Attn: Geo-TH,IN Distributor Cap Issue

Sprint 6

Well-known Member
On your 4.3 eating cap and rotors, I would recommend having the Cam Position Retard checked by someone with a full function scan tool. It is listed in the PID list as CMP Retard and is shown in degrees. The V8s were adjustable, but the V6s have a locked out distributor clamp. I like the see the CMP Retard between -5 and +5. If it is farther out either direction, it is correctable. First, slot the distributor clamp or install a V8 clamp. Watch the reading on a scan tool, raise the RPM to 1500, and turn the distributor until the scan tool reads between -2 to +2, and tighten the clamp. Then do a Crank Shaft Position Relearn for good measure. I have found on all the Vortec V6s I have seen with chronic cap failures, the retard is way off. If it is way off, I believe the cap and rotor are worked hard because the terminals and rotor tip are not in optimum alignment when the coil fires. This may sound strange, but that "distributor" is really just a switch, the computer completely controls when the spark happens. In fact, you can turn that distributor as far either way as you want and it will run, the spark just has to jump farther to the terminals internally. Most I have seen that were eating caps were around 15 degrees.
 
Never thought of that, but it makes sense! I had an 89 Silverado 350 that ate rotors and coils. Could nave been the problem, it's long gone now.
 
Sprint 6,
When engine was under warranty, it had a leaky head gasket. Is it possible the distributor wasn't put back in the right place? While under warranty I had oil leaks. They finally replaced the oil pan and I think they damaged the plastic timing cover, which if I recall, may be where the cam position sensor is. Does any of this make any sense?

Engine has 83K, doesn't use a drop of oil. Just checked today, getting 19 mpg. Seems to run great.

Should I have the dealer do these checks? .
 
My mistake, cam sensor is in distributor, crank sensor was in the plastic timing cover case, I think. So is it possible my distributor could have been put back in engine a gear off? Engine runs great, doesn't miss, spit, sputter. Won't start on damp morning. Replace cap and rotor and all is well after that. But if the spark has to jump a great distance, that might explain why there are parts of the rotor cap and metal pieces inside cap.

How expensive is the scan tool? What brand and where can I get one? Or should I leave this to the pros?
 
This would be a job for a pro. A scan tool that can read this would be cost prohibitive for a job like this. I have a Mac Mentor, which was about $2500 new.

Not likely the distributor is a full tooth off, while it might run, it will set a code if the CMP Retard gets over about 25 degrees. The CMP Retard being over 5 either positive or negative can also cause phantom misfires that cause a Check Engine light but aren't really there, or real random cylinder misfires that nothing corrects. I have seen both scenarios. The CMP Retard is affected by timing chain stretch.
 
I thought some of the distributors were marked for 4,6,and 8 cyl and there were marks for more than one motor. Meaning the phasing can be off and the distributors looks like it is in right.(I haven t even read a TSB for 15 years so what do I remember) :)
 
Align the timing marks at the damper, then position the distributor so the "6" mark/arrow on the periphery of the distributor base lines up with the tip of the rotor and lock down the distributor. NO scan tool or voodoo chant needed.
 
I don't believe in voodoo. That mark is to get you in the ball park and make it run, CMP Retard needs checked to make sure it is correct. There is a difference between doing a job and doing it right. The mark can line up, but the CMP Retard reading is dynamic. The marks do not account for timing chain wear and other build variences.
 
Many thanks, I have a good mechanic in mind. Very likely distributor may not have been installed properly when head gasket was replaced at dealer. Let you know what he finds.
 
Sprint 6, My trusted mechanic told me this morning, if there is no engine code, there is no problem. This place is the #1 place in Terre Haute, used him for years, until I bought a new 2005 car and a new 2007 truck. Then dealer did all my work under warranty. I will ask dealer the next time I get an oil change. Pick other mechanics brains too.

As for now I'm carrying a spare distrubtor, rotor and tools in truck.
Thanks.
 
As I said, the engine is setup to electronically deal with the variation and not set a code, but that is not the problem. If the CMP Retard setting is more than about 5 degrees either way, the rotor tip is not in good alignment with the cap tower when the computer fires the coil, causing the spark to have to "reach". This is what causes early failure of the cap and rotor, IMO. My reasoning for this is the V6 does not, according to GM, need adjusted, but cap and rotor failure is high on V6s. On the 5.0 and 5.7 Vortec V8, GM requires the CMP be set at +/- 2 degrees, and also have a lower failure rate of cap and rotors. Do what you wish, but it should not cost much to check it, and your mechanic may learn something. Not all driveability issues set codes. What the CMP Retard is telling you is the difference, in degrees, between the crank sensor reporting #1 TDC and the cam sensor in the distributor reporting #1 TDC firing position. The cam sensor is the only thing that shows the computer firing position, the crank sensor shows TDC every crank revolution. I have seen the reading be over 15 degrees when "set it and forget it" like Bob suggests. On a V8, it will set a code, but a V6 will deal with it and fire #1 with the tower still 15 degrees away. Computer controls work on cold, hard facts, not voodoo as some believe.
 
Sprint 6, I agree with you. For me to find someone to fix it is another problem, especially when they don't think there is a problem without an engine code.

Moving distributor a tooth will be off set more than just a few degrees. So finding someone willing to replace v6 distributor hold down with a v8 hold down is another story.

Thanks, I'll keep looking for someone with a scanner who knows more. Let me know if you are ever in my neighbor hood, Terre Haute, In.

Mean time, I'll replace cap and rotor in 2 years. Last one lasted 2 years and 3 months. Also carry parts in truck. Thanks again, Geo
 
Yes, I agree an verifying it with a scan tool.

In my experience, if you carefully set the distributor to the marks, turn the engine over two turns to take up any play in the timing chain and distributor drive, then double check, and correct the alignment of the marks, if needed, it will be spot-on when started and verified with the scan tool.
 
"set it and forget it" like Bob suggests"

Only trouble with your statement is that I do NOT suggest "setting it and forgetting it".

I suggest carefully setting it statically using the timing marks, then verifying it with a scan tool.

(TRUST, but VERIFY???)

My point was that in my experience most of the time setting it statically will get you so darned close most of the time it's not necessary to go back and tweak it after checking it dynamically with the scan tool.
 
Align the timing marks at the damper, then position the distributor so the "6" mark/arrow on the periphery of the distributor base lines up with the tip of the rotor and lock down the distributor. [b:ee27b6e43e]NO scan tool or voodoo chant needed.[/b:ee27b6e43e]

Only trouble with your statements that I do NOT suggest "setting it and forgetting it"

I suggest carefully setting it statically using the timing marks, then [b:ee27b6e43e]verifying it with a scan tool[/b:ee27b6e43e]

HUH?
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top