Author Topic: No start  (Read 186 times)

Offline AlphaLimaRomeo

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No start
« on: October 11, 2017, 11:46:15 PM »
Hi everyone. I'm new to the forum. About a year and a half ago I picked up an '86 LWB Silverado C10. Got it cheap from my father in law as a project. The body is great but I'm working out a few issues.

For some background , the truck has mainly sat since I got it due to some other problems. A few months ago my battery died so I got a new one. It just wouldn't hold charge. After I replaced it I began starting it and letting it sit once a week to let everything loosen up. It worked flawlessly for months.

Last week I went out to mow and moved the truck. Once again, flawless start. But I go back an hour or two later and it won't start. The starter will engage for a split second and then all power shuts down. I checked the battery and I'm reading 12.4vdc and my cables look good. Small things such as the clock or dome light will come one but as soon as you try to pull a load (in any ignition setting) the power shuts off. This is including the fan and headlights. It's the same symptom. It will work for a split second and then nothing. I also tried letting it cool down for a while and still had the same problem.

While digging around I did find that the previous owner had tried to "splice in" a radio power wire (and by splice I mean strip an 18 gauge section of wire from a hot battery wire at the fuse box and wrap the radio wire around it, leaving the mess of wire strands exposed.) I snipped that and repaired the battery wire but that made no change.
Also my ground wire to the radiator support burned up so I'm going to have to track the short there, but that's been that way for sometime before this happened.

I'm going to check my fusible links tomorrow and if they check out I'll try to do some wire checks. I have a lot of schematics and a good understanding of electronics (I worked on Osprey electronics for the Marines for 5 years).

I was going to see if anyone had any other suggestions. I have seen alot of threads on here about it but none of them had the same symptoms I have. Thanks for your help.
« Last Edit: October 12, 2017, 12:06:07 AM by AlphaLimaRomeo »
1986 Chevy Silverado C10 >LWB!<
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Online bd

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Re: No start
« Reply #1 on: October 12, 2017, 01:20:29 AM »
Hello and welcome to the site!  Thank you for your service!

What's the battery voltage reading while cranking?  In addition to the fusible links, check for a loose battery cable connection at the starter solenoid 3/8" stud.  Measure the voltage drops across the battery B+ and B- cables while cranking.  Pay particular attention to the voltage drop measured between the battery negative post and starter case while cranking.  The melted radiator support ground wire implies the primary starter ground path may have been compromised.  Refer to the factory 1986 Wiring Manual as needed.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline AlphaLimaRomeo

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Re: No start
« Reply #2 on: October 12, 2017, 02:05:37 AM »
Thank you and my pleasure.

I will try to do the crank tests tomorrow. I also want to check the amps running from the battery to make sure it's up to spec. as well troubleshoot that radiator support ground. Thanks for the diagram download. Those are much better quality than mine.
1986 Chevy Silverado C10 >LWB!<
USMC

Offline AlphaLimaRomeo

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Re: No start
« Reply #3 on: October 12, 2017, 06:10:01 PM »
Ok so I went out and checked the battery input on the starter and power is getting there anytime the key is turned on. It doesn't drop out when everything goes dead. I checked through the two fusible links next to the solenoid and they both read .3 ohms. While looking for the one behind the alternator, I noticed the black wire on the connector had a pretty good nick in the insulation down to the wire so I fixed that but that had no effect.

The last thing I tried was I hooked up to the ignition terminal on the solenoid and turned the key on. The meter jumped to about 1-2 VDC for a split second and then back to 0. I'm wondering maybe if my ignition switch might be faulty, allowing a few accessories to get power but nothing with a heavy draw.

I didn't get a chance to fix the ground wire to the radiator support yet. I need to pick up some wire. I did notice that that wire had a lot of corrosion even under the insulation so that may have caused it to burn.

Also a quick off topic question. I found a harness out of the firewall (just behind the transmission dipstick tube) that has been cut. I'm thinking it's probably emission related but I would like to know. Here's a picture:



« Last Edit: October 12, 2017, 06:16:29 PM by AlphaLimaRomeo »
1986 Chevy Silverado C10 >LWB!<
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Online blazer74

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Re: No start
« Reply #4 on: October 12, 2017, 07:20:39 PM »
Have you tried jumping the starter solenoid with screw driver or remote start switch to see if it will crank over.
If so will it start with the ignition switch in the run position.

Offline AlphaLimaRomeo

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Re: No start
« Reply #5 on: October 12, 2017, 08:43:22 PM »
I haven't tried jumping the solenoid yet. That's what I was going to do next but I ran out of time.

I did hook up to the battery and switch to start and there was no change in the voltage since it's not being pulled by the starter.
1986 Chevy Silverado C10 >LWB!<
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Online bd

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Re: No start
« Reply #6 on: October 12, 2017, 08:52:58 PM »
You can try jumping the solenoid as suggested.  If that doesn't provide a solution continue with the following...

Ok so I went out and checked the battery input on the starter and power is getting there anytime the key is turned on. It doesn't drop out when everything goes dead. I checked through the two fusible links next to the solenoid and they both read .3 ohms. While looking for the one behind the alternator, I noticed the black wire on the connector had a pretty good nick in the insulation down to the wire so I fixed that but that had no effect.

