Author Topic: G40 injector isssues  (Read 3222 times)

Offline mr. clive

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G40 injector isssues
« on: January 24, 2019, 05:18:44 pm »
Hi guys,

I have a 1991 Polo G40 (saloon shell with G40 engine conversion).
A few years back I started having major running issues; car would run for 5 miles then cut out, wouldn't start for 10-30 minutes, then would run for 10 miles and cut out again. this would continue until i finished the 50 mile journey home, the car hasn't started since.

I have tested for spark, good spark. I have checked if the fuel rail is receiving fuel, yes fuel rail receiving fuel. Pulled injector and fuel rail assembly from inlet manifold, cranked engine, and no spray at all, injectors bone dry.

Its had numerous different second hand distributors and even a brand new G40 specific distributor, still nothing (Injectors on G40 are controlled by the hall sensor correct?).

After testing for all other faults i could think of (earths, earth crimp inside wiring loom, ect.) I decided to buy a Kdata ECU for the G40 form their website, hoping the fault was with my ECU or could be diagnosed using MegaSquirt, but after installing and testing i am having the same problem and am unable to see any problems in MS (says the reading for injector pulse width is around 6ms).
The Kdata supposedly came with a G40 specific base map, however, I'm not yet sure how to tell if that is the case as most of the engine constants where incorrect when i first connected MS to the ECU.
Also with the Kdata ECU I'm yet to get a spark no matter what i do with the ignition settings.

So i have;

.Good Spark  (with standard ECU,  but no spark with Kdata MS)

.Good compression

.Fuel rail receiving fuel

.Injectors not firing / not receiving any voltage

so i obviously have an electrical problem somewhere.
Please could anyone suggest any possible causes for the injectors not to be firing or suggest anywhere i could find more info?

Hoping to get this problem sorted soon so i can start to tune using MS  ;D ;D.

Any help, advice or assistance would be immensely appreciated.

« Last Edit: February 05, 2019, 01:36:05 am by mr. clive »

Offline NealPeal

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Can you check there's 12v on the Red/Yellow wire that goes to the injectors while the engine thinks it's spinning. If there's not, that should come straight from the fuel-pump relay output... You can apply 12v just to test, the fuel pump will run too being on the same circuit. (Immobiliser defeatist style-e)

You probably know but to "turn the engine over" plug a spare dizzy in (just the sensor plug, keep the HT leads where they are) and spin the rotor by hand with the ignition on (or mark yours' and pop it off). 4 times a turn it should spark audibly and the injectors should click.
The injectors are all wired together, the ECU feeds a ground to activate release of fuel. Can you stick a meter from 12v to the activation-wire to see if that's reading a quick voltage spike when the dizzy is spinning..?

Worth a try, but I often bark up the wrong tree!!! trust in yourself, that feeling of "fixed it" will soon be yours.!

Offline mr. clive

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Re: G40 injector isssues
« Reply #2 on: February 05, 2019, 01:40:26 am »
Cheers Neal, will give it a go and let you know.

and yeah sorry guys, i didnt end up mentioning what i though of the  Kdata ECU so i changed the thread title,
 will put up another thread with my thoughts when i get the thing going and start tuning lol