Problem with my 72 fleetside yesterday

[wwotr]

OK I'm NO Mechanic, but I need some opinions on a problem I experienced with my 72 GMC Fleetside yesterday.

Drove down the Mountain into the Big City for a set of new Tires.

Truck ran Flawlessly!

Then heading over to the Muffler Shop, I was n the Left Hand turn lane and started to take off.
All of a sudden it was like somebody "Flicked a Switch" and cut out 4 of the 8 Cylinders!
The Trucks idle dropped to about 400 RPMs and when I hit the Gas, I couldn't get any RPM's. No Smoke, No Backfire.
Every time I tried to put my foot into it, it would just "Bog" and I couldn't get it to go any faster. I'd just have to let my Foot up off the Gas and Idle/Coast about 15-20 MPH.
I checked under the Hood and didn't see any loose Vacuum Lines, Spark Plug Wires, Gas Smell, (but like I said I'm no Mechanic).
Its a Vortec 350 out of a 1994 1500 Pickup with HEI Ignition.
Had it towed to my Mechanics. He got in it and it started up, but upon revving it up, it "Sputtered" slightly. He took it for a Drive and jokingly asked me if I was out of my mind. The DID ask me if I looked at the see-thru Fuel Filter (at the time it happened) to see if there was Gas in it (which I didn't).
The initial consensus is Electrical. He's gonna check it out and get back to me.
****, I didn't even drive far enough to get the Paper Sticker off my new tires!

;+(

Roger
"RATIKLE"

[special-K]

Do you have a carb or EFI?It does sound like a clog in the fuel line/filter to me.

[wwotr]

Originally Posted by special-K

Do you have a carb or EFI?It does sound like a clog in the fuel line/filter to me.

Sorry, It has a Carb.

Yea I was wondering if it was a Fuel Pump problem?
Maybe at the time it quit, it was just running on the Fuel left in the Carb Bowls/Lines?


Roger
"RATIKLE"

[68C15]

or the ignition module took a crap and is now allowing a very short dwell time. you need a flat screwdriver and a 1/4" nut driver to replace it.
when I take my truck out of town I carry 2 or 3 spare modules, a test light, and a multi-screwdriver just in case.

[LockDoc]

-
I think I would check the in tank pick up tube to see if the sock filter is still on it. It may be gone and a chunk of sediment temporarily plugged the pick up tube. If the strainer is gone your local GM dealer my have one, or can get one for you.(if you still have one) Part number is 5651705 and it is listed as a filter.

LockDoc

[Shyguy]

It sounds like a fuel problem. It can be anything from a plugged sock in the tank to collapsed rubber fuel hose to clogged filters to a bad fuel pump or a sticking float in the carb.

Start simple first and worry about the fuel pump and float in the carb last.

As stated about it could be a bad module, but they normally just quit and won't allow it to run. It wouldn't hurt to have it checked, most chain auto parts stores will do it for free if you remove it and take it in. While you are in the distributor check the cap and rotor.

Good luck, these kind of problems can be a pain.

Danny

[Skirkpat]

How much do you drive it, nad how often? Do you keep a FULL tank of gas in it if you let it set for long periods? Were you at an 1/8 th of a tank or less when it "bogged"? Or had you filled up recently? Any of these factors could cause an issue. Sounds like debris in the tank/fuel lines, but can't answer W/O more info.

[mclairmo]

Sounds like something the suddenly broke, not something that would degrade over time. Maybe a vacuum leak? I've seen engines run really really bad like yours with a vacuum leak. Check all vacuum hoses, not just the ones under the hood. A buddy of mine had a loose vacuum line under the dash that went to the a/c unit and it ran so bad he had to have it towed home. Also check brake booster for leaks, it is vacuum operated. If it was ignition, I would think the engine would not run at all and same for fuel pump. What about the carb? Power valve could be ruptured? I don't think it is electrical but I'm no expert either.

[nbrfd007]

I agree where Skirkpat was going, sounds like water in the fuel. Buy some HEET pour it in the fuel tank, buy a couple spare fuel filters, run it. See if it improves, less than a $10.00 try.

[wwotr]

The Truck had about a 1/2 tank of gas in it and had been driven about 3 times in 3 weeks.
Yesterday morning I went and filled up the Tank.
Something JUST occurred to me!
I know there is an evaporative emission canister under the hood and that extra line on the Fuel Filler neck, but I THINK I have one of those Cheap non Vented Fuel Caps on it.
With a full tank of Gas and driving it about 60 miles, could there have been a Vacuum in the Tank from not having a Vented Cap!!??

Roger
"RATIKLE"

[LockDoc]

Originally Posted by wwotr

The Truck had about a 1/2 tank of gas in it and had been driven about 3 times in 3 weeks.
Yesterday morning I went and filled up the Tank.
Something JUST occurred to me!
I know there is an evaporative emission canister under the hood and that extra line on the Fuel Filler neck, but I THINK I have one of those Cheap non Vented Fuel Caps on it.
With a full tank of Gas and driving it about 60 miles, could there have been a Vacuum in the Tank from not having a Vented Cap!!??

Roger
"RATIKLE"

If it has a working evaporative emission system it would use a non-vented cap.

LockDoc

[Muleman100]

Could be the power pump in the carb. Happened to me once and I drove 30 miles home at 15 mph. Rebuilt the Quadrajet and everything was good.

