Here’s some background because it might be relevant and it helps my embarrassed anger to talk about it a bit.
About a month ago, we bought a used 1996 GMC Suburban (Not Chevy, but essentially the same thing) from a guy in our town. Our minivan is on its last legs and my wife regrets getting rid of our last suburban. Also, I can fit 4x8 sheets of plywood in it for my wood working hobby. I’ve also been wanting to learn more about fixing cars, so I figured a older truck should be just what we need.
We took it on a 20 minute test drive and everything was great. Maybe some hesitation in acceleration, but not noisy and pretty smooth for an 18 year old truck. So we paid for it and took it home. Got it about halfway home and it died. We had to have it towed to the mechanic. The alternator was dead. $300 to fix it. Grrr…
The mechanic also mentioned that it was misfiring. Boy, was it ever. I only live about a mile from the mechanic but it was slow and rough going all the way. Wasn’t like that at all on the test drive.
After the test drive, I noticed the license plates had expired in 2006! Nearly 7 years ago. But the body was in great condition, except a few minor dings here and there, which - again - is to be expected on an 18 year old truck. No rust at all.
We met the previous owner at one of his rental properties when looking at the truck. I’m guessing that he kept it in the garage of the rental since 2006 and did little to maintain it.
I’m in the process of changing out the spark plugs and spark plug wires. It is taking me longer to do this since it is my first time (see above about wanting to learn car maintenance). But I’m worried that doing that will solve the issue.
Should I worry about the 7 year old gas? Or the oil? Would adding new gas possibly help? Or just make things worse?
My biggest concern is that the fuel injectors are all gummed up. Is that something I might try to fix on my own?
But my biggest question is why did everything work so well for the long test drive then go to hell so quickly afterward?
Seven year old gas could definitely be a concern. Gas will turn to gummy varnish in a shorter time than that. Unless the spark plug wires look rotted (or chewed by vermin) they may not be the issue, nor the plugs. More likely the injectors, whose malfunctioning will feel & sound exactly like bad spark plugs. Most definitely put a tank load of new gas into it along with some high quality injection cleaner (i.e. NOT just dry gas). Don’t bother even considering draining the tank first as this is impossible w/o removing the whole gas tank (and not really necessary). Also don’t bother using premium gas as it won’t do anything extra to help fix this situation (unless the vehicle requires it which I doubt it does).
Your crankcase oil will not be a concern (as long as it’s full). Though it wouldn’t hurt to get it changed (and have all the fluid levels checked, i.e. the differential(s), tranmission, transfer case if 4x4, after you solve this problem).
Is your CHECK ENGINE light on? People bemoan car computers but they are actually a huge help for things like this. If it’s throwing a code a mechanic will be able to better find the problem (possibly just a bad sensor).
Be sure to check the condition of the spark plugs as you remove them and note which cylinder they’re from if they’re anything other than normal looking. Here’s a chart, or else virtually every service manual has a version of it: http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp
If any of them look really gnarly, you might want to buy or borrow a compression tester (the big auto parts store chains lend them out) and do a compression test while you’ve got the plugs out.
With regards to the gas, I’ve been able to resurrect some old cars with 5-10 year old gas simply by draining out a few gallons and topping off with fresh stuff and then keeping it topped off. That was on a carbureted car though. How full is the gas tank now? If it’s mostly empty, adding a few gallons of fresh gas to see if that improves the situation may be a good idea. You probably don’t want to make the major investment of filling it up all the way unless you get it running well.
What was the weather like on the test drive and subsequent drives, by the way? If it was dry during the test drive and wet during the later drive with the misfires, it could just be old cracked plug wires. So fingers crossed that that fixes it.
You probably could not lose by doing a tank drain, line flush and then a fill with a double dose of injector cleaner. (Don’t exceed 1 bottle/10 gallons but don’t dilute it much more than that, either - one bottle in a Suburby tank is too thin.)
Fresh gasoline? Yes.
Oil change? Almost certainly.
Antifreeze? Before winter at the latest.
Transmission fluid change? Couldn’t hurt.
