85 gmc p/u cutting out under load - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Dia · 01-13-2003, 05:37 PM

Hello,
This is my first visit to this forum. I am glad you are here.
I have a question.
When we drive up hill, the truck it cuts out badly. It started slowly, seeming like it was not getting fuel, but now it is getting very bad, so we can barely drive even on a flat road.
It is now parked and I am getting ready to look at the carb, fuel filter, etc. I am wondering if someone could tell me a good order of approach to diagnosing the problem.
I wonder if the fuel pump could be giving out, or if I have a clogged jet, etc, so I would like advice on running through all these systems in logical order.
Greatly appreciate all help and advice!
Dia

J-Spec C10 · 01-13-2003, 06:34 PM

Go in the order of expense/maintnance. Filters are cheap, so replace it first. While the line is off, turn the engine over.(hold the line in a big pop bottle) see if a lot of fuel pumps into the bottle. then if there's still a problem, get into the carburetor.

Dia · 01-13-2003, 06:38 PM

Is there a certain way I can be check the fuel pump to see if it is going out?
Thanks

**swervin ervin** · 01-13-2003, 07:21 PM

First thing I would do, is replace the plugs. I'd also change the wires too, if they haven't been changed in awhile.

Cutting out under normal driving usually isn't caused by the carb. Most think it is because it's the easiest to mess with. A true cutting out/missing is ignition related.

Dia · 01-13-2003, 08:33 PM

Ok, you are saying that I probably have spark issues? Not fuel? Like, when I drive up a hill, it acts like it is about to run out of gas, and when I push harder on the gas pedal, it gets much worse, and even stalls out if I persist. I was told it could be a distributer issue, and that goes with your suggestion, but I was also told it sounds like a fuel pump that could be pumping enough fuel to run at regular idles, but does not put out enough gas to power up a hill...hmm, I just used carb cleaner and took it for a test drive, and it seemed better, until it began to cut out again, now maybe cut out is not the right phrase, but it ceases to accelerate, then does again, then...you get it...would it help if I told you it is an S-15 V-6 engine, and I cannot get the darn fuel filter off...hmmm, new spark plugs, I hate to throw parts at it...would rather figure out a good way to check each system. I do have a volt meter, could I use that to diagnose the spark plugs, wires, etc? How?

pkbinplano · 01-13-2003, 08:59 PM

Its always good to know the condition of your plugs, cap,wires, filter ect. If you don't know or have never changed them do a complete tune up. Its about the same price as a tow truck ride home.

ElGracho · 01-13-2003, 09:09 PM

Sounds like a clogged fuel filter to me.

Grim Reaper · 01-14-2003, 03:49 PM

Fuel filter.
Had that happen on both my 75 and my 79. If the fuel filter is plugged the gas just goes back to the tank. The carb runs dry.
Old truck rust and crud in the tanke comes loose on occasion or you fill up at a station that just had a fuel drop off and their tank is full of crud.
Rule with gas stations. New parking lot new tanks. Old parking lot old tanks for sure.

01-13-2003, 05:37 PM	#1
Dia Registered User Join Date: Jan 2003 Location: Northern California Posts: 3	85 gmc p/u cutting out under load Hello, This is my first visit to this forum. I am glad you are here. I have a question. When we drive up hill, the truck it cuts out badly. It started slowly, seeming like it was not getting fuel, but now it is getting very bad, so we can barely drive even on a flat road. It is now parked and I am getting ready to look at the carb, fuel filter, etc. I am wondering if someone could tell me a good order of approach to diagnosing the problem. I wonder if the fuel pump could be giving out, or if I have a clogged jet, etc, so I would like advice on running through all these systems in logical order. Greatly appreciate all help and advice! Dia

01-13-2003, 06:34 PM	#2
J-Spec C10 Whats this wire for?.... Join Date: Dec 2002 Location: Barrie, Ontario, CANADA Posts: 378	Go in the order of expense/maintnance. Filters are cheap, so replace it first. While the line is off, turn the engine over.(hold the line in a big pop bottle) see if a lot of fuel pumps into the bottle. then if there's still a problem, get into the carburetor. __________________ Kyle CANADIAN CONNECTION '82 C10 Resto-Custom--> * 2 1/4" manifold back dual exhaust with Hooker Aerochambers & High Flow Cats Taylor Ignition Wires Centerline 15" Telstars with 32"x10" mudders

01-13-2003, 07:21 PM	#4
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	First thing I would do, is replace the plugs. I'd also change the wires too, if they haven't been changed in awhile. Cutting out under normal driving usually isn't caused by the carb. Most think it is because it's the easiest to mess with. A true cutting out/missing is ignition related. __________________ Mike 1985 Chevy C-10

01-13-2003, 08:59 PM	#6
pkbinplano pkbinplano Join Date: Nov 2002 Location: Plano Texas Posts: 370	Its always good to know the condition of your plugs, cap,wires, filter ect. If you don't know or have never changed them do a complete tune up. Its about the same price as a tow truck ride home. __________________ http://www.picturetrail.com/gallery/...7496&members=1 84 chevy silverado aka The Bananna Boat

01-13-2003, 09:09 PM	#7
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,553	Sounds like a clogged fuel filter to me. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

01-13-2003, 06:38 PM	#3
Dia Registered User Join Date: Jan 2003 Location: Northern California Posts: 3	Is there a certain way I can be check the fuel pump to see if it is going out? Thanks

01-13-2003, 08:33 PM	#5
Dia Registered User Join Date: Jan 2003 Location: Northern California Posts: 3	Ok, you are saying that I probably have spark issues? Not fuel? Like, when I drive up a hill, it acts like it is about to run out of gas, and when I push harder on the gas pedal, it gets much worse, and even stalls out if I persist. I was told it could be a distributer issue, and that goes with your suggestion, but I was also told it sounds like a fuel pump that could be pumping enough fuel to run at regular idles, but does not put out enough gas to power up a hill...hmm, I just used carb cleaner and took it for a test drive, and it seemed better, until it began to cut out again, now maybe cut out is not the right phrase, but it ceases to accelerate, then does again, then...you get it...would it help if I told you it is an S-15 V-6 engine, and I cannot get the darn fuel filter off...hmmm, new spark plugs, I hate to throw parts at it...would rather figure out a good way to check each system. I do have a volt meter, could I use that to diagnose the spark plugs, wires, etc? How?

01-14-2003, 03:49 PM	#8
Grim Reaper Registered User Join Date: Jul 2001 Location: Atlanta GA Posts: 1,704	Fuel filter. Had that happen on both my 75 and my 79. If the fuel filter is plugged the gas just goes back to the tank. The carb runs dry. Old truck rust and crud in the tanke comes loose on occasion or you fill up at a station that just had a fuel drop off and their tank is full of crud. Rule with gas stations. New parking lot new tanks. Old parking lot old tanks for sure. __________________ Grim-Reaper 70 Pontiac LeMans Sport Convertible, worlds longest resto in progress Looking for 71-72 2wd Blazer or Jimmy Project



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