There is a mark on the distibutor body for the #1 plug lead have a look @ this 6N 8v Ignition Dizzy.doc

Thanks for the info confirming the mark on the dizzy.

But I think I'm back to my initial problem that fuel gets to carb but only an initial spray comes out of the single injector and no fuel follows.

- All rubber lines have been replaced, all plastic lines have been air pressure cleaned

- there is gas.

- carb has been cleaned when I brought it down but wasn't disassembled so only passages, etc seen from the external have been cleaned and sprayed with carb cleaner

- injector opens at 12VDC and was ultrasonic cleaned

- throttle body and TPS have been cleaned

- throttle valve is working

Could it be that the fuel pressure diaphragm opens up too soon, making fuel pressure not go through the injector? Spring seems to be OK.

It is like something is telling the ECM not to open the injector after the initial spray. Lambda seems new and replaced by previous owner. And shouldn't the lambda sensor not affect starting as it only gets active when engine is at warm temperature?

Edited 18 September, 201411 yr by HardcoreShad

Is the fuel pump running after it's intial prime?

No, the pump is not running after the initial prime. It only primes when I reattach the fuse 21 from the fusebox. After that, it does not run anymore. So what I did was to install an aftermarket electric pump to bypass that concern. But since the old pump is still installed, I can still determine if the old pump gets juice.

Whenever I pull off the fuel line going into the carb, it has fuel and pressure as I thought the fuel pressure from the electric pump may be a problem.

Could the spring inside the return line area of the carb be the problem? I am thinking of taking that out to make it longer so the pressure builds up more in the injector area instead of going back to the tank.

I did run the pump without the air filter cover and the injector so the fuel is visible when the electric pump is on. And it does a hearty flow. So I doubt if that area is clogged inside.

Either the ECM is not giving full 12v to the injector whenever the engine turns or the injector does not respond to fast 12VDC pulsing. But it does open up on initial spray when the engine is cranked.

Could there be a switch on the clutch pedal or brake pedal that might tell the ECM not to run if it is busted? Or is there a fuel cut off solenoid inside the carb that could be a concern (like the non injected carbs)?

Edited 18 September, 201411 yr by HardcoreShad

I can't find any interlink between the fuel system and fuse # 21 ??? Unless it's something only applicable to the Asian market vehicles and not covered in my dealer wiring diagrams??

In my diagrams the fuel pump relay coil gets it's supply from the ignition on (15) supply inside the fusebox and the earth is provided via the ECU pin 25 (comes out of the fusebox on plug G1/3 Red/Brown 0.5mm wire) The pump power comes from the battery supply (30) via connection in the loom in the engine bay it comes into the fusebox on plug G2/9 2.5mm Red wire and the output from the relay to the pump is via fuse #18 20 amp to plug M/2 Red/Yellow 1.5mm wire to the pump

Here's the testing procedure for the fuel pressure and holding pressure

MonoMotronic Fuel Pressure Test.doc

Yes, the fuse 21 is not the power to the pump but to diagnostics as indicated on the fusebox legend. So when I take this out and reattach it, the pump priming is triggered by diagnostics initializing whenever the system gets 12VDC.

However, when I test the power to the pump with the key on RUN position, it only gets 4-5v. Using both the ground and the power wires of the pump plug.

Thank you for the fuel pressure test! I did not know that doc exists. Will run it through tonight.

Does the voltage to the injector vary from 12v aside from it pulsing? I do not think it is getting full 12VDC on fast pulse but around 8VDC. The initial is surely 12VDC.

Edited 18 September, 201411 yr by HardcoreShad

My list shows #21 is for the interior light, Speedo & diagnostic plug.

There should be 12v on initial ignition ON then 0v then a pulsing 12v as you crank it over, but the pulse is very short (1.5ms) so a multimeter might not register it correctly needs an oscilloscope to see it properly

I see. That is the reason why I only read 8-9VDC on injection pulsing. The multimeter I have only registers what it can capture during the pulse duration.

The doc says .5bar. Surely, the pressure build up exceeds that whenever I pull the fuel line off. Can't find my fuel pressure tester so I am just basing it on what I have seen on other pumps.

But what got my attention was the coded radio phrase on the doc. The polo I have here is equipped with a coded Blaupunkt radio. This could be the one causing the ECM to not respond properly. It would be a hassle to take this out as the dash covers for the radio have cracks so please pardon me for asking this instead of just trying it. I've tried pulling the radio out before but the dash cover is very brittle already.

