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Engine Won't idle

 
waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 03/26/10 10:28 PM

got a hand held vacuum gauge..  and a large  ID hose to hook it up...   is the manifold vacuum steady???? or jumping around...

i have been following along..  i worry that you don't have enough valve to piston clearance..  so if you have a set of 1.5 rockers laying around..  pop them on..  at least until you get the carb issue figured out..

first..  pull the distributer  cap...  bump the motor around till the rotor points toward the number one wire..   bring the timing marks up on the damper.. set it to 6 degrees..  look at the reluctor and the pick up coil tips.. are they lined up perfectly???? ><      if not... this is going to be the time to set the base timing...  this only takes a few minutes..  lock the housing there..

then back off the idle speed screw on the base plate ...   if equipped with a choke.. hold it wide open while doing this so the fast idle cam will be off the fast idle steps....      back the screw out until the throttle blades close completely.. then turn it in one turn after it starts to move from totally closed...   more if the throttle sticks..

if you have the carb off..  you can set it do the idle transition ports are not exposed...   then run the idle mixture screws in.. back them out 3/4 of a turn...

i wonder if your carbs have the center idle screw?????  where you pull the air cleaner hold down stud.. put a screw driver down the middle to adjust the idle air bypass or idle speed..   yes.. there is a hidden screw in some..

with the base idle set...   and the idle speed set low..  the idle mixture screws at a normal setting.. you should have a place to start..

are your carbs set up with rear metering blocks with idle 4 idle mixture screws????    is the secondary idle stop screw adjusted properly... ?????

i think i would also back off on the fuel pressure for a try also..  drop it to 5 psi.. this is for a trial...  to try to solve a bunch of problems...

decades ago...     my autoshop teacher..  a 200MPH club member had a 4500 carb that he had loaned out..  when it came back.. it would not idle on his twin turbo methanol bbc..  somebody had plugged the idle transition ports.. and he was the guy who taught me.. fresh eyes on the subject.. ????   who would expect the carb to have been modified???

the stuff i listed above.. except for the rocker arms.. is the first things i would check if i came over..   i know i have visited this thread before..   it still bothers me.. that something small is going wrong....

can you list what the motor does now... be descriptive..  it might help...  

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 03/26/10 10:38 PM

if the above fails...  which is should not.

how about a bench test for the HEI?????

got a battery booster box for jump starts???    or some jumper cables and some jumper leads..  ( leads are small..)

hook a the big jumper cable negative to the housing..    hook a test lead from the jumper  a metal plate...   turn the complete with the cap on it HEI over onto the grounded metal plate...  top down..  so all the output terminals are equal distance from the grounded plate..  

now.. hook up the wire from the BAT connector on the cap to the positive battery.. then spin the shaft..  you should get even spark from each of the terminals even at low speeds...      warning.. failure to ground the plate and the housing with a jumper .. or one or the other.. but not both.. might result in a big shock..    you should be able to throw a 3/4 inch spark out each of the coil terminals..  if you don't get that much.. and your battery is fully charged..  and your connections are properly grounded..   you might have a bad coil...    and take a look.. make sure there is a connector in the cap.. that fits under the coil and connects to the 3 wire harness  up from the module..

if you wanted to pull the module..   and have a digital volt meter.. you can set the digital volt meter to 2K ohm scale...   measure the pick up coil... you should get between 500 and 1500 ohms...    but before you disconnect the wires.. spin the digital volt meter knob to 20 volts AC...    then spin the shaft.. you need to get close to one volt AC.. if you don't there is a problem..  with the pick up coil magnets or the reluctor on the shaft..  this test takes about a minute...  

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gettnlarge01
Everything in my driveway’s a Chevy
Posts: 545
Joined: 01/10
Posted: 03/27/10 05:27 AM

another great read wayne. keep'm coming  
luck is when skill and opportunity meet

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 03/27/10 10:54 AM

this is what i was talking about...

http://www.barrygrant.com/demon/default.aspx?page=10

snip...

The new Idle-Eze™ Baseplate eliminates the need to drill holes in your carburetor's butterflies, or other modifications to obtain the proper idle speed and transition response. It provides a quick and easy way to acquire the best idle quality, throttle response, and driveability.

