Help my 4k 20vt get good spark, I'll send you cookies

[rallyfreak202]

Hey Project Pad guys, I need some help. I have no idea what my problem is any my car has not run in over a year. I want to sell it but don’t want to give up on it. Any help or ideas would be appreciated.

Car:4000 with 20vt swap. 034 IB engine management using distributor/coil for spark.

Problem: weak and infrequent spark. Coil has 9-10v while cranking with battery fully charged.

Prior diagnosis: Here’s what I’ve tried: new coil, coil spark wire, tested hall sender, cap/rotor, checked negative and positive wires to coil, good grounds, and putting 12v from battery charger on positive side of the coil. When I manually trigger the coil with 12v hooked to the coil, I get GOOD spark off the coil but still won’t fire.

I miss this car and want to drive it! I’m 1.5hrs away from the car while I’m at college so I can work on it on some weekends with help from knowledgeable Audi guys. Any help is appreciated!

[loxxrider]

So... do you know you have the proper amount of fuel?

[chaloux]

Want to sell it? dude that's a bummer!

It literally has to be something simple that's being overlooked. It's gonna be one of those "start from scratch" and when you find it you're going to want to smash your head against the wall.

[rallyfreak202]

So... do you know you have the proper amount of fuel?

I believe so. I've messed around with the injector scaler setting and pulse width setting. The fuel pump comes on and I have fresh gas in it.

Here's something I've been thinking about: if I manually trigger spark off the coil and can't get good spark without having a 12v hooked directly to the coil, my problem lies in the +pos to coil circuit (which I've rewired recently) OR in the negative circuit to the ECU (which I've rewired too!).

Has anyone ever had a Hall Sender work intermittently?

Here's what I'm going to test next time I'm with the car. Any input is appreciated!

1. Test spark at coil.
2. If weak, measure Voltage on +pos of coil. Test spark at coil with 12v hooked to +pos side.
3. If still weak, manually fire coil and check spark off the coil. If that makes it strong, fault must be in negative side of coil wiring.

[85oceanic]

Just out of curiosity, have you tried a different coil? Also, when I was getting my 4k up and running, grounds where the main things I had problems with. If you have noisy grounds, the ecm won't be very happy.

[rallyfreak202]

Just out of curiosity, have you tried a different coil? Also, when I was getting my 4k up and running, grounds where the main things I had problems with. If you have noisy grounds, the ecm won't be very happy.

Thanks for the reply. I know I have good grounds and I also have a good coil in the car (tested it on my GTi).

Keep the advice coming, it helps me think!

[85oceanic]

Just wondering, but how did you route your grounds? At first I used a shared ground point, which in theory is a great idea to simplify diagnosis when things go wrong, but in practice it created WAY to much signal noise for the computer to sort through. You might try moving stuff around, or maybe even make a jumper wire with some alligator clamps so that you can just test different spots.

[rallyfreak202]

Just wondering, but how did you route your grounds? At first I used a shared ground point, which in theory is a great idea to simplify diagnosis when things go wrong, but in practice it created WAY to much signal noise for the computer to sort through. You might try moving stuff around, or maybe even make a jumper wire with some alligator clamps so that you can just test different spots.

I routed my grounds from engine head and block to chassis. Grounds are not on shared point. Sanded surface contacts on chassis. Battery is in trunk and negative lead is about 2ft long and goes to a sanded ground. Tested resistance from block to chassis and there is none. Positive lead goes from trunk to starter with a union splice. I don't believe grounds are the problem but I'll look over them again. Thanks!

[crimson ghost]

How long was the car running right after the swap ?

[Hank]

What have you done with the Ib to verify all drivers are working? Has 034 looked at the ECU at all? They are great about putting their eCUs on the bench and testing all the outputs and drivers for functionality, and can fix them if they are boogered.

[rallyfreak202]

How long was the car running right after the swap ?

About a 1-2months. Longest drive was 2 miles (and it was so awesome!!)

