out of ideas

[Carrierx]

86 c-10  4.3l v6

Been fighting this one for a while now and I'm stumped.

Some days I get absolutley no spark.  No matter what I do, I get no fire at the plugs.  Wait mabey 3 hours or a day after cranking on it, fires right up usually.

It seems like when its humid out, the engine runs really rough IF it starts.  Not sure if this is related or not. Seems like days after it has baked in the sun, it likes to start more often than on rainy days.

What I have replaced:

plugs (wich get fouled really bad after cranking with no spark)
wires
cap
rotor
coil in cap
igition module tested fine at Napa  2x
pickup coil tested fine (per haynes manual)
battery
grounds have been removed and cleaned
Ive inspected wires coming out of distributor
I have 12v at the coil


This just got gradually worse and worse over time.

Any advice would be greatly appreciated.  I've had 4 differnt people other than me look at it and no ideas.

[Z28 c10]

Is she carbed or TBI, I can't remember what year GM started the 4.3 TBI. Are you absolutely sure about the module and pickup?? They do have a tendency to test out good sometimes and not work others, as you have already experienced, it runs one day and not the next. Also, try some dielectric grease or equivelent in the connections, a little bit of moisture can cause a lot of headaches at times.

 JayTater

 Z28 C10

Edited by: Z28 c10 at: 4/11/06 6:40 pm

[Carrierx]

Thanks for the responce JayTater


Carbed.

I suspect the pickup coil is bad, but every test I can find says dont go through the trouble of pulling the distributor.

Oh,, one more thing thats kinda odd, when its not sparking and you turn the key to off after cranking on it, the motor bucks slightly somtimes.


Thanks again.

[Lt.Del]

If you have 12 volts coming to the distributor during one of those non-firing episodes...it is definately in the distributor.  If you don't have 12 volts coming to the distributor during a non-firing episode, 'tain't in the distributor.

When Napa checked the ignition module and tested fine, it was while the module would fire (i suppose)....I'd replace that joker any way and your problems would be solved.  

I had a similar problem w/ my 79 big 10.  I would run great.  I would park it for a few minutes and then come back to it to start it up...she would'nt fire.  I would have to wait for about 20 minutes until cool enough to fire.  Sometimes I would actually take the dist. cap off to help it cool, then put it back together and she'd fire. After a few of these episodes, I got that truck home, took the distributor out, and put another distributor I had in the garage in it so quickly, NASCAR would be amazed.  

SgtDel

[Carrierx]

Well, last weekend it wouldnt fire, so i tore everything i could get to down.  Tested and checked everything I could think of.  Took ignition module back to nappa and watched them test it again (I really wished it had failed horribly).


Might still get another ignition module as its easy to replace though.

Money is kinda tight, so I really cant afford another distributor right now, and I've never changed one to be honest (Yes im a newbie).  Im afraid of getting it back into the motor withought messing up the timing.

[Lt.Del]

The trick to not messing up your timing when replacing the distributor is really quite simple.

Take the cap off the distributor.  Put a chalk mark on the housing of the distributor to note the direction of the rotor.    Put a similar mark on the actual base of the distributor where it meets the intake and a mark on the intake....the marks will show where it all lines up.

The key is to not turn your engine over or move the crank at all while the distributor is out.  Then you can just drop it bak in...everything will line up and your timing should be right on.  You may have to jiggle the distributor a little to get the cam gear to match perfectly and get the oil pump rod to go in to the bottom of the distributor correctly.   I usually just turn the rotor a little left or right...very little so as to not throw off your marks.

If you are putting a brand new distributor in and it wont have the marks, take a mental note where a certain plug wire on the cap is next to or points towards,say, your firewall or your throttle cable, etc.  

SgtDel

79 big 10



 

Edited by: SgtDel at: 4/12/06 10:12 am

[Carrierx]

ahhh,, Thanks Sgt .

Nice pictures.  You always feed the drum to your dog ?    

[Lt.Del]

That dog of mine, I can't take him in the boat fishing anymore...each time someone catches a fish and takes it off the line, he goes to it and  picks it up.  He thinks they are his toys.

silly dog

Edited by: SgtDel at: 4/12/06 11:58 am

[cruppert77]

This happend to mine a few months ago. I had  to replace the distributor. I had gone through the same list of things that you have, and each one seamed like it helped, untill the next day. Finally put a new distributor and all is fine.

[Carrierx]

little update...

Replaced the disty with a reman and everything seemed fine.  Drove it all over town.  I was very careful to get it installed acording to my marks and that it was totally flushed out with the motor.  

3 days later however, no start.  Cranked the piss out of it for a while, meddled with the carb, nothing .... Frustration..

Figured its gotta be wiring or something and out of desperation i just started looking everywhere for a water leak or messed wires or something.

"Does it have a computer" .... hehe

Low and behold, I find a silver box behind the glove box with 7 wires.  I was dead set on the fact that it didnt have anything like that.  Guess I was wrong.

Un plugged it, plugged it back in and it fired right up....

I took it out tonight (3rd short turn started) and drove it a while.  Frontage roads and such, around town.  35-55 mph.  

Motor is tappin slightly when i got home.  Got a bad feeling about that.


 

[roundedline]

Does the Distributor have a plug with 4 wires hooked to it?  If so, it is ESC, which is crap.  Look here to remove it if it that is the case:
www.73-87.com/7387garage/...screpl.htm

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[Carrierx]

Thanks for the info Roundedline.

It sure does have that plug.  I'll look into taking that thing out soon.  Just hoping the motor holds up.

Thanks for the link.

[roundedline]

No problem.  You can use your existing distributor and just bypass the ESC box, just cut and splice as indicated in the small section near the end.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[Stewart G Griffin]

What would be the consequences of just leaving the thing unplugged?  Note, i have totally switched engines (and thus a different, non-esc distributor also).

[Stewart G Griffin]

P.S.

It's not clear in the description, but from what i read, you only need to plug the pink clip into the "bat" side of the distributor AND you could just leave the ESC components as is;  He was just taking them out because he wanted neatness.

NOTE: i have a non-esc distributor in the truck now.  Obviously it has not run yet.