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dead van diagnostic tools, wiring bypass
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crazyvwvanman
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PostPosted: Fri Mar 27, 2009 7:16 pm    Post subject: dead van diagnostic tools, wiring bypass Reply with quote

Here is a wiring tool that bypasses several of the wiring faults I have seen in various vans, mostly 2.1 wbx models. It is meant as a driveway testing tool when trying to isolate a won't start or won't keep running problem. Many other things could cause such symptoms and this won't help with them but at least it is an inexpensive way to reduce the possibilities.

It consists of a long fused wire connected to the battery positive terminal. The other end splits into 3 separate leads, each to be connected in a certain spot to the fuel injection/ignition wiring. With this installed the engine will run even if the ignition switch is bad, or the FP or ECU relays are bad, and even if a bunch of other wires or connections are bad. If it starts and runs after this tool is installed you have then eliminated most of the expensive stuff as possible causes.

The 2 male spade ends plug into the ECU and Fuel pump relay sockets, where leg 87 of each relay would have gone. The diode protected female end goes to the empty + post of the ignition coil where there are usually 2 black wires also.

The fuse is 20 amp, the long wire 12 gauge ten feet. The short wires are 16 gauge so all 3 can be fit inside one crimp connector meant for 10 gauge. The diodes are from Radio Shack, #276-1661 pack of 4. The 2 diodes are in parallel with their marked ends pointed away from the 3 wire crimp. The diodes are there as a one way valve of sorts, to let the jumper power the coil but not let the coil power the jumper. This is important to prevent vehicle wiring damage as the jumper would otherwise possibly allow higher loads on wiring not meant to carry them.

Put the fuse in after everything else is connected. The fuse acts as a switch to turn every on/off. You must pull the fuse to stop the engine after it is started. The key is still used for starting but won't stop the engine with this tool connected. You need to pull the fuse out when not running the engine! The fuel pump will run constantly and the ECU will be powered up along with other FI components until you pull the fuse. Do not plug or unplug things with the fuse in or the key on.


This tool is meant for driveway type use, not for driving! Use at your own risk. Don't leave out the fuse or the diodes! If you don't want to build it right, you probably shouldn't do this at all.

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If your engine starts and runs with the tool when it would not without it, you can know the fuel, fuel filter, fuel pump, fuel pressure regulator, injectors, coil, dizzy, sensors, AFM, etc were NOT the cause of the problem. This leaves a wiring problem as the most likely fault. By removing the 3 jumper ends one at a time and putting in the relays as you go you can narrow down where the wiring problem is. DO NOT plug or unplug any of this with the fuse in. Take the fuse out, do your thing, then put it back in to check the result whenever you are changing something.

Mark


Last edited by crazyvwvanman on Fri Mar 27, 2009 8:19 pm; edited 1 time in total
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fusername
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PostPosted: Fri Mar 27, 2009 7:34 pm    Post subject: Reply with quote

thats really cool, you didn't mention how long the long wire needs to be? I love the inginuity.
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danfromsyr
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PostPosted: Fri Mar 27, 2009 8:01 pm    Post subject: Reply with quote

why can't you grab +pos power from right in the engine compartment?
from the lug in the little black box?
from the back side of the Alt?

I too have often bypassed many of the stock systems. \with the primary question, just what does it need to start/fire/run?
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crazyvwvanman
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PostPosted: Fri Mar 27, 2009 8:24 pm    Post subject: Reply with quote

You can, but that is part of the vehicle wiring that often fails and that this long setup bypasses. That is also part of why the long wire is detachable from the shorter pieces. The piece with the ring terminal and fuse holder can be moved from the battery post to that power post in the engine wiring box and the the 3 wire section plugs right into it. The ring is too big but can still work there.

Mark

danfromsyr wrote:
why can't you grab +pos power from right in the engine compartment?
from the lug in the little black box?
from the back side of the Alt?