Brake fluid change? I’d at least drain the reservoir and fill it with fresh fluid. Have the brake system flushed the next time brake work is done.
My brother-in-law left a truck sitting for a few years, and I had the joy of getting it to run again. It actually ended up not being too difficult, but after only two or three years the gas was starting to go bad. The truck would run on it, but not well.
The first thing I did was just get the truck engine running. That took about an hour. Once that was done, I drove the truck around the neighborhood and constantly accelerated hard and slammed on the brakes just to get the brakes loosened up and working properly again. Only when I could reliably both go and stop did I take it out on the main road.
The first place I took it to was the gas station. The truck had about half a tank of old crappy gas in it. I filled it the rest of the way, and with the mix of old gas and new it ran a lot better. I drove the truck around until that tank was pretty darn empty and filled it completely again, and after that it ran perfectly fine.
Completely draining the tank is better, but it can be a bit of a pain to deal with temporary storage for all of that crappy gas. Mixing a lot of fresh gas in the tank will usually be “good enough”.
There may be some rust and crap in the bottom of the gas tank that will likely end up in the fuel filter at some point, if it hasn’t gotten stuck in there already. A fuel filter change fairly soon would be a good idea.
Also, run the engine a little hard for a bit. Take it out on the highway and stomp on the gas. Any water that may have condensed in the oil will flash into steam and will get ejected from the engine. Also, any gunk built up on the spark plugs will get burned off. They call it a poor man’s tune-up for a reason.
ETA:
Personally, I’d wait a month and then do the oil change.
The gas tank is pretty empty. One thought was that we might actually be running out of gas, but I wanted to make sure it was ok to mix the old and new. I’d like to avoid dropping the tank if at all possible. I’m a novice DIY’er. But I have a suspicion that I will be replacing the fuel pump, filter and lines to get it running smoothly.
Oil level was just a tad bit higher than the max line.
The brake level was between min and max on the reservoir.
Didn’t check transmission fluid nor differential. I figured if I could get the engine running smoothly, then I’d worry about how well it moves.
The Check Engine light is on (as are the ABS and BRAKE lights, but one thing at a time) but I have not had the codes read because I’m afraid to take it on the road to get to to AutoZone or Pep Boys or whatever.
Once I get the plugs and wires changed, I’ll add some fresh gas and see if that helps. I’ve read that most of the tank added fuel injector cleaners on the market aren’t worth it. Should I bother?
The claim that you should be running them with every X tanks is baloney, but if you’ve got a suspected fuel system problem (which you do) they are firmly in the “worth a try” category.
Did the previous owner confirm it had just been sitting for the past 7 years? If that is indeed the case then I’ll throw another vote for “start with the fuel.” Also, start with the fuel filter.
One reason it may have run well at first and then got shitty with you: Fuel was old but still combustible, and any crud was resting peacefully at the bottom of the tank. So while the beast was sitting still the fuel pump was still sucking reasonably clean fuel. Motion got the sediments stirred up and sucked into the fuel system where, I’d be willing to bet, they hammered your filter. If you’re lucky, the filter may have done its job and kept your injectors from getting gooey. But a clogged filter will severely limit the fuel that gets to the injectors, and what does get there will be under low pressure and may not atomize well possibly causing a misfire & generally crummy performance. Misfire will trip the engine light.
Replace the battery, too, before it takes out your new alternator. And be thinking about new tires. The tread may look great, but the rubber ages. Tires aren’t meant to last many years.
And since we’re being all DIY, complete with ‘poor man’s tune-up,’ get up to 40-ish mph and stomp the brakes like a baby just walked in front of you. Make sure nobody is behind you–do this in a business parking lot on a weekend or something. Do this a few times (like maybe 10 or so). It will re-calibrate (wrong word, sort of) the brakes, loosen up the caliper pistons, blowout weakened brake lines, expose other weaknesses in the system, and at the very least it will give you a good idea of how well the vehicle stops. Get a Haynes or Chiltons manual from the parts store and be bold. The best way to get good at DIY is to build confidence and familiarity with the systems, and you don’t get that without getting way outside your comfort zone. Enjoy!
