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SCM
Samba Member
Joined: January 26, 2011
Posts: 3115
Location: Bozeman MT
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 Posted: Mon Aug 05, 2013 2:37 pm Post subject: Can jump starting ruin ECU? |
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My buddy's van just konked out on him. The headlights had been left on and drained the battery. He attempted to jump start start and it wouldn't work. Had it towed home and recharged the battery.
Now, the starter will crank, engine gets gas, and spark but the engine won't start. He (ex-pro VW/Porsche/Mercedes mechanic) says he thinks the ECU went bad but hasn't really had time to investigate.
Under those circumstances, what would have caused the ECU to die if indeed it has?
_________________
'91 Westfalia GL Automatic (GTA "Turbo" Rebuild w/Peloquin) and 2.3L GoWesty Engine |
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greebly
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Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Mon Aug 05, 2013 3:02 pm Post subject: |
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| If voltage was extremely low it could cause a brownout condition which raises havoc with regulated electronics, supplying systems that expect 12 vdc with less than 12 vdc can increase current draw and destroy components. |
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Wildthings
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Joined: March 13, 2005
Posts: 50337
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| Posted: Mon Aug 05, 2013 5:34 pm Post subject: |
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| Hooking the cables up backwards would probably do it. |
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crazyvwvanman
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Joined: January 28, 2008
Posts: 9923
Location: Orbiting San Diego
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| Posted: Mon Aug 05, 2013 5:45 pm Post subject: Re: Can jump starting ruin ECU? |
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What year van is it?
Mark |
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insyncro
Banned
Joined: March 07, 2002
Posts: 15086
Location: New York
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| Posted: Mon Aug 05, 2013 5:49 pm Post subject: |
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| A shock to the system as Wild suggests will fry components. |
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SCM
Samba Member
Joined: January 26, 2011
Posts: 3115
Location: Bozeman MT
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| Posted: Mon Aug 05, 2013 6:24 pm Post subject: Re: Can jump starting ruin ECU? |
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| crazyvwvanman wrote: |
What year van is it?
Mark |
87
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'91 Westfalia GL Automatic (GTA "Turbo" Rebuild w/Peloquin) and 2.3L GoWesty Engine |
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stubear334
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Joined: August 24, 2009
Posts: 152
Location: Montgomery, AL
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| Posted: Mon Aug 05, 2013 7:53 pm Post subject: |
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At least our ECUs are dirt cheap. My old 1999 Sea Ray boat required a new ECU. Turns out Mercruiser only used that ecu for 1 year only. They had 2 left at a new cost of $4,000. I had sold the boat a month earlier & firmly believe the new owner jump started the thing after complaining it wouldn't start. He bought a used ecu for $1,800.
If you get the jumper cables crossed for whatever reason, a back-current can damage the ecu. You're sending juice back thru the ground channel.
Stu |
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RCB
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Joined: September 05, 2005
Posts: 4143
Location: San Francisco-Bay Area
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| Posted: Tue Aug 06, 2013 6:14 am Post subject: Re: Can jump starting ruin ECU? |
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| SCM wrote: |
My buddy's van just konked out on him. The headlights had been left on and drained the battery. He attempted to jump start start and it wouldn't work. Had it towed home and recharged the battery.
Now, the starter will crank, engine gets gas, and spark but the engine won't start. He (ex-pro VW/Porsche/Mercedes mechanic) says he thinks the ECU went bad but hasn't really had time to investigate.
Under those circumstances, what would have caused the ECU to die if indeed it has? |
That was a very interesting question you asked. Here's my story which may be just a coincidence.....or not.
I left my side marker lights on. The battery was an 8 year old Interstate. Next morning my van would start, but it was slow to start.
A few days later it became more difficult to start and I jump started it a time or two until she fired right up. Off I went to buy another Interstate.
Ran like a champ for about a week...until it crapped out. It would start up fine but putting it in gear and trying to move it would lurch and backfire.
No power whatsoever but man would it lurch. I now have a respect for Bull riders 
Had it towed to my mechanic and wouldn't you know it...it ran fine for them.
Told them to keep it until they figured out the problem. Every morning they would start it up and drive it around town to try and replicate the problem.
BINGO....on the third day what had happened to me, happened to them.
The diagnostic games began. It wasn't until they removed my computer and replaced it with their "in house test computer" did they discover the problem.
My computer was biting the dust. Being a pack rat when it comes to 1982 California Vanagon parts, I had a new one that I picked up from a Vanagon repair shop that was going out of business. I've had it in my "stash stock "for 3 years and almost sold it.....damn glad I didn't. 
