Short on "G104" With Diagram

Short on "G104" With Diagram

Postby OldSchoolNoe [OP] » February 13th 2021, 11:58pm

Hello AstroSafarians or Safastrovians, whatever you like, I bring you a high-level circuit diagnosis. Anyone familiar with the tool "ECT3000?" No? well you plug it into a fuse circuit or into a relay circuit, it then notifies you whether you have an "open" or a short on that circuit, pretty neat eh?

Well I've been pestered by the nastiest electrical gremlin ever conceived...but we got it cornered. The Starter Enable Relay has 2 short circuits. I've included a modified wiring diagram to help visualize the problem.

Plugging the tool into the slot pin 86 occupies yields a short circuit. Same with pin 87. The rest are A-OK. I've followed the black cable that runs from the fuse box to Ground 104 (See Diagram) and everything looks good.

Question is if the short is located between battery and that "B" connection on the starter solenoid, will that fool pin 86 into thinking it has a short?
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Re: Short on "G104" With Diagram

Postby albrow100 » February 14th 2021, 1:29am

What symptom are you having? You say shorted, but is it shorted to power or ground? If pin 86 was shorted the relay coil ground would be grounded again and cause no issues
If pin 87 was shorted to ground the engine wouldn’t crank over and it would blow a fuse
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Re: Short on "G104" With Diagram

Postby OldSchoolNoe [OP] » February 14th 2021, 2:22am

This is the symptom https://www.youtube.com/watch?v=za8ciw5amTE
no blown fuses. Crank no start with 0 PSI at fuel pump. I'm just going to go ahead and change the fuel pump, maybe this whole thing fixes that way.



edit: Embedded video BK
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Re: Short on "G104" With Diagram

Postby N6KB » February 14th 2021, 4:28am

I know nothing of an ECT3000. I use the Ohmmeter function in a DMM (Digital Multimeter) to determine whether there is a short to ground. Without a measurement in Ohms how can you, or an ECT3000 tell whether you have continuity of a value you would expect from a relay coil or lamp filament (not a fault) or a lower resistance that would indicate a short to ground fault?
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Re: Short on "G104" With Diagram

Postby OldSchoolNoe [OP] » February 14th 2021, 7:07pm

You make a great point. I've been using these "fancy" tools, but I need to go back to basics. I'll start by running a continuity test on these problem wires.
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Re: Short on "G104" With Diagram

Postby sixsix » February 14th 2021, 7:39pm

Is this the same situation you had w/ fancy stuff back in Jan...?

OldSchoolNoe wrote:Hello all using a relay circuit tester to find a bad wire or bad ground. It is Cal-Van Tools 76. Simple tester the tool shows 2 lights, green = connected to battery and red = connection to ground. It tests battery to relay wiring (30) relay to switch (86) and relay to component (85)

Currently seeing what these lights tell me about the wires, what do you see? Van has crank no start condition. Fuel pump 60 psi, no blown fuses all relays passed a relay tester test.

Simple right? Here it is testing the fuel pump circuitry


Testers with a gadget are still testers... but it ends up being cheaper than an Overpaid Certified Mechanic.
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Re: Short on "G104" With Diagram

Postby dcsleeper » February 14th 2021, 8:09pm

You have to know how to use the multimeter correctly so you make sense of what the magic bubblegum machine is telling you.


pin 86 to g104 is all one thing, that is tied to ground at g1o4. with a multimeter it would be 0 ohms

pin 87 is reading the continuity thru the coil of the relay to ground. from 3 PPL strait down to ground.

Which means it is lying to you, NOT a short. It has the resistance of the relay coil.
Throw it away.

Don't take the shortcut to learning how to use a multimeter properly, by relying on shortcut tools (which confuse you).
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Re: Short on "G104" With Diagram

Postby AstroWill » February 14th 2021, 8:40pm

I would say it's not lying, but you still have to know how to interpret the results. All of these new threads, fancy tools, fun stuff but get back to basics and maybe not spread everything out over 8 different threads might make it a bit easier for others to follow along.
My ground wire is a direct 'short' to ground as well ;)

Edit:
https://en.wikipedia.org/wiki/Short_circuit wrote:A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit. The opposite of a short circuit is an "open circuit", which is an infinite resistance between two nodes.

https://www.merriam-webster.com/dictionary/short-circuit wrote:short circuit noun
Definition of short circuit (Entry 2 of 2)
: a connection of comparatively low resistance accidentally or intentionally made between points on a circuit between which the resistance is normally much greater

https://www.dictionary.com/browse/short-circuit?s=t wrote:short circuit
noun Electricity.
an abnormal, usually unintentional condition of relatively low resistance between two points of different potential in a circuit, usually resulting in a flow of excess current.


Now if we want to talk about a 'dead short', well different words have different meanings.
Regardless, have to use the proper testing methodology.

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Re: Short on "G104" With Diagram

Postby dcsleeper » February 14th 2021, 8:49pm

It's lying.
Q: When is a short not a short?
A: When it's NOT

It's low impedance, I'd guess 25-100 ohms but not 0 ohms.

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these often on sale for 3 bucks or so. Always check the leads with the ohm setting, then switch to volts dc
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Re: Short on "G104" With Diagram

Postby albrow100 » February 14th 2021, 9:06pm

If you have no fuel pressure I would get a multimeter and check for power and ground at the pump. If you have proper voltage and a low ohm reading on the ground side
I’d say bad pump.

If you don’t have voltage or ground then you should start chasing the diagram figuring out where your problem lies.


Relay circuits vary and the testers don’t take that into consideration.
Sometimes ground is always present, sometime a transistor switches ground.
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