73-87chevytrucks.com

73-87 Chevy _ GMC Trucks => Electrical => Topic started by: primemover on October 19, 2016, 05:22:00 pm

Title: 1986 c7000 box truck 366 engine won't start
Post by: primemover on October 19, 2016, 05:22:00 pm
Electrical issue: For a few days, I had dash lightup when switching on ignition, engine rotation when switching to "start," but no fuel feed. Added gas to tank, changed a _very_ old filter, and tried again. Switch to "ignition," and everything lighted up; switched to "start," and I got maybe a second of starter action, then everything quit. No further electricity movement. I have power to the ignition (same voltage as at Battery). I figure it must be the switch or some fault after the switch. How do I diagnose this??
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: VileZambonie on October 19, 2016, 05:25:03 pm
check your battery connections
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on October 20, 2016, 07:46:16 am
Positive and negative battery connections are firm. Correct voltage at battery, correct voltage at cowl junction. Correct voltage incoming at ignition switch. Nothing going through the switch. Are there other connections I should be aware of before the switch?
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: Jon87V20 on October 20, 2016, 10:34:02 am
Just out of curiosity, has it been sitting for a long time?
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on October 20, 2016, 01:15:51 pm
Oh, sure.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: Irish_Alley on October 22, 2016, 07:19:42 am
check your connections at the starter also. theres a chance that you may have contact to get 12v but a poor contact so it cant carry the amps
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on October 27, 2016, 09:08:58 am
I wish my schedule would allow me to stay on this project until fixed:( Oh, well:), on we go!

I have 0.2 amp coming in at the ignition switch. i don't have the specs available, but that wouldn't seem to be enough. What has anyone found to be the right # of amps coming into the ignition switch?

 
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on October 27, 2016, 11:40:03 am
I have 0.2 amp coming in at the ignition switch. i don't have the specs available, but that wouldn't seem to be enough. What has anyone found to be the right # of amps coming into the ignition switch?

Are you confusing voltage with current?  Current flow is based on the electrical load that is operating at the time.  To clarify, describe how and where your meter was connected to the circuit and what you were attempting to measure.

More than likely the truck has connection problems or a damaged fuse link.  Base your diagnosis on voltage drop measurements while the circuit is operating.  For instance, check for voltage at the ignition switch while attempting to crank.  Did you check the battery cable end and its connection to the starter solenoid as suggested?  The cast exhaust manifold on MD trucks prior to the introduction of TBI concentrated heat in the area of the starter, baking the solenoid and its connections, causing them to gradually loosen with use.  Even a slightly loose cable connection at the starter can rapidly degrade and burn, severely limiting current flow.  Occasionally, there will be sufficient electrical connection to supply voltage down circuit until an electrical load is applied, causing the connection to instantly open.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on October 27, 2016, 12:29:05 pm
Thanks, bd!

So, with current flow based on  the electrical load operating at the time, if I have no load operating, I can expect no current (or maybe something small, like 0.2 amp). Do I have this part right?

As the circuit will not operate, I can not measure any voltage drop while it _is_ operating (as, e.g., while attempting to crank.

I cannot (yet) reach the connections on the starter solenoid, as the heat shield is in the way and rusted in place, until I can get the nuts loose:( Therefore, I am only wishing (while I wait) to check those connections.

The MD truck heat concentration issue at the solenoid seems like a reasonable possibility for my situation. Twice, I have had this scenario. With appropriately charged battery, turn on ignition. Everything works that is supposed to. turn key to "Start." Starter turns over for a couple of seconds or less, and all power is lost, suggesting a connection supplying power was burned up or jarred loose. Working with the "burned up" assumption, I searched unsuccessfully for a burned wire or fusible link. Finding neither, now I working with the "jarred loose" assumption. Could the starter being jolted with an impulse to start from the ignition in "Start" position be enough to "jar loose" a bad connection elsewhere on the solenoid -- where the battery cable joins the solenoid and a wire that might supply power to the ignition switch?

Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on October 27, 2016, 01:03:49 pm
What type of ammeter are you using - inductive or series connected?  If a circuit is "open" there will be "zero" current flow.  Current indication on an ammeter means that either a circuit is connected and operating (even if not effectively) or the ammeter isn't zeroed, or it isn't stable and it drifts.  Avoid using an ammeter to diagnose this problem.  Use only a voltmeter and analog test light.

As the circuit will not operate, I can not measure any voltage drop while it _is_ operating (as, e.g., while attempting to crank).

