Author Topic: 85 K10 Boggs Up Hill/Under load  (Read 4812 times)

Offline Patman

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85 K10 Boggs Up Hill/Under load
« on: February 26, 2019, 11:06:20 PM »
Howdy folks!

Question for you guys:

Ive made great headway on the truck this past week. A buddy came into town and he and i took to wrenching and this thing and we got her on the road.

Now I need to fix the headlights, replace the window motors and lock actuators and rebuild the calipers and do the interior and so many more things, but she’s goin down the road and Im a happy camper. Here’s the thing.

When I go up a decent hill, and I have a few where we live, she really bogs down. I know its not the cat because its only a couple years old. It also passed smog a few days ago here in SoCal so the carb seems to be dialed in fine. Its the original Rochester Quadrajet and its been rebuilt a couple years back. It sat for a year and a half after the rebuild.

So, I just had the trans and transfer Case rebuilt and replaced the cap/rotor and coil as well as the plug wires. WHen I got it back from the trans guy it ran terribly which is how I realized that I had a spark/coil problem. NOw that all of that stuff seems to be managed for the moment, I am having this bogging down under load. It kinda feels like it could be vacuum related but it also feels like its starving for fuel when it boggin down. I want to replace the fuel pump (mechanical) but Im not sure which PSI to use. Summit has so many options...

The truck had a 305 but now its got a 350 with an RV cam and an edelbrock performer intake. Everything else is stock. It stil has the ESC distributor though I did replace the ICM and that resolved a loss of spark after warm up issue I was having a while back.

So, what Im guessing is that my fuel pressure is dropping on an incline and I can resolve that with a new mechanical fuel pump. Just need to know what to look for in a fuel pump.

THanks!
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33’s
All stock except for the motor, used to be a 305.

Offline Irish_Alley

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #1 on: February 27, 2019, 03:28:14 PM »
ill be more inclined to believe its vacuum related. i broken or bad connection will cause the engine to lean out and bog down
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When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline 75gmck25

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #2 on: February 28, 2019, 02:11:17 PM »
Start out with a simple check to see if the secondaries are opening.  Have a friend push the accelerator to the floor while you look at the carburetor.  Push the spring-loaded secondary air doors open with your finger, and look down into the carburetor so you can see the secondary throttle plates.  With the pedal on the floor you should see the secondary throttle plates at 90 degrees and completely open. 

What transmission do you have - a 700R4?   When it was installed did they adjust the TV cable properly?   Or if you have a TH350, is the kickdown cable adjusted?

I'd also verify TDC, plug the vacuum advance line and and get an adjustable timing light to verify the base and mechanical timing.  Base should be about 12 degrees BTDC, and mechanical should add about another 20 degrees.  You want mechanical advance to come in quickly, preferably all in by about 2200-2500 rpm.

Bruce

Offline MIKE S

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #3 on: February 28, 2019, 05:16:55 PM »
I would replace the mechanical pump to begin with. Todays fuels are not kind to the diaphragm inside so if its been more than a few years its cheap insurance. I would just match up the pump to whatever it calls for in the parts book to your application. As long as it is a small block pump with the correct number and line size it will work. There is no need to put a "high performance" pump on. The carb can only handle stock pressure with out  pushing the needle off the seat and causing a rich condition.

Offline JohnnyPopper

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #4 on: March 01, 2019, 12:59:28 PM »
The incline will not affect the pump performance.

When you say it 'bogs down', can you describe more detail, i.e. loss of power, dies, have to down shift to keep going...

Is it during the entire way up, or does it bog half way, or at the top?

A lot of variables, need more information for the respondents.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #5 on: March 06, 2019, 06:12:33 AM »
This was not a fuel issue. It ended up that the road I was on was a bit rough and the clip that holds the hot wire to the coil on the Distributor Cap wiggled/vibrated loose. Thanks for hte help folks!
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33’s
All stock except for the motor, used to be a 305.

Offline JohnnyPopper

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #6 on: March 08, 2019, 03:10:41 PM »
Well, with these old things it's either fuel or spark, or BOTH!

Glad you found it.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #7 on: April 27, 2019, 08:40:45 AM »
I believe that I may have found the main issue all along. After speaking with a carburator guy, he successes that it might be the fuel vapor canister. I have a new one ordered and it;ll be here on Tuesday. Ill let ya know how it goes...

Still having issues after the truck warms up. Ive replaced the carb, distributor, cap & rotor, plugs and wires fuel filter, fuel pump, fuel tank selector valve, sending unit and repaired a few vacuum leaks. Still no resolution.

THe symptoms Im experiencing are:

Once the truck is warmed up, as I’m driving down the road, the motor will sometimes surge a bit, like the engine is running strong, then it’ll all but loose power. It stays running, most of the time but it runs like crap.

