Help me diagnose a truck issue that's 200 miles away!

[colbystephens]

I posted before, but can't find the thread... Sorry!

So my grandpa left me his pick up. It's an '84 C20, 454/400/14bff, 95K original miles. Likely hasn't been driven more than 100 miles in the last 5 years. Grandpa didn't maintain it well - didn't do oil changes, but just added oil. Of course, he never really drove it so it's probably not that big of a deal. The truck is actually in pretty damn good shape though. Straight, good interior, etc. It's just been sitting in the shop of YEARS. Paint is a bit scuffed and whatnot, but it's been a farm truck so it's to be expected.

The truck is about 200 miles north of me. I want to bring it home in a couple weeks. Obviously I'm going to change the fluids before I drive it, but additionally it runs a bit funny. If you push the gas pedal down faster than "moderately slow," the engine tries to stall out. I assume it's flooding. I know NOTHING about carburetors beyond the fact that they deliver fuel.

So, what sorts of things should I look at? Sounds like it should be an easy fix/adjustment/etc. I'm also wondering if the truck just needs to be run for a while and perhaps that will clear the issue up.

Can you post a picture of what you're talking about? I don't have a carb to look at.

 

[4X4HIGH]

It will have bad fuel. Bad fuel clogs the carb passage ways and will destroy the fuel pump diaphram. ALL old fuel must be drained and then the tank properly boiled clean (failing to do this could result in a valve being stuck open because of the bad gummy fuel) which then leads to a piston hitting the stuck valve and then dissasster happens quickly. I've seen MANY failures because of bad fuel and a persons lack of knowledge or not willing to accept the proper method to avoid this situation.

 

[colbystephens]

Good tip. Thanks! The fuel pump was replaced a few years back, and like I said, it hasn't hardly been run since then. Should I bother with the pump? I think the truck's fuel is pretty much empty all the time - people just dump a little in when they need to drive it. Do you think this is still an issue? Does putting a new fuel filter in the line address my issue?

 

[George_Pimpdaddy]

You think a quick drain of the old gas and some fresh gas with some additive or even seafoam would get it drivable? Heck id probably do a full tune up with spark plugs, cap and rotor, and a new air filter before i touched the key

 

[colbystephens]

You think a quick drain of the old gas and some fresh gas with some additive or even seafoam would get it drivable? Heck id probably do a full tune up with spark plugs, cap and rotor, and a new air filter before i touched the key

those things are definitely on my list of to-do's before i drive it.

 

[4xcrazy]

If you push the gas pedal down faster than "moderately slow," the engine tries to stall out. I assume it's flooding. I know NOTHING about carburetors beyond the fact that they deliver fuel.

Sounds to me like the accelerator pump isn't working right, not flooding, but not getting enough for it to go, if you push slow, you're not needing that extra boost (squirt) of fuel for the quickly needed demand.
give the carb a good cleaning, fresh fuel with an additive and i'll bet it'll drive fine.

and depending on how much gas is in the tank would determine to me if i would drin out the old gas, i had a vehicle i had sitting the back yard for years, kept it running from time to time, just added fresh higher octane fuel and everything was fine.

 

[Chevy305]

It will have bad fuel. Bad fuel clogs the carb passage ways and will destroy the fuel pump diaphram. ALL old fuel must be drained and then the tank properly boiled clean (failing to do this could result in a valve being stuck open because of the bad gummy fuel) which then leads to a piston hitting the stuck valve and then dissasster happens quickly. I've seen MANY failures because of bad fuel and a persons lack of knowledge or not willing to accept the proper method to avoid this situation.

x2, classic case of bad fuel and gummed carb

1st step is to drain all old gas out, then rebuild the carb.

Since carbs make about as much sense as chinese calculus to you, I'd say just drain out the gas, put fresh gas in with an overdosed amount of carb cleaner. It should remove some stumble enough to get it home.

