V6 vortec 4.3 has a hard time starting on humid rainy days

Brandon87 · October 3, 2014

I have noticed that about every humid rainy day my truck has a very hard time starting. When the key is turned into the on position I can hear the fuel pump turn on. The truck will crank and try to fire up. I noticed that if I gas it while trying to start it, it will start up as long as I keep reving it up and then after it runs for a minute everything seems fine and it will stay idling with no problems at all. Whats going on guys? I have some ideas but need your opinions before i go blowing money.

Doug_Scott · October 3, 2014

What ideas do you have? You have the most information and experience with what is happening, maybe your thoughts will help gives us a better idea of what is happening.

Generally, hard start in wet conditions, is caused by ignition problems. Plug wires to be more precise. No idea what your engine has for ignition system, does it have distributor? If it does, check out the inside of the cap for any carbon tracking. Same for ignition rotor, take it off and look under it for any black marks.

Next time it is humid, rainy or in whatever condition you need for the engine to be hard starting, and wait till after dark. Open the hood, disconnecting any under hood light, and get someone to start engine. Make sure it is very dark around the engine, too dark to see is best. Look for any halo or sparking from plug wires. If they are causing the issue, you will be amazed at the light show. The more humid the better.

8.1HD/ALLISON · October 3, 2014

I would start with distributor cap and rotor. Bet they are corroded up.

Brandon87 · October 4, 2014

What ideas do you have? You have the most information and experience with what is happening, maybe your thoughts will help gives us a better idea of what is happening.

Generally, hard start in wet conditions, is caused by ignition problems. Plug wires to be more precise. No idea what your engine has for ignition system, does it have distributor? If it does, check out the inside of the cap for any carbon tracking. Same for ignition rotor, take it off and look under it for any black marks.

Next time it is humid, rainy or in whatever condition you need for the engine to be hard starting, and wait till after dark. Open the hood, disconnecting any under hood light, and get someone to start engine. Make sure it is very dark around the engine, too dark to see is best. Look for any halo or sparking from plug wires. If they are causing the issue, you will be amazed at the light show. The more humid the better.

I tried this method the other night and I seen no sparking at all jumping off of the wires, I even misted the plugs wires and the distributor and ignition coil with water to try to get it to act up but it didnt phase the engine at all. I took the distributor cap off the other day and all of the points under the cap were corroded up so i scraped them clean. What are the signs that a distributor needs completely replaced?

Brandon87 · October 4, 2014

I would start with distributor cap and rotor. Bet they are corroded up.

I checked the distributor cap the other day and all of the points were corroded up so I scraped them clean and the hard starting problem still exist.

Brandon87 · October 4, 2014

I tried this method the other night and I seen no sparking at all jumping off of the wires, I even misted the plugs wires and the distributor and ignition coil with water to try to get it to act up but it didnt phase the engine at all. I took the distributor cap off the other day and all of the points under the cap were corroded up so i scraped them clean. What are the signs that a distributor needs completely replaced?

I wil take the cap back off and look closer for any black marks, distributors are new to me and I had no idea what to look for beside corroded contact points

Doug_Scott · October 4, 2014

I would not look at replacing the distributor, not likely to fail so badly that replacement is necessary. Take the rotor off the shaft after the cap is off, and look at the underside of the rotor. At the very centre, look for any discolouring or rainbow colours. Chances are very good that the cap and rotor have never been changed, I would swap them out, they are a standard maintenance item.

To get your own version of Aurora Borealis under the hood, the humidity needs to be just right, and wires need to be leaking. Having worked at a Chrysler dealership for a length of time, saw more than my share of hard start when humid (dodge had a very bad reputation for slant six being hard start wet, even spitting under the engine would make it damp enough to make it hard to start) and would impress the hell out of customers when we would find a car in for repair that would perform for us.

8.1HD/ALLISON · October 4, 2014

I checked the distributor cap the other day and all of the points were corroded up so I scraped them clean and the hard starting problem still exist.

You cant scrape a distributor cap clean. Replace cap and rotor. They are cheap.

Silverado4x4 · October 5, 2014

Right you cant scrap them clean, the older they get the farther the contacts points get from the rotor and cap, buy a new cap and rotor. Sometimes caps will get a hair line crack in them also letting moisture in. If you had corroded contact points the cap is shot.

Brandon87 · October 6, 2014

I just ordered a new cap and rotor set on ebay, I heard bad things about after market stuff but I just figure its worth a shot especially since it has a 1 year warranty. After I put this cap on, is there anything I can do to prevent future corrosion?

Duelin · October 6, 2014

You can take a look at this.

http://www.aatecusa.com/obdIIpro/membersonly/technical-tips/obdii/GM_TSB_03_06_04_041A.pdf

Doug_Scott · October 6, 2014

I just ordered a new cap and rotor set on ebay, I heard bad things about after market stuff but I just figure its worth a shot especially since it has a 1 year warranty. After I put this cap on, is there anything I can do to prevent future corrosion?

EBay warranty is not really of any advantage. Don't you have any of the big name auto parts stores around? Most will carry AC Delco ignition parts, or Echlin, Standard, maybe BlueStreak. Standard is likely the largest aftermarket manufacturer around, and makes most of the in-house branded parts.

What you want to get is the heaviest weighing cap and rotor. Some of the crap out there now is unreal how long they don't last.

Brandon87 · October 7, 2014

You can take a look at this.

http://www.aatecusa.com/obdIIpro/membersonly/technical-tips/obdii/GM_TSB_03_06_04_041A.pdf

that is good to know, I will check the screens when I put the new cap on. Thanks for sharing that

Brandon87 · October 7, 2014

EBay warranty is not really of any advantage. Don't you have any of the big name auto parts stores around? Most will carry AC Delco ignition parts, or Echlin, Standard, maybe BlueStreak. Standard is likely the largest aftermarket manufacturer around, and makes most of the in-house branded parts.

What you want to get is the heaviest weighing cap and rotor. Some of the crap out there now is unreal how long they don't last.

We have all the big auto part stores here. I Ordered the one off of ebay because it was a good deal for $15. I knw maybe I should have ordered better quality but I'll give this cheap one a try and if it acts up then ill just go get one down at auto-zone. When I get this cap should I use some kind of conductive grease like the spark plug stuff? maybe it will help with corrosion?

Doug_Scott · October 7, 2014

We have all the big auto part stores here. I Ordered the one off of ebay because it was a good deal for $15. I knw maybe I should have ordered better quality but I'll give this cheap one a try and if it acts up then ill just go get one down at auto-zone. When I get this cap should I use some kind of conductive grease like the spark plug stuff? maybe it will help with corrosion?

I never used anything inside a cap.

Dielectric grease is non-conductive. It is used on spark plug boots to help seal out moisture, and also prevent the plug wire cap from sticking to the plug. The grease helps keep the wire on simply due to vacuum. The wire cannot vibrate off because the boot will not let air into the space between the end of the plug and the actual socket of the wire.