Fuel or firing or more serious problem? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Brainchild · 12-04-2004, 11:47 PM

OK today I took out and drove 10 miles to work,and the truck ran great,drove around checking fence,loading wood,and ECT.on the way home about half way it just fell on it's face.Sounded like it was missing

After 20-30 seconds it straightened out and ran great the rest of the day.
I have noticed this on a couple of other occasions,but if I let up on the gas,and stab it again it was fine,today it took a 3-4 times of this to pull it out of the stumble.
I only notice this at hiway speeds,and it has no problems around town at all.No dead spots in the carb,nothing like that.
It doesn't cut out completely,just sounds like a plug wire fell off for a few seconds.

It is a 350,did a complete rebuild with valve job,and springs,cam and lifters 3.5 years ago.The fuel pump is a corvette model with the deep canister on the bottom.Not sure how old it is.

I cleaned the tank and lines 6 weeks ago when I dropped the motor in the truck.

It has an HEI,new plugs,wires,cap,and rotor,and a new wire to the dizzy from the fuse block.

Q-jet carb.

TIA

68C15 · 12-05-2004, 08:51 AM

hmmmm, sounds like a good one. vacuum advance?, module?, pickup coild(or broken wire)?, ignition coil?, power valve plunger in carb sticking in the up position (what # is on the carb?)
these are in order of likelyness

Zeke · 12-05-2004, 09:34 AM

Check the fuel filter, I had a similar problem. I would get on it or at highway speeds it would sometimes stumble. When I let off the gas it seemed to fix itself and would run fine. I thought it was ignition and spent $ changing ignition parts. Changed fuel filter and problem was gone. I kept the old filter and cut it open when it dryed out couldn't see anything but when you flicked the element a fine dry powder would fall out. Figured it was just clogged enough that the pump couldn't get enough fuel passed it to fill the bowl under certain conditions. Good thing I now have plenty of spare ignition parts if I ever need them. :p

Brainchild · 12-05-2004, 02:12 PM

Fuel filter is fairly new,but the old truck sat for 10 years,so that's a likely cause.I'll swap it out tomorrow,and see if that fixes it.Cheapest things first

Brainchild · 01-13-2005, 01:50 AM

OK Still having the same problems,just not as often.

I changed the filter,and again last week for good measure.Drone 25 mile round trip to a friends house.It ran great all the way there,and half way back,and then has an episode.For 5-10 seconds sounds like a plug is fouled,and misses like crazy.
I let off the gas,and a stabbed it a couple of times and it straightened right out.Ran great the 7-10 miles home.
It only does this on the higway,and only intermittently.What is going on with this thing,it's driving me nuts.

Thanks

12-04-2004, 11:47 PM	#1
Brainchild Still drivin' a Rat Rod Join Date: Sep 2004 Location: Monett Missouri Posts: 4,925	Fuel or firing or more serious problem? OK today I took out and drove 10 miles to work,and the truck ran great,drove around checking fence,loading wood,and ECT.on the way home about half way it just fell on it's face.Sounded like it was missing After 20-30 seconds it straightened out and ran great the rest of the day. I have noticed this on a couple of other occasions,but if I let up on the gas,and stab it again it was fine,today it took a 3-4 times of this to pull it out of the stumble. I only notice this at hiway speeds,and it has no problems around town at all.No dead spots in the carb,nothing like that. It doesn't cut out completely,just sounds like a plug wire fell off for a few seconds. It is a 350,did a complete rebuild with valve job,and springs,cam and lifters 3.5 years ago.The fuel pump is a corvette model with the deep canister on the bottom.Not sure how old it is. I cleaned the tank and lines 6 weeks ago when I dropped the motor in the truck. It has an HEI,new plugs,wires,cap,and rotor,and a new wire to the dizzy from the fuse block. Q-jet carb. TIA __________________ Rusty Member #13872 Instead of saying.....you are a discomfort in the back of my front.....one should be able to say...... you are a pain in the a$# 71 GMC LWB 49 Chevy 85 Chevy G20 Check out my website

12-05-2004, 08:51 AM	#2
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	hmmmm, sounds like a good one. vacuum advance?, module?, pickup coild(or broken wire)?, ignition coil?, power valve plunger in carb sticking in the up position (what # is on the carb?) these are in order of likelyness __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

12-05-2004, 09:34 AM	#3
Zeke Active Member Join Date: Jun 2002 Location: L.A. Lower Alabama Posts: 453	Check the fuel filter, I had a similar problem. I would get on it or at highway speeds it would sometimes stumble. When I let off the gas it seemed to fix itself and would run fine. I thought it was ignition and spent $ changing ignition parts. Changed fuel filter and problem was gone. I kept the old filter and cut it open when it dryed out couldn't see anything but when you flicked the element a fine dry powder would fall out. Figured it was just clogged enough that the pump couldn't get enough fuel passed it to fill the bowl under certain conditions. Good thing I now have plenty of spare ignition parts if I ever need them. :p __________________ 1969 C10 350 3spd 1995 GMC 3500 XC 350 dually When Thomas Edison worked late into the night on the electric light, he had to do it by gas lamp or candle. I'm sure it made the work seem that much more urgent. George Carlin

12-05-2004, 02:12 PM	#4
Brainchild Still drivin' a Rat Rod Join Date: Sep 2004 Location: Monett Missouri Posts: 4,925	Fuel filter is fairly new,but the old truck sat for 10 years,so that's a likely cause.I'll swap it out tomorrow,and see if that fixes it.Cheapest things first __________________ Rusty Member #13872 Instead of saying.....you are a discomfort in the back of my front.....one should be able to say...... you are a pain in the a$# 71 GMC LWB 49 Chevy 85 Chevy G20 Check out my website

01-13-2005, 01:50 AM	#5
Brainchild Still drivin' a Rat Rod Join Date: Sep 2004 Location: Monett Missouri Posts: 4,925	OK Still having the same problems,just not as often. I changed the filter,and again last week for good measure.Drone 25 mile round trip to a friends house.It ran great all the way there,and half way back,and then has an episode.For 5-10 seconds sounds like a plug is fouled,and misses like crazy. I let off the gas,and a stabbed it a couple of times and it straightened right out.Ran great the 7-10 miles home. It only does this on the higway,and only intermittently.What is going on with this thing,it's driving me nuts. Thanks __________________ Rusty Member #13872 Instead of saying.....you are a discomfort in the back of my front.....one should be able to say...... you are a pain in the a$# 71 GMC LWB 49 Chevy 85 Chevy G20 Check out my website



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