V8 fuel injectors.

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Originally Posted by bee utey

Low voltage might slow down the injectors opening time if the ECU switches the whole battery voltage across the injectors plus resistors. Be interesting to confirm with an oscilloscope.

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That word again.. oscilloscope..

From my reading, the resistor should only allow 3v to pass through each injector, totalling 12v at the ecu. This is happening. The new injectors are 2ohm compared to 3ohm of the originals.

I cant be sure what's happening. I have had it started and running, albeit a bit rough, since the last post and the alternator amps are back to 35 currently. Used to hover around 15amps when driving.

Well, I think I have it going..

Although we shouldn't say anything too loud as it can still hears us.

I'm not sure as to how or why, but winding the CO screw right in and backing fuel off to 36psi seems to have helped.

Have been for a couple of drives with and with AC on and it has been it's usual slow self!

Going to apply some car wash and have another shot.

I have a feeling it's not over yet though.

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Originally Posted by Konradical

That word again.. oscilloscope..

From my reading, the resistor should only allow 3v to pass through each injector, totalling 12v at the ecu. This is happening. The new injectors are 2ohm compared to 3ohm of the originals.

I cant be sure what's happening. I have had it started and running, albeit a bit rough, since the last post and the alternator amps are back to 35 currently. Used to hover around 15amps when driving.

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If a 3 ohm injector runs at 3 volts, a 2 ohm injector will run at a lower voltage unless you change the series resistor to a lower value too. Not sure what voltage your 2 ohm injector needs but you may not be getting it. Making sure your alternator can supply a guaranteed 14 volts might be beneficial, perhaps you need a bigger one.

Quote:

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Originally Posted by bee utey

If a 3 ohm injector runs at 3 volts, a 2 ohm injector will run at a lower voltage unless you change the series resistor to a lower value too. Not sure what voltage your 2 ohm injector needs but you may not be getting it. Making sure your alternator can supply a guaranteed 14 volts might be beneficial, perhaps you need a bigger one.

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Well I can't right now and I think it's because of a half dodge battery.

Some time ago I found a online article about the poor alternators in RRCs and a alternative from a VW. I managed to find one that fit the instructions given and as a result I now have a 140amp Bosch alternator from a VW Golf.

The reason I did this was since the installation of my Redarc volt gauge with amp readout, I found the standard alternator was running at about 60amps with dual batteries, AC and spotlights going. After say 5 minutes the alternator must have overheated then cut out, not cutting in for some time. Now with the VW one, I can drive 15hrs straight and it just charges.

The battery is a bit on the south side from sitting around and I guess a charger not really keeping it super. I have seen funny things with unhealthy batteries.

Saying that though, I do honestly think there are a few elements at play with this issue. Haven't started I yet since I washed it, just cleaning up, bit I do wonder if it will behave..

So it must of heard me..

Now won't start again..

I washed it, but was ultra careful not to get water within one hundred metres of the engine..

So in frustration, it will fire up with aerostart, but won't go on its own. It has fuel pressure and I have jumped the fuel relay to have contact pressure while I crank and still nothing.

I will test for power at the injectors again and if there is, there is some buggery going on in the ecu. It's the only thing..

The ECU needs power from the ignition switch to turn on the EFI relay, test the white wire or white/green stripe wire at the harness plug by your left foot. Then check the relevant relay next to the ECU.

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Originally Posted by bee utey

The ECU needs power from the ignition switch to turn on the EFI relay, test the white wire or white/green stripe wire at the harness plug by your left foot. Then check the relevant relay next to the ECU.

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I will do that and get back to you..

Just a wild thought.
There are two wires that run to the coil on the old 3.5s.
One is a resistor wire and is white AFAIR.
The second wire is just a wire.
The normal wire is on a blade connector on the starter while the resistor wire goes form the ignition switch.

The plain wire is to give 8+volts to the coil while the starter is cranking and creating voltage drop and as soon as the engine fires it switches to the resistor wire which supplies 8 volts to the coil.

If the plain wire falls off the starter , it is sometimes very hard to start the car as it depends on the engine catching while still moving after the starter has been released.

Regards Philip A

Quote:

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Originally Posted by PhilipA

Just a wild thought.
There are two wires that run to the coil on the old 3.5s.
One is a resistor wire and is white AFAIR.
The second wire is just a wire.
The normal wire is on a blade connector on the starter while the resistor wire goes form the ignition switch.

The plain wire is to give 8+volts to the coil while the starter is cranking and creating voltage drop and as soon as the engine fires it switches to the resistor wire which supplies 8 volts to the coil.

If the plain wire falls off the starter , it is sometimes very hard to start the car as it depends on the engine catching while still moving after the starter has been released.

Regards Philip A

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Electronic ignition as fitted from 1985 onwards doesn't run a resistor coil system, just straight 12V from the key.

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Originally Posted by Konradical

I will do that and get back to you..

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Ok.. as follows..

REF Battery voltage 12.68V

Ignition wire at EFI relay:

Ignition off 0.5V (difference between earth points)
Ignition on 11.47V and will drop to 9.8V on crank.

Relay has a audible click and can be felt actuating.

With ignition switch on, there is 12.46V at pins 30, 87 and 87a.