68 c50 loses power up hill

[abilityonline]

Curious if I could get some feedback on possible causes of power loss going up hill. It's to the point the truck is at a low crawl. (not that this truck is made for speed lol). I have a crack in the exhaust manifold, I will try to JB weld it and see if it makes any difference. Other possibilities? Fuel filter? could this be a carb issue?

[69GMCLonghorn]

Sounds like you need to analyze the situation further and eliminate the "usual suspects". The manifold leak won't cause a lack in power, just a lack of quiet.

Hit these bases first, then see where you're at:
Change the plugs, wires, cap, points, and rotor. (Install a Pertronix Ignitor if you can afford the $100 or so).
Check your timing advance with and without the vacuum advance hooked up and make sure it's doing what it should.
If there's any doubt, a new distributor is not that much money, unless you upgrade it.
Check and/or replace the fuel pump and filter.
Could the tank be dirty? Maybe run it down to empty and clean it out to be sure.

If you hit all these bases, it is bound to improve.

Make sure to post your results. We all like a happy ending!!

[68gmsee]

A few questions:

Automatic or standard?
Is it any hill?
Do the rpms also go down?
Does it sound like it's just gasping for air?

Aside for the possibilities mentioned by 69GMCLonghorn check for clutch slippage, weak gas flow (bad fuel pump), clogged filters or fuel line, vacuum leak in the carb or even float level adjustment since it's using more gas going uphill.

[abilityonline]

Automatic or standard?
Standard 4+2

Is it any hill?
Today was the first day I took it out on a real road trip (2 miles). Happened every hill

Do the rpms also go down?
Yes
Does it sound like it's just gasping for air?
Not sure it's air or gas or what. I has a new air filter on it.

Aside for the possibilities mentioned by 69GMCLonghorn check for clutch slippage, weak gas flow (bad fuel pump), clogged filters or fuel line, vacuum leak in the carb or even float level adjustment since it's using more gas going uphill.

[69GMCLonghorn]

I guess it goes along with everything else I mentioned, but also check the base timing and make sure the dist didn't rotate on you... I had a distributor do that, and it was idling at 3° AFTER TDC. It wasn't happy until I reset it to spec. Then it ran like a top!

[thebrown83]

These trucks arn't fast and are very heavy (I have been driving a c60 with a 366 during harvest). What motor does it have what gear are you in and how fast are you going and how big are the hills? In our wheat trucks driving down a flat road (45mph) then comming to a big hill if you are in 4th and overdrive you slow down to maybe 30mph by the time you get to the top (even empty). If its loaded its even slower. So if yours sounds about like this it might just be that you will have to downshift and take the hills in a lower gear to keep the rpms up.

[abilityonline]

I'm in 2 high/low and it's RPM's are going down to the point I should down shift to first. It's going so slow that I'm probably going 10 mph up a 4% grade road by my house in second gear.

[knsmodels]

when this happened on my truck it ended up the cam was wiped....if this is the problem the valve train will start making noise soon enough....wasnt making any noise on me for a little while but it was my dd and slowly got worse....

[69GMCLonghorn]

We're all pretty much talking out our rear ends without more info.

Tune it up; run a compression check; replace the basic external stuff to rule that out, and go see how it does. Then get back to us and let us know how it is.

Heck, even if the cam/motor is toast, the tune up, etc can't hurt!

[abilityonline]

After some more testing, I think it's fuel related. It runs well on flat or downhill. but going up hill it loses power and starts to back fire then dies. I had to put a little gas in the carb to get it to start again so I could turn it around and go back down hill. It normally will start with out pumping the gas so I doubt it's a fuel pump. I'm wondering if it's a clogged gas tank. That's my next hurdle. Any other thoughts from what I've blabbed on about as always are much appreciated.

[69GMCLonghorn]

Well, it sounds like you're well on your way to finding the problem(s). Check the carb first, just since it's easier. Take a can of carb cleaner and just blast the living crap out of the venturies. Or just crack the top of the carb loose and see if there's any junk in the float bowls. This is a lot easier than dealing with the tank.

[haysonj]

I had a C60 that was doing this and it ended up being a restricted fuel line. there was a three way valve by the seat and it had a bunch of gunk in it from sitting before i bought the truck. Truck would actually run out of fuel when under a heavy load. I used it to tow a backhoe.

[Captain Underdog]

My 68 C50 ran fine with no noises whatsoever and just kept running until she couldn't get out of her own way. I finally tore down the engine to find severe valve seat recession. No hard seats on unleaded fuel will eventually wear the valves into the heads and you end up with 1/16 inch valve lift. Pretty weak runner.

Could be happening to yours.

[DANTIP]

Old gas can cause problems like that (But a C-50 probably goes through fuel quickly enough to keep the fuel supply fresh). I like the advice of checking for fuel delivery problems (restriction, clogged-filter, collapsed fuel line, overheated fuel line, etc.). The high load obviously requires additional fuel flow and it is essentially being leaned out of power.

Please let us know what the true problem ended up being.

[69GMCLonghorn]

If it's possible, park it on a hill and see if it runs while it's parked. Not sure what the heck that'll tell you, but if it's not running right while parked on a hill, then maybe it is (as stated before) fuel delivery.

I still say go through and tune it up if it hasn't been done in the last fewe months or so. It can only help, whatever the problem might be.

[abilityonline]

cleaned the carb and replaced the plugs and it runs like a champ! Old gas has crystalized in the carb.

How can I tell the engine size? The VIN only shows a v-8 is there a chevrolet engine block identification code on c-50's?

[DANTIP]

Thanks for letting us know what the cause/fix was!!!