electric choke issue

[cwilson jr]

my 85 k10 with 350 and quadra-jet were running great until today.  started fine, and i didn't get a mile away from the house and it started to stall.  after a few minutes i tried it again and started and it ran just fine, until a couple of miles more and started to miss a little while at a cruise and it kept driving fine with the gas and then a couple more miles it started missing more to where i couldn't keep it running at all.  it quit and would not start again.

i haven't tried it again after that because i had it towed somewhere where i'm going to start messing with it tomorrow, and i'm just trying to get an idea of the more common problem areas to look at first and go from there.

it cranks and turns over fine.  it does not try to fire at all.  i'm getting fuel and i have nearly brand new plugs and wires, which look good.  the first thing i am going to try is to see if i'm getting spark at a plug.

after that where is a good place to start.  i'm thinking this is probably an ignition issue and i know someone replaced the ICM around 5? years ago.  not sure if those good bad every so often.  i also have HEI with vac. adv. and no ESC.

[chengny]

CRANKS, WON'T START

Description
The starter will engage, and the engine will crank, but it will not start.

Explanation
Four primary elements are required for proper engine starting:


-  Spark
-  Fuel
-  Compression
-  Timing (Valve and Ignition)

Spark
The ignition system provides the spark required to ignite the air/fuel mixture. The ignition system is made up of two subsystems, the primary and the secondary.

The primary ignition system triggers the spark, while the secondary ignition system distributes the spark to the individual cylinders.

Primary Ignition System
A failure of any one component in the primary ignition system may result in a no-start condition. The primary system is composed of:


•Ignition Switch - Provides power to the primary side of the ignition coil. See: Steering and Suspension\Steering\Steering Column
•Ignition Coil Primary Windings - The primary windings of the ignition coil are used to create the primary electric field within coil. The buildup and collapse of the primary field is what generates the spark output voltage in the secondary windings of the ignition coil. See: Ignition System\Ignition Coil
•Pickup Coil - Used for initiating the spark. The pickup coil sends a signal to the ignition control module, telling it when to trigger the spark. See: Ignition System\Pick-Up Coil
•Ignition Control Module - Used as an On/Off switch to control power to the primary windings of the ignition coil. The ignition control module turns the ignition coil primary ground circuit "ON" and "OFF" to build up and collapse the primary field. See: Ignition System\Ignition Control Module
Secondary Ignition System
A failure of a secondary ignition component does not always lead to a no-start condition. The secondary system only distributes the spark, for a no-start condition to occur a component common to all cylinders must fail. Secondary components which may cause a no-start condition are:


•Ignition Coil Secondary Windings - The secondary windings develop the high voltage which is necessary to initiate the spark.
•Ignition Coil Wire - The coil wire transfers the secondary voltage of the coil to the distributor.
•Distributor Rotor - The rotor distributes the secondary voltage to the individual terminals on the distributor cap.
•Distributor Cap - The cap distributes the secondary voltage to each of the individual ignition cables and spark plugs.
Testing


-  With the key "ON" and the engine "OFF", verify the ignition coil positive terminal is receiving 12.0 V.
-  With the key "OFF", inspect the coil wire and check for high resistance or evidence of arcing or burning.
-  Inspect the distributor, verify the rotor is undamaged and that all components are completely dry.
-  For detailed information on testing, see Ignition System. See: Ignition System

Fuel
Starting a cold engine requires a rich mixture, while starting a hot engine does not. If the fuel system does not deliver the correct amount of fuel for the current conditions the engine may not start.

Causes
No Fuel
The Fuel pump is not operating or the Carburetor is not delivering fuel to the incoming air.

Testing


•Check Fuel Pressure, verify there is fuel in the tank.
•While cycling the throttle valve, check that the accelerator pump injects fuel into the throat of the carburetor (this verifies that fuel is reaching the carburetor bowl).
Not Enough Fuel
A rich air/fuel mixture is required for cold starts. The choke is used to temporarily richen the mixture while the engine warms up.

Testing


•With the engine cold, cycle the throttle valve and verify the choke plate shuts.
•While cycling the throttle valve, verify the accelerator pump operates.
•Inspect all vacuum lines for proper routing or signs of leakage. See: Emission Control Systems\Diagrams
Too Much Fuel
Warm engines require a leaner mixture than cold engines. Excessive fuel may richen the air/fuel mixture to the point where it will not ignite. The spark plugs may become fuel or carbon fouled.

Testing


•Apply vacuum to the choke unloader and verify that the choke opens slightly.
•Verify that fuel is not overflowing from carburetor bowl vent or venturis (from a stuck open needle valve).
•Attempt to start the vehicle with the choke blocked open. If the vehicle starts, the air/fuel mixture is too rich.
Compression
For a compression problem to cause a no-start condition, multiple cylinders must be involved. Low compression in only one or two cylinders will not normally prevent an engine from starting. Low compression on all cylinders may be caused by:


-  Broken Timing Chain - Prevents camshaft rotation and valve movement.
-  Broken Crankshaft - Prevents piston and timing chain rotation.
-  Camshaft/Crankshaft Alignment - If the camshaft and crankshaft are not properly aligned, the intake and exhaust valves will not open and close at the proper times.
-  Bent Valves - Intake or exhaust valves which have been damaged/bent by over-revving or a broken timing chain will prevent compression from developing.