So...was it just a coincidence my computer screwed to pooch after jump starting it a few times OR was the computer really on its last legs.
P.S. the computer that crapped out on me was the original BUT it was rebuilt by FIC Corporation in Livermore California back in 2004 and it gave me boo-koo trouble free miles up until May of 2013. |
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Xtremjeepn
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Joined: October 21, 2012
Posts: 1539
Location: Colorado
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| Posted: Tue Aug 06, 2013 6:29 am Post subject: |
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No.
Connecting two batteries together the way you would for a jump start only increased capacity. It doesn't increase anything that should harm the system. (its still 12v with one or two batteries) Cars, trucks and campers of all shapes and sizes run dual battery set ups wired exactly the same way as a "jump start".
If there is a problem if came from another source. |
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RCB
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Joined: September 05, 2005
Posts: 4143
Location: San Francisco-Bay Area
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| Posted: Tue Aug 06, 2013 7:05 am Post subject: |
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| Xtremjeepn wrote: |
No.
Connecting two batteries together the way you would for a jump start only increased capacity. It doesn't increase anything that should harm the system. (its still 12v with one or two batteries) Cars, trucks and campers of all shapes and sizes run dual battery set ups wired exactly the same way as a "jump start".
If there is a problem if came from another source. |
Whoops. I may have made a mistake whilst describing my tale. I did not get a jump start; I got pushed started. Would that matter to the ECU ? |
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greebly
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Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Tue Aug 06, 2013 7:10 am Post subject: |
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| Xtremjeepn wrote: |
No.
Connecting two batteries together the way you would for a jump start only increased capacity. It doesn't increase anything that should harm the system. (its still 12v with one or two batteries) Cars, trucks and campers of all shapes and sizes run dual battery set ups wired exactly the same way as a "jump start".
If there is a problem if came from another source. |
If the draw was severe on the disabled vehicle and the cables or connection were poor it's more than likely voltage will drop. Just turning the lights on your vehicle can drop the voltage, connect it to a vehicle with a bad battery, resistant cables and put a big load on it by activating the starter and voltage will not be 12 volts on the disabled vehicle. |
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greebly
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Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Tue Aug 06, 2013 7:15 am Post subject: |
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| RCB wrote: |
Whoops. I may have made a mistake whilst describing my tale. I did not get a jump start; I got pushed started. Would that matter to the ECU ? |
Even more likely that voltage was insufficient. You do not spin the alternator fast enough to produce adequate voltage when push starting. |
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Xtremjeepn
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Joined: October 21, 2012
Posts: 1539
Location: Colorado
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| Posted: Tue Aug 06, 2013 8:40 am Post subject: |
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Low voltage shouldn't kill an ECU. Ever had a radio or laptop get damaged because the battery went low?  |
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jordauto
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Joined: August 12, 2011
Posts: 218
Location: Sorrento,BC
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| Posted: Tue Aug 06, 2013 9:19 am Post subject: |
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| As stated above, hooking the booster cables up backwards will fry computers. Its common on modern cars to see multiple modules fail when someone has attemped to boost start and hooked the cables up incorrectly. But, as always your diagnosis should start with the bascis. Check all fuses,find a wiring diagram for your specific year van and check all power and ground circuit to the ECM. You already said you have fuel and spark. Are the injectors firing, or was just the fuel pump running. Computers do fail but rarely,its always more likely that there is a wiring fault,bad ground,blown fuse or a bad sesnor. |
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greebly
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Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Tue Aug 06, 2013 9:29 am Post subject: |
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| Xtremjeepn wrote: |
| Low voltage shouldn't kill an ECU. Ever had a radio or laptop get damaged because the battery went low? |
Yes, I have seen radios that died because of low voltage. I operated a consumer electronic repair shop for 6 or 7 years. Generally what kills a car radio is being hooked up backwards and replacing the fuse with tin foil . Or shorting out the speaker wires will kill the final amplifiers easily as very few have speaker protection circuitry due to space limitations. When you see evidence of excessive current on the front end of the power supply it's indicative of low voltage operation. Brown out. Laptops have a little more elaborate power supply sensing that shut them off when battery drains beyond their rated capacity. I have repaired a slew of them as well. For other reasons, they mostly die from being dropped. I chip tuned ECU's for a living, and have repaired a few of them. Most consumer electronic designs weak point is the power supply. As an Electronic Engineer I find that most electronic designs neglect or pay little attention to the power supply. |
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