Would the car run without the radio harness connected? If it is coded and prevents ground pulses to reach ECM, disconnecting it will prevent this immobilizer effect? The radio acts as a trigger right and not a series-connected-device that the circuit needs to pass through it? Radio is acting up on this one, such as turning it on ON will not make it work. The volume knob needs to be pressed all the time to have it turned ON.

Edited 18 September, 201411 yr by HardcoreShad

Here's the info on the injector voltage

Ignore that bit about the radio, it's only mentioned as if you disconnect the battery then reconnect the radio will be asking for the code before it will work again it has nothing to dowith the engine control

Ok, will leave the radio as is then. Glad to know it has nothing to do with this.

The pic of the injector voltage is accurate. That is what happens when I test it.

Here is the rub...VDC on injector wires show pulsing and the initial 12VDC. However, injector only sprays once during the initial 12VDC. If I take off the injector and attach it to a car batt for testing, it opens and closes as fast as I imitate pulsing action with its supply. But fuel does not seem to pass through it after the first steady 12VDC. The first VDC current it receives last about a second or so. Enough time for fuel to get through the injector.

I will try running the injector tomorrow without the "green plastic strainer" (surrounding the injector input holes) as the strainer may have varnished up and ultrasonic cleaning it may not be enough - preventing sufficient fuel volume to pass through the strainer holes. The reaction of the injector after the first spray is that fuel just drips and then engine dies out. Hence, fuel just passes through the return port. I installed a fuel filter after the electric fuel pump anyway so this should be sufficient for the test.

Edited 18 September, 201411 yr by HardcoreShad

That would indicate there is no pressure after the intial pulse, but if the pump is'nt running after the intial prime then you will not have any pressure @ the injector

Yes, correct. The pressure is present before the carb input port. The fuel line leading to the carb has pressure.

The way the electric fuel pump is installed - bypasses the old fuel pump via a separate electrical input provided by an independent relay. Relay is triggered by the ON position of key. Old fuel pump is only electrically connected but does not supply or is not used as a feed line. Feed line of the new electric pump is separate and is anchored to the old pump housing so it gets fuel from the bottom of the tank.

The fuel filter I installed serves as the mini fuel reserve in case it misses on the sipping action.

If there is not enough pressure going to the injector, that means the return spring may be faulty in providing sufficient pressure action on the return hole. Using a higher tension spring may keep the diaphragm from opening too early with the new electric pump installed.

Scenario 2: If the ground and +VDC lines of the old pump are shorted, will that tell the ECM to stop the engine? I remember the heater core flooding the inside of the car twice. And when I was doing the fuse box a few days ago, the bottom of the carpet was still soaked. I will check for continuity of the voltage lines of the old pump then. If that is the problem, I will sort it out.

Edited 18 September, 201411 yr by HardcoreShad

This replacement pump you have installed is it for fuel injection? does it have a sufficient fuel flow rate? as it's sounding like it just cant keep up with the demand! I wouldn't start messing with the regulator springs

The only connection between the ECU and the pump is the switched ground (pin 25) to the original pump relay, shorting the original pump connections will not tell the ECU to stop running.

If you put a 12v supply direct to the original pump will it run? if it does, then reconnect the pipework to standard and see if the injector will keep squirting

Could be! The replacement pump may not be providing sufficient flow.

I will run the old pump tomorrow via a separate voltage source and verify if it would perform under load. But it does run if taken out of the housing. Fingers XD.

If the original pump will run, then you just need to sort out the pump relay, see if the ECU pin 25 is providing a good ground, then if required just rewire a new relay into the circuit to replace the original

I will do that then.

Really hope the old pump will still run... It does prime. The ground connection may just be the prob.

Success Nige!

Updates for today:

- old fuel pump is indeed out-of-order

- and even if I pull out the fuses related to the fuel pump power, the low voltage in that circuit was still present

So I concentrated on getting it running via the new electric pump, which we suspect as having low pressure to the injector. Pressure is strong and fuel flows fast - can fill a 500ml bottle in about 5 seconds. At least that was my red neck gauge since I don't have my fuel pressure tester here.

I then took apart the injector and that foil like substance on the strainer was really bugging me. Injector was then ran without the strainer for testing...and there it was. The sound of an idling engine and power when I crank from the engine bay! Tried turning it off and on for about 3x and it was steady.

i'll do a temporary "fix" on the strainer until I get a new one this week. At least I got it going.

Note: Injector will not seat properly without the green strainer on so I had to break the foil temporarily until the new one arrives.

The Polo will still be tested in the garage tomorrow before test drive. It's now running.

Thank you Nige for the help!

Well you got there in the end ! so another Polo will stay on the road :)