As long as voltage is connected to a circuit, you can measure voltage drop.  You just need to understand what the measurement is telling you.  You measured B+ at the ignition switch.  Was that while attempting to crank the engine?
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on October 27, 2016, 01:14:14 pm
My Ammeter is the 10Amp function on a multimeter -- I assume that is series connected. Induction is the type that wraps around a cable, right?

Voltmeter and analog test light -- I will:)

What is B+? I was not attempting to crank the engine as it seemed that no power was going through the switch, either in "Start" or in "Run" (ignition switched on).
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on October 27, 2016, 01:41:44 pm
You have a series connected ammeter.  Using a series connected ammeter for diagnosing power delivery problems imposes a high risk of blowing the internal meter fuse if there is any possibility that the circuit being measured can draw greater current than the selected scale of the ammeter - in this case 10 amps.  Had the starter solenoid actually engaged, in combination with ignition, etc, it probably would have blown the meter fuse.

B+ is battery hot, or 12.6 volts for a fully charged automotive lead-acid battery.

For a list of automotive acronyms see, Common Automotive Acronyms (http://forum.73-87chevytrucks.com/smforum/index.php?topic=32586.msg276108#msg276108) in our Technical Pages.

I was not attempting to crank the engine as it seemed that no power was going through the switch, either in "Start" or in "Run" (ignition switched on).

Retest using the voltmeter or a test light, probing all of the ignition switch cavities in turn while attempting to crank.  Include the red B+ wire that feeds power into the ignition switch when performing this test.  Post what happens.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on October 27, 2016, 03:30:32 pm
Good to know that about the multimeter Ammeter function. That must be why I never tried to use it before now -- too scary!

I was afraid we'd get around (sooner or later) to probing connections. Seems simple, but I never did figure out how to do that. And I can't seem to figure it out this afternoon. I've poked a big paper clip down next to the terminal block connection on the ignition switch, but I can't seem to make contact. With the switch disconnected from the terminal block to expose the blade connectors, I do get 12.65 volts on the "BAT" blade, but, of course then I can't see if the switch will transfer that to the other blades connected to wires. Leaves me kinda stumped and feeling silly.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on October 27, 2016, 03:54:41 pm
...With the switch disconnected from the terminal block to expose the blade connectors, I do get 12.65 volts on the "BAT" blade, but, of course then I can't see if the switch will transfer that to the other blades connected to wires....

Not following you.  Post a pic of what you are doing along with the meter and its test leads.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 04, 2016, 08:16:48 pm
Here are three photos of the ignition switch parts I'm working with. I have voltage to the hot wire connector from the battery, but I'm not getting any voltage to show up downstream through the switch or bypassing it. On any other vehicle that lost power through the switch, I've always been able to bypass the switch by pulling the terminal block off the back of it and making up a set of wires to leave the switch out of the stream. I can't seem to figure this one out.

I'm getting battery voltage from the BAT connector to the IGN connector on the terminal block but not to any other connector.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 04, 2016, 08:25:10 pm
I was having trouble uploading photos (too big). Here are the other three.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 04, 2016, 08:40:56 pm
The absence of a wiring diagram will slow this down a bit.  Nonetheless, you measure B+ (12.6 volts) on the red wire, correct?  What do you measure on the red wire when the harness connector is plugged into the ignition switch and the ignition is turned on?  Does the red wire continue to measure B+?
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 05, 2016, 07:03:25 am
OK. Now we are at the problem I had when you suggested that before. With the switch installed, I can't seem to get access to the red wire (or any of the others) to measure voltage. The ends of all those wires are well protected by the terminal block that mates with the switch!
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 05, 2016, 07:54:22 am
HaHa!  Reminds of a song sung by Harry Bellanfanti in the 1950s, "There's a hole in the bucket...."

You have at least four choices: 1) fabricate short, 14-gauge wire jumpers using bare terminals that insert between the connector and the switch, then probe the bare terminals, 2) use a terminal tool (image) or pocket screwdriver to depress the locking tabs on the backsides of the terminals to remove the wires from the connector and plug them directly to the ignition switch, 3) force the meter probes down alongside the wires in the connectors until you make contact with the terminals, or 4) pierce the wire insulation with the sharp point of the test lead (not a problem, since inside the cab the wires are protected from exposure to corrosive elements - though, not a good idea for wires exposed to weather and road salt outside of the cab).
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 05, 2016, 08:07:10 am
Fantastic! Now, I'm learning stuff:) Some that I can use on this project, and a bunch for other applications. Oveer the next few years, I might even get some things done in less than a week:)

Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 05, 2016, 09:09:48 am
Yup, definitely a hole in this bucket -- with a very circuitous path to understanding how to find it:)

Terminals removed from block and attached directly to switch. No voltage now at red wire, either with switch on -- or off! New (possibly misleading) symptom. Thinking maybe I left the battery disconnected when last here, I went around and _opened the hood_. Voila! Loud buzzing noise!! Sounds like ignition is on. Yup, ignition in on position. I have 12.7 volts on red (ignition off), 11.8 volts on red (ignition on), 9.6 volts on red (switch in start position) with starter motor turning over.

