# Digifant starting/running issues



## MentalFloss (Dec 10, 2009)

Yes I know this has been discussed before, BUT. . yes a big BUT, I chased all the normal issues and still same result.

what it is ... 1991 Jetta ( German ) with 1.8 8V stock with Digifant and an Auto trans, 51,000 original miles.

Here we go...

Starts and will run for a moment of two then just dies. might rev to 2k but still dies, open throttle dies, don't throttle dies. :banghead:

what's been done or checked -

CPU swapped from a running car - running car runs with non-running cars CPU runs, Non-running car with known good CPU, result - see above.
Air flow meter swapped from running car, result - see above.
New blue coolant sensor, result - see above.
New in tank pump, result - see above.
fuel pressure at fuel rail - gauge is at 35-40 psi, just like running cars. result - see above
Swapped injectors to a set from a running car, results see above
vacuum lines all checked and replaced flexible line with silicone lines, result - see above.
grounds for engine, trans, CPU checked, result - see above.
Fuel pump relay checked, jumped relay out to get pressure reading and start, result - see above.
Ignition switch swapped and checked, result - see above.
Engine will run if I introduce a little brake cleaner to the intake, it will keep running as long as brake cleaner is flowing. Yes this means a fuel issue but where ??

any good ideas ??

David in NC


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## Mr.loops (May 27, 2010)

Are you getting any injector pulse when cranking?


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## MentalFloss (Dec 10, 2009)

LED test light used at the injector harness connector - flashing when started and when running the brief moments. :banghead:

Help ??

David in NC


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## Butcher (Jan 31, 2001)

When you crank the engine, does the air flow flap move? Do you have fuel pressure? If so how much? 

I suspect that you have a large vacuum leak, such as a hose not installed/missing


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## MentalFloss (Dec 10, 2009)

swapped flow meter with one from a running car, runner ran, non-runner No Run, same with CPU, ISV, still no Joy. fuel pressure at rail is 40-45 Psi and it hold so no leaking injector. Smoke machine to see vacuum leaks, two minor fixed with hose clamps, - No Run

I am going to run the Bentley manual tests on the CPU harness to see if something is amiss there.. . last hope.


Other ideas ?


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## Mr.loops (May 27, 2010)

MentalFloss said:


> swapped flow meter with one from a running car, runner ran, non-runner No Run, same with CPU, ISV, still no Joy. fuel pressure at rail is 40-45 Psi and it hold so no leaking injector. Smoke machine to see vacuum leaks, two minor fixed with hose clamps, - No Run
> 
> I am going to run the Bentley manual tests on the CPU harness to see if something is amiss there.. . last hope.
> 
> ...


Next...
I would recheck timing and run diagnostic tests on ICM and ECU

You'll get it 


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## MentalFloss (Dec 10, 2009)

I'm going to look in the harness, the ICM and ECU have been swapped into the running car and well, they work, but the non-running seems to insist on doing the same thing. Actually the running car is using the air flow meter now. . so not the actual parts, only thing still the same is the stuff in the car, wiring, engine, sensors, etc. my best guess is the harness.

OR . . something that shifts or changes after the inticial start up, the start and the rev up then it dies, is that something that gets the revs to settle at idle ? Throttle switch ? would that effect the running ? I've blocked the throttle partly open to see if it is the something along those lines. . can will still die, helper start is and I grab some throttle to try to keep it alive .. dies. . 

Anyone ??


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## Fat Rabbit (Nov 18, 2001)

Maybe a bad ignition switch. Those tended to go bad a lot -- especially if using a key fob with a lot of keys on it. A common symptom is that the car will start OK but the drop out when the switch moves back to the "run" position. Not a very expensive part -- usually under $10 mail order. Could also be a bad connection behind the fuse and relay panel. You can reach around behind and snug those up. An inexpensive check. FR

OOPs I missed the ignition switch part above. The symptoms are 100% bad ignition switch.

I think that at this point I would remove the fuse and relay panel and then re-install it to assure those connections. Then get a wiring diagram and start tracing the wiring. Checking it for continuity. I've had some issues with the O2 sensor wiring, the CTS wiring, and the MAF sensor wiring -- usually around the connectors. The wires seemed especially prone to breakage at the connectors. Check them from the sensor back to the ECU connector. I don't think you have mentioned checking the distributor, ICS and the coil. I think I would also try replacing or jumpering the Digifant Relay. My spare parts kit always included two relays -- The Digifant Relay (357-906-381)and the Fuel Pump Relay (191-906-383). BTW the throttle switches are an easy check with a multimeter -- either open(no continuity) or closed (continuity). You might also want to check the air intake tube -- I've seen some of them ripped open in a crease where lots of unmeasured air could get sucked in and kill the engine. FR


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## vw4x4 (Jan 7, 2002)

Getting goo fuel pressure to the fuel rail, and adding brake clean keeps you running definitely points to an electrical issue.
Something fairly weird for sure. I would do a point to point on the ECU wiring harness. Its a lot easier than you think.
ERIc


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## Seax_Smith (Jun 1, 2007)

3 Months after I finished rebuilding my current daily I had an impossible to find digi II issues. Everything tested positive (even tested my multi meter at one point). 