What have you done with the Ib to verify all drivers are working? Has 034 looked at the ECU at all? They are great about putting their eCUs on the bench and testing all the outputs and drivers for functionality, and can fix them if they are boogered.

I sent the ECU to 034 and they verified that it was working correctly.

[Hank]

hrmmm...

[85oceanic]

Did you change anything before it stopped running?

[rallyfreak202]

hrmmm...

Did you change anything before it stopped running?

I remember it was having a hard time starting. Cranking and not wanting to fire up all the way. I played with the injector pulse width and scaler. Changed the timing with my hand on the dizzy. This didn't seam to help much so I coasted it down the driveway and popped the clutch. Still no start. Hasn't run since.

Who has seen hall senders go bad? I tested the hall sender and it checked out fine.

Thanks guys!!

[loxxrider]

Wait... you can't change timing with the dizzy, you can only de-sync it and thus end up in a no-fire condition. Make sure that thing is timed right before proceeding further in my opinion.

[85oceanic]

Wait... you can't change timing with the dizzy, you can only de-sync it and thus end up in a no-fire condition. Make sure that thing is timed right before proceeding further in my opinion.

x2

[themagellan]

Sounds like you may have your answer!

I remember being so excited when I saw the 3B's distributor. I wanted to buy a manual boost controller and start dialing back the timing. Oh well.

[carl]

The 1b system uses only the cam trigger, doesn't have a secondary trigger, so ignition should fire but if you have sequential injection it could play a role for running rough. Personally i'd check and swap the pos and check that the distributor has proper wiring. I've had a bad pos give me weak spark on my old 87 cgt, engine would run but just didn't run right. Is the hall signal steady? You can use a led to test. Not sure if the 1b gives any logs on this? I've had issues with grounding on vems, since battery is located so far from engine, the engine grounds were giving it noise/missing sensor signal issues while cranking. Worth a try to move ecu and hall sensor grounds to car body.

[my2000apb]

whats the status on this?

[chaloux]

Second!

[rallyfreak202]

whats the status on this?

Update: I put 12v on pos side of coil and still not getting good spark. I'm going to test the hall sender again (tested it a year ago and can't remember result).

Is the hall signal steady? You can use a led to test. Not sure if the 1b gives any logs on this? I've had issues with grounding on vems, since battery is located so far from engine, the engine grounds were giving it noise/missing sensor signal issues while cranking. Worth a try to move ecu and hall sensor grounds to car body.

Going to check hall sender with test light. I'll move my ECU ground to the body and see if that changes anything. Thanks.

Getting inspired to work on this thing is hard. I'm over it but only because I feel like it has beaten me! Must make it run this Summer.

[chaloux]

Don't give up! We need more epic running 4ktq cars around!

[rallyfreak202]

Summer is coming to an end. I start a job in Asheville NC in 1 month. I want to sell it but can't bring myself to list it.

-tested hall sender, it's good
-sh1tty spark. Bright enought but not frequent enough. I'm thinking about buying a new harness ($45) from 034 and wiring it up. I don't want to switch it over to motronic.

[jretal]

have you verified the timing on this thing yet? You're sounding strangely familiar to an issue I had when trying to get my 20vt running on the Ib...

Take all the plugs out and in the dashboard of the 034 software click the "zero timing" box. Then as you turn the motor over, maneuver the distributor until you verify zero timing (will take 2 people and you should mark the TDC mark on the flywheel w/ whiteout or something visible). This is critical, and something I fought when originally trying to start my 20vt w/ the Ib initially, and was fighting recently to get my Ic running properly after upgrading from the Ib recently.

Also, you can move the distributor back/forth when someone else turning the car over to see if it fires, but what I described earlier is more exact w/o getting the car running.

FWIW, You set your max timing with the distributor on the Ib, and then the ECU pulls timing after that. IIRC, I had my 20vt set to 10-12 degrees advanced (going from memory, and it's been 5+ years) and then had the ECU pull it as necessary.

I'd put a nickle on that being one of your issues, maybe not the main one, but the distributor timing is critical in getting a Ib motor running.