I too have often bypassed many of the stock systems. \with the primary question, just what does it need to start/fire/run?
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danfromsyr
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PostPosted: Fri Mar 27, 2009 8:29 pm    Post subject: Reply with quote

if yer not getting a good or least decent +Pos on the back of the Alt then the rest of the system is the least of your troubles..

the Alt +pos connects directly to the Starter Battery cable then directly to the +pos battery side.. so it's essentially the same circut track as adding a +POS lead to the battery...

but I don't want to dissuade this any, it's handy to know where & what to hook to eliminate the key & relays..
in fact I have an Audi 5000 turbo dead in the yard with a new Ign switch just came in.. that fueling & wiring system is a pita..

Dan
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crazyvwvanman
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PostPosted: Fri Mar 27, 2009 8:42 pm    Post subject: Reply with quote

The wiring you describe changed a few times over the years. In any case I have seen several times where the wire from the alt to the starter cooked internally and made a poor connection. The last time on my friend Brian's 87 Syncro the voltage was fine when measured with the key off but would start to drop out when the key was on and disappeared entirely while the starter cranked. I did not need this bypass tool to find his problem but the tool might help someone who did not know what to look for. That is the whole point of it , bypass many known problem areas in one step. If it fixes the symptom, then you break it down and look at smaller sections of the wiring. It the longer setup does not help, you know to look outside of the bypassed wiring sections. Divide and conquer.

Mark

danfromsyr wrote:
if yer not getting a good or least decent +Pos on the back of the Alt then the rest of the system is the least of your troubles..

the Alt +pos connects directly to the Starter Battery cable then directly to the +pos battery side.. so it's essentially the same circut track as adding a +POS lead to the battery...

but I don't want to dissuade this any, it's handy to know where & what to hook to eliminate the key & relays..
in fact I have an Audi 5000 turbo dead in the yard with a new Ign switch just came in.. that fueling & wiring system is a pita..

Dan
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Alan Brase
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PostPosted: Tue Jun 02, 2009 12:02 am    Post subject: Reply with quote

crazyvwvanman wrote:
The wiring you describe changed a few times over the years. In any case I have seen several times where the wire from the alt to the starter cooked internally and made a poor connection. The last time on my friend Brian's 87 Syncro the voltage was fine when measured with the key off but would start to drop out when the key was on and disappeared entirely while the starter cranked. I did not need this bypass tool to find his problem but the tool might help someone who did not know what to look for. That is the whole point of it , bypass many known problem areas in one step. If it fixes the symptom, then you break it down and look at smaller sections of the wiring. It the longer setup does not help, you know to look outside of the bypassed wiring sections. Divide and conquer.

Mark


Right, Mark! The big starter end of that alternator wire has corroded off in several of my rust belt cars, both Vanagons and type 2 Bays.
Al
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insyncro
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PostPosted: Mon Jan 04, 2010 3:09 pm    Post subject: Reply with quote

Thanks Mark.
Really is a great addition to my Vanagon toolbox.

dylan
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AZlab
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PostPosted: Sat Mar 27, 2010 5:26 pm    Post subject: deadvan diagnostic tool Reply with quote

Will this work in vans that have the 5 pin relay in the power supply
position, or will it require an additional wire to 87A?
I ask because I have an '88 Westy that would crank but not start. I swapped ecu, coil & dizzy from a '90 and still no start. Finally got a 5 pin relay, but not the correct one, from NAPA and it started right up.
I need to order the correct.
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tencentlife
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PostPosted: Tue Mar 30, 2010 8:05 am    Post subject: Reply with quote

If you apply it the way Mark says, it should work. I don't believe your late ECU needs to have pin 23 powered to function, I agree with Mark that that is probably just an auxiliary OBD function that they decided not to put into use.

If you suspect either relay you can always simply jumper each relay circuit one at a time with a simple double-male jumper (connect 30 to 87). I have always kept one handy in my tool kit and usualy leave one in my cars so I can fake a relay closure on any circuit in a car. A bent wire or paper clip even works in a pinch.
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crazyvwvanman
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PostPosted: Tue Mar 30, 2010 8:28 am    Post subject: Reply with quote

Also since Jerry said he has the earlier TA ECU anyway the pin 23 has no connection inside the ECU so no reason to put any power to that pin. I'm not sure why he would have the early TA ECU and the later 321919505A ECU relay together in the same van unless some parts swapping had been done.

