter what the pressures going to go up. What do you think the regulator does? The way to check it is 1. start the car and make sure the pressure is up in the fuel rail. 2. turn the car off and pinch the return line. If the the pressure doesnt bleed off within a hour or so then the problem is the regulator. If it still bleeds off then the problem is the pump. If you have air bubbling up through the schrader valve then its bad and should be replaced. But it should be spiting out gas not air. My car bleeds of with in a couple of hours but thats a characteristic of every svo injector set ive seen.

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87z 383,afr 190's, crane hyd roller(224/230-.509/.528,112 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, strange 12 bolt, tremec 5spd, , 1,3/4" slp headers.

[This message has been edited by 87Z-ya (edited January 04, 2001).]

jmon92conv

Thanks, I am looking for a rubber return line. I bought new valve stems tonight for the valve. Any help on where a rubber line is would be nice.

Jeremy

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92 Z conv
5-spd B&M shifter
home-made ram air, air foil, headers, no cat, TB bypass, kevlar pads, slotted rotors, BMR panhard, alston SFC
when it warms up Edelbrock STB maybe springs

I ROCK

I posted where the rubber lines are on the other board. Basically is you have less than 40.5 psi and there are no blockages in the lines or filter, apply voltage to the fuel pump relay (i just turned the key to ON) and pinch the return line. If the pressure rises above 47 psi the problem IS the regulator. If the pressure is less than 40.5 psi at this point, you probably have a bad pump. This info is straight out of the GM Helm service manual and I can scan you a copy of the diagnosis chart if you need it - just email me.

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89 Iroc-Z LB9 305 TPI auto 2.73 posi:
3" Dynomax "cat" back,K&N filters, TB bypass, 3" pipe in place of cat, cleaned and flow-matched injectors, 180' thermo, mild ignition mods, synthetic oil, kicker sound system, soon to attempt engine swap...

JakeJr

I think we have some mis-communication here.

First, when the key is turned on the fuel pump is energized for about 2 seconds. If the ECM doesn't receive a signal from the distributor within that time, the fuel pump is turned off. A leak anywhere in the system will cause the pressure to drop almost immediately after the pump turns off.

Now comes the task of finding out where.

If you wire the relay and send the pump 12 volts then pump remains on. If you then clamp the fuel return line, what would you suspect will happen to fuel pressure?

If all is well within the engine the pressure's going to build and build and build until it reaches the max pressure that the pump can output. It's going to build because there is no way for the excess fuel to be returned to the tank. What you've done, in effect, is create an UNregulated fuel pressure situation.

If the injector(s), regulator or Schrader valve are leaking, the the pressure will not build as high because the pressure has an avenue of escape. Fuel will enter the intake manifold (injector), be forced into the vacuum hose or onto the manifold (regulator) or squirt/drip all over the engine (Schrader valve).

What you can do is this. Turn on the ignition key which will energize the pump and while the fuel pressure remains clamp the return line (or clamp the line then turn on the key). If the pressure holds you do not have an injector/regulator/Schrader valve leak. If it doesn't, you do.

Next you need to energize the pump and clamp the pressure line. If the pressure begins to fall rather quickly, it's at the pump; probably the pulsator/vibrator or whatever they call that gizmo attached to the pump. You've already eliminated the possibility of a leak up to the front, so it's got to be going to the back.

Hope this helps.

Jake

BTW, some guys remove and replace that gizmo with a piece of gas line using screw clamps. I've never tried it so I can't vouch for how it works that way.

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9



[This message has been edited by JakeJr (edited January 08, 2001).]

jmon92conv

the pump is only a year old. when I clampo the hose I loose about 10lbs for 30min. Is this a lot for an injector? Hell, this is my first tpi and I don't know. BTW there has not been a decrease in performance that I can tell, what is the harm of just letting it go for awhile?

Jeremy

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92 Z conv
5-spd B&M shifter
home-made ram air, air foil, headers, no cat, TB bypass, kevlar pads, slotted rotors, BMR panhard, alston SFC
when it warms up Edelbrock STB maybe springs

I ROCK

That's true but I was only relating what the Helm manual says. It also says to only do the test if you get less than 40.5 psi at idle, and if clamping the hose makes it go above 47 than the regulator is bad or else the regulator would get it over 40.5 since the pump is ok. even though ohm testing is not a valid check for leaking injectors, it can tell you if they are bad. Hook up a voltmeter and test to see if they are all around 16 ohms. if some are below 14 and especially below 10 they need replacing b/c the coils are bad in them. hope that helps

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89 Iroc-Z LB9 TPI auto 2.73 posi:
3" Dynomax muffler, K&N filters, TB bypass, 3" pipe in place of cat, cleaned and flow-matched injectors, accel 300+ wires, cap&rotor, synthetic oil, flexlite transmission cooler, afpr, !air pump&diverter valve, kicker sound system, soon to attempt engine swap...