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Matt, Engineer
Category: Audi
Satisfied Customers: 21626
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Have 2001 audi tt 1.8l. just completed a valve job .got

Customer Question

hi,have 2001 audi tt 1.8l. just completed a valve job .got engine all back together and engine wont start. have good spark,and good fuel pressure up to fuel rail but no injector pulse. here is what i have tried so far.replaced crank sensor, double checked timing marks,all connections,all vacuum lines .computer is saying there is low voltage to the system so i replaced the battery,and still no start.please please HELP.
JA: How old is the battery? And have you tested it with a voltmeter?
Customer: i replaced it with a brand new battery.
JA: What is the model of your '01 Audi?
Customer: tt 1.8lt not a quattro.
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: double checked all connections,vacuum lines,timing marks,replaced pulse sensor.crank sensor,and new battery.
JA: Anything else you think the mechanic should know?
Customer: i am a little embarase about the screw up and i am not putting the blame on my brother in law but i am pretty sure he put the head gasket in up side down. when we started the car it ran awesome until i discovered a massive oil leak shortly after starting the car. it was when we put the engine back together that it would not start.
Submitted: 1 year ago.
Category: Audi
Expert:  Matt replied 1 year ago.


I'd start with some basic testing

1st check for spark by removing one of the spark plugs and plug it back into its lead and rest it on 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 fat blue 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 a meter. 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 present by 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

Also its worth checking that the electric pump that feeds the injectors is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If you remove the filler cap to the fuel tank and listen inside while your assistant flicks the ignition you should hear it clearly

if this is all OK then I'd do a compression test across all cylinders as they should all be within 10-15 psi of each other

Customer: replied 1 year ago.
all the things you have suggested have been done.motor has strong spark, and good fuel pressure up to the fuel rail.there appears to have no injector pulse.dont know were to go from here.
Customer: replied 1 year ago.
Matt, I appreciate what help you could give, but I can't agree to pay the amount requested unless it actually fixes my problem, Then I will gladly pay!
Thank you,
Expert:  Matt replied 1 year ago.

Hello Richard

Ok so there's spark but no injector pulse ? in which case I'd check the condition of the main earth connection between engine block and battery earth / chassis

and there should also be some small earth connections that run out of the wiring loom and terminate onto the engine with small ring terminals and bolts

I'd also check if you have 12V present on the ECU fuse with the ignition on and also check the connection of the cam position sensor as this is used for injection timing

Customer: replied 1 year ago.
Matt, thank you for replying! I'm anxious to try your suggestions, however it is 9:15pm here and I will only be able to get to it tomorrow now. So I will gladly get back with you then! Thank you so much! Richard
Expert:  Matt replied 1 year ago.

no problem

just get back to me on this post