71 k10 lunging? when driving please help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ooimpalaoo · 01-23-2017, 02:48 PM

ok so once again im calling on your help. my k10 was running great then one day im going to use the word lunged forward. i only use it 3 days a week on the highway and last week it got to the point where it did it like 6 times on the way to work. now my truck is stuck at work i cant move it 20 feet without it doing the same thing. the motor runs great. starts great idles great. revs great. what the hell is going on? any ideas where i should start? thanx for the help

**landy** · 01-23-2017, 03:38 PM

Provide some more details such as which engine, is it stock, have you done anything to it recently, more detailed description of the problem, etc. Typically, if engine is hesitating or missing, which I assume is what you're describing, it's a fuel-related or spark-related problem.

ooimpalaoo · 01-23-2017, 03:48 PM

its a 350 has a intake and a 4 barrel carb nothing fancy. as far as saying mor about it i dont know it hops.bucks.jerks???? going to put me through the window the tranny is a sm465. i changed the cap and nothing. i dont want to just start tossing parts at it. fuel filter is clean just swapped it out few weeks ago.

geezer#99 · 01-23-2017, 04:28 PM

Fuel pump could be quitting.
Pull the line off the carb, stick the end in a litre jar and crank it for 30 seconds. It should fill it strongly and quickly.
If not then it's fuel pump time.

**HO455** · 01-23-2017, 05:02 PM

Can you define the symptom a little better? You say it lunges. That implies when running down the road the truck suddenly accelerated on its own. As if the throttle had been winged open. Is this what your experiencing?

ooimpalaoo · 01-23-2017, 05:31 PM

ok a kick back like trying to break in a wild horse

El Dorado Jim · 01-23-2017, 05:40 PM

Quote:

Originally Posted by geezer#99

Fuel pump could be quitting.
Pull the line off the carb, stick the end in a litre jar and crank it for 30 seconds. It should fill it strongly and quickly.
If not then it's fuel pump time.

x2

rmneder · 01-23-2017, 05:43 PM

Could you possibly be in 4 wheel drive? On a hard surface it will feel like that.

towbar · 01-23-2017, 10:56 PM

Starts, idles, and revs fine....all with no load from the way it sounds.

My first look would be at the fuel supply. As geezer#99 said, a fuel pump test is a good place to start. I myself would check the simple stuff first...fuel filter for clogs, fuel line for kinks (metal or rubber). Sometimes old rubber fuel lines deteriorate inside...especially with ethanol fuels, this could be partially blocking the fuel supply from the engine. I have personally experienced cracked fuel lines sucking air from the outside creating the same problem you described. Don't forget the fuel strainer in the fuel tank.

Good luck

**HO455** · 01-24-2017, 12:05 AM

I would look at the power to the coil including the ignition switch. A momentary loss of voltage will cause the engine to die then jump back to life. A quick check would be to run a jumper wire from the battery positive post to the coil to see if the problem disappears. If your still running a stock points ignition system it would be safe for a short time at full 12 volts.. With points another trouble spot would be in the advance mechanism ground wire inside the distributor. Just pull the cap and give it a tug to be sure it's not broken. You could also check it with an ohm meter. If all this checks out pull a plug wire and hook up a spark tester then take it for a spin while watching to see if you losing spark. Or if you have any "so called friends" just have them come over and hold the plug then if they quit hollering you know you lost spark.

I'm a believer in the old adage "80% of all carburetor problems are electrical". Just a couple of quick and cheap checks to narrow the list of culprits.
Good luck

ooimpalaoo · 01-31-2017, 01:54 AM

yes it was the power to the coil. thanx for the help. that is a great great tip. it seamed to be a fuel or spark problem, i dont know if i would have ever figured it out. thanx again

El Dorado Jim · 01-31-2017, 05:17 PM

Quote:

Originally Posted by ooimpalaoo

yes it was the power to the coil. thanx for the help. that is a great great tip. it seamed to be a fuel or spark problem, i dont know if i would have ever figured it out. thanx again

how did you find and fix your problem?

ooimpalaoo · 02-01-2017, 01:20 AM

well the last guy tied in a wire that was the wrong gauge so i replaced the whole wire with the right gauge and problem solved. it was a crazy thing to look over seams so simple. i wonder how long it would have taken me to get it on my oun....never? who knows. thanx again.

**HO455** · 02-01-2017, 10:14 AM

Glad to hear you found the problem and are "On the road again"

GASoline71 · 02-01-2017, 11:12 AM

Quote:

Originally Posted by ooimpalaoo

yes it was the power to the coil. thanx for the help. that is a great great tip. it seamed to be a fuel or spark problem, i dont know if i would have ever figured it out. thanx again

What distributor and coil? HEI with an in cap coil? If so... it needs a dedicated 12v wire that comes directly off of the fuse block from a lead that is only hot when the key is on. If the original coil wire (which has an inline resistor wire) is being used from the stock canister coil... you will have problems with voltage drop.

Gary

ooimpalaoo · 02-01-2017, 11:10 PM

that was it exactly. it was getting a voltage drop. the PO must have just used the original wire.