Mark

tencentlife wrote:
If you apply it the way Mark says, it should work. I don't believe your late ECU needs to have pin 23 powered to function, I agree with Mark that that is probably just an auxiliary OBD function that they decided not to put into use.

If you suspect either relay you can always simply jumper each relay circuit one at a time with a simple double-male jumper (connect 30 to 87). I have always kept one handy in my tool kit and usualy leave one in my cars so I can fake a relay closure on any circuit in a car. A bent wire or paper clip even works in a pinch.
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PostPosted: Mon Sep 12, 2011 1:24 pm    Post subject: Reply with quote

I am having similar problems on an 86 syncro - cranks but won't start - not hearing the fuel pump buzz when ignition key is turned on - I think the idle valve is supposed to buzz also? I am not hearing/feeling that either. I have swapped the relays and they are good. If I short relay pins 87 and 30 I get the fuel pump buzzing.

I am thinking its an ECU... Sad

-Brian
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PostPosted: Fri Sep 16, 2011 10:13 am    Post subject: Reply with quote

It turned out to be the D15 corrosion/carbon problem. Someone said there was a way to bypass this weak line with a relay in the back - any tips?

Thanks,

-Brian E
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PostPosted: Fri Sep 16, 2011 11:27 am    Post subject: Reply with quote

The is only one wire going from the dash area to the engine compartment that is needed to run the engine. It comes from D15.

You can easily put a relay in the back that is controlled by the wire from D15. This will remove about 95% of the amps from the D15 wire but the wire is still needed and will carry a fraction of an amp to activate the relay.

If the D15 pin is damaged to the point where it can't be trusted to control the added relay you can still add the rear relay and then connect the wire that went to pin D15 to spade G2 or G5 on the back of the fuse/relay panel. This puts the wire on a fuse when it had no fuse while on D15. Now fuse S18 is in line with the wire to the back so anything that blows that fuse will kill the engine too. Some vans have almost nothing connected to fuse S18 but there are options that use it so vans with those options have an increased chance of a blown fuse that would also keep the engine from running. I would not use G2 or G5 in such vans for this reason. If you look at both G2 and G5 on your panel and nothing is plugged into them I would consider it safe to use either one for the D15 bypass.

Mark


bserret wrote:
It turned out to be the D15 corrosion/carbon problem. Someone said there was a way to bypass this weak line with a relay in the back - any tips?

Thanks,

-Brian E
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PostPosted: Tue Sep 20, 2011 9:31 am    Post subject: Reply with quote

Thanks for the info! What kind of relay should I use? Is there an inline mount for them that works well? Where do you pick up power in the back?I have heard of people putting the relays up by the ECU as well?

-Brian
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PostPosted: Mon May 28, 2012 6:50 pm    Post subject: Reply with quote

This should be on the Hall of Fame thread page.
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PostPosted: Mon May 28, 2012 6:57 pm    Post subject: Reply with quote

nemobuscaptain wrote:
This should be on the Hall of Fame thread page.


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PostPosted: Thu Jul 05, 2012 3:06 pm    Post subject: Reply with quote

nice - I think a big alligator clamp for the battery + end might be best - that way if you "smell something" you can snatch the thing off the battery fast from the driver's seat w/o having to grope for the fuse
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PostPosted: Tue Apr 30, 2013 8:49 am    Post subject: Reply with quote

Mark, I just posted in another thread regarding your diagnostic tool but it occurred to me that a quick post here would bump this thread so that others could benefit. It allowed me to find a frayed wire at my alternator which significantly reduced power to the ECU relay.

I'm amazed how such a simple tool can help troubleshoot so many possible issues.

Thanks again!
-Mark
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PostPosted: Tue Apr 30, 2013 8:53 am    Post subject: Reply with quote

I too use this tool all the time.
It really helps get to the bottom of wiring issues.
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