 

[scrappyk5]

It will have bad fuel. Bad fuel clogs the carb passage ways and will destroy the fuel pump diaphram. ALL old fuel must be drained and then the tank properly boiled clean (failing to do this could result in a valve being stuck open because of the bad gummy fuel) which then leads to a piston hitting the stuck valve and then dissasster happens quickly. I've seen MANY failures because of bad fuel and a persons lack of knowledge or not willing to accept the proper method to avoid this situation.

This post you should consider first. Doesnt matter how much gas is in the tank, it will start to gel up after sitting and not being used.
But if you are not wanting to clean the tank and taking a chance, atleast do the following :

drain the tank.
add new gas
change fuel filter
clean out carb, including the bowl.
change the plugs
change cap and rotor.
consider putting on new fuel pump.

You could always bring a spare tank , secure it in the bed and hook up the lines , then clean the original tank later.

 

[colbystephens]

You could always bring a spare tank , secure it in the bed and hook up the lines , then clean the original tank later.

good idea!

 

[Burbdood 74]

I'd take some Seafoam to put in the tank and the engine. Chances are, after you do your tune-up and do the Seafoam treatment, just taking it out on the highway could clear out the stumble.

And if the tank has been mostly empty for all these years, I'd take 2, maybe 3 fuel filters with you. There's bound to be a lot of rust in the tank and you don't need that leaving you stranded.

 

[Fordum]

The stalling when you try to start off, is almost certainly the accelerator pump like he said.

NOTE, this is not the fuel pump. Its a little rod dingus (technical term) that sticks out of the front of the carb and squirts a shot of gas in when you hit the accelerator.
Yours either has a hole in the diaphragm or is stuck in. Given the age, it may just be stuck.

Either way, I would not worry about it now. You can get home without it working just fine. Just start off easy.

There is a possible problem that is much more serious. Given the age, the fuel pump diaphragm might be dry rotted or about to go bad.

If so, you might trash your engine on the way home.

If the diaphragm goes bad, it can start pumping gas into your oil without your knowing it.
Sooner rather than later, the diluted oil will cause major bearing failure.

Suggestions? Hard to say.
The obvious answer is to change the fuel pump.
But, I would want to wait to do that until you get the rest of the fuel system cleaned out so as to not possibly mess up a new pump.

Of course, its not guaranteed that it would mess up a new pump, and even if it did, two new pumps are way cheaper than a new engine.

The first symptom of the problem is an increase in the oil level in the engine. If you find the oil overfull now, it may already have failed.

I will let the other folk here chip in with their opinions, but I think all of them are going to agree that a new fuel pump is a good idea sooner or later if for no other reason than reliability.

Of course, the best idea all around, is to find a friend with a trailer.....

J.

 

[colbystephens]

You're referring to the mechanical pump that runs off the camshaft, right? My uncle and I replaced that a short few years back, so it should be fine.

 

[Fordum]

Yep, thats it. Great, one less thing to worry about.

 

[4X4HIGH]

You're referring to the mechanical pump that runs off the camshaft, right? My uncle and I replaced that a short few years back, so it should be fine.

It's not a matter of how few years ago you replaced it as it is the old gas that starts going bad after 6 months and then gums up the carb and deteriorates the fuel pump diaphram.

Take my professional advice or leave it, it's up to you but I can't even count how many of my customers with old cars or cars that have sat for a couple years didn't listen and ended up with the engine apart with bent valves because they stuck in the guides from the gummy fuel and then the pistons hit them.

 

[gotblazers]

i got a 76 k5 blazer that had been sitting for 10 years when i got that did the same thing. I'd Suggest replacing your vacuum module on the distributor and possibly the thermostat(thats up to your discretion whether its needed or not). Let it warm up properly and with a new vaccuum module it should be able to pick up quite a bit better, this solved the problem for me. Best of luck

p.s im running my stock fuel pump and my girl still runs up hills with my grill facing the sky, motor screaming, all 4 wheels spinnin like hell and has never let me down short of when my ignition module failed after 34 years which aint bad IMO.