Fuel Pump? Truck died... Can't diagnose.

[Spool]

Hey guys,

73' C20 here.
It's been far too long since I've worked on my truck or the forum, August to be exact.
Specifically because I took on too much school and work simultaneously.

However, I'm back on the truck and appreciate all of you.

My truck died at a stop sign 300 yards from my house.
2 nights before that; it ran out of gas as I have a broken fuel gauge and I lost track of my mileage.

It started fine, took it around the block and then it died in which I lost power steering and brakes.
I'm thinking a fuel pump? What do you guys think?

[bd]

Let me drop a couple of coins into my crystal ball....

    ...Well...

That didn't work....   


Will the engine start and run?  Are you certain it has adequate fuel in the tank, now?  You should verify spark and then fuel.  Pull a wire off of a spark plug and hold the open end near the exhaust manifold while an assistant cranks the engine.  Does it produce a bright blue spark?  Can you start and keep the engine running if you mist a little starting fluid or aerosol carburetor cleaner into the carburetor?  If you let a drop of engine oil fall onto a clean fingertip from the dipstick, does it hold a tight circular shape or track outward along your finger ridges?

Why not rent a proper test gauge and check the fuel pump draw (>20" Hg of vacuum), pressure (~7 PSI) and delivery volume (>1 qt in 30 seconds of cranking)?  That way you'll know whether the fuel pump is the issue rather than guessing.   

[Spool]

Thanks BD.

The engine will not start. It cranks but will not turn over.
There is roughly 5 gallons in the tank; 1/4 tank.
I removed the air filter and sprayed a touch of starting fluid in the carb with no avail.
My last oil change was 6 weeks ago (20/50) and the color is good. The drop stayed on my finger tip when I tested with the dipstick.

Now for my newbie questions as I've never worked with my spark plugs.
How do I remove it correctly and does it matter which one I check?
Per your instructions, am I to remove the spark plug, hold the wire connected to the spark plug away from the block/carburetor and observe the color of the spark while someone else turns the ignition?

Thank you as always.

[bd]

Just FYI - The words "cranking" and "turning over" with regard to an engine convey the same basic meaning.  I think you meant to say the engine cranks (turns over) but doesn't start.

Any idea how many miles are on the spark plugs or when the last major tune-up was performed?

There are several ways to check spark, but they all amount to the same thing.  Assuming you have a conventional (non-HEI) ignition system, with the engine cool remove the coil wire from the distributor cap.  Grasp the coil wire with your fingers as far away from its free end as you can and hold it 3/8" - 1/2" away from a bare metal ground.  Have an assistant crank the engine.  Be sure to keep your hand away from the free end of the coil wire to prevent an eye-opening shock.  A healthy conventional ignition system should generate a blue spark across a free air gap of up to about 1/2" wide.  After you verify adequate spark remove a spark plug for a visual inspection of gap wear.  Post a clear pic of the spark plug and its gap if you can.  Note that when removing or installing spark plugs, always use an appropriately sized spark plug socket containing a rubber insert and a ratchet with a suitable length extension to prevent cracking the plugs.

[Spool]

It's been years since a major tune-up.

I don't know much about the distributor but when you helped me re-wire my starter a few months ago, I remember we determined the distributor was HEI.

Do I need to remove power to my distributor before checking spark on a spark plug?

I have a neighbor who may be able to help me with this, but may I ask...
Are my spark plugs inside the engine? I was expecting a grab/twist/pull action.

Am I to expect something similar to this dry video?
https://www.youtube.com/watch?v=Zeq_8b3uzhg

EDIT**
Perhaps this video? More informative:
https://www.youtube.com/watch?v=L2bOqOhpqrg

[bd]

The spark plugs are located in the cylinder heads, directly below the exhaust manifolds - four each on opposite sides of the engine.  With HEI the process of checking spark is a little different since there is no coil wire and voltage production is much greater.  Leave the power lead connected to the distributor.  With a cold engine, grab the spark plug boot of the most accessible spark plug wire.  Give the boot a half-revolution twist back and forth to break it loose from the spark plug then pull the boot and wire toward you to separate them from the spark plug.  Slip the boot up the wire to expose the metal terminal end of the wire.  Grasp the wire at least 6" away from its free end to prevent a nasty high voltage shock.  Hold the free end of the plug wire 1/2" - 3/4" away from a bare metal ground (such as the exhaust manifold) while an assistant cranks the engine.  HEI should produce a bright blue spark across a free air gap of up to about 3/4".  As mentioned earlier, remove and check the spark plug associated with the wire you removed.  Post a pic of the plug if you are able.

Unfortunately, I'm experiencing Internet crawl this evening and cannot access the youtube video you linked.

[Spool]

Got it.
So I'll be looking at the end of the wire after slipping the boot back in order to observe the color of the spark.

Meaning the spark plug itself, is still inside the engine? I would need a spark plug ratchet to remove that?

[bd]

Both of the videos you linked convey the general idea to R&R spark plugs  (as long as you realize they are picturing only half an engine  ).


