1g-gte misfiring on first few seconds of startup - common?

[auto351]

I have got a better wiring diagram and the Circuit Opening Relay has two coils one from the start line & the other from the air flow switch. (this provides power to the fuel relay) the fuel pump relay has two poles and a resistor which switches during starting this gives about 9V to the pump at all times (even during starting).

To prove the problem is related to the delayed pump start & low fuel presure. the pump would need to be wired to the ignition for testing (keping the fuel relay in circuit) . dont know how hard that is do.

Any other ideas ?

[jimmmayyy]

he could just check the fuel pressure.

[RA35GT]

Most bosch fuel pumps contain a one way valve in the outlet. to stop the fuel rail losing pressure when the pump isn't on.

The return to the tank is via another hose. The fuel pressure regulator maintains the fuel pressure in the rail and only bleeds excess fuel to the tank to maintain pressure.

[jimmmayyy]

do toyota pumps have one? (bosch?) i've never had to take one out.

in any case, overnight the pressure will drop as leakage and cooler temperatures take effect.

[auto351]

sounds simple but may be difficult to watch presure and see if it coincides with the misfire, we would need to know the minimum working presure of the system??..

[RA35GT]

Not sure on factory systems, but the point is, if everything is working properly the fuel pressure will only drop if fuel is leaking back through the fuel pump. otherwise its stays pressurised.

[M_Green]

To update my earlier post, i started the soarer cold after a week of sitting there and it started fine, straight up to 1k-1.5k rpm. No hesitation.

[timbosaurus]

one way valve????

i think you are misunderstanding the whole concept of a return fuel system there matey. excess fuel is returned to the tank, it doesn't stay pressurized; only if the pump is running.

Not quite true. Excess fuel is only ever 'returned' when the rail pressure exceeds the regulator's set point.

As soon as the engine and fuel pump shuts off, the rail pressure will only drop to zero if it bleeds back through the pump. I'm not sure what pump you're running, but my 044 has a one-way valve in it to ensure rail presure is there waiting

[jimmmayyy]

yup.

actually it'd be interesting to see how much of a drop in rail pressure there would be leaving the car overnight.

[auto351]

a) is fixing the problem as simple as fitting a seperate one way valve.

b) or do you need to add a timer to run the pump on startup for a while

im thinking as the injectors age they will not hold the presure for long periods (12hours) so option B would be the sure fix ?

[Z2TT]

Hi,

So would it be fine if I get a one way valve and fit it in the fuel line that goes from the Tank to the engine, just to see if that makes any difference?

Could leaky injectors cause this problem on startup, as fuel would flood the combustion chamber causing it to hesitate especially when the engine is cold?

If that could be a possibility how do I determine if the injectors are leaking?

Thanks.

[Z2TT]

Double Post

[timbosaurus]

fit a rail pressure gauge.

[auto351]

fit a rail pressure gauge.

before fitting the valve, if you can mesure the presure on both your car and a car which dosn't have the problem.

if the problem is caused by leaking injector flooding one cylinder, then fitting the timer or the one way valve would not fit the problem.

Manuel

[cambelt]

Very very slight BHG will do this but not show any real signs of BHG . Take the plugs out after a week of sitting and crank it and see if you have any moisture.
Dave