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Manual conversion on vq25det (No Spark) need help

roadhazzard1
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roadhazzard1 Apprentice

roadhazzard1

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Posted

Manual conversion on vq25det (No Spark) need help

Hi all

have just finished transplanting a vq25det into a v35. We have used a z33 6 speed manual gearbox and clutch to bolt it all together. everything is in the car at this point and for some reason we are not getting any spark. 

I read that the starter motor relay needs to be bypassed so am using a trigger wire and button to turn the motor over while ignition is set to 'ON' (this will be relayed off ignition circuit later) 

The v35 has been converted from returnless fuel to return setup to suit the new motor 'vq25det'. Fuel pump is currently relayed triggered by 12v ON circuit so we definitely have fuel reaching the rail.

The idea was to get the car running on the standard ecu before going haltech and front mount turbo in future. We have the matching ecu from this motor so auto turbo stagea ecu. currently the auto transmission error light flashes with the auto gearbox ecu unplugged and it stays solid if the gearbox ecu is plugged in while trying to start the vehicle. currently the plugs that would have gone to gearbox are not plugged into anything as the manual has almost no sensors. 

My belief is that the car cannot tell if it is in P when trying to start the engine so it is stoping the motor starting through no spark even though we are forcing the starter motor on. 

Any thoughts on putting a resistor in the right place to trick the ecu into thinking it is in Park so the motor will start?

the only other thing i can think off is the immobilizer due to a different ecu but its still the same key and lock barrel? 

Any advice would be great.

Thanks all

20170709_152936.jpg

Duncan Grand Master

Duncan

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Posted

Well firstly, I'm not familiar with VQ series so I might mislead you...

You didn't say what actually happens when you try and start it? Does it crank but not fire? Does it crank quickly?

When you say you know it's not fuel is that for sure? I would run the fuel hose return to a bucket/jerry can/whatever temporarily and crank it to see plenty of fuel coming out. If so I'd take the CAS off, turn the ignition on and listen for injector clicking as I turned the CAS. Also, do you have some sort of fuel pressure gauge to be sure the base pressure is right?

With the spark I'd take a coil pack off, put a spark plug on it and crank to look for physical spark at the plug

Do you know the timing is right? That would also stop it starting.

And yes, I would expect an auto will not start unless you have bridged the neutral and/or park signal at the auto loom. If you don't want to connect the auto loom wires to the gearbox neutral switch at least bridge the park wires. No resistor required it will just be either a simple connected (or not) circuit that you can bridge. But I guess it will not even crank unless the park or neutral signal is there (maybe that's why you said you needed to bridge the starter solenoid)

Finally, the ECU probably needs a start signal as well as the starter motor. So if your bypass does not apply 12v to the start signal at the key the ECU may have decided the engine has stalled and to turn the fuel and spark off.

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roadhazzard1 Apprentice

roadhazzard1

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Posted (edited)

Thanks duncan that gives me alot to work with.

Id say your righr about the gearbox because the injectors are not clicking either. I can force fuel in with 12v relay direct to pump but this isnt triggering off the stock ecu wire either. 

Going to spend some time today trying to figure out which is the neutral switch plug and try jump it. The motor came out of a running car so should be setup ok. 

Thanks for the help will update if i have a win.

Edited by roadhazzard1

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