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DIGI II Troubleshooting (Help me to get my car running please)

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NAVI51

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Discussion starter · #1 ·
My Cabby 93 doesn't want to run. On Friday it wan really good and travelled a long distance with no problem. It turns out that I try to started to leave from work, and the car will crank but not start. So I checked if there was fuel on the rail, and sure there was. I checked the spark, and sure there was too. I've had lots of problems with many ECU's before, so I suspected that the ECU was faulty, so I went ahead and got a new one, plugged it into the car last night and still didn't want to start, so I removed the intake tube, put gas in there and start the car and it wan with no problem, while coming back home, I went to get gas, refueled and this time it wouldn't even start with the gas in the TB. Had to tow it home and I got to work on it, same symphtoms as the begining but this time I checked more into depth. I checked the pressure from the gas pump, it looks good to me, checked spark, it was completly fine and the timing is perfect because I used a timming gun last time to set it perfectly. I checked pulses in the injectors and there were pulses from the ECU so it isn't shot. Got more gas into the TB and still nothing. I need the car running soon because I need to get my butt to school and work. I have noticed that when the car tries to start it just like blocks and kinda makes a clicking sound, but the timming belt is in perfect condition and it's tight as it should be. Any suggestions? or previos experiences?.
As a matter of fact I'm washing my injectors and replacing the O-rings, just like I will replace the vacuum hoses tomorrow, eventhough I know that's not the problem
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Discussion starter · #3 ·
Re: DIGI II Troubleshooting (cwcabrio)

I actually checked if it was flooded and it didn't seem like it, but I unplugged the spark plugs anyways and cranked it to get the gas out, plugged them again and nothing
Image
 
Discussion starter · #5 ·
Re: DIGI II Troubleshooting (cwcabrio)

Actually the car was sitting just a couple of hours before I tried to start it again the first time. When I got it to run it hadn;t reach the working temp. The plugs weren't wet, but there was a little bit of gas in the tip
 
#7 ·
Re: DIGI II Troubleshooting (NAVI51)

If you have gas, spark and timing the only thing missing is air. If the air flow meter isn't sensing airflow the ECU won't send gas. Also, if the rubber air boot is torn you may get the same symptom with too much unmeasured air. You may want to snug up the relays on the fuse and relay panel and reach around behind the panel and snug in the connectors. FR
 
Discussion starter · #10 ·
Re: DIGI II Troubleshooting (cwcabrio)

Quote, originally posted by cwcabrio »
Do you smell gas when attemting to start your ride?
How long since last coolant temp sensor change?

No no smell like gas. The last time that I changed the coolant sensor was like a year ago
 
#11 ·
Re: DIGI II Troubleshooting (NAVI51)

how much resistance are you getting across your CTS? don't sue me if this fries your ecu but you could try shunting the cts harness to simulate full hot (proper method is to use a proper resistor)
have you tried pushing the maf up while cranking? flooring the gas pedal while cranking? so you're sure you have the right amount of pressure? both fuel pumps coming on?
 
#12 ·
Re: DIGI II Troubleshooting (NAVI51)

It could be as simple as a bad MAF connection. I've run into loose connectors and broken wires on those several times over the years.
When the MAF goes bad it is usually in a certain throttle range along the wiping resistor that sends the readings to the ECU. You can test the resistance measurements with a multimeter. IIRC the reading will change as the sensor air flap is moved. Then it will start over at a certain point -- so that discontinuity in the reading is normal. The key is that the resistance runs smoothly to the discontinuity and then above.
As to why it would run with some gas in the intake tube. You reached a stoichiometric (correct fuel/air) mixture which caused the engine to run. The running engine would demand air through the intake system and perhaps that caused the air flap to move.
A different AFM should run around $25 or so at a junkyard. FR
 
#13 ·
have you checked relay 30/32 on the fuse box? normaly this switches on the ecu, but if your getting spark and fuel that could be ok, worth a check as its an easy fix. i held mine and you could feel it click when you turn ignition on.
I've got a faulty maf and it runs, but if i unplug it it will fire but die after it turns over a couple of times
 
#15 ·
oh check the wire to the lambda as well, had a few cases where the wires shorted out and kills the ecu, im replacing my ecu because of this tonight ;-) depends on your type of ecu though different digifant wires in different ways
 
Discussion starter · #16 ·
Re: DIGI II Troubleshooting (NAVI51)

well as for right now I'm going outside and put in new spark plugs and put the clean injectors along with the new o-rings, also I'm going to replace some vacuum hoses and the ignition module that goes on top of the ECU and see what it does.
I have put the gas inside the manifold, tried to start it with the gas pedal all the way in and still nothing. I checked for lose MAF conections but they seem totally fine. The O2 sensor will be replaced soon as well but as far as the wiring it seems totally fine. I will report back in about 30 mins http://****************.com/smile/emthup.gif
 
#17 ·
Re: DIGI II Troubleshooting (NAVI51)

I had an issue with my car not strating.My timing belt slipped a few teeth,but you say your timing is good.This is a tough one.
In regards to the coolant sensor I can run without it.Same with the o2
Timing is good
spark is good
fuel is good
ecu is good
coolant sensor is good.
So what`s left
MAF?
Vac leak?
Compression?
 
