3tgte not starting - problem solving steps

[mattlock]

Hi all,

I need sum fresh thoughts thrown my way.....
I have just finished building my mates 3tgte in a ta22 all wiring had been previously done bout 15 years ago running standard comp and knock control so has all still in place. was running b4 we took out engine a month ago, but my mate decided to re rute all wiring behind fire wall and did seem to do a good job as everything has signal or power.
when we crank it it starts for about 3 seconds then cuts out..... Has spark.. timming is spot on, has fuel in rail and pressure. TPS is good, injectors have power/signal, seems to be running out of fuel, one weird thing is the fuel pump dosnt prime, works on crank then continues to run when fired, but has always been wired like that. Could it be running on cold start injector only??

Would be a big help if anyone out there has had this b4 or could chuck an idea my way

Cheers

Matt.

[frag_dog]

I've just got mine going again after re-wiring and it wouldn't start. Turned out I wired the pump the wrong way around..... But if your getting pressure then that wouldn't be the issue.

[79GT]

hey mate, when you say the injectors have signal, can you actually here them pulsing....

i had an issue with mine where one of my injectors where locked open, and none of them where firing....this being said mine didnt start initially for a few seconds. (but mine also hadnt been run in years). I replaced all 4 injectors with a spare set i had and i got her running. (after a fair bit of priming). sounds like something similiar may have occured.

if he hasnt changed anything mechanical on the engine since last run, it would be less likely there would be anything else seriousely the issue, and since you say he has signal at all places where necesary it doesnt leave many things.

Injectors being the nature they are (electrical coil etc) it is very possible one may have just carked it. keep in mind, if one isnt working none will work..

Good luck, keep us posted.

[mattlock]

Thanks guys, yeh im gonna change the injectors and re-wire the fuel pump to see if i can get it to prime at ignition, thinking it may be injectors as i forgot to mention above we have re-built a spare motor he had after he dropped a timming chain, didnt change injectors as the ones on the spare motor lookd to have much better seals and clean jets..... but at least i know the other ones work.......
The injectors have power at them but i havnt checked the resistance while cranking.

Cheers

[79GT]

yeah that would make a lot of sense.

get onto those injectors, if some have a better flow/seals just change one at a time till they start working.

easiest way to test if they are getting the correct signal un plug all the injectors and connect a globe up to one of the plugs. the light should pulse, if they dont when all plugs (injector plugs) are unplugged there is an issue with ecu or wiring. If they do, swap in those other injectors and see if she runs.

[3jcelica]

The fuel pump should only run when cranking and when air is flowing through the air flow meter (there is a switch on the air flow meter vain), as you have found.

It is done this way for a reason, i.e the fuel pump will not run unless the engine is running, particulalry important in an accident. If you wire it to the ignition then regardless of engine running the fuel pump stay on in an accident, not ideal.

if you need to prime during testing or getting the thing running put your hand down the air flow meter and move the vane.

Sounds like your injectors I have a spare set and in SA if required.

Use an LED test light (a globe does not provide the resistance required and could overload the computer injector drivers) on the injector plugs while cranking to check you are getting a pulse signal.

Roger

[79GT]

wow, i was unaware there was a switch feed from the afm to the fuel pump....learn something new everyday. (can you wire this feed directly to your fuel pump relay)....

anyway, roger what you say about the led test light is on the money, and i should have been more specific about the globe.

i looked for an LED test light and none of the general autostores even new what they where...regardless....idealy get an LED test light, but i couldnt, so i found an indicator globe i had lying around that had a high resistance. (ie needed a high amperage to glow bright).
On testing the filament barely glowed, but it did show a pulse and that is all i was looking for. all in all no harm done, prob a bit dodgy but it did the job.

GL.
on ya roger.

[mattlock]

Thanks heaps, the injectors are now out, 2 of them looked dodgey dropped off 8 to get tested and cleaned and will use the best 4. The fuel pump primed fine by moving the vane in the air mass so hopefully it is just injectors.

Cheers once again,

Matt.

[mattlock]

Hey guys, still no luck getting this 3tg fired on the main injectors... need to know how there sposed to be wired, we have power at them at ignition at both sides of the plug... is this normal?? the cold start power slowly fades on during crank dull on side of the plug a litlle brighter the other, i thought this would be how the main injectors would work, but they have 12.3 volts at both sides?? car only still runs for about 3 seconds then cuts out, dose this wether main injectors are pluged in or not, even dose it when ecu is unpluged. Was running b4 but we did re-rute some wires while swapping engines, is wire to temp sensor on standard loom meant to pulse? ours dose sold at ignition then after a couple of seconds starts to pulse???? WTF? any help please we need to get this fresh engine started

Cheers

Matt.

[frag_dog]

Your injectors should have 12v at both sides, but only one side connected to the 12v IGN. One side hooked up to IGN Power, the other to the ECU and the ECU earths the injectors to cause the magnets to fire the injectors.

If it will run without injectors hooked up, it sounds like they are leakng, and pretty badly.

Grab your mulitmeter and check the resistance on the injectors. I can't remember exactly what the resistance should be for stock 3T injectors, but Google is your friend. Also, make sure you are getting 12v at the ECU plug where the injectors connect.

[wa5]

Is the Fuel pump continueing to run after you stop cranking the engine...?

If not, is it possible to "hotwire" the pump.....

is there a decent earth from the block to the chassis?

[WDE_BDY]

Check all your earths, especially the ECU.

[mattlock]

thanks, i'll try all earths, all injectors are reconed, we ended up taking 12 to get tested and used the best flowing 4.

keep ya posted.

cheers

Matt.

[3jcelica]

Matt,

On the standard 3tgt computer, there are a couple of pressure switchs, one with a fuel cut based on boost pressure and one with a fuel addition again based on fuel pressure. These are designated Pf and Pc if I can remember correctly.

If you are not running the pressure switches then both the fuel cut and the fuel addition one needs to be earther.

If the fuel cut one is not earthed then the injectors will not pulse. The measurement you have for the injector voltages seems correct.

Sounds like you are running off cold start which does not require the computer to run. You really need to check whether you are getting a pulse on the main injector connections with a test light, if you are not getting the pulse, what I mentioned above is the most likely cause. If you don't have it running by the weekend I might come down and take a look if thats ok.

Roger

[3jcelica]

Matt,

On the standard 3tgt computer, there are a couple of pressure switchs, one with a fuel cut based on boost pressure and one with a fuel addition again based on boost pressure. These are designated Pf and Pc if I can remember correctly.

If you are not running the pressure switches then both the fuel cut and the fuel addition pin outs need to be earthed.

If the fuel cut one is not earthed then the injectors will not pulse. The measurement you have for the injector voltages seems correct.

Sounds like you are running off cold start which does not require the computer to run. You really need to check whether you are getting a pulse on the main injector connections with a test light, if you are not getting the pulse, what I mentioned above is the most likely cause. If you don't have it running by the weekend I might come down and take a look if thats ok.

Roger