Hey guy's,

Believe it or not, I still have not got the damn race car to fire up. After checking everything that had been previously suggested (and More), i put it on hold while working on other areas of the car. Now it's time to get serious......

We have tracked the problem down to the wiring of the injectors (we think)..... the car will start on Aero start, we have good fuel flow to the rail, and it is holding pressure at the rail. The injectors have been tested and are fine (Bosch Motorsport 550cc). I have had someone who knows Motec help set the CrIP, which is shown in the car firing on the aero start.

Here are the current symptoms......

1.When you first crank the car, it goes to fire...sounds very promising, but after that is basically dead until you turn the ignition off and then on again (resetting the Motec). When you try to crank after restting, it does the same, tries to fire initially...then nothing.

2. When doing the diagnostic test...... the injector will test OK for about 2-3 seconds.... then a weird message flashes on the screen. The messages says something about being unable to test due to the engine running?????? Which of course it is not.

3. All injectors have been tested while cranking, and all of them are pulsing.

The question is....are the first two symptoms related?...I think they are.

Has anyone come across this before, or know what may be causing this?

We have also tried increasing the Overall trim on the fuel...right up to 50%. The result on cranking was the same. We checked the plugs...and they did not show signs of bathing in avgas....which should have been apparent with 50% overall trim added. They did show signs of fuel getting in there, but I think this is from the initial cranking...... and then for some reason the injectors are not doing there job.

Sorry for the long post..... any help will be greatly appreciated. This thing is driving me INSANE!

_________________
www.full-throttle.com.au
www.boostcooler.com.au

When the Flag drops........... the Bullshit stops
Go hard or go home!

What ignition switch? I didn't think you would have this problem on a sunny but on the 1600s we have problem where the accessory +12v switches off when you turn the key to 'start'. Most people use that for the ign 12v to the ECU so get caught out when they turn the key to start!

PS Just checked a sunny manual and looks like you could have this problem!

Not using the standard Sunny ignition switch....

I am using a master kill switch/ isolation switch....than a toggle switch for ignition on...and a start button wired directly from kill switch to starter.

Therefore the starter can turn wether the ignition is on or off.

_________________
www.full-throttle.com.au
www.boostcooler.com.au

When the Flag drops........... the Bullshit stops
Go hard or go home!

yeah this problem crops up a lot when people switch to fuel injection. i'd put money on zac being right.

_________________
1971 Datsun 1600 - Z18ET
1996 Suzuki RGV250 VJ22
1996 Suzuki RGV250 SP VJ23

OK scratch that one

thanks anyway...... any other ideas, we have been racking our collective heads..... can't seem to pin point the problem.

I believe it is something to do with the injectors not firing after the initial cranking..... but I don't know why we are getting injector pulse. it's bloody strange.

We know it is definately a fuel issue...as we sprayed some Aero start down it's throat and she roared into life....and roared pretty smoothly.... no back fires etc.

_________________
www.full-throttle.com.au
www.boostcooler.com.au

When the Flag drops........... the Bullshit stops
Go hard or go home!

Do you have to 'tell' the MoTec about the injector impedance?
Are you getting a solid rpm signal on cranking?
Disable the secondary ignition system & run an injector into a container - do you get a nice spray?

_________________
Ben
Adelaide,
South Australia
L28ET 240Z
RB25DET WGNC34 Stagea RS-FourV

Checked the impedence of the injector....1ohm.....this was checked with the computer...everything seemed fine.

Definately gettig solid signal on cranking. Rises and falls when the engine kicks.

Injectors were flowed tested recently... all had good spray. As there is good pressure at the rail, the injectors must not be opening.

_________________
www.full-throttle.com.au
www.boostcooler.com.au

When the Flag drops........... the Bullshit stops
Go hard or go home!

Have you considered what inputs could be acting to shut the injectors down? Eg there may be a sensor that is giving a false reading or is being wrongly interpreted.
260DET, definately not a MoTec guru.

260DET,

Someone suggest that the computer may be receiving some interference or something weird when the injectors fire. This inturn tricks the computer into thinking that the engine is turning.

