Thread: 86 classic over fuelling (flapper injection)

Three things worth checking before you buy in parts

1. Fuel pressure regulator, check pressure, check vacuum hose, check for fuel leakage into manifold.

2. ECU temp sender at front of inlet manifold, check warm resistance.

3. Return line to tank, check for blockage, put a temporary line to a Jerry can or to the tank filler neck.

Originally Posted by bee utey

Three things worth checking before you buy in parts

1. Fuel pressure regulator, check pressure, check vacuum hose, check for fuel leakage into manifold.

2. ECU temp sender at front of inlet manifold, check warm resistance.

3. Return line to tank, check for blockage, put a temporary line to a Jerry can or to the tank filler neck.

Will these things effect injector opening time?
Like my train of thought was the ECU is holding injectors open too long?

But you're saying high fuel pressure, is pumping more fuel in and, while the injectors are opening at their normal rate?

I was thinking the AFM potentiometer is faulty and telling ecu, full throttle all the time,
Or ecu is just assuming full throttle..

i've had fuel pressure regulators die causing huge pressure in the fuel rail, so massive overfueling.... the reason bee-utey mentions the temp sender is if it is unplugged or dodgy the wiring.... the car will think its minus fifty degrees and massively overfuel the engine.... same deal with blocked fuel return, this will cause huge pressure in the fuel rail, so overfueling.

I don't like just throwing money and parts at something ..... hoping that'll fix it. much better is to figure out exactly what is wrong, then buy only what you need!

seeya
Shane L.

Thanks Shane that makes perfect sense.
I was looking at it all wrong.
I've got a Haynes manual and it's a good read in conjunction with what you guys have said.
I shall go Tinker.

Also thanks bee-utey .

Originally Posted by Grunter620

Will these things effect injector opening time?
Like my train of thought was the ECU is holding injectors open too long?

But you're saying high fuel pressure, is pumping more fuel in and, while the injectors are opening at their normal rate?

I was thinking the AFM potentiometer is faulty and telling ecu, full throttle all the time,
Or ecu is just assuming full throttle..

The easiest way to check the AFM is to pull the lid off and manually operate the potentiometer to adjust fuelling while its idling. You can also measure voltages while the ignition is on, engine not running. Temperature and pressure are of course just as important to correct fuelling, 25% too rich and it won't run properly.

Oh and injector on time can be measured by suitable probes, or just wire up a LED test light and see how it visually changes with different AFM positions. Adjustable fuel pressure regulators can be bought at stores complete with pressure gauges, usually bought by ricer boys for their turbo toys.

I am having similar issues with my 89 currently. Except mine will run without a fuel pump. Even fitting a rising rate regulator, blocking vac line and clamping return line, it will run, albeit richly. It will die out if I clamp or remove the supply line.

Currently waiting for a set of injectors, as the spray pattern was woeful when tested out of the engine. So I am hoping that they are so stuffed that vacuum was drawing in through them.

The reason for this conclusion was that all electrical tests in the manual came back spot on.

AFAIR the flapper has a cold start injector at the RH rear of the manifold. There is also a Thermo time switch at the front.
If the Thermo time switch malfunctions the cold start injector stays open. You can disconnect the cold start injector to see if it makes a difference.

Regards Philip A

Cold start injector has been disconnected for testing.

New plugs and leads. Old ones were fouled enough to stop it even starting.

Still has a miss at high idle, and fuming out the rear..

Next is check air temp sensor.
Any tips?