Damn thing just cranks & cranks but wont fire over. Mods are Unichip, K&N, BB Exhaust & billet DV's. Last week, lost power (limp mode?) then difficulty starting. Cut ECU power, restored and now just cranks. Pressure checked boost / intercooler system and have small leak somewhere behind DV's. At 20 PSI, system takes about 3 to 4 minutes before hissing dissapears so I think I'm good there. Pulled MAF connector - still wont start. Any ideas? Should I invest in code reader?

 

Uh...a code reader is required equipment if you are going to mod the vehicle (even if you don't IMHO). Of course we can play "let's spend your money with 1000 guesses" (that sounds like fun!)...so here goes. Check the clutch pedal switch, check fuses, can it be jumped started? How old is your battery? (Check battery). Next level is more $....LOL

 

Allrighty then - ordering today. Battery, fuses & pedal switch all good to go - even checked blinker fluid! Throw me a bone here - are fuel pump relay or pump itself prone to failure?

 

If its cranking but not firing check the fuel pump.

 

I agree with wross996tt and pauliewalnuts. reader is great to have and the fuel pump may work but you have to check the rubber hoses on the top. they burst in a way were it looks like a razor slit.

good luck, hopefully nothing big...it usually isn't.

 

do you have a check engine light on? if so then you got boost leaks. But what bill said above is correct, get yourself a code reader, everyone should have on when they mod their cars or not. Sounds like you disconnected the battery as well? if not do so, and let it sit for more than half an hour, this will cause the capacitors to discharge and everything will reset. May not solve the problem, but may get rid of part of it, or point you in a better direction

 

Can you hear the fuel pump prime when you put the ignition in the start position?

 

Just a couple of thoughts... boost leaks will never cause the car not to start. Car will start and run with MAF disconnected, so that is also very unlikely. If the clutch sensor were broken, the car would't crank.

You either have no fuel, or no spark. If you don't smell fuel then leak is unlikely. As mentioned above, listen to find out if fuel pump is running. If not, then it could be fuse, relay or pump itself.

If you take it to someone with a real program reader, he will plug your car into his laptop, you will crank it, and the computer will tell you what is wrong. This is the really the smartest thing to do.

Jon

 

There are a bunch of things that could be causing your no-start issue. Fuel supply related issues as mentioned above certainly one posibility. Fuel pump, fuel pump relay (relatively common- it is in relay carrier 1 above fuse panel in front floor board- position #13. You can test your fuel pump for operation if you don't have a Durametric or Porsche factory scan tool by removing #13 relay and jumping terminal 30 and terminal 87 with a male spade connector jumper wire with inline fuse- you can make one easily. PLEASE do not attempt to use a piece of tin foil or similar** PM me if you need help on that.) If fuel pump doesn't activate when jumped, you may have a dead fuel pump or no terminal 86 (trigger for FPRelay). If FP doesn't activate when jumped, you need to ck for power with multimeter at terminal 30 and if present, power at the fuel pump plug connector.
Also, DME FI relay could be bad. Could even have a failing DME control module. Crankshaft top-dead center sensor is also a posibility as that tells the DME where TDC is in order to start the firing event.

You also need good compression for the motor to start however it would have to be a pretty significant loss across multiple cyls for the car not to start (missed shift as example) so rather unlikely in your sit.

If it were scanned with a factory scan tool and Anti-Drive Block active were found, you could have a bad alarm control unit or other alarm system component.

Might need something as simple as an ignition switch. They are crap and fail pretty often- Its an Audi part number.

As you can see it could be a number of things but i'd start with fuel pump/fuel supply/actuation and move on from there if unsuccessful.

 

From my measurements with a multi-meter, the pump doesn't prime in the on position. The relay kicks in once it turned to start, then continues in on. The noise you hear up front which I thought was the pump priming was the anti-lock system cycling, not the pump.

My pump has died.... twice.
Check you pressure at the filter housing fitting. I bet it's your pump too.
GL.

 

Many thanks to all for the excellent tech advise! Durametric came in today and will plug & play tomorrow - results to follow.

Mike

 

Glad I got the Durametric - unit reads:
PO335 Fault Code 110 - RPM Input Circuit

I'm guessing this points to the flywheel speed reference sensor.
I've read corrosion destroys the mounting bracket and if the air-gap increases - no signal to DME and car won't start.

Easy to replace?

 

Here are the pages from the manual on this fault code. Looks like it could be a corroded connector.

Hope this helps.

Jon