I was gonna get my new carb rebuilt by a specialist near LA and he suggested that I check the canister. Hoping that this is the issue. Getting frustrated...
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33’s
All stock except for the motor, used to be a 305.

Offline Irish_Alley

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #8 on: April 27, 2019, 12:56:03 PM »
cant you unhook the vapor canister to test this?
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #9 on: May 14, 2019, 10:06:56 AM »
Ok, so this is still an issue. Not just going up hill but rough running in general. When the truck is warming up, I can hold my foot on the gas pedal to keep the truck running and the engine will rev and then it’ll almost cut off if I don’t feather the gas pedal. Sometimes it’ll die and not start up for 10 or so min. Sometimes I can drive it around town for an hour with this rarely happening and sometimes, I cant even get off of my own street. It’s driving me crazy. Sometimes it’ll idle with no problem and drive around with no problem but once it gets warmed up, it starts running rough like someone is either messing with the carb or timing.

I live in california so I need to keep all the smog stuff on the truck to pass smog inspection.

Heres what I’ve done so far.

REplaced the ESC distributor with an HEI and it made no difference. The smog guys had me put the original ESC distributor back on and it actually passed smog.

Rotor, cap, plugs and wires have been replaced

Tanks Selector valve was replaced

Drivers side sending unit (dual tanks) replaced

All vacuum lines replaced and verified for placement

Fuel Evap Canister (charcoal canister) replaced

Ignition control module replaced

Heres what Im thinking.
I can still replace the ESC distributor with a new ESC distributor to see if the issue is in the distributor itself. - Just picked one up at the boneyard that looks to be in great shape. It’s from an 84 but its still the same 4 wire connector so it should be okay...

I can replace the ESC module

I can replace the ECM

I can rebuild the carb

I can see if there is a bad check valve or component in my vacuum system

I can replace the knock sensor

OTher than that, Im at a loss. I will say that my oil pressure pings to 60 as soon as I start it up and that does not seem right to me.

Any ideas or suggestions are appreciated...
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33’s
All stock except for the motor, used to be a 305.

Offline JohnnyPopper

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #10 on: May 14, 2019, 02:02:51 PM »
Is the carb a Quadrajet? If yes, did you check the fuel filter that is in the carb? It gets overlooked quite a bit.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline bd

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #11 on: May 15, 2019, 07:26:04 PM »
Rig up a voltmeter between a verified stable ground and the B+ terminal on the distributor so that you can monitor the distributor supply voltage while you drive.  Go for a road test and have an assistant drive.  Watch the voltmeter while the symptoms are occurring.  Does the voltage become erratic or is it constant at 14+ volts?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #12 on: May 15, 2019, 11:55:39 PM »
Yes it is a Q-Jet and I have an inline filter in front of the carb so I dont use the filter in the carb it self. So I have removed the filter and the little spring it sits on.

bd,

Im not sure what the B + terminal is but I have google. I get the idea of what you’re saying though. Thats a stinkin’ great idea man. Thanks!

So I can connect a wire from the B+ terminal on the distributor and run it into the cab, and touch a know ground and observe the voltage. It should read 14+ volts consistently. If it varies too far from that mark when the issue is happening then its something in the distributor, if not then its a fuel or vacuum issue.

Does that sound about right?
 
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33’s
All stock except for the motor, used to be a 305.

Offline bd

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #13 on: May 16, 2019, 09:44:31 AM »
That's not right!

B+ (i.e., battery positive) is the terminal marked BAT on the driver's side of the distributor cap.  It should have a 12-gauge pink wire connected to it.  The BAT terminal receives power from the ignition switch.

Connect a voltmeter set to the 20 DC volts scale (black meter probe to a known good ground, red meter probe to the distributor BAT terminal) so that you can clearly see the meter readout from inside the cab while the vehicle is moving.  Have an assistant drive the vehicle while you monitor the voltmeter.  When symptoms occur, does the voltage remain constant at ~14 volts?  (FYI, 14.2 - 14.7 volts is the charging system voltage with the engine running, assuming the battery is fully charged).  If the voltage supplying the distributor is erratic or significantly less than the voltage measured across the vehicle battery, then there is a voltage supply problem into the ignition system.  You won't know where the problem actually lies without additional tests.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Patman

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Re: 85 K10 Boggs Up Hill/Under load
« Reply #14 on: May 16, 2019, 11:54:16 AM »
Thanks for the correction. I’ll follow up once I get this done. Really appreciate the advice...
85 K10 350, 700R4, NP208, Quadrajet, Long Bed w/ 33’s
All stock except for the motor, used to be a 305.