Besides slipping the boot up the wire, you will also remove the wire from the spark plug.  Then hold the plug wire terminal 1/2" - 3/4" away from a bare metal ground while an assistant cranks the engine.  Be sure to keep your hand a respectable distance from the bare end of the spark plug wire.  If you forget and grab the wire too close to the end, you won't have any trouble remembering in the future!  To remove spark plugs from the engine and reinstall them without damage, you will need a spark plug socket with a rubber insert, a 3" - 6" extension, and a ratchet (3/8" square drive flex-head ratchets work best).  If you have to procure the tools, best to pick up a spark plug gap gauge at the same time (attached images - I prefer the wire type gauge).

[Spool]

Much easier than expected and no one was shocked; I love learning this stuff.
However, no luck on getting the truck started.

Taking your advice and removing the spark plugs, I realized they were dirty, grimy and some of them, even rusty.
So I took a trip to AutoZone and picked up 8 new ones; ACDelco made of copper. The same type I removed.

However, after replacing them all, the truck still wouldn't start.
My neighbor came to help but we observed no spark with the new spark plugs.

Two questions on installing spark plugs if I could?
1. Do you know the gap measurement for a spark plug on a 350/4Barrel? The ones I removed were .30 and I settled for .40 on the new ones after referencing a few
other topics here on the forum.

2. Do you happen to know the torque specs for tightening a spark plug? I made it carefully snug for now as my service manual gave no specific torque; it simply said "adjust spark plugs and torque to specifications"

My spark plug cables don't look all that great either; even inside the boot is looking a little beaten and tired.
Think my distributor could be shot?

I've attached photos. Thanks BD.

[bd]

Spark plug gap should be set to 0.045"; torque spec for the plugs is 22 ft-lbs.

Regarding this image of the spark plugs...



Post another image that better shows the electrodes and gaps of the plugs you removed.  Did the spark plug terminal ends inside the boots of the wires appear sooty or discolored with greenish colored ash?

With the ignition switched on, check for 12.6 volts on the primary feed wire connecting to the distributor.  Remove the distributor cap and visually inspect inside the cap and the rotor for wear, heat damage, ash buildup and carbon tracking.  Post some pics.

[Spool]

Thank you.
I noticed in the manual it said not to bend the spark plug to adjust measure;
Would I use a filer to go wider from .40 to .45 or do you think I could get away with just pushing it a little bit?

I've attached better photos of my the old spark plugs and my progress on the distributor.
I didn't see anything green colored ash on the spark plugs, but they certainly are sooty.

As for the Distributor, I numbered them all before removing them but noticed one of them is terribly corroded as you'll see in the photo.

Also, I couldn't get a solid reading on the primary feed wire.
I grounded out my multi-meter before grounding the negative, but when I begin prodding the primary feed it's anywhere from 2.0 to 7.0 and sometimes 22.0

I remember when we were working on my starter configuration we found that there was a split on the 3/7 circuit with a resistant wire still in place instead of the necessary 12v straight from the bulb head. I'll copy/paste those comments below.

[Spool]

This was a part of our conversation from "Topic: 73 GMC Truck Wiring Diagrams/Battery Cables"

I've attached the photos. It's still in garbage condition...
I recall leaving the split as it was; but maybe it's time to power that straight from the bulkhead?

^^^ More than likely the 20-gauge yellow wires running between the starter, distributor and bulkhead connector will need to be stripped out and a new 12-gauge wire running between the bulkhead connector and distributor will need to be substituted.  This will ensure that the HEI system receives suitable primary power.

[bd]

I'm taking a conservative approach hereon out (one-step-at-a-time) to try and minimize confusion.

Step 1 - Verify that the distributor is actually receiving full battery voltage with the ignition switched on.  Set your voltmeter to its 20 VDC scale.  Clip the negative lead of your voltmeter to the battery negative terminal (B-).  Probe the battery positive terminal with the meter's positive lead to verify you have a good connection to B-.  The meter should indicate 12.6 VDC if the battery is fully charged.  Now, move the meter's positive lead to the wire connected to the BAT terminal of the HEI distributor and switch the ignition on.  What is the voltage reading?

Post a clear, close-up pic of the inside of the distributor cap.

[Spool]

I will gladly and appreciatively follow your lead.

The battery is brand new; I swapped it out a few days ago when I thought that might be the issue.

I use the DCV function on my multimeter. (Is this the same as VDC?)

I've attached photos showing the readings.

When taking the readings of the power lead to the distributor, the negative lead was on B- at the battery.
You'll see my voltage readings are all over for the distributor, even after cancelling out my terminal leads to zero and trying again.

[bd]

You either have a poor connection between the meter positive probe and the I+ wire feeding the distributor or an erratic connection somewhere in the I+ wire.  To easily determine which, try using your incandescent test light instead of the meter. 

The reason for substituting the test light is that the voltmeter doesn't impart a significant current load on the circuit under test.  The resistance of the meter is so high that all of the circuit voltage is used across the meter.  A poor connection that introduces unwanted resistance elsewhere in the circuit can prevent the circuit from functioning and yet not show up on a voltmeter as low voltage.  An incandescent test light, on the other hand, demands sufficient current to illuminate the bulb that circuit voltage will be divided between the bulb and the unwanted resistance, causing the bulb to be dim.

DCV is Direct Current Volts and synonymous with VDC (Volts - Direct Current).