#18 ·
if its a alloy maf with the flap in it, you can test with a multi meter, pins 2 + 3 and 2+4 open and close the flap and resistance change should be smooth and constant 2+3 should be 280 ohms closed from memory and 780 ish ohms when open and 2+4 should be 60 closed i think to 660 ish. can't remember 100% but its more that it should be smooth climb in resistance
 
#19 ·
Re: DIGI II Troubleshooting (NAVI51)

From IM,
"NAVI51 (9:08 PM 1-20-2010): Hey Ron could you please help me out to get my car running again. Thanks!
http://forums.vwvortex.com/zerothread?id=4730436 "
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1st, are you sure it's DigiFant II, not DigiFant I?
II uses two wires to the injector loom, common to all, I uses 5 wires to the injector loom, common power and separate signal (grounded by the ECU) wires.
---
See this thread regarding a busted hose in the tank between the fuel pick up and the in-tank pump.....
http://forums.vwvortex.com/zerothread?id=4670839

While you are there, check the in-tank pump's output volume, it's pressure is irrelevant. Pull the output hose off the sending unit cover, put another hose in it's place, other end of that hose into a quart oil can or similar. Best I recall, volume spec is a quart (more or less) in 30 seconds. Consult your Bentley for a for sure spec keeping in mind that close is good enough.

You really should measure fuel pressure at the fuel rail. There's a 7 mm hex bolt plug that can be removed and a gauge hose fitted directly to the fuel rail, alternately, tee into the fuel lines. Expect ~45 PSI with no vacuum to the fuel pressure regulator, ~35 PSI with vacuum at the FPR.

If in-tank quantity is good but fuel rail pressure is low, replace the main pump.
I refused to pay the price for new, stock pumps, installed a single Chevy pump in the tank with a Dodge pickup fuel filter under the hood. It's noisy but works just fine.
http://reflectionsandshadows.c...rsion/
---
Re-check timing. Here's a static thread, reads a bit hair brained, sorry, read it anyway, do it.
http://forums.vwvortex.com/zerothread?id=3281138
I've compared that static method to, by the book Bentley, the static method is spot on every time, does not require a running engine.
Digi Hall voltage should go HIGH at TDC clockwise (same for points, CIS-E and Motronic, opposite for CIS lambda).

If timing won't stay put, and it certainly should, eyeball the timing belt, tensioner etc. for slop, then read briano1234's fargin horror story at
http://forums.vwvortex.com/zerothread?id=2542541
and one guy's fix for a spun crank gear at
http://forums.vwvortex.com/zerothread?id=1598023

If it turns out that the car is indeed DigiFant I, replace the ignition coil. Digi I uses a transformer looking coil, very different in appearance from Digi II's old style cylindrical coiil.
The eCoils (I just created that name) used on Digi I, Motronic and others have several failure modes, I experienced one such failure mode with symptoms identical to yours.
Here's another .........
Image

That particular coil was on my old A3 Jetta, it's identical to the one on my '92 Digi I Cabby, I swapped them back and forth.
If your car's coil doesn't look like that, it's not Digi I.
---
Click the neoBentley+ link in my sig, see what you can find from there.
---
I think there's a link to MAF voltage readings on the nB+ page.
Check voltage on the oxygen sensor signal lead with the fuel pumps powered up. If you see battery voltage, the heater element has shorted to the sensor lead, unplug the heater connection.

A quick, easy, temporary way to power the pumps with the key is to swap the load reduction relay in place of the fuel pump relay.
See http://www.cabby-info.com/elec...#Fuse
for relay locations.
---
That's all that comes to mind at the moment.
 
Discussion starter · #20 ·
Re: DIGI II Troubleshooting (tolusina)

The car is indeed a Digi II, have bought already 3 ECU's for it previously. So today, I put the new plugs, the new ignition module, and saw that the injectors were just fine. I have a Chevy fuel pump in my car inside the tank as well but I do have the Digi II on the outside. So I went ahead and tried to start the car again and nothing. However something caught my attention. There was gas comming out of the exhaust manifold, so I unplugged the spark plugs and got all of the gas out of there, went to Autozone and loaned a Compression gauge. Damn my engine is pretty strong, the weakest cylinder had 160 psi and the strongest showed 190 psi. I was impressed!!!. So tried to start it and nothing, my timming is in the right possition but still nothing will fix it. This is a freaking interesting problem that I had never had before and it's catching my attention ore and more but it's making me run out of patience, toughts, and time
Image
 
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