distributor venting

I had to replace my distributor because the plastic screw tabs cracked so I bought a new distributor from the local parts store. 10 months later had major build up of blue crud inside cap and cap/rotor problems. Turns out he 2 screens in my new distributor vent holes were pressed in so tight from the factory they did not allow any air pass through and ozone built up. I punched the screens out and drilled out the 2 holes to make them bigger, and added a third hole for even more venting. Problem solved. Inside cap stays clean and dry, and probably cooler. Most electrical motors or spark-creating things like caps/rotors need venting to get rid of ozone and heat.

I also have an issue with distributor cap brass contacts vs aluminum contacts. I used to think brass was best but now I think GM used aluminum for a reason. Aluminum has better electrical conductivity than brass, and AC Delco aluminum contact posts are thicker than (Accel at lest) brass contact posts. Aluminum = less electrical resistance. Thicker posts = less electrical resistance. Brass = more electrical resistance = more chance of arcing and electricity trying to find a different path = cap/rotor malfunctions. Brass might even throw off spark timing a bit, not sure though. Astros have finicky ignition systems. I just bought all AC Delco ignition parts for a reason at my last major tune up. Brass might have better corrosion resistance than aluminum but that's the only benefit and aluminum contacts makes the engine run better I think.

Second page:

http://www.wellsve.com/sft503/counterp_v8_i4_2004.pdf

To Jamie, try this, I feel it would help you out...

Bulletin No.: 06-06-04-046

Date: September 12, 2006

INFORMATION

Subject:
Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0420 or P0430

Models:
1999-2007 Cadillac, Chevrolet, GMC Full-Size Pickup and/or Utility Trucks

with 4.8L, 5.3L, 5.7L, 6.0L or 6.2L VORTEC GEN III, GEN IV, V-8 Engine (VINs V, C, T, Z, B, 3, M, 0, J, R, U, N, Y, K, 8 - RPOs LR4, LY2, LM7, L59, L33, LC9, LH6, LMG, LY5, L31, LQ4, LQ9, L76, LY6, L92)

with Active Fuel Management(TM) and E85 Flex Fuel

If you encounter vehicles that exhibit the above conditions, refer to SI for the appropriate DTC(s) set. If no trouble is found, the cause may be due to an ECM ground terminal that has corroded with rust over time. Inspect the main engine wiring harness ground terminal (G103) for this condition.

The wire terminal (G103) attaches either to the front or to the rear of the right side cylinder head, depending on the model year of the Full Size Pickup and/or Utility Trucks. If the ECM ground terminal has been found to be corroded, then follow the service procedure outlined in this bulletin to correct the corrosion issue.

Remove either the nut or bolt securing the main engine wiring harness ground terminal (G103) to the right cylinder head. Refer to the above illustration to determine where the ground is located on the vehicle (1).

Remove all rust from the ground terminal, the cylinder head and the retaining nut or bolt.

Position the main engine wiring harness ground terminal and install the nut or bolt.

Tighten:

Tighten the retaining nut or bolt to 16 N.m (12 lb ft).

Apply some type of electrical moisture sealant to protect the harness terminal from further corrosion.

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File In Section: 06 - Engine/Propulsion System

Bulletin No.: 00-06-04-024

Date: June, 2000

TECHNICAL

Subject:
Engine Misfire, Water in Fuel, Service Engine Soon Lamp illuminates, DTC P0300 Set ( Replace EVAP Canister Vent Hose Asm/Replace EVAP Canister If Necessary)

Models:
1999-2000 Chevrolet and GMC C/K Pickup Trucks (Silverado and Sierra) Built Prior to August 31, 1999

Condition
Some drivers may comment about the Service Engine Soon lamp illuminating. The Powertrain Control Module (PCM) may have stored a Diagnostic Trouble Code (DTC) P0300, Engine Misfire Detected. The engine may be exhibiting a misfire, possibly in the # XXXXX and # XXXXX cylinders. This condition may also affect the six cylinder models. This condition may be more prevalent in areas with high amounts of rainfall.

Cause
Diagnosis of the fuel system may reveal the presence of water, possibly in the fuel rail near the # XXXXX and # XXXXX fuel injector. Water entering through the evaporative emission (EVAP) canister vent solenoid may cause this condition. Because of this, an engine misfire may develop.

Correction
A new EVAP canister vent hose assembly, P/N 15759042, that includes the valve and the solenoid has been developed to correct this condition.
The new solenoid has a revised mounting bracket and a sealant has been applied to the top lid seal surface of the solenoid to address water intrusion. Use the procedure and the part numbers listed below.

If standard diagnostics do not lead to the resolution of the misfire, do the following steps:

1. Remove the fuel rail at the # XXXXX and # XXXXX fuel injector from the engine and drain the fuel into a suitable container. Inspect the drained fuel for the presence of water. Refer to the Fuel Rail Assembly Replacement procedure in the applicable Service Manual.

2. If the presence of water is detected in the fuel rail, remove the fuel tank and inspect the fuel for the presence of water. Refer to the Fuel Tank Replacement procedure in the applicable Service Manual.

3. If water is present in the fuel tank (other than from a water enriched fuel fill), replace the EVAP canister vent hose assembly. Refer to the EVAP Vent Valve Replacement procedure in the applicable Service Manual.

4. Disconnect the EVAP canister line connections and remove the canister. Inspect for the presence of water at the canister line connections and inside the canister. If water is present, replace the EVAP canister. Refer to the EVAP Canister Replacement procedure in the applicable Service Manual.

5. Flush and clean the fuel system. Refer to the Fuel System Cleaning procedure in the applicable Service Manual.

Parts Information

Parts are currently available from GMSPO.

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chevymaher said:

I am just spitting out words to see where they splatter. The vent holes in my opinion seem to be the problem themselves. Anything that does not have them does not have this problem. They are letting the moisture in the first place. They just seem like another one of GM's failed attempts at new things. That cap design and those vents just seem like the biggest nightmare for nothing.
Okay I vented I will shut up and go sit in the corner now. :dunce:

Click to expand...

I dont know if anyone is looking at this stuff anymore but THIS GUY IS 100% correct.. this is the problem.. I had so much trouble , I tried a new "all metal distributor" even. Then I saw a story a guy mentioned where he had this issue on a hotrod that you could not easily reach the distributor one (had to pull the blower) and how he fixed it with adding a tube to connect the vent to some vacuum and never had the issue again. SO I DID THIS TO MY 97 AND YEARS AND MUCH EXPENSE IN TOWING AND "REPAIRS" OF PROBLEMS ARE GONE! THIS IS THE ANSWER WE HAVE ALL BEEN LOOKING FOR! I think these vents get clogged (bugs love to build homes in them) or they simply dont work.. moisture gets in, doesnt get out. End of story. This fixes that. I even ran a tube from the fresh air side inside my van so it never pulls wet outside air. I connected the vacuum side end to the air cleaner on the backside of the filter box. ALWAYS STARTS NOW WITH A TOUCH OF THE KEY and that is with it sitting around more which used to be the worst thing I could do. Before I did this there would be corrosion on the contacts after very short times (I live in NH) and if you clean them of it works fine. Suddenly one day I realized that also the screws on the rotor are so rusty and I said wait.. this is not getting a little wet.. its getting very wet! So I set up the tube idea I had read and 100% no issue now... now that my van is rotting out it runs... ha ha..