360 Won't Start when warm

[larry060748]

Sent: 1/1/2004 9:21 PM

So I have had time to work a little more on the 79 brave. When I drove it home a couple months ago it was running average. I put in new spark plugs and wires on it and new cap/rotor. That was a mistake. It has not run right since. However, today after I take a close look at the old dist. cap compared to new one I believe they have given me the wrong cap. The problem now is the engine after warming up will not start again until it becomes cold(like next day). This has happened the last 3 times I have started it. I thought it maybe the coil, so went out this evening and purchased a new coil and still nothing. I am getting fire to plugs and gas in the carb. but will not attempt a hit. After checking coil resistor with amp gauge I feel this mabe the problem but will have to wait until tomorrow to get new one. If  this is not the problem I am out of theories. I am hoping some of you guys or ladies out there may have some solutions.

larry




From: Sea Hag
Sent: 1/2/2004 12:20 PM

The Engine should fire in the start position when cranking it even if the ballast resistor is bad as it supplies reduced votage to the coil only in run position , it's bypassed in start position supplying a full 12 volt for starting . Take your old cap and plugs with you and make sure the parts are for a 360 3 truck motor not the cars motor . also take your ignition modual some places can test them and they are not expencive  --- Sea Hag 




From: ned
Sent: 1/2/2004 3:04 PM

The wrong anything in the ignition system can do that, that's four sure.

Truth is. I don't know how a '79 Brave engine works. But I don't have
anything else to do this morning and you sound like you might let me bend
yer ear, so I'll plink away with you at the problem, if you want.

I guess first thing is, Does it have electronic ignition? I had an '84
breakerless electronic ignition distributor (not HEI, just plain old
resistor and coil) that failed at 160,000 miles--it was predicatble, lots of
people with that model engine had distributors fail electrically at that
mileage. But I think '79 was a leetle early for that. Besides, this isn't
a problem with a component that went ka-fritz of a sudden, this problem came
up after pulling/changing the tune-up parts in your ignition.

Does your ignition have a ballast resistor (or maybe even a resistor wire--
I think '79 was right about the time they changed over to resistor wires).
Anyway, the ballast or wire resistor kicks in only after the engine starts.
It is there to reduce voltage to points/plugs once the engine is started--it
helps keep them from burning up as soon as they would on full 12+ volts.
Until the engine starts (while you're cranking it), there is supposed to be
a second wire (apart from the wire with the resistor in its circuit) that
brings full 12v+ (battery) voltage directly to the distributor--this higher
voltage helps get the engine started by making hotter sparks. When you let
go the starter switch, this full batt voltage wire drops out of the ignition
circuit ('cos it comes from the starter solenoid, I think, and isn't
energized unless you're energizing the starter), and the ignition system
falls back to lower voltage provided through the ballast resistor). I only
mention this because these wires can get a little fiddley from heat damaging
the insulation or if the connections aren't good-- I would look real hard
for any wires that might have become loose whereas they used to fully
participating in the business of the distributor. You've got at least one
high voltage and one low voltage going to the coil, 'cos you have spark. If
ya got 5 hands you could try and verify that you have battery voltage while
the starter is energized, and less than that once you let go the starter
switch (key on). That ought to take care of diagnosing any
resistor -versus-batt startup ignition voltage issues.

Another thing that affects spark temperature is the spark plug wires and
caps. Best test I know is to use the resistance tester on your volt/ohm
meter to compare sparkplug wire resistance to the specified range of values
in your shop manual. A time will come when a spark plug wire get old and
really start to drag the spark down by having too much resistance, leaking
voltage through the insulation, etc.

Hmmm, maybe we're barking down the wrong tree with this electrical system
stuff, since you have spark, assuming it is a big fat blue-white spark. I
guess that leaves only fuel and air to be investigated. Unless of course
you can't rule out the distributor's vacuum advance mechanism. The advance
mechanism could be stuck at some advanced point in its curve, especially if
a piece of distrib cap gasket fell down in there while you were changing the
cap. So, is there a small diameter vacuum hose going to the distrib, hmmm,
is it connected on both ends? If you have a hand-held vacuum pump, hook it
up to the vacuum line hose barb on the diaphram (flat tin can) on the side
of the distributor (take the advance's vacuum hose off first). Take the
distributer cap off and verify that the vac advance is working--as you pump
up the vacuum on your hand-held pump, the distributor's rotor should twitch
and turn a few degrees in the opposite direction it turns when you crank the
engine. When you release the vacuum, you should see the rotor spring back
to its resting position. If ya got no hand-help vac pump, take distributror
cap off and twist the rotor to see that it twists a few degress toward
advance, and then positively springs back to un-advanced when you stop
twisting the rotor. If that's all working right, then the problem must be
either fuel or air.

