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dead van diagnostic tools, wiring bypass
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joebus
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PostPosted: Thu Feb 08, 2018 2:49 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Yes Sir, true, very few!
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joebus
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PostPosted: Sat Feb 10, 2018 11:58 am    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Gents,
I used the tool, still no success, please help, what should be checked next? Any advice????
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16CVs Premium Member
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PostPosted: Sun Feb 11, 2018 12:12 am    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Have you swapped in a known working ECU?
Have you pulled the injectors and checked them for spray?
Have you pulled a plug and checked for spark?

Maybe some Photos might help, there may be something glaringly obvious that is being missed.

I've just finished messing with this system and feel quite familair with it.

Stacy
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vanmarc
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PostPosted: Thu Jun 06, 2019 8:32 am    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Great tool. I'd like to take make one and keep it packed in the van.

These 6amp diodes could work in place of the Radio Shack diodes, correct?


https://www.amazon.com/NTE-Electronics-GI754-Recti...amp;sr=1-3
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crazyvwvanman
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PostPosted: Thu Jun 06, 2019 9:29 am    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Those should be ok. The diodes I originally chose were just ones commonly in stock at RadioShack stores at that time. Back then RadioShack stores were everywhere so you could just buy what you needed the same day you wanted it. There are lots of choices now online.

Mark
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WestyWonderland
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PostPosted: Mon Mar 22, 2021 8:21 am    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

A bump in appreciation of this thread -- I found some valuable information in it and will comment more when I've fix the beast.
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BonzoVan
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PostPosted: Wed Feb 09, 2022 1:30 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Help!

I just discovered this post and I'm hoping it can save me. 1987 Vanagon 2.1

Everything was fine (as it usually is) then all of a sudden my engine turns off while going up a hill.

I pulled over to have a look. It cranks fine. it just does't start. I'm not getting spark and I'm not getting pulses from the injectors.

There was no warning. It just turned off like a light switch.

I'm concerned it may be a problem with the ECU, but I would like to try to diagnose things with this tool.

My problem is I'm trying to build this tool with parts I'm scrounging. I can not find the diodes mentioned in the instructions.

...I don't have the best understanding of diode ratings. Is it possible to use smaller diodes? possible to add more than just two?

I've been taking apart various electronic devices looking for these diodes. I've managed to find four diodes, but I believe they're smaller than described.

The markings on the diodes read "IN5399 MC"

Is there anyway to make these work? Otherwise it will be a few days until I can source the proper ones.

Thank you for your help!!
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DanHoug
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PostPosted: Wed Feb 09, 2022 2:12 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

those diodes are 1.5amp rated. Mark used 2 5amp diodes in parallel for a total of 10amps capacity without overheating.

you could try putting all 4 in parallel... that'd give you 6amps of current handling and that MAY work but they may get hot too.

5 or 10 amp diodes are pretty easy to find.. don't focus too much on the part number but on 'silicon diode' or 'rectifier diode'... you DON'T want a zener diode. you can go higher in amperage, you just want to target 10 amps or more.
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BonzoVan
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PostPosted: Wed Feb 09, 2022 2:25 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Thanks for your reply! That helps a bit. I'm going to keep looking around in the hopes I can find something today.

I may try to run these 4 in parallel (after doing a bit more research). The last thing I want is to damage something on the van
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DanHoug
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PostPosted: Wed Feb 09, 2022 2:32 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

with overcurrent, diodes usually fail open, meaning it would just disconnect you like unhooking the wire. diodes CAN fail shorted but that is usually with high reverse voltage, not present in the van engine unless you hook it to the spark plug!
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60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

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BonzoVan
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PostPosted: Wed Feb 09, 2022 2:40 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Good to know! So it sounds like the worse case scenario is I damage the diodes
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shizam
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PostPosted: Fri May 06, 2022 12:20 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Couple questions on this setup:

* If the fuel pump is just going to run non-stop while this is wired up is that bad?

* How frantic should I be to crank and get the truck started once I plug the fuse in given the fuel pump is running?

* Why not use a 20A switch (in addition to the fuse) to make flipping it easier?
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VicVan
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PostPosted: Fri May 06, 2022 1:45 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

shizam wrote:
Couple questions on this setup:

* If the fuel pump is just going to run non-stop while this is wired up is that bad?

* How frantic should I be to crank and get the truck started once I plug the fuse in given the fuel pump is running?