...I didn't get a chance to fix the ground wire to the radiator support yet. I need to pick up some wire. I did notice that that wire had a lot of corrosion even under the insulation so that may have caused it to burn.

There are several points to clarify, here:
  • The positive battery cable to the starter solenoid should measure battery voltage (~12.6 volts) at all times, not just when the ignition is switched ON.

  • Don't waste your time using an ohmmeter to diagnose wiring issues on a vehicle.  First, unless you possess a lab-grade ohmmeter or bridge, the ohmmeter won't offer sufficient sensitivity to accurately measure resistance less than about 5 - 10 ohms.

    Second, ohmmeters provide totally misleading information when used to evaluate medium- to high-current electrical environments.  For example, let's assume for a moment that your ohmmeter measured the cable resistance accurately: 0.3 ohm resistance in a battery cable will prevent a starter from cranking.  This is because the effective impedance of a 150-amp draw starter motor is ~0.08 ohm - meaning that the battery cable would have ~4 times the resistance of the starter... 4/5 of the available voltage would be lost across the cable.  Only 2.5 volts would actually reach the starter motor while cranking.  Get the idea?  A slightly loose battery cable connection to the starter could stifle your efforts to start the engine.

    Closer to home, regarding the 0.3 ohm measured resistance of both fusible links at the starter, suppose there occurs a 30-amp draw through either link.  Under normal circumstances, according to Ohm's Law (R=V/C), a 30-amp draw (C) with an applied battery voltage of 12.6 volts (V) would mean that the circuit resistance (R) would be 0.4 ohm.  Using simple ratios (0.3/(0.3+0.4) = 0.3/0.7 = 0.4286), you can calculate that the 0.3 ohm fusible link will consume ~43% of the available voltage, or 0.43 x 12.6V = 5.4 volts.  In other words, only ~7 volts would actually power the 12 volt appliance.  What do you suppose would happen? 

    Always rely on voltage drop measurements to evaluate routine automotive electrical issues!  Measuring voltage loss directly will eliminate metering and calculation errors and indicate instantly where a problem exists, since in a perfect world, all of the voltage in an operating circuit should drop across the load.

    With that stated, measure the DC voltage drop with the voltmeter connected between the battery positive post and the 3/8" battery cable stud of the starter solenoid; it should measure <0.3 volt while cranking.  Repeat the process with the voltmeter connected between the battery negative post and the starter motor frame (starter case); it should measure <0.3 volt.  DO NOT replace the melted battery-to-radiator support ground wire until you perform this measurement or you could damage the new wire!

  • The last thing I tried was I hooked up to the ignition terminal on the solenoid and turned the key on. The meter jumped to about 1-2 VDC for a split second and then back to 0.  I'm wondering maybe if my ignition switch might be faulty, allowing a few accessories to get power but nothing with a heavy draw.

    Which solenoid?  Elaborate please.  Thus far, your description implies a poor or burned cable connection or compromised fusible link.  Give all of the links a firm tug to see if any stretch or pull apart.  Make sure all are securely tightened to their respective studs.

  • The abandoned firewall feed-through was probably for Electronic Spark Control (ESC) that previously moderated the ignition timing advance.
Good luck and keep us apprised.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline AlphaLimaRomeo

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Re: No start
« Reply #7 on: October 12, 2017, 09:23:47 PM »
The reason I was using resistance was only to check the wires to ensure I didn't have something broken or shorted. That and as of right now the only power I seem to be getting is from the battery to the starter. If I can get it started by jumping the starter solenoid then I can do a lot more voltage tests to determine where I do or don't have power and if there's enough or too much going somewhere.

Sorry for being vague. That last test was from ground to the starter solenoid terminal to see if the ignition switch was routing power to it when turned to start. It jumped to 1 or 2 VDC for a split second and then 0.

Also I made a mistake in saying the battery is sending power to the starter when the key is on. There are 12VDC sitting at the starter battery lug at all times.

I will go over the fusible links again tomorrow and see how they all look and then try to jump the starter solenoid.

Thanks
1986 Chevy Silverado C10 >LWB!<
USMC

Offline VileZambonie

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Re: No start
« Reply #8 on: October 13, 2017, 05:56:01 AM »
Quote
The reason I was using resistance was only to check the wires to ensure I didn't have something broken or shorted.

To bd's point, it is an invalid test. Always use dynamic measurements and effective voltage drop testing whenever possible.

Maybe I missed it, but did you clean the battery terminal connections and re-secure them?
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Offline AlphaLimaRomeo

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Re: No start
« Reply #9 on: October 13, 2017, 08:56:52 PM »
Yep. Not long after I got it the positive connecter broke so I replaced both and cut about half an inch back from the original location to get good clean wire. I may check under them again to ensure that the wires haven't corroded since then. But it looks fine. And the terminals are still as clean as when I bought the battery. I do need to pull the wires from the starter and check that end. It looks fine but I want to make sure.
1986 Chevy Silverado C10 >LWB!<
USMC