[68C15]

a little info as to what is contained in an HEI module and how they operate. they contain a series of transistors and a logic module. the transistors are basically tiny switches. the logic module looks at engine speed and decides how much dwell time (coil saturation) is needed for each RPM range.
it is in fact possible for a module to be bad but still run. the logic module can stick on the "engine cranking" (400 RPM or less) rate or even a higher range as what I believe is your case. they are so easy to replace and fairly inexpensive. if I am wrong at least then you will have a spare for the glovebox.

BTW, did you know if you have a no spark condition and want a quick test to see if it's the module or the pole piece you can trigger the module with a high wattage soldering iron? turn the key on and hold the iron against the side of the dizzy.

[Greaser]

I think ignition module, when they go, they go in a second, and do wierd things. The good thing is you can have it tested easily, to eliminate it as the problem at any parts store. - Todd

[Blazer1970]

Vapor lock? How hot was it (outside)?

[wwotr]

Originally Posted by Blazer1970

Vapor lock? How hot was it (outside)?

I don't know about Vapor Lock, but it was 80 Degrees coming down 2 sets of Mountains.
Then it sat at the Tire Shop for about 90 Minutes (started up fine BOTH times).
It was after the Tire Shop, driving to the Exhaust Shop (about 5 miles in City Traffic and 92 Degrees).

Roger
"RATIKLE"

[wwotr]

OK, Like I said I'm no Mechanic but I love MY Mechanic, so forgive me if I chop this explanation up.

He said that there's plenty of pressure from the Fuel Pump, because they put a Gauge on it.
Right now he says everything in pointing to a gummed up carburetor.
He said they did an "Old Style" test, where they put a Vise Grip on (and crimped) the Fuel line, and just before the Engine would die, they'd unclamp the line and it would flush out the Needle/Seat and the Truck ran fine. They also asked me if I was able to put it into Neutral and Rev it up,
(which I didn't think to do).
So they're going to see if there's a rebuild kit for the Carb.
If not I have my eye on a Holley 650 CFM that was on my last 67 Chevy C-10 that I really liked.

Roger
"RATIKLE"

[mclairmo]

If the carb has not been cleaned out/rebuilt in a long time, then that could be it. Considering the labor cost, it would be cheaper for you to purchase that new Holley than to have your mechanic rebuild your old carb. Also, carbs do wear out where the butterfly shaft rides in the carb base. I love Holleys, have a 3310 750 cfm on my 396 and it was perfect right out of the box. Has never let me down after 15 years. Not even one leak. Have a brand new 600 cfm vacuum secondary w/ elec choke ready to go on my truck. I rebuilt my buddy's 600 cfm Holley on his 66 Mustang myself. They are easy to tune, adjust and rebuild.

[hilandr452]

Switch out the module just in case before you rebuild the carb. It's cheap and if that wasn't it, you have a spare for your glove box.



Dan

[wwotr]

Originally Posted by mclairmo

If the carb has not been cleaned out/rebuilt in a long time, then that could be it. Considering the labor cost, it would be cheaper for you to purchase that new Holley than to have your mechanic rebuild your old carb. Also, carbs do wear out where the butterfly shaft rides in the carb base. I love Holleys, have a 3310 750 cfm on my 396 and it was perfect right out of the box. Has never let me down after 15 years. Not even one leak. Have a brand new 600 cfm vacuum secondary w/ elec choke ready to go on my truck. I rebuilt my buddy's 600 cfm Holley on his 66 Mustang myself. They are easy to tune, adjust and rebuild.

So I'm thinking of The Holley Avenger Carb (w/Electric Choke).
What size should I get for a 95 Vortec 350 thats pretty much stock?

Roger
"RATIKLE"

P.S. Also on the Modual, do the make a "High Performance" Modual and if so what are the benifits or is it a waste of$$

[leddzepp]

Originally Posted by wwotr

So I'm thinking of The Holley Avenger Carb (w/Electric Choke).
What size should I get for a 95 Vortec 350 thats pretty much stock?

600 CFM....anything more and you are drowning it.

[mclairmo]

Street Avenger 670 CFM should be correct for your engine. If going with the Traditional carbs, go with 600 or 650 cfm. Don't want to go too big, because you may lose some low end torque and streetability.

[wwotr]

So here's the "skinny" on my Truck repairs for today.

The Ignition Module is going to be replaced (at my request, because I'm OCD).
They ordered/received a Carb Rebuild kit, today for it, and will be rebuilding the Carb.
Changed the Fuel Filter to a Heavy Duty one.

The "problem" that I was having with it, actually replicated itself for them.
He said when it happened, he pulled off the Air Cleaner and there was all kinds of Raw Gas dumping into the Engine/Carb.
I guess the Needles have Rubber Tips on them nowadays, and after awhile they start disintegrating/not seating properly.

Roger
"RATIKLE"

[mclairmo]

Glad they found the problem, save that old module as a back up. Sounds like it is still ok.

[68Stepbed]

What kind of carb does it have on it? If it's and Edelbrock, all of mine have done that. That's why I run Holleys now.

Also, if it still does it, try changing the distributor itself. My dad's ElCamino was doing almost the same thing. As it turned out, something was going haywire in the dist. It would run OK when cold, but bog and barely run when warmed up. We tried changing everything in the dist. before just sticking a new one in it.

It also started suddenly as yours did. It had been running fine for years. All of a sudden, we were out in it and, PFFJJFFTT!!