Very unusual no-start condition

[Dave532]

Gentlemen,

I have an extremely difficult no-start condition on my rally car ('90 Talon tsi) I wanted to throw by you.
I haven't rallied this car since 2006...it's been stored and not running since then.

This spring I patched everything up and tried to start it...here is the problem:
The fuel injectors will not fire during cranking only. They DO fire for a second when the key returns to the run position.
I can 'prime' the engine by hand turning the cam sensor (key in ON position)which fires the injectors. The engine will then start and run fine. It will even start again as long as there is still some fuel remaining in the cylinders.

I have swapped\tested the following with no change in behavior:
ECU
cam sensor
fuel injector resistor
water temp sensor
grounds (ground directly to battery now)
Main power relay
unplugged the TPS
fuel pressure is good
spark during cranking

Bottom line is no fuel injector trigger during cranking only.

Since there is spark I can't believe it's the igniton switch but maybe I am wrong.
Motor is completely stock.

Anyone have any ideas?

Thanks,

-Dave
#532

 

[Maverick4g63]

Your sure the fuel pump is maintaining pressure once the ign cyclinder moves from the start cycle to the run position? It sounds like its using the remaining fuel in the line and then dying.

 

[Dave532]

Yes, the pump maintains pressure during cranking (I open a fuel port required for racing) and it also maintains pressure during run.
The difference being during crank the injectors won't fire.
During run, the injectors will fire if I turn the motor over (turning the cam sensor by hand) like they are supposed to.

While cranking the motor spins and spark plugs fire but injectors don't open. I am assuming the ECU isn't grounding the injectors and completing the circuit.
But I don't understand why the computer is happy to fire the injectors during run and not crank. I figured it may have been a lazy ground so I grounded all the 'grounds' right to the battery. No change.

Thanks,

-Dave
#532

 

[Dave532]

Problem solved.

The injectors were actually working but their pulse signal was extremely short. The reason for that was because the coolant sensor was open...telling the ECU that the engine was hot and needed very little fuel to start.

-Dave