Valve is easily accessed with a screwdriver through the air cleaner stud hole. Can be fine-tuned after the throttle shaft position has been set.

~~~~~

it is important to read this page...   i seem to recall that some holleys might have a similar adjustment..

that is actually a great idea... allows the owner to keep the throttle blades in the proper location for normal operation..

if this screw it wide open... or totally closed... this might be why it won't idle...

please everybody .. copy and paste the link...  as many times i have posted.. i still have not figured out how to make it a link...  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 03/28/10 05:12 AM

I do have a vacuum guage hooked up to the engine and it is steady when the engine is running at 2000 and above.  No reading at a lower rpm since the engine won't idle.  The engine builder would have checked for piston to valve clearance.  This issue has happened on 2 different engines.  the first was on the 350 after the bent valve was replaced, and now on the 421 I had built, I wanted a bigger engine.  I don't think it is anything internally on the engine.  The carb on the engine now is a holley 4779 dp with a manual choke, I am fairly sure that these do not have the idle eaze like the demon.  The only common component between the two engines is the distributor.  I will check out the distributor and module and see where everthing is.  Thanks for all of your help guys, it is very appreciated.  

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 03/28/10 06:31 AM

i just thought of a quicker test for the HEI...

got a timing light.. hook it up... tape the trigger in the on position...    watch the light as you back off on the throttle..  if it stops flashing before the engine comes to a stop...    the spark is quiting so look into the HEI....  

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redneckjoe69
Everything in my driveway’s a Chevy
Posts: 612
Joined: 02/10
Posted: 03/28/10 06:36 AM

good idea wayne. thats going in the redneck hei test file.lol  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 03/28/10 09:53 AM

I did some testing.  I took the cap and rotor off, still had the power wire to the HEI coil plugged in, as well as the 3 wires that come from the distributor that plug into the cap just behind where the power wire plugs in.  I checked the voltage at the battery, 11.9 volts.  then I check it at the power wire where it would attach to the distributor cap, 11.9 volts. I then checked it at the little button that is in the center of the cap that rides on the rotor, 11.9 volts as well. Then I checked the voltage at the one side of the module and it was 11.9 then the other side of the module and it was at 1.  I don't know if that is suppose to mean anything or not.  I have got the charger hooked up and am going to try the other test in a little while.  

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redneckjoe69
Everything in my driveway’s a Chevy
Posts: 612
Joined: 02/10
Posted: 03/28/10 11:27 AM

how did you make out today kempfer?  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 03/28/10 03:28 PM

After what I checked early, and while trying to crank the car there looks to be spark to number 1 since the timing light is flashing.  Had trouble getting it to fire, waited for a little while and still getting some combustion on some cylinders but not all, pulled a couple of plugs and they looked wet.  I am wondering if there is spiratic spark.  The only time I was able to check spark was when my wife was able to give me a hand for a few mins.  I did have some flame come back through the carb a couple of times.  which made me think I was a little advanced.  Do you guys know what the voltage reading should be on either side of the module?  If the four pins are angle away from you, while still in the distributor and hooked up with the ignition on, the left side read 11.9 which is what the battery read. The other side was really low, around 1.  I am not sure if that is what it is suppose to be.  Tomorrow I am gonig to try and get the voltage on either side of the module while the engine is being cranked.  

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 03/28/10 10:16 PM

on a 4 pin HEI module...

B is battery voltage...  same as the cap...

C is the coil ..  the module pulls this to ground to saturate the primary windings of the coil.. when the module breaks this connection.. the coil discharges high voltage..

one of the module hold down screws grounds the module to the housing.,...




there should be 2 connectors on the other end of the module...   a large connector and a small connector.. these go to the pick up coil......


the upside down test is for a COMPLETE Hei..  out of the motor..  

you can put tape on the trigger of the timing light to keep it flashing..  so you can aim it at the drivers seat  while you start the car....

see if the light flashes while you are running the car...  when you drop the idle.. does it stop flashing as the motor dies .. but before it comes to a stop....


how hard is it going to be for you to drop the fuel pressure...???   just for testing????  like 3 or 4 psi   down from 6.5????  

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redneckjoe69
Everything in my driveway’s a Chevy
Posts: 612
Joined: 02/10
Posted: 03/29/10 12:12 AM

being that the distributor is the only part you have shared between engines, i would get the module checked out. its free at the parts store, if you have any doubts about testing.   auyo-zone prices, 4-pin module-$22.00,  coil-$23.00,  pick-up coil-$23.00.  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 03/29/10 03:32 AM

I will try the timing light test.  If I can't find anything from that I will take out the module and get it tested.  Which parts store is the best one to take it to, Advance, Auto Zone, or Oriely.  

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redneckjoe69
Everything in my driveway’s a Chevy
Posts: 612
Joined: 02/10
Posted: 03/29/10 04:04 AM

thats a good question. im not gonna recommend any of them.lol. those prices are from auto-zone. im lucky, the one near us has some very knowledgeable people in there. i guess it all depends on the people working behind the counter.        i seem to remember a post on here where a guys car ran fine til it warmed up. he took his module to get tested, slightly warm, no good.  when it was cold, it was o.k.     maybe you could try waynes test real quick while its cool. then warm it up & try again?  just a thought.    hope today is your day!  

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 03/29/10 12:29 PM

when having the module tested....  have them run the test 6 times in a row... this will heat the module and show up any heat related failures...

i wish there was some racer or serious mechanic / carb guru near you...

this usually takes less than 30 minutes to figure out everything... in person..

check your Private messages above...  

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