Last thing I did, out of having nothing better to try, was replace the CE2 fuse/relay panel and the digi and fuel pump relay with yard parts. No start disappeared.

Wierd thing: I eventually swapped back in all the original parts to find out what I missed. Was a huge kick in the balls to have all the original parts back in the car and have no no-start issue. Wrote it off as a semi-faulty plug/socket connection somewhere.


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## Eric D (Feb 16, 1999)

Have you verified the timing belt isn't stripped? At this mileage and age I would suspect an original belt on the vehicle.

Also check static timing, and finally base timing per the Bentley.

I didn't see you post any compression test #s. 

Here is a PDF that goes into greater detail than the Mk2 Bentley. Its for a Vanagon, but its a ProTraining manual that VW put out for its techs. The info is great to help those that can't make heads or tails out of the Bentley.
http://www.vanagonauts.com/files/Vanagon Digifant Fuel Injection System.pdf


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## Fat Rabbit (Nov 18, 2001)

Any solution yet????? FR


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## georick (Jan 29, 2008)

*digi issues*

Hi,

I too have a similar issue with a 90' gl 5 speed.

Car runs and starts great... every so often( usually in heavy traffic- far from home) it will shutoff and not start.... Had several tows....

I think power supply drops from Digi control unit.... Not sure if fed by terminal x- load reduction relay... feed from ignition switch... all components check out ok.... 

Too much garbage in wire harness..

I am ready to part ways with car..... too much hassle.

good luck- regards,
george


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## vw4x4 (Jan 7, 2002)

George,
In your case, you could easily wire a small light bulb directly to the positive side of the coil. If the bulb
goes out, your assumption is correct, that you are loosing power. In this case I would suspect the ignition switch.
This is exactly what I'm going to do when I get home.... My 92 Jetta died on the road last night...





georick said:


> Hi,
> 
> I too have a similar issue with a 90' gl 5 speed.
> 
> ...


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## Fat Rabbit (Nov 18, 2001)

Try some of the simple things I suggested above. I had an issue with the CE2 connectors coming loose in the back of the Fuse and Relay Panel with a root cause of the panel not being locked properly (there are some pegs on the panel that fit into the metal bracket) into the panel bracket under the dash. Another time with similar symptoms it was the Digifant Relay that was dropping out. And yet another time it was the electrical part of the ignition switch. Ignition switches tended to go bad -- especially if you had a lot of keys (weight) on your key fob. FR


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## matty kirk (Jul 2, 2007)

Shot in the dark here.
Pull the dizzy cap off and verify that the shaft is tight side to side, and that the trigger wheel is secure on the shaft. 
Had an issue with my Digi2 Cabriolet similar to what you describe. Turned out the shaft in the dizzy was loose. Must have wacked the trigger wheel on something because it was loose, rotating independent of the shaft, and setting the timing wherever the hell it wanted. Took me forever to track that one down.


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## georick (Jan 29, 2008)

*digifant again*

..After running well for months.. the 90' jetta will not start again.. fuel supply good.. i ordered a ignition switch to swap and try- now that no-start issue returned. I will also swap out the distributor... Checked harness connectors behind fuse panel; fuel and digi relays replaced.. Checked coolant temp sensors... i also checked grounds, replaced some connectors..checked the ground contact within distributor harness. This is really pissing me off..

I'm about ready to use the sledge....

thanks,
george

The plastic wire protector around harness kinks, maybe causing breaks... whatever happened to the old slinky style wrap on the mk2's??? CHEAPNESS....


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## Butcher (Jan 31, 2001)

Have you done any real testing or just throw a bunch of time and parts at it. Typically following a good diagnostic path and real testing will point you to the problem real quick. Do you have a wiring diagram? Bentley? Volt meter?

So what are you missing? Spark? Fuel? You say you have a good fuel supply but how much fuel pressure do you have? 

Help us help you.


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## garryt (Dec 22, 2016)

so you have checked for pulsing at the loom plug to injectors, but what about the injector loom itself???


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## mk2 boss (Oct 6, 2012)

MentalFloss said:


> Yes I know this has been discussed before, BUT. . yes a big BUT, I chased all the normal issues and still same result.
> 
> what it is ... 1991 Jetta ( German ) with 1.8 8V stock with Digifant and an Auto trans, 51,000 original miles.
> 
> ...


I have a Digifant 2 and I had the same symptoms. Took me a while but I figured it was the idle valve. What I did was unplugged it *with the engine OFF*, when you go to start you might have to give it a little bit of gas to start the engine. If the engine is cold, you might have to hold down the pedal to about 2krpms to let it warm up a bit. If it stays running and idles, then you have a bad ISV valve. If you plug it back *engine OFF* and go to start, it should die again.

Let me know if that helps.


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