Testing


-  Perform Compression Check.
-  Verify Timing Chain is intact and aligned properly. See: Engine, Cooling and Exhaust\Engine\Timing Components

Timing (Valve or Ignition)

Ignition Timing
Ignition timing which is excessively advanced or retarded may result in a no-start condition. If the timing is advanced, the engine will be difficult to crank and rotation will tend to stop rapidly. If the timing is retarded the engine will have a distinctive low and dull sound while attempting to start.

Testing


-  Check Ignition Timing and adjust as necessary.

Valve Timing
Incorrect valve timing will result in low compression across all cylinders. The valves may remain open during the compression stroke or closed during the exhaust and intake strokes.

Testing


-  Perform Compression Check.
-  Check Timing Chain alignment. See: Engine, Cooling and Exhaust\Engine\Timing Components

[chengny]

[Irish_Alley]

a lot of info above but couple quick test you can do. spray carb/tb cleaner in the carb, see if it fires up if it does its fuel problem, did you replace the filter in the carb? how did you verify it was getting fuel?
next take a spark plug, you can even use one you have just laying around. but take a pair of jumper cables attach the neg to a ground or neg terminal on the battery and the other neg to the spark plug then you can set it up in the engine bay and try to turn it over and look for spark by yourself.

[cwilson jr]

well, after letting it set overnight.  it fired up again with a miss.  after giving it heavy throttle a couple times it is running fine again at the moment.  i just replaced everything fuel related a month or so ago and bypassed the carb filter with a clear external and we seem to be getting plenty of fuel.  i also did the plugs and wires.  i don't have any vacuum leaks, so i'm thinking there may be something going on with the distributer/ign. system.
i printed out the chart and now that i'm getting spark, (at least some of the time), i have to figure out where to go from here.  (the chart dead ends immediately if spark is found.)  is there something, such as the icm, or other component that may work only some of the time and crap out when warm?

[sbx22]

I had a SIMILAR issue. I changed fuel filter, and it runs fine now, worth a shot if you haven't changed it yet.

[flips87c30]

The ICM could be malfunctioning when the truck warms up. especially if the last person to replace it didnt apply enough of the gel that helps protect it from the heat. You should be able to tell pretty quick if you pull your icm and look at it.

[cwilson jr]

well, i let it run for a while trying to heat it up more to see if it would act up again and it was running fine, then i started messing with the carb a little and see if i saw anything.  i was moving the choke plate and when i closed it, it obviously missed and died, however i noticed 2 different positions where i could "click" between two different open postions.  after a couple of times the choke plate and the choke brake "locked" to where i couldn't move them anymore.  with this i set off the choke light, took it for a couple test runs and its running absolutely fine.  now, if i can't move anything, i would assume i probably won't be able to get it started cold.

is something bad and needing replaced or does something need adjusted?

on a side note, i noticed as my choke light is lit, my seatbelt indicator in the neighboring gauge section is dimmly lit.  is this an electricial issue, or is this basically an overspray of light getting behind the lens?

[Irish_Alley]

after the choke lock you should be able to press the gas and it should release the choke to the open position. or it might be controlled by the oil temp sensor. i am somewhat unfamiliar with the quads the seat belt light could be just from chock light lighting it up, you could take the dash apart and see. ot it might be from a bad ground and the light back feeding into the seat belt light.

[diphthong]

Ok here is the deal...

A engine running good, then missing, then running bad again would not indicate a problem with any timing issue, save maybe broken gear on the distributor, or the gear on the cam that drives distributor, which is very unlikely.  Ditto to this also also being a compression issue. No compression testing needed here.

You said nothing about any smells which would about 90% eliminates a rich fuel problem.  And about 20% eliminates a lean fuel problem.   That said, a bad carb or fuel pump, are in the realm possibilities.  But, I'm assuming your going off the carb's working accelerator pump, which has convinced you your getting fuel. 

If this is true, in temperatures above freezing the combination of a working accelerator pump (3-4 good Squirts) and a complete "no firing engine," all but eliminates a fuel problem being the issue.  Exclude missed high CO smell and completely fouled plugs.  Spraying B-12 or carburetor cleaner down the carb with working accelerator pumps is probably a waste of money here.


If your accelerator pump is working as previously describe, I would lean toward a primary or secondary ignition problem here.  That means SPARK is most likely your problem!  You either don't have any, or it's getting to the plugs weak or at the wrong time.  If your problem started in damp weather this could be as simple as a bad distributor cap, ( carbon tracked, or cracked.)

Do this:

Make sure your rotor is turning!!

Remove a plug, always remove your plugs never use one sitting around, plugs are a window into what's going on in your engine's power center, look at them!  What if you have gas fouled all the plugs, or ruined them with preignition unless you actually looked at the plugs or scoped the engine, you could be chasing your own tale for hours.


