My injectors wont fire

[sammy]

Hi
I've finally got to the point where by MSII is almost complete and installed.

I’ve been running the car on carbs with MS controlling ignition until I could get around to installing the ITB.

Today I finally installed the ITB, Injectors etc.

After I was done, I held my breath and turned the ignition key.

The engine turned over..... but it didn’t start.
I confirmed there was spark, so the next thing was to check the injectors.

I tried running the Injector test mode.
The fuel pump ran and the Test seem to be running, but the injectors wouldn’t fire.

The Megasquirt passed all the tests with the stim when I was building it. so I assume I've got something messed up?

The injectors are high Impedance, 315cc denso injectors. I know they are ok because I bench tested them in
a harness I built before I built the Megasquirt

Is there anything I may be missing?

Sam

[Matt Cramer]

Are you getting an RPM signal?

If you remove the MegaSquirt, turn the key on, and ground the injector output wires at the DB37, do the injectors click?

[sammy]

Hi Matt

Thanks for your help

I just noticed your reply, its midnight and I’m about to go to bed so I’ll try it tomorrow night when I get home from work.

Meanwhile here is some more information about the setup
• I have been running the car on MS for quite a while, but only controlling Ignition up to now.
• Everything else seems to work ok. i.e. I get a correct tach signal, Temp and O2 sensors all ok. The EDIS4 is working fine too.
• On the Weekend I installed the fuel pump and it also works as I expected with about 50 PSI at the fuel rail.

I forgot to mention in my previous post that I’m using a MS relay board.
• I have each injector wired to the 4 x 12v injector connectors on the Relay Board & the multimeter confirms there is definitely 12V on each of them
• I have the remaining 4 wires going to each of the INJ1, INJ1, INJ2 INJ2 connectors. (i.e. 4 wires to 4 connectors)

Tomorrow night I’ll try what you said …….i.e. I’ll disconnect MS, then ground the output wires at the DB37 wiring harness with the ignition on , hence power to the Injectors through the Relay board.
I’m assuming this is to isolate the problem and make sure it’s not somewhere between wiring harness from the MS or the Relay board.
Sam

[trakkies]

Do you have a stim? The injector LEDs on those only flash if the entire MS injection circuit is ok. If they do, chances are it's a problem with the external 12v feed to the injectors. Don't just unplug this and see if there is 12v there with a DVM - it needs to be tested while drawing the current needed to drive the injectors.

[sammy]

Hi Trakkies & Matt

I'll test the 12 volts while it’s drawing the current needed to drive the injectors.
I'm assuming I just need to put a VM across the 4 injector connectors on the relay board to see what the current is like while its cracking or while I'm in Injector test mode?
So it’s to confirm the battery is delivering enough current? The car’s battery is brand new so I’m not sure that’s the problem , but at this stage – I’ll give it a go anyway.

Test #1
1) I unplugged the MS but left the DB37 cable, relay board and injectors all wired up
2) I turned the ignition and confirmed there was 12v going to the 4 injector connectors on the relay board.
3) I inserted a wire into the DB37 - pin 35 and ground it. One of the injectors fired (i.e. it clicked)
4) I repeated this across pin 34, 33 and 32 and all worked successfully.

So I assume this confirmed that the DB37 , Relay board and injectors are ok.


Test #2
I then hooked up the MS to the STIM and started up Megatune.
In Megatune all the gauges seemed to work ok.
I turned the TPS VR and the injector pulse responded accordingly.
On the front of the MS, the LED closest to the DB9 plug flashed indicating that the Injectors were ‘supposedly’ firing.(i.e. Diode14)


I’ll do Trackies test tomorrow night and see what that shows.

I also started reading the MS Trouble Shooting Guide.
It suggests some things to try, but they involve some serious prodding

thanks for your help so far guys

Sam

[sammbo]

I’m sorry but I misunderstood Trakkiespost, It was 2am when I read it the first time and I must have been half asleep
Initially I thought it was referring to the LEDs on the MSII flashing, but now I realize Trakkieswas talking about the LED on the STIM – I hope my response wasn’t too confusing.


Anyway

I pulled the board out of the case and checked over everything and I noticed that C14 is burnt out.
I can’t visually see any damage to other components.

This Cap is polarised, Its too burnt to tell, but maybe I had the polarity around the wrong way ?

I'll put a new one in and see how that goes


sam

[trakkies]

It's a tantalum cap, and sadly these can self destruct for no real reason. After replacement, check you have 12v at pin6 of U4 - and at the positive leg of C14. It sounds like it shorted when failing and may well have damaged a track, or the series diode feeding it.

[sammy]

hi Trakkies

yep your right , C14 and the diode needed replacing, but the track was ok
After replacing them, the injector LEDs are flashing on the STIM again.

Its now time to install it into the car and get a basic idle running - fingers crossed

thanks for all your help with this.
Sam