# Electrical problem, keep frying Digifant ECU.



## hooray4rayray (Nov 27, 2007)

So my Digifant ECU in my '92 Cabby went up on Sunday, causing the engine to cut off and it couldn't be restarted. I went through the car checking out power, fuel, compression, all good it seems. Finally had a buddy tap on the ECU with screwdriver while I was cranking, she started and ran fine in idle for about 15 minutes while I burned off all the quick-start and excess fuel. But then I pulled out to the street , it started sputtering, idling high-to-low, then she cut out again. Got a new ECU, checked all my grounds and went through the fuse box with an electrician buddy of mine and a multi-meter. Installed new ECU, started her right up. she sat idling just fine, but as soon as i pulled away and turned on the lights and a turn signal, she died again. I'm going to pull the alternator and test the voltage regulator, hopefully the problem is that it's faulty and has been spiking the voltage when accessories are on. Any thoughts?


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## hooray4rayray (Nov 27, 2007)

*Re: Electrical problem, keep frying Digifant ECU. (hooray4rayray)*

bump


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## Fat Rabbit (Nov 18, 2001)

*Re: Electrical problem, keep frying Digifant ECU. (hooray4rayray)*

Well, how did the alternator check out? How do you know that the ECU went out?
If the alternator is good check/replace the in-tank fuel pump. ($40-50) One of the failure modes for that pump is that it will start up and then quit. Then the car will quit after the small tank under the car runs out of gas. If the main tank is full gas can syphon into the small tank. After that I'd check the Fuel Pump Relay and the Digifant Relay those two relays can start-up and then drop out. They run $5-10 each on line. FR


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## Southcross (Jul 2, 2004)

*FV-QR*

check your engine & engine bay grounds... sounds like a either a bad connection or a broken wire.


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## hooray4rayray (Nov 27, 2007)

*Re: FV-QR (Southcross)*

Thank you, everyone. The alternator and voltage regulator checked out OK. I'm definitely getting gas to the engine, seeing as I had to excess off when i got it running for a few minutes (before the new ECU went out), and when i crank it there's a heavy fuel smell. I will check those relays and grounds, though, and keep you posted. One question: are both the fuel pump and Digifant relays on the fuse panel under my dash, or are they located in the engine compartment?


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## hooray4rayray (Nov 27, 2007)

*Re: FV-QR (hooray4rayray)*

bump


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## The_Hamster (Jul 31, 2000)

*Re: FV-QR (hooray4rayray)*

Fuel pump relay is in the fuse panel.


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## vbp (Jan 29, 2008)

*Re: Electrical problem, keep frying Digifant ECU. (hooray4rayray)*

Load reduction relay? I still don't understand if this controls the whole load on the fuse panel or what? I would think your are having problems with things in the fuse panel area for sure. I think I fried mine too, I just hope I did it myself doing tests, or it got wet from sitting in the rain. Not from the cancerous vw wiring! Ever have only the injectors not work? All tests at the control unit harness check out, but I get no pulse at the main injector lead, I'm thinking ecu, any thoughts? Let us know what it is.


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## Fat Rabbit (Nov 18, 2001)

*Re: FV-QR (hooray4rayray)*

Both relays are on the fuse and relay panel. I am now confused with what you are saying. Previously you indicated that the car would start and run for a time -- now the car will not start? 
FR 
VBP -- how are you checking for the injector pulse? You need to use an LED test light accross the injector wiring terminal - female (wire) end. Then if you get no pulse reverse the leads and try again as the LED test lights are polarity specific. Then if you get no pulse it is likely the ECU or wiring. I'd "ring out" the wiring first. If you replace the ECU you need to check for good grounds because a bad ground will fry it again (and again, and again) until the grounding issue is fixed.
FYI: The load reduction relay cuts off non-essential power draws (headlights, fan, rear window defroster etc.) to reduce the electrical load so the starter has more power. FR 

_Modified by Fat Rabbit at 7:38 AM 8-15-2009_

_Modified by Fat Rabbit at 7:42 AM 8-15-2009_


_Modified by Fat Rabbit at 7:47 AM 8-15-2009_


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## hooray4rayray (Nov 27, 2007)

*Re: FV-QR (Fat Rabbit)*

All's well and good. ECU was fine. Of all the dumb things, I had a really loose connection in the starter and accessory wires off the battery, causing low voltage to the starter even though I was getting spark and fuel just fine. When it did start, it seems likely that the vibration from moving in 1st gear just loosened that connection and cut her off. Tightened it all up, changed the oil to get the gas out of it, presto. Thanks for all your help, dub nation!


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## TDForNow (Sep 30, 2003)

I'm glad yours was an "easy' fix. Just got through getting my son's Wolfsburg going.
We'd shut the hood with the car running and the car shut itself off. No fuel pump, no pwr to ECU. Fixed a bunch of s^!t splices accumulated over the last 20 yrs between the battery and the fuse panel to no avail.
I Found that the ECU pwr relay had no ground INSIDE the fuse/relay panel. 
Over the cars life, water had leaked into fuse/relay panel and corroded some of the bus bars and contacts. The ground contacts for the ECU pwr relay inside the panel were so corroded, that one side had broken off from the vibration from shutting the hood that last time.
Didn't help that all I had to go by was a POS "Haynes" manual to find that "needle in the haystack".
Also, that cured most of the idle and drivability probs we had been chasing down.


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