01-23-2017, 02:48 PM	#1
ooimpalaoo Registered User Join Date: Jul 2011 Location: Vernon BC Canada Posts: 287	71 k10 lunging? when driving please help ok so once again im calling on your help. my k10 was running great then one day im going to use the word lunged forward. i only use it 3 days a week on the highway and last week it got to the point where it did it like 6 times on the way to work. now my truck is stuck at work i cant move it 20 feet without it doing the same thing. the motor runs great. starts great idles great. revs great. what the hell is going on? any ideas where i should start? thanx for the help

01-23-2017, 03:38 PM	#2
landy Senior Member Join Date: Jun 2000 Location: alb, nm Posts: 413	Re: 71 k10 lunging? when driving please help Provide some more details such as which engine, is it stock, have you done anything to it recently, more detailed description of the problem, etc. Typically, if engine is hesitating or missing, which I assume is what you're describing, it's a fuel-related or spark-related problem.

01-23-2017, 03:48 PM	#3
ooimpalaoo Registered User Join Date: Jul 2011 Location: Vernon BC Canada Posts: 287	Re: 71 k10 lunging? when driving please help its a 350 has a intake and a 4 barrel carb nothing fancy. as far as saying mor about it i dont know it hops.bucks.jerks???? going to put me through the window the tranny is a sm465. i changed the cap and nothing. i dont want to just start tossing parts at it. fuel filter is clean just swapped it out few weeks ago.

01-23-2017, 04:28 PM	#4
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,736	Re: 71 k10 lunging? when driving please help Fuel pump could be quitting. Pull the line off the carb, stick the end in a litre jar and crank it for 30 seconds. It should fill it strongly and quickly. If not then it's fuel pump time.

01-23-2017, 05:02 PM	#5
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,393	Re: 71 k10 lunging? when driving please help Can you define the symptom a little better? You say it lunges. That implies when running down the road the truck suddenly accelerated on its own. As if the throttle had been winged open. Is this what your experiencing? __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

01-23-2017, 05:31 PM	#6
ooimpalaoo Registered User Join Date: Jul 2011 Location: Vernon BC Canada Posts: 287	Re: 71 k10 lunging? when driving please help ok a kick back like trying to break in a wild horse

01-23-2017, 05:43 PM	#8
rmneder Registered User Join Date: May 2012 Location: San Diego Posts: 86	Re: 71 k10 lunging? when driving please help Could you possibly be in 4 wheel drive? On a hard surface it will feel like that.

01-23-2017, 10:56 PM	#9
towbar Registered User Join Date: Jul 2012 Location: Marshall, NC....heart of the Appalachians.....aka, Gods country!! Posts: 537	Re: 71 k10 lunging? when driving please help Starts, idles, and revs fine....all with no load from the way it sounds. My first look would be at the fuel supply. As geezer#99 said, a fuel pump test is a good place to start. I myself would check the simple stuff first...fuel filter for clogs, fuel line for kinks (metal or rubber). Sometimes old rubber fuel lines deteriorate inside...especially with ethanol fuels, this could be partially blocking the fuel supply from the engine. I have personally experienced cracked fuel lines sucking air from the outside creating the same problem you described. Don't forget the fuel strainer in the fuel tank. Good luck

01-24-2017, 12:05 AM	#10
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,393	Re: 71 k10 lunging? when driving please help I would look at the power to the coil including the ignition switch. A momentary loss of voltage will cause the engine to die then jump back to life. A quick check would be to run a jumper wire from the battery positive post to the coil to see if the problem disappears. If your still running a stock points ignition system it would be safe for a short time at full 12 volts.. With points another trouble spot would be in the advance mechanism ground wire inside the distributor. Just pull the cap and give it a tug to be sure it's not broken. You could also check it with an ohm meter. If all this checks out pull a plug wire and hook up a spark tester then take it for a spin while watching to see if you losing spark. Or if you have any "so called friends" just have them come over and hold the plug then if they quit hollering you know you lost spark. I'm a believer in the old adage "80% of all carburetor problems are electrical". Just a couple of quick and cheap checks to narrow the list of culprits. Good luck __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

01-31-2017, 01:54 AM	#11
ooimpalaoo Registered User Join Date: Jul 2011 Location: Vernon BC Canada Posts: 287	Re: 71 k10 lunging? when driving please help yes it was the power to the coil. thanx for the help. that is a great great tip. it seamed to be a fuel or spark problem, i dont know if i would have ever figured it out. thanx again

02-01-2017, 01:20 AM	#13
ooimpalaoo Registered User Join Date: Jul 2011 Location: Vernon BC Canada Posts: 287	Re: 71 k10 lunging? when driving please help well the last guy tied in a wire that was the wrong gauge so i replaced the whole wire with the right gauge and problem solved. it was a crazy thing to look over seams so simple. i wonder how long it would have taken me to get it on my oun....never? who knows. thanx again.

02-01-2017, 10:14 AM	#14
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,393	Re: 71 k10 lunging? when driving please help Glad to hear you found the problem and are "On the road again" __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

02-01-2017, 11:10 PM	#16
ooimpalaoo Registered User Join Date: Jul 2011 Location: Vernon BC Canada Posts: 287	Re: 71 k10 lunging? when driving please help that was it exactly. it was getting a voltage drop. the PO must have just used the original wire.



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