I like what I have, but what did raising the hood have to do with power to the ignition switch (if anything)?? [I love internittent electrical faults~:(]
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 05, 2016, 10:43:44 am
Does the truck have an alligator hood or tilt?  Are there one or two long terminal strips on the firewall?  Post an image of the engine compartment firewall on the driver side.  Have you removed the starter heat shield and checked the battery cable and solenoid connections yet?  When you do, inspect the phenolic end-cap of the solenoid for evidence of heat damage and deterioration around the battery cable connection, especially if the cable was loose.  If the battery cables are original, replace both with 00 copper cables - terminal ends securely crimped, soldered and shrink sealed.  Do not use battery cable ends that attach to the cables with a metal strap and two bolts.  Be mindful of routing new cables away from high heat sources such as the exhaust.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 05, 2016, 01:22:01 pm
Lots to reply to:) Here is a start.

Alligator hood -- hinge partially visible in one photo.
Two long terminal strips -- visible in same photo with labels on plastic flap (cover).
Heat shield not yet off. Comments taken under advisement for when it is.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 05, 2016, 01:25:51 pm
How about those pictures I can never remember to attach on the first message:(?

And there is a partial view of the other hood hinge in the final photo.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 05, 2016, 01:26:57 pm
one more try on that last photo
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 05, 2016, 02:41:16 pm
(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=33878.0;attach=34167;image)

Since the problem is intermittent...

Check/replace the battery cables and inspect the cable end connections and solenoid as previously described.  Disassemble and burnish the Upper Block terminal strip connections 2, 3, 5 and 7 then reassemble with antioxidant (e.g., Truck-Lite NYK-77 Corrosion Preventive Compound (http://www.truck-lite.com/webapp/wcs/stores/servlet/ProductDisplay?urlRequestType=Base&catalogId=10002&categoryId=13124&productId=50965&errorViewName=ProductDisplayErrorView&urlLangId=-1&langId=-1&top_category=15555&parent_category_rn=15555&storeId=10001) or equivalent).  The preferred Truck-Lite product should be available at most commercial truck dealers and truck stops.  Otherwise, pick up some GB Ox-Gard from your local hardware/electrical supply.  Don't waste your money on the clear dielectric compound available from the local auto parts store.  It's not as effective.  Check the cab and frame grounds.

IIRC, there is a fusible link jumping between two of the power terminals.  The length and gauge of that link is crucial to calibration if the truck has a factory ammeter.  If any of the terminals are suspect, be sure to mechanically crimp, 60/40 rosin solder and shrink seal the replacement terminals.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 05, 2016, 04:01:48 pm
Thanks Rich,

This plus the starter access and terminal clean-up (plus finding and cleaning grounds) will keep me busy for a day or two, this week:)

Gene
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 07, 2016, 01:35:18 pm
Companion problem: No gas to carb (carb seems to be dry after cranking for better part of a minute -- choke on). Mechanical pump on engine. ~5 gallons of fuel in tank. New filter(large canister between tank and pump. Any thoughts?
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 07, 2016, 04:07:00 pm
With the battery fully charged, use a test gauge to check fuel pump vacuum (>20" Hg), pressure (~7 PSI) and volume (typically ~1 Qt in 20 seconds of cranking).  Does a drop of engine oil from the dipstick hold its circular shape on your fingertip or does it quickly track outward along your fingerprint?  Dual saddle tanks?  Some MD configurations had an electric transfer pump in the secondary fuel tank.  Make sure it works.  Check the condition of all of the fuel lines.  In rare cases, the fuel standpipe will develop a crack near the fitting at the top of the tank, causing it to draw air.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 07, 2016, 05:32:55 pm
Incidentally, five gallons of fuel may not be sufficient depending on tank capacity, especially if the fuel was added to the secondary tank.  Check the condition of the o-ring on the f/filter canister.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 07, 2016, 06:55:38 pm
All helpful thoughts, Rich. Would this pump need to be rimed, after having sat a while with an empty tank. I'll be back into this effort with the rising sun:)
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 07, 2016, 06:59:24 pm
The GM pumps are self-priming.  But, if the pump check valves are gummed up or corroded, or if the diaphragm is perforated, replace the pump.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 09, 2016, 04:24:32 pm
...if the diaphragm is perforated, replace the pump.