Ground a plug on the engine with a plug wire attached, have someone crank the engine and observe the spark and its color.  The HEI system can develop up to 50,000 KV, which is quite an impressive spark. This is the same energy as law enforcement tazers.

If your ignition rotor is turning and you have no spark, you'll have to methodically check the primary and secondary systems to find your problem.

I'lll say this; 70-80% of the time of troubleshooting a no spark issue in a HEI system, the problem was in the secondary.


Ignition secondary parts = rotor, cap, wires, plugs, most of the coil.


Good luck







I once had a shop owner tell me "it's possible to have just one plug wire crossed"   :-)

[Irish_Alley]

About the spark test, this is why I said use a jumper cable. It keeps you safe and you can test by yourself. Another thing before you go replacing parts in the distributor its cheaper to replace the whole thing off ebay. And you can't read plugs that aren't fairly new. The reason is running different fuel air temps/humidity will effect how your plugs fire. To get a true reading you need to just run it once ie. Drag strip after you pass you shut it off and get a tow. Then you can read them. The reason I said to use one you had laying around that was to see if you have spark. Never had one of these engines not produce a hot enough spark. Some times certain parts when warm will start to malfunction like a coil icm had a pickup coil go but it just died flat on her face. A coil will act up once warm and work fine when cold

[diphthong]

Morning Irish_Alley,

In the many of ignition problems I've troubleshoot I pretty much exclusively used remote starts, which in them-self's can be Inherently dangerous, which is why I shy away from recommending them here.  My point here is, this method gets you right there in the engine compartment in the spark's backyard..

I've never used the method of essentially extended the spark plug wire by using a set or jumper cables.  I have a question about this method.  I'll preface this with, I've seen even mechanics once they see any spark they move on down the troubleshooting tree, which can be a mistake. Can even HEI push an accurate spark through the 5-8 feet of a jumper cable?  Can you see the snapping blue-yellow gap jumping spark that is the HEI using your method?


The choice of cables with pre-fab clamps at both ends I'm sure Isn't coincidental, the size of these cables would give you your best shoot at an accurate spark.   But off the top of my head I would think the Milliseconds that is the burst from the coil could degenerate by the time it reached the grounded dash or whatever is used to complete the circuit.


I'll end with this, once I got lit-up by an HEI so bad my funny bone ached for days,  so I certainly could be wrong about that tho...


Good day
 




I once had a shop owner tell me "it's possible to have just one plug wire crossed"   :-)

[diphthong]

This is a place of learning so here are a few tricks of the troubleshooting trade.


If your engine problems is one of these three things, fuel, ignition primary or secondary problems.  The following tips should help.

What is helpful about these problems is they usually manifest themselves differently.


Primary Ignition:

Going down the road and your engine dying like someone turned off the key would tend to indicate a primary ignition problem.  The engine coming back to life just quick as it shut off, definitely puts it in this category. Rarely does backfiring or stumbling accompany intermediate primary ignition problems, but it can occur. Remember primary problems tend to happen at the speed of a on and off switch.


Secondary Ignition:

This is characterized by stumbling engines,  backfiring, engines loss of power, Popping and coughing engines. Secondary ignition problems also can be intermediate. Secondary problems usually take more time, they Kind of just lobe along. There's usually not a sudden power loss of power to the ignition system, like with the Primary Ignition.


Fuel:

Rich mixtures can mimic secondary ignition problems but with a very important distinction, you should smell this! And or see it.  Learn the smells of automotive hydrocarbons and put them to memory.  Essentially, black smoke or spark plugs means there is too much fuel for the amount of 02 (oxygen) present In the combustion process.


Lean mixtures means hot! Pinging hot, a hot catalytic converter smells different then a catalytic converter on engine running fat or in other words rich.


Adding the sense of smell to your troubleshooting tool-belt Pays back in spades.



                                                            *************************

A fast way to troubleshoot a engine dying problem, i.e. to eliminate a primary ignition problem from a secondary or fuel problem is this.

Try running your engine with a timing light on it.  If you can duplicate the problem with a timing Light attached, you'll see in real time the difference in speed the engine will die in a primary ignition problem versus a secondary Ignition or fuel problem.

If the timing light stops just before the engine does the problem is In the primary ignition.



Good troubleshooting...










I once had a shop owner tell me "it's possible to have just one plug wire crossed"   :-)

[Irish_Alley]

The jumper cable is to have a ground, not extend the spark plug wire. But you attach one end to ground and the other to the plug. So even if you holding the cable the spark will take the path of the cable but if you remove #1 plug wire you can mount the cable on the firewall so you can see it from sitting in the drivers seat and test by yourself

[diphthong]

Correction:

Actually the timing light test works best at distinguishing Ignition (both Primary and secondary) problems, versus a fuel problems.  A bad coil could resemble a intermediate open in the Ignition module wires, bad Ignition module, or a loose power lead going to the distributor. But in 25 years I never traced a engine dying problem back to a defective coil in a HEI system.



I once had a shop owner tell me "it's possible to have just one plug wire crossed"   :-)