Nope, wait a minute before jumping to the fuel/air stuff. If yer getting
spark at the plug, then maybe it isn't firing in the right order, and
therefore doesn't run 100% well and is fouling your plugs with unburned or
poorly consumed fuel due to timing being off due to wrong plug(s) firing.
Maybe, in other words, what ya got is a flooded engine due to scrambled
firing order. As the engine sits and cools, the spark plugs dry out, the
excess fuel in the cyls (fuel that didn't get a spark when the fuel/air
charge was compressed) dribbles away past the piston rings, and eventually
it drys out enough to start again. Especially if you can say that it
doesn't run quite smooth since the tune-up...then check your firing order
(it is documented somewhere, auto parts store could look it up and also tell
you which plug is #1, if you don't have the manual), then find your #1 spark
plug (are all V8's front left = #1 plug?), pull the distributor cap off
while you crank the motor to see which way the distrib rotor turns, and then
make sure your cylinders are getting their spark in the proper order.

Now here's what I really suspect the problem is: Sun spots have disrupted
your electrical system. HAHAHA! Just kidding. Take a squint at the choke:
remove the air filter, start the engine, and watch while the choke opens as
the engine warms up. I'm guessing that it either isn't opening--so it is
fine for starting a cold engine, but is all wrong for starting a hot
engine--or opens normally but doesn't close until the engine gets real
chilled down again. Choke opens and closes with heat (either from engine
heat or an electric choke heater). I can't tell you how to diagose choke
heat problems--brother, I have sticking choke problems on my '84, and it is
a booger of a thing to check out all the choke and idle linkages and
breakers, emissions vacuum lines, and the cursed choke heater (I hate
automatic chokes, especially electric one but at least when electric choke
breaks you know to check the wire that brings them juice, and then replace
electric heater if needed. Engine-heated automatic chokes like mine look
like I need to carefully remove all the emissons hoses, pull the intake
manifold, clean the choke heat passages....).

So Larry, I did bend yer ear I know, and my advice probably reads like I'm
the poster child for disorder of written speech, but I think we covered a
lot of ground, it remains fun, and maybe we came within shot of the cause
of the problem you're working on. Good luck, I'll kick it around with you
some more if you want.

Ned Bedinger




From: larry060748
Sent: 1/10/2004 8:35 PM

Ned
Been out of town for a while and read your reply but since I was gone my brother-in-law stopped by and decided he knew exactly what was wrong with the ole brave and proceeded to move the wires 180 degrees and then after trying to start the 360, my wife said she thought a bomb had with off in the back yard. Now after I have put the wires back and then try to start the engine it will shot gasoline up in the air from the carb. and will not start. I thought about killing my brother in law but he did mean well so my wife says. Any ideals? I thing it may have broke the timming chain or worst.
Larry




From: Im-still-Lefty
Sent: 1/10/2004 9:56 PM

Sounds like a classic case of an engine that is out of time. You will need to start from scratch to put the engine back in time, but the good news is that you can verify the position of the timing chain without removing the timing cover. First, Locate which cyl. is no. 1 and remove the sparkplug. Then have an assistant slowly rotate the crank by hand while you feel inside the cyl. with a piece of coathanger straightened out. What you want to feel is the top of the piston rising in the bore. When you feel the piston is all the way up, verify that the timing mark on the Harmonic Balancer is at 0 deg. . This will let you know the keyway on the Balancer hasn't sheared. Then, Remove the Distributer Cap and note the direction the rotor button is pointing. Most caps will have a small mark designating the no. 1 position on them. Now, remove the valve cover from the side the no. 1 cyl. is on. You will need to see if both valves are closed or if one is open. If one is open, rotate the crank 180 deg. and the valves should now be closed. What all this does is put the engine in a known position for reference. (no.1 at TDC firing stroke) if the crank says 0 deg. and both valves are closed on no. 1 then the timing chain is probably fine(as far as in time is concerned) Now, check and make sure that the rotor button is pointing directly at no. 1. You can now use the firing order to replace the wires on the cap in their correct location taking note which way the rotor button rotates (CCW, or Clockwise). After you finish you can check for play by rocking the crank back and forth noting how far you can turn the engine before the rotor button moves. more than a half-inch and the chain is shot, and will need replacing. If everything checks out, You can try to start it. After it cranks set the timing with a timing light to know it is correct.  Lefty




From: ned
Sent: 1/10/2004 11:30 PM

D-aaa--aaa--mmmn! 

