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  #91 (permalink)  
Old 03-24-2013, 10:56 AM
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My 4.3L has about 55psi at a steady idle. If I goose the throttle I see it jump to about 60psi. This is after I replaced the fuel pump and the regulator with new parts. The pressure stays over 50psi for a while after I shut it off.
I thought I'd mention that my truck would "buck & jerk" pretty bad under load on days with a lot of humidity(rain or fog) recently. After it sat for a little while after a good warm up it didn't do it nearly as bad. It seemed that there was moisture in the distributor cap that caused a misfire, and after it sat after being warmed up, it dried out the moisture somewhat, and ran ok, or at least a lot better. On dry days it didn't do it.
I had changed out the distributor cap about 2-3 years ago, and didn't think that would be a problem. The cap is the kind that have built in circuits that transfer some of the terminals from one side to the other. I believe that's just asking for a crossfire/misfire.
I removed the cap and saw a lot of corrosion(white chalky crap) on the terminals,(zinc not brass) and even on the screws that secure the rotor. I replaced the cap and plugs about two weeks ago, and its been running fine ever since with the exception of an unrelated spark knock that I've been trying to cure for a while. I believe the spark knock is from a mixture that is a bit lean that might also have aggravated the misfiring ignition by making it that much harder to light off the mixture, but the misfiring under load on rainy days has stopped.
FWIW,
ssmonty
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  #92 (permalink)  
Old 03-24-2013, 11:31 AM
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OP said he replaced cap....earlier in the thread. Said symptoms did not clear up .
Solid diagnostic info for basics section SSmonty.
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Old 03-24-2013, 12:30 PM
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I missed that, and was responding to a post 89 where he said he would check the cap. Oh well.
I see he said he also replaced the plugs as well as most all of the ignition system. Thought I'd mention that when I got my plugs recently(Advance Auto) he strongly recommended the expensive($6+) Delco Platinum plugs gapped @ 0.060". I asked to get a cheaper Bosch plug when the guy asked another person behind the counter "what plug do you need for a late model Chevy". The other person didn't hesitate and replied the Platimum plugs. The guy I was talking to then asked the other "why", and the other's reply was that the other plugs were too cold and would cause misfiring, the same the guy I was talking to had told me just before. I bought the platinums. Just thought I'd mention that.
I noticed the OP's pics of the plugs, and with the one exception they seem to be extremely light in color as if almost too lean a mixture. I know that a lean mixture is harder to light than a rich one(especially under a load) and since he has already replaced most of the ignition(I hope he got the right plugs), I'm with those that suspect the fuel system.
I don't think he has the same injection system I had. I had the "Central" injection system with the "poppets" at the ports instead of individual injectors at the ports(MPI). If he has the poppets I'd replace them without hesitation for the retrofit conversion kit with MPI as I did.
If he has the individual injectors at the ports I'd remove them, and take them to a shop, and have them professionally cleaned. At approximately $40 a piece new its worth a try to save them by cleaning IMO.
ssmonty
PS Before you do anything, try what I suggested on post 74 about listening for a leak with a piece of hose. Only cost $1. A leak can make it lean. Might think that a leak would make the MAP sensor read low(under load) and richen the mix, but not necessarily.

Last edited by ssmonty; 03-24-2013 at 12:53 PM.
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  #94 (permalink)  
Old 03-24-2013, 01:12 PM
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I am Going to take the cap off and check it. I am not sure why I keep burning up plug wire #6. Its a good thing there under life time. LOL. I will call a shop to see if they can clean the injectors with out pulling it all apart. The other thing is I do know this thing is running rich all you can smell is gas coming out of the tail pipe.