This previous post was incomplete.  If engine oil dropped onto your clean fingertip quickly tracks outward along the finger ridges, the oil is contaminated with fuel.  Fuel dilution generally occurs when the fuel pump diaphragm perforates.  So, if there is fuel in the oil... replace the mechanical fuel pump.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 10, 2016, 06:52:21 pm
So, I'm down to the part of this saga where the fuel pump has been identified as not pumping fuel. I have it out and I'm having fun scraping the mounting surface of old gasket material. long, but I'm getting it. I took a break to assess installation of the new pump, and I'm looking at the area around the mating surface I'm trying to clean. underneath that surface, on the exterior of this 366 engine, there is a bolt screwed into the engine. Is it of no consequence in this saga, or is it an access point for the pump's push rod, such that I could remove the bolt, push up the push road, and insert the new fuel pump?

Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: bd on November 10, 2016, 09:14:30 pm
Remove the B+ primary lead from the distributor and have an assistant tap the engine over with the starter until the fuel pump pushrod is fully retracted into the block.  Be careful not to trap your finger with the pushrod while cranking.  The bolt hole on the front of the block maybe drilled through into the pushrod bore.  If so, you can use a nylon (preferred) or soft metal bolt to lightly retain the pushrod in the up position.  Be careful not to score the pushrod so that it binds in its bore.  Stabbing the replacement pump can be a little tricky, since the spring under the fuel pump arm will compress as the pump is slipped into place.  Pay close attention that the fuel pump arm doesn't slip off to the side of the pushrod as the pump bolts are installed and tightened.  Don't forget to remove the pushrod retaining bolt from the front of the block when you are done and reinstall the short bolt that you initially removed.  Then reconnect the distributor B+ lead.
Title: Re: 1986 c7000 box truck 366 engine won't start
Post by: primemover on November 15, 2016, 04:42:39 pm
Engine is running with fuel from the tank! 5 gallons in the 75-gallon tank was enough to get it going, but I'll add more now:)

Quite a saga. To start the diagnosis, I removed all the pump connections, then hooked up 6 feet of clear hose to a five-gallon gas can outside the wheel. Pump produced no fuel. Double-checked everything, tried again to no avail. Pulled the pump for positive ID of a replacement. Of course, I pulled the pump without looking for instructions, as all of my mechanical pump pulling was back many decades on cars that had push rods up from the top of the crankshaft, so they didn't get lost in the engine:( I could not access the bolt on the front of the engine to put in a nylon bolt to hold the push rod up. I did find an access bolt on the bottom of the push rod. After nudging the crank around to let the push rod up, I was able to get a dowel of a size to go into that hole and brace against the bottom of the push rod to hold it high enough to let the fuel pump arm in under the push rod where it displaced the dowel and allowed the pump to seat against the engine block while I screwed in the retaining bolts. (On my back in the driveway with a droplight, a collection of tools of destruction off to one side on a board to keep them out of the gravel, next 24 hours spent with a pretty sore shoulder -- but ok after that.) I let the Permatex 2 on the gasket cure overnight, as I surely do not want to do this job again!

Next, I moved to the carb, removed the old hose and took out the carb connection to find a filter -- none there. I decided on an inline filter just before the carb which was easy to cut into the new fuel line between the tubing from the pump to the top of the engine and the carb. Keeping some of the old lines, I wanted to be able to catch any line crud there might be before the carb.

Hooking up the pressure line to the carb (with Anti-Seize to ease the re-mating of the old pressure conn) and the return line, I put the clear plastic supply line from the gas can back on and cranked. Nothing but _leakage_ at the pressure side conn on the pump:(

Finding Permatex Aviation (#3) locally [not an easy search!], I cleaned off the remaining Anti-Seize and wire brushed out rust remnants, carefully put Aviation (#3) on the threads only, and eased it all back together. Turning the key in the ignition, I was rewarded with a running engine. I let it warm up out of the gas can before turning it off. Finally, I reattached the old hose from new inline filter back on the frame and the tank. Turning the key in the ignition gave me the satisfaction of a running engine without the life support of the gas can:)

Thanks to everyone, especially Rich for holding my hand through this adventure. now I'm into the braking system to see if I can replace enough lines to get at least front brakes working. The line to the rear has been out for years, and I'm just moving it around the yard or maybe selling to a farmer for mobile goat housing in the field, also flat terrain.

Gene