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Matt, Engineer
Category: Audi
Satisfied Customers: 20384
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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My 2000 audi a8l cranks but won't start after replacing the

Customer Question

my 2000 audi a8l cranks but won't start after replacing the tranny
Submitted: 2 months ago.
Category: Audi
Customer: replied 2 months ago.
My 2000 audi a8l cranks but won't start after replacing the tranny. The tranny was used. I took the tranny back out to check the the wires to make sure no wires were trapped or broken. I checked the fuses and relays.
Before I changed the tranny i put a timing chain on.
Expert:  Matt replied 2 months ago.


I'd agree that checking for trapped wires is a good idea and its also worth checking that the crank position sensor at the back of the engine is in good condition and not damaged

was the flex plate transferred over from the old transmission? as some have a trigger wheel on the back to provide an engine speed signal

without this the engine won't start

and it would also be worth checking the compressions on all cylinders as this they should all be within 10-15 psi of each other and this provides a rough indication that the cam timing is correct

Expert:  Matt replied 2 months ago.


do you still need help?

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Customer: replied 2 months ago.
I have tried all that you suggested but the car still starting
Customer: replied 2 months ago.
We just noticed that the gear shift goes in all gears but drive 2 . Does the transmission need to be programmed to the car? Or not?
Expert:  Matt replied 2 months ago.


yes the transmission will need programming up to match the engine ECU and car body controller

but it shouldn't prevent it from starting

I'd suggest to do some basic tests

1st check for spark by removing one of the spark plugs and plug it back into its lead and rest iton the metal of the engine ( DO NOT hold it on place by hand) then have your assistant turn the engine over whilst you watch the plug. It should give a fatblue spark at regular intervals.

If not then check that there's power to the coil pack (at the other end of the plug lead) using ameter. If there’s 12V at the pack but no spark then check the ECU power supply(fuse and relay) and also the connections to the crankshaft speed sensor.

If there is a spark and its still not starting then its likely that the ECU isn't opening the fuel injectors, if the injectors are working you can hear them click - its difficult to hear them with background noise so use a long screwdriver like a stethoscope, placing the handle end in your ear and the metal tip against the body of the injector whilst your assistant turns the engine over.

If you can't hear anything check the ECU power is presentby measuring voltage at the fusebox and on its relay socket if OK then check the connections to the crank speed sensor and consider replacing this sensor if the wiring / connections look OK

If the car will start using a squirt of quick/ easi start into the intake then this confirms the problem is lack of fuel

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