Larry, most distributor caps I've seen can go on only one way or else they won't seat all the way.  Hope bro-in-law didn't break the cap?

Not sure what carb you've got, but some (Holly 4bbl, e.g.) have a "power valve" that is replaceable, usually comes in every rebuild kit.  The power valve will get hammered by backfire, maybe that's what you got going on now.  Otherwise, I've spawned lots of fireballs erupting out of carbs, mostly by fwissling with timing settings and getting them wrong--it isn't the end of the world, even if it looks a little like it. 

But ya gotta bear with this spark plug wire thing because it sounds like you might have switched a pair or spark plug wires while changing them over to the new distributor cap.  So, after you make real sure that you do have the correct distributor cap, so the following if you think you might need to fix the order of the plug wires in the  distributor cap: 

Find your #1 spark plug (probably the front left one (viewed from behind engine), but ask someone who knows your engine).  If you've lost track of which hole in the distributor cap the #1 plug wire is supposed to go into, then you'll have to bring a piston to TDC (top dead center). Its easiest for me to describe this for #1 cylinder. 

With piston at TDC,  see where the distributor rotor is pointed--it is pointing to the spark plug wire for the cyliner currently at TDC (its pointing to where the wire for the TDC cylinder should be when the cap is assembled correctly with wires and on the distributor), Put the distributor cap on (make sure it fits right, you had said earlier you thought it was the wrong one), and *mark* the number of the cylinder currently at TDC on the distributor cap at the hole the rotor is pointing to. 

Now make sure you know which direction the distributor turns when the engine';s running:  take the distributor cap off and crank the motor a little while watching the rotor.

Now you'll also need to find out what the firing order of your motor is. 

Again with the distributor cap and knowledge of the firing order and the direction the distributor turns, write the firing order, one number per plug wire hole, on the distributor cap.  Don't trust to memory, don't leave room for error because if you don't, then engine won't get much better abd could get a lot worse.

Example:  IF your firing order was 1-3-7-8-6-5-2-4 and IF your rotor turns counter-clockwise, then you must find (or know) which hole in the distributor cap is #1 plug wire  when the cap is seated correctly on the distributor.  With the #1 position on the cap firmly established, finish up by counting off each plug wire hole in the distributopr cap, starting with 1 and moving from top to the left (counter-clockwise).  In this example only, when you're finished the holes would be numbered (and written on the cap in magic marker) starting with 1 then 3 then 7 then 8 then 6 (by the way, this should be opposite #1) then 5 then 2 then 4 (last one, next to 1).

Hope this helps.




From: denison
Sent: 1/10/2004 11:39 PM

I have another way to tell when the distributor is pointing to the #1 cyl at its top dead center, versus being one crankshaft revolution off. I turn the crankshaft pulley about 90 degrees past top dead center. Then I blow into the #1 cylinder with the long hose of my compression tester - but unscrewed from the pressure gauge. If its really on its power stroke, I can't blow air through it. But if I can blow air into that cylinder, its because its reallly on the intake stroke, the intake valve would be open, and the air would just flow into the intake. in which case the rotor should be pointing at the opposite side of the firing order, cylinder #6. You have to be ready to do this check pretty soon after turning the crankshaft, like ten minutes, because eventually the lifter might let that valve go most of the way shut. I tred to send a long winded email about the diagnosis of starting problems to larry, but i got an email delivery failure notification. So I am going to bed. denison




From: UluzYarx
Sent: 1/11/2004 9:08 AM

Hi,

Have you considered fitting a new condenser?

My experience is that they get heat sensitive before they pop their clogs.

Your big noise was probably a just a backfire.

Typically, random plug connection finds a cylinder full of petrol vapour and an open exhaust valve to have fun with.

The spark plug starts a fire.

The flame front spreads down the exhaust system until it arrives at a silencer full of petrol vapour.

The resulting explosion is usually interesting.

I recommend you to check your exhaust system.

Happy camping

Dave




From: larry060748
Sent: 1/11/2004 4:22 PM

Thanks guys for all the help. I will try test out some of the advice hopefully tomorrow but the tem. here has been in low teens most of week-end and not been motivated enjoy to go out and try anything. Let you know if I do any good this week.
Thanks
Larry12@wwgap.net