Date: Mon, 28 Jan 2013 16:05:42 -0800
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Now: Jetta ECU-Coil Amp Draw Was: Ignition Switch "Su"...
In-Reply-To: <CAB2Rwfg=ZWAxMKf3_gLE02qB=FODoiQtzBsW2zYOgS_YGOX4og@mail.gmail.com>
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I just stubled across this neat little tool in my electrical box, forgot
I had it.
Think I got it at Radio Shack ..
small boxwith digital readout ..
this one does up to 30 amps.
It very convenienty plugs in where a fuse was ..
the more modern spade type fuse .
I have this 93 subaru2.2 engine conversion in for some work..
it it's handy to do so I'll plug in that box and see what current the
ecu is drawing while running.
so all this time you really don't have any idea why your it had a
'highway speed stall' .
did it start right back up ?
How many times did it do that highway speed stall thing ?
Could be all kinds of reasons for that to happen,
besides inadequate current flow .
I use 'substitute and bypass' as a diagnostic strategy a lot..
if I thought the ign sw wasn't supplying enough juice..
I'd just operate it off another power source for a while..
heck ..even a fresh battery sitting on the rear floor, or whatever.
drive with a timing light flashing where you can see .so if ignition
quits ..you can tell..
though often a tach will tell you that too.
or fuel supply ...
all kinds of possibilities.
scott
On 1/28/2013 3:32 PM, neil n wrote:
> Hi all. This is for a 1981 formerly air cooled Vanagon with a self
> installed Jetta 2.0 OBD1 engine.
>
> My good DMM (20 Amp rated) had a blown fuse so I took a chance using
> my 10 Amp rated DMM.
>
> With DMM connected in series between 30 (B+) and 30 of an added relay
> to carry power to ECU and coil, engine cold, DMM set to 10 Amp scale:
>
> engine off: no current draw (makes sense)
>
> idle: 1 - 1.5 Amps
>
> 2K RPM: roughly 2.5 Amps which increased as RPM increased. Highest
> was about 3K - 4K RPM.
>
> I also ran the test with the new relay UN-installed; DMM in series
> between 30 and coil/ECU wire, effectively bypassing the ignition
> switch. Same results. (btw. When I inserted the DMM probe to meter,
> the fuel pump primed each time I made the connection. I'm certain that
> supplying + to 38 of ECU energizes the ECU so that it can energize the
> fuel pump relay by supplying a ground)
>
> This is somewhat embarrassing!
>
> Unless I'm doing and reading things wrong, well, even though it's a
> long wire, I guess the OEM #16 wire should handle the load(s) created
> by the Jetta ECU and coil. Like one chart shows #16 wire at 12 Volts,
> 10 Amps, has a maximum length is 25'. And, any increased wear and tear
> on the Vanagon ignition switch is likely small, they fail at some
> point regardless, so I highly doubt any of this caused the mysterious
> highway speed stall I had.
>
> Caveat: I have NO idea if increases in engine temperature, ambient
> temperature, etc. would affect the actual current drawn. i.e. in a
> real life driving scenario. Also, I am not a scientist, electrician or
> qualified in any other related way. ;^)
>
> The instrument cluster was not connected to the 15 circuit while
> testing so the VSS, dynamic oil pressure board, etc. did not load the
> circuit. My guess is that any current increase due to those parts
> would likely be negligible.
>
> Thanks
>
>
> Neil.
>
> On Sat, Jan 26, 2013 at 3:50 PM, Scott Daniel - Turbovans
> <scottdaniel@turbovans.com> wrote:
>
>
>
>> how much current do you figure your ECU draws ?
>
> On Sun, Jan 27, 2013 at 1:10 PM, Ryan Press <ryan@presslab.us> wrote:
>
>
>> I think it would help if we knew how much current the ECU actually draws,
>> and how much the coil draws. Can you measure these with an ammeter both
>> while running and not?
> --
> Neil n
>
> 65 kb image Myford Ready For Assembly http://tinyurl.com/64sx4rp
>
> '88 Slate Blue Westy to be named.
>
> '81 VanaJetta 2.0 "Jaco" http://tubaneil.googlepages.com/
>
> Vanagon VAG Gas I4/VR Swap Google Group:
>
> http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
>
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