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  View original topic: When is battery voltage NOT battery voltage? SOLVED
bobhill8 Sat Aug 22, 2020 11:20 am

Hey - working on a crank/no start issue on a recently reinstalled 1986 2.1 waterboxer after new heads installed. I am working through the Digifant Training manual as well as the amazing flow chart created by Sanchius and of course the work of Crazyvanman. So I think I have narrowed it down to the Hall Sender. Testing the outer terminals of the Hall plug, I am getting 11.7 V while the battery is 12.6. So is that enough of a difference to be my problem?
I know the following:
Fuel pump works and there is fuel at the T screw.
Plugs are dry
FI NOT spraying
Weak spark from coil
Full battery voltage at starter, alternator, red wire under wiring box in engine compartment and relays
Switched in spare Ig switch - no diff
Switched in spare Ig coil - no diff
Switched in spare ECU - no diff
With CVM's diagnostic tool, the engine will NOT start.
The engine turns freely and strongly but is not getting what it needs.

Since this is a recent engine reinstall, I am aware that I may have not plugged something in, but I have looked over and over carefully and found nothing awry.
Thanks as always - hopefully most of you are in the wilderness and not reading this.

Vanagon Nut Sat Aug 22, 2020 12:25 pm

Maybe check

- for wire breaks, intermittent breaks, wire resistance, to hall and possibly coil.

- presence, quality of grounds particularly the braided ground between engine and frame.

Since starter turns engine well, I'd say you should see less than the ~ 1 volt difference between battery and hall. So, I'd be curious of wire resistances and/or poor or MIA ground.

Neil.

bobhill8 Sat Aug 22, 2020 1:17 pm

thanks Neil. I think it's in the wiring too. I will double check the grounds although I have been good about those. I am unwrapping electrical tape from various locations, looking for surprises.

VicVan Sat Aug 22, 2020 1:51 pm

Fuel injection relay?

Vanagon Nut Sat Aug 22, 2020 2:17 pm

Vanagon Nut wrote: ..... I'd say you should see less than the ~ 1 volt difference between battery and hall.

Or, maybe not, per se. ;)

Bentley p 28.43 shows minimum 10 volts at outer terminals on hall at dizzy. It also shows a hall function test. Dan Haug recently posted of a home made hall tester. Alternately, as crazyvwvanman outlines here, turn rotor by hand, see if FI's spray? But, since your's don't, yeah, maybe fault is at hall, wiring to it or ?

Check the green wire to hall; it connects to ECU 18. A white wire splits off from ECU 18 to idle control module in front of RH tail light. Unplug module, test spark etc again?

VicVan: if Digifant relay at fault, OP wouldn't see voltage at the hall connector?

Neil.

bobhill8 Sat Aug 22, 2020 6:11 pm

Had continuity from green wire to Hall Sender and ECU. Tried the module behind the tail light but no difference. Signs seem to point to the Hall itself. Going to repeat the flow chart steps tomorrow but then I have to wait for a new distributor.......Thanks to my friends from BC - I'll root for the Canucks tomorrow night.

Vanagon Nut Sat Aug 22, 2020 6:25 pm

If you have time....

hall tester I referred to. (I misspelled posters name though):

https://www.thesamba.com/vw/forum/viewtopic.php?t=701391

bobhill8 Sat Aug 22, 2020 6:36 pm

I have seen that cool tester in a pen, but not sure how long it will take to gather the bits and pieces. Also read VicVan's long thread about his issues with the green wires and dash. Helpful too.

bobhill8 Mon Sep 07, 2020 5:46 pm

Just to close out this thread, I did get a new aftermarket dizzy from Gowesty and the problem was gone. Had to do some work getting the timing right, but now it is running smooth with the new wiring to the Hall Sender.



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