This is certainly one thing we will investigate further. I think if we can solve the problem with the injector test.....we will go along way to solving the problem completely.

I might try removing the Crank angle sensor (Hall effect) wiring from the loom..... to see if that makes a difference. It is bound to be something simple. This engine combo has run previously, so it has to be something that happened when either removing from the old car, in storage, or during installation in the new car....... just need to track it down prior to losing my mind completely.

Thanks for the help.

_________________
www.full-throttle.com.au
www.boostcooler.com.au

When the Flag drops........... the Bullshit stops
Go hard or go home!

Indeed, what I meant was crank the engine with an injector spraying into an alternative vessel & make sure that it is opening & delivering fuel via ECU control.

Another alternative is to manually trigger the hall effect with a ferrous body (thin screwdriver etc), or turn the dizzy by hand (if practical) to 'fake' rpm's.

_________________
Ben
Adelaide,
South Australia
L28ET 240Z
RB25DET WGNC34 Stagea RS-FourV

The injector test you describe could be very difficult. The injectors plug straight into the rail, so have no "tails" attached, makes it difficult to aim one injector in a different direction.

Motec have told me that the only way the injector test would be stopped in the way that it is, is if the "ref" input wire is receiving voltage from somewhere. The fact that the error message pops up only after starting the test indicates that when the injector(s) fire, there is some sort of electrical "noise" leaking into the ref wire. If it is not that, then the Hall effect is sending a signal for some crazy reason.

Also, they suggested I check the resistance of the injectors, at the ECU end of the loom, to make sure there is not a large drop in voltage through the loom. This could result in a lack of voltage to drive the injectors - but still have enough to show pulsing on the node light.

Thanks to everyone for the suggestions, I'll report back later in the week with results...hopefully the car will be running very soon.

Mark.

_________________
www.full-throttle.com.au
www.boostcooler.com.au

When the Flag drops........... the Bullshit stops
Go hard or go home!

can u get access to another computer to test the motec system it self, I know I got the wrong computer when I got my half cut and my would kick but didn fire, like they said are u running constant power to the injectors and also to the computer, how is the ignition switch wired??, I have the switch goin to relay that way the computer is getting power on turn over.

_________________
====================
Cheerio

Mick Taylor
http://www.drive.to/MT510
SR20DET Datsun P510/1600
OZDAT MEMBERS PAGE
http://www.ozdat.com/forum/viewtopic.php?t=8470
====================

Mick,

I can get hold of another Motec, but that will be the last resort. I have had the Motec checked previously, it was found to be ok..... so that shouldn't be a problem. Also, people get funny when you start changing the programming in their computer - even though it can be saved and re-installed.....just one of those things I guess.

Thanks for the tip.

_________________
www.full-throttle.com.au
www.boostcooler.com.au

When the Flag drops........... the Bullshit stops
Go hard or go home!

datman,

I'm no MoTec guru, but I've seen similar problems when wiring up factory systems. Most systems have a safety mechanism which will ensure that the EFI pump shuts down if the engine stops turning (helps prevent fuel fires in the event of an accident). This often trips people up as the system will force the fuel pump on while it is getting the cranking signal but once that dissappears the fuel pump stops. Mazda do this by having a switch in the airflow meter which holds the fuel pump relay closed - as long as there is more than zero air flow the switch remains closed. Obviously your MoTec doesn't use an airflow meter but maybe they do it some other way?

I'd suggest that you monitor fuel pressure (or just put a test light on the EFI pump terminal) and see if the fuel pump is being turned off once the engine fires.

Another test would be to monitor the 12V going to the injectors. Make sure it remains there after the engine fires.

You could also try disconnecting the wires from ECU to injectors and then manually batch fire them by just tapping the injector -ve's to GND while cranking the engine (and furiously working the throttle!). I've done this and it works fine.

If it will run with aerostart then the EFI system is basically happy as it is firing the plugs so I suspect it will also be sending a signal to fire the injectors.

Good luck
PL