CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

83 Chevy Suburban, 350 Engine & a great young man who needs a hand

The great young man in question, my not-my-son, has purchased an 83 Chevy Suburban. Now it’s having issues. I know very little about cars, but have a great memory and the way it’s acting, my first instinct is to change the fuel filter. Neither of us have any idea where the fuel filter is on this thing, and online searches are leaving us with nothing. This is SO not the right time for Car Talk to be ending. I really wish they had checked with me first.

Anyway, any help?

The local Chevy dealer parts department should be able to print an “exploded view” drawing of its location for you.

What are the symptoms?
How many miles does ot have on it?
Do you know anyything about its history?

It will start, but won’t idle, so you have to give it gas or it will die. It will drive, but only if you give it gas as soon as you put it in gear (or it will die).

It’s got… well, the odometer says 11304, but I somehow think it’s rolled over at least once since 1983.

I don’t know a lot of it’s history. The man who sold it to him said he THOUGHT it had maybe one previous owner, but he wasn’t even sure on that count. Someone has been under the hood getting “creative”, that much is certain…

We’ve got other theories in the idea pipeline, but I thought we’d start with that one.

This truck is carbureted, I would turn up the idle screw… That should solve your issues.

By the way does this truck have AC, is it working and does it do it with the AC on or off?

As for the filter I think its in the carb’s fuel intake. Should be a big nut where the fuel line goes into the carb… GENTLY turn this nut (if it resists soak it with PB blaster or the like and let it sit, you don’t want to mess up the fuel line)… The fuel filter is a small insert).

This pic should help, although your carb may look a little different (the top has been removed from this one), but you get the point.

I’d be more inclined to think that the carb needs work in the float bowl, or perhaps a clogged fuel circuit.
If there were a plugged filter, the engine would be more likely to feel a loss of power under load than at idle. Stalling at idle and running when the throttle plate is opened usually suggests that either the carb has a clogged circuit that won’t allow enough fuel through to idle, the idle set screw has unadjusted itself. or the float is hanging up, keeping the needle valve closed until enough vacuum develops from the orafice end to help the float drop and open the valve. The absolute pressure at the orafice does drop when you open the throttle plate.

If you are LUCKY, since it’s a truck, it MAY have escaped having a “feedback” (computer controlled) carburetor…Even so, most of the adjustments will be sealed making tuning very difficult…These vehicles (1981-1989) are smog nightmares and trying to get them to run properly today can be mission impossible. They did not run very well when they were brand new…

If it won’t idle, check for vacuum leaks allowing air to dilute the fuel mixture…Also check that it’s EGR valve is not stuck open, which will destroy its ability to idle…

Now, back in those days, MANY owners got disgusted with these emissions control problems and they simply “de-smogged” the engines, removed all the emissions controls and put the engine back into 1969 configuration…If yours has been “converted” in this manner, it should be fairly easy to get it running properly…

Choke sticking, bad float etc. dirty needle and seat valve or clogged low thottle adjuster come to mind first. A sea foam treatment and some carb cleaner sounds good, shoot the whole carb, linkages and orifices wearing safety goggles of course. Is this a model you have to press the gas pedal once to set the choke? Try it if you are not sure or I get no response to this question. Gas filter probably is along the rail behind the driver seat, underneath the car. Follow the gas line and you will find it. Check the air filter also just for kicks.

Setting the idle speed and mixture can be difficult without this tool

http://www.ebay.com/itm/NEW-LISLE-CARBURETOR-CARB-ADJUSTING-TOOL-55250-/110341141032

but raising the idle speed would seem to be the place to start in correcting the problem. It is difficult to see and very difficult to get a tool on the adjusting screws.

See if you can get to idle nicely by spritzing some starter fluid around air hoses and the base of the carb. If you hit an area and it suddenly yet temporarily idles nicely, you may have an air leak in that vicinity.

A minor vacuum leak on a carburated engine will usually increase the idle speed. The engine may die when shifted out of park in spite of the increased idle speed though. Ether will certainly aid in finding a vacuum leak but a beginning DIYer might need some close supervision by an experienced gear head to try it.

Aw, eyebrows:
What are they good for, Rod? :slight_smile:

My old rambler it was stumbling all over the place last week until I snugged the carb nuts up. The gasket must have not been in full contact.
Just be careful.

This truck should have a Rochester Quadrajet carburetor on it, which would have the fuel filter located where gsragtop’s picture shows. Remove the fuel line, then loosen the 1" nut at the fuel inlet, then pull out the fuel filter. I doubt this is the problem, though, but couldn’t hurt to try. I would first eliminate any vacuum leaks and thoroughly clean the carburetor. An easy and quite thorough method is to remove it from the engine as a whole and use a can or two of carb cleaner to make it shine. Also concentrate on sending the cleaner into the fuel inlet and accelerator pump circuit (fill the float bowl through the fuel inlet where that filter is with carb cleaner and repeatedly open and close the butterflies). Removing the fuel filter prior to doing this is also a good idea. Reinstall the carburetor and see how it runs. I recently did this with a 750 Quadrajet on an '86 Chevy truck with a 350 that sat for six years with a carb full of fuel. It ran prior to cleaning, but barely. This method worked like a charm and took less than a half hour to complete. If this doesn’t work, you may need to find a mechanic with lots of gray hair to rebuild the carburetor for you.

If your fuel filter was letting so little fuel flow that the car wouldn’t idle, the engine would not run at all. The most likeiy culprits are, vacuun leaks, egr circuits or carb problems. The drive ability of these was marginal when new and even good mechanics had a hard time diagnosing their problems.

Thank you, everyone! All those votes against it being the fuel filter: you can rest easy knowing you were right…

But now we have some more theories (given by what I assume are people who are much more knowledgeable about these things than I) to look at, so it’s all good!

An unlit propane torch can be used to find vacuum leaks as Remco suggested with the starting fluid…The idle will respond when the engine sniffs the propane…If adding a little propane directly into the carb cures the idle problem, then you know the carb is the problem…

Look closely at the carb. It will have one wire connected to the choke heater. Does it have any other wires connected to it ?? If so, it’s a “feedback” carb, making repairs more difficult…

Well, I think we’ve either killed the truck or his enthusiasm for spending any more money on it. Now I’m going to need to post questions about the best place to get a good-yet-cheap vehicle, and if anybody has any recommendations… or is there a spot on here for that already?

Before you give up hope, check all the vacuum lines. The idle mixture screws on this are capped off and hard to find. If you can find the caps, located at the front of the carb on the base, remove then, unscrew the mixture screws and remove them. carefully clean the tips and squirt carb cleaner into the holes.

Insert the screws and gently turn them until they stop. Do not apply any torque to tighten them. Back them out 1.5 turns. Start the truck and continue to adjust the screws for best idle. If the idle gets high, back down the idle speed adjustment and then continue to adjust the mixture screws for best idle.