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  #95 (permalink)  
Old 03-24-2013, 04:19 PM
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Quote:
Originally Posted by tommyboy8072002 View Post
I am Going to take the cap off and check it. I am not sure why I keep burning up plug wire #6. Its a good thing there under life time. LOL. I will call a shop to see if they can clean the injectors with out pulling it all apart. The other thing is I do know this thing is running rich all you can smell is gas coming out of the tail pipe.
If you can smell gas it does not indicate it is rich it indicates you have unburnt fuel. There is a big difference.
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Old 03-24-2013, 04:23 PM
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I did another tune up. Didn't help I think Its injectors. That's the only thing left. Hey CHET what would cause unburnt fuel ?
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  #97 (permalink)  
Old 03-25-2013, 10:16 AM
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Quote:
Originally Posted by ssmonty View Post

I removed the cap and saw a lot of corrosion(white chalky crap) on the terminals,(zinc not brass) and even on the screws that secure the rotor.
Yeah, this is a classic example of "Cheaper is not always better".



NAPA sells both the Echlin #RR253 with brass contacts (~$80.00 CAD MSRP)
and the "Mileage Plus" brand #RR253MP with aluminum contacts (~$34.00 CAD MSRP)

I usually offer the customer both choices / prices ... and if asked for my opinion ... I ask how long they plan on keeping this vehicle?

Maintainance costs are a relative thing, IMO.

------------------

Reading further down in this thread, someone mentioned a recurring problem on the same cylinder. This is likely caused by high resistance (bad wire or plug), and will likely eventually lead to cross-fire as the spark will follow the path of least resistance.

We had one of these 4.3 Vortec's in our (Ford Dealership) shop a few years with a severe stumble / misfire / kick-back while cranking issue ... which was worse when cold and damp. They had a few different techs quite stumped ... changed cam and crank sensors, replaced starters with broken nose-cones, sheared drives, even ring gears.

This went on for months, it seemed, until somebody actually had a HARD look at the cap and rotor. Yup, evidence of carbon tracking!

Replaced the cap, rotor, wires, and plugs ... and this thing now ran like a swiss watch.
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  #98 (permalink)  
Old 03-25-2013, 04:04 PM
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Quote:
Originally Posted by tommyboy8072002 View Post
I did another tune up. Didn't help I think Its injectors. That's the only thing left. Hey CHET what would cause unburnt fuel ?
No spark on a cylinder, injector stuck.
I would concentrate on try to find why that one wire keeps burning up.
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Old 03-27-2013, 11:08 PM
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I found part of the problem the screw that holds down the cap is striped out.
Hey 66 Gmc I have the same cap. That's the only one they sell at Auto Zone.
I paid $ 80.00. for Cap and rotor. 5 year replacement.
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Old 03-30-2013, 10:27 PM
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What kind of Distributor should I go with the MSD or reman
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  #101 (permalink)  
Old 03-30-2013, 11:15 PM
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dISTRIBUTOR

Everyone loves to have a mallory or MSD distributor...but the truth is, a good HEI reman distributor is a great distributor. I've used one on several of my race cars over the years without issue. Its only when you start getting a very well built performance engine that you require anything more then a factory HEI. Its up to you of course, but weigh out the cost of each.
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Old 03-31-2013, 09:09 AM
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Thanks Snakebit68. Your right about that. The pricing is crazy. I will buy a factory HEi Distributor.


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Old 04-01-2013, 08:06 PM
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Does anyone know if the distributor is the same on a HEI and on (SFI)? .
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Old 04-11-2013, 11:46 PM
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Ok guys I took the truck to the shop. And I was told that it could be a couple of things that could cause this .

1.exhaust manifold gasket

2. cam sensor ( New distributor Installed before I took it to the shop )

3. 02 sensor

I also am going to take it to another shop for a 2 opinion. I asked about the injectors and he said they where fine. He hooked it up to his computer.
I don't think any of this would cause it to run like this.
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Old 04-15-2013, 10:59 PM
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have a question about a distributor

on my 96 Chevy c3500 5.7 Vortec. I was wondering if could I run a one wire distributor. And eliminate the cam sensor / pickup coil or do I have to run the HIE with the cam sensor/pick up coil. Let me know thanks.
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