When the engine is running, the fuel pump is running continuously anyway. So don't worry about it.
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shizam
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PostPosted: Wed May 11, 2022 9:19 am    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

The last photo is blurry and I can’t tell from the phrasing but should the diode protected wire connect to the coil IN ADDITION to the existing 2 black wires there or should I remove the 2 black wires?

Thanks
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crazyvwvanman
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PostPosted: Wed May 11, 2022 12:16 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

crazyvwvanman wrote:
..... The diode protected female end goes to the empty + post of the ignition coil where there are usually 2 black wires also.
......
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shizam
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PostPosted: Wed May 11, 2022 12:32 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

Doh, "the empty", I swear I read that sentence several times but totally missed that. Thanks, RIH!
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wehrbüchse
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PostPosted: Thu Jul 06, 2023 1:59 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

I just fabbed up one of these for use on two no-start 2.1 waterboxers. Maybe you guys can point me in the right direction about my results.

(1) 1st van is being weird. Fuel pump gets no power without the tool installed.

With the tool installed the fuel pump buzzes really loudly. With the inline fuse removed the fuel pump buzzes less loudly, but still louder than one hears in a normal van for a few seconds when turning the key to the on position. To reiterate: even when i disconnect the tool from the batter, leaving it connected to the 87 ports where the relays were, the fuel pump still buzzes loudly.

It's also getting only 7V at the starter.

(2) 2nd van belongs to my kid & has been the bane of my existence for 1.5 years. I spend a month on it last summer, a couple weeks this past spring, then finally surrendered & took it to a well reputed VW mechanic who conducted all the same tests I had already tried last summer before he too gave up and charged me 1k to hand backs keys to a non-running van.

I was very hopeful the tool would help me figure this out. Still won't start. Van gets spark and has 32psi on the fuel tee. It just turns over & over but will not start. Maybe someone can help me remember what possibilities this leaves.
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crazyvwvanman
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PostPosted: Thu Jul 06, 2023 4:30 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

The purpose of the diodes is to prevent the power from backfeeding from the coil connection to the relay sockets.
If you leave out the diodes or install them backwards the 1 coil connection wire can also power the 2 relay wires and that is a bad thing.
Also if the diodes are installed backwards then the coil connection is invalid from the battery connection and that is a primary test function of the tool.


Mark


wehrbüchse wrote:
I just fabbed up one of these for use on two no-start 2.1 waterboxers. Maybe you guys can point me in the right direction about my results.

(1) 1st van is being weird. Fuel pump gets no power without the tool installed.

With the tool installed the fuel pump buzzes really loudly. With the inline fuse removed the fuel pump buzzes less loudly, but still louder than one hears in a normal van for a few seconds when turning the key to the on position. To reiterate: even when i disconnect the tool from the batter, leaving it connected to the 87 ports where the relays were, the fuel pump still buzzes loudly.

It's also getting only 7V at the starter.....
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wehrbüchse
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PostPosted: Thu Jul 06, 2023 6:31 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

crazyvwvanman wrote:
The purpose of the diodes is to prevent the power from backfeeding from the coil connection to the relay sockets.
If you leave out the diodes or install them backwards the 1 coil connection wire can also power the 2 relay wires and that is a bad thing.
Also if the diodes are installed backwards then the coil connection is invalid from the battery connection and that is a primary test function of the tool.


Mark


Believe it or not that did occur to me but I had faith in my brother who is a physics professor in germany, I built it while I was facetiming with him and i briefly showed him the diode and quickly asked which end was which and HE steered me wrong. I should have known, as he also failed to rig my vintage 1979 Mattel Vertibird to run on AC instead of C batteries Brick wall

I suppose I should ask if anyone knows off the top of his head what damage I should look for from my latest circus clown blunder.
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wehrbüchse
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PostPosted: Thu Jul 06, 2023 6:53 pm    Post subject: Re: dead van diagnostic tools, wiring bypass Reply with quote

They seem to be correctly oriented unless I'm missing something. Which I suppose would actually be bad news in the grander scheme of things

Image may have been reduced in size. Click image to view fullscreen.


EDIT well I tested the diodes and they are indeed working as as a one-way voltage path, in the correct orientation. then I discovered the fuel pump gets power from merely jumpering the two female position 87 slots together. it would be nice if the other van worked so I could check to see if that’s normal
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