I’d put ¼-½ tank* of fresh gas in it along with a big bottle (20 oz.) of Techron fuel additive. There’s a reasonable chance that this will help significantly. For the next step I’d replace the fuel filter.
It’s rather unlikely that spark plugs or plug wires went bad since you bought the truck.
*I’d hold off on filling the tank until I was sure that the fuel pump was okay. A full gas tank makes fuel pump replacement much more of a chore.
Yes to what Gary T said because, in case you don’t know, the fuel pump is inside the gas tank and to change it you must drop the tank. Unless they’re severely rusted and/or leaking there’s no reason to replace the fuel lines.
Turns out one of the spark plug wires wasn’t even attached to a plug. Must’ve wiggled off after the test drive. When all was said and done, I pulled 4 different spark plug brands out of that engine.
I went to replace the fuel filter. The instructions online say to pull the fuel pump relay and crank the engine to relieve pressure in the fuel lines. I pulled the fuel pump relay, cranked the engine and it started up! WTH?
The other way to do it, so say the manuals, is to attach a fuel pressure gauge to the fuel pressure valve and bleed off the pressure. Aside from spending another $40 on a fuel pressure gauge, they never say HOW to bleed the pressure off with the gauge. Any help there?
I also found some kind of clear liquid dripping on my driveway. It had a weird smell. After sniff testing all the fluids in the car, I think it is brake fluid. And my brake fluid reservoir is empty. But isn’t brake fluid red? Or should this be another thread?
Most likely, wrong relay. Have you tried pulling the fuse instead? Now that you mention it, though, I had the same problem on a similar vintage Buick once, where I pulled the fuel pump fuse (and I think the relay) to relieve the fuel pressure but the thing fired right up. Maybe there is some sort of subtlety of 90’s GM wiring I’m missing. I just let it sit for a couple hours and opened the fuel line connection slowly and it was fine, just be prepared for a little bit of gas to come out.
No, brake fluid is clear. You’d better get that checked out.
I’m sure I pulled the correct relay. I triple checked the diagram on the relay box cover. It also matches what I’ve seen in videos of similar era Chevy and GMC trucks getting their fuel filter changed. Didn’t know about any fuses for the fuel pump.
A bit more of reading around and someone mentioned the fuel pump oil pressure switch or something. Post #5here. I guess the Fuel Pump Relay and the oil pressure switch are in parallel.
Would diagnosing and fixing brake line issues be something a newbie could attempt? Or should I cut my losses and get it to the mechanic? Any idea how much that might cost? Ballpark…
They sell a “brake system stop-leak”, but it never worked for me.
Fill the reservoir and drive the thing slowly. See how the brakes feel. Spongy? Need to bleed them. Massive loss of fluid? Put it in park and pump the brakes. That will tell you where the leak is. (Hint: Look for the spot!)
I’ve tried using the Mighty-Vac to do a “one man brake bleed”. Can only get it to work on a motorcycle. When bleeding car/truck brakes I make my kid pump the pedal. Works much better.
Give it a shot. For me, I have all the time in the world and no money, so I avoid mechanics like the Clap. I’ve got tools, research material and a place to work, so I try it first on my own. So far, so good. I have to recognize my limitation, however, and didn’t try to disassemble my auto transmission. I pulled it, took it someone and then re-installed it. But I’ve learned brakes, belts, hoses, cooling systems, fuel systems, timing, suspension and all kinds of stuff, and feel better for doing it myself.
Good luck! By the way, you didn’t mention how well it ran after what you’ve done so far.
I’d guess it’s the old gas causing the problem. I’d see if there’s a way to drain it and refill, and barring that, fill it as full as you can with fresh gas and that Techron additive mentioned earlier. It’ll un-crud pretty much anything that can be un-crudded without being replaced.
It can’t hurt to pull the plugs and take a look as well. There are quite a few plug condition photos on the web for comparison.
I doubt the plug wires need replacing, but on a truck of that era, it should be pretty much unplug the old ones and plug the new ones in.
I’d get a helper and flush the brake fluid; it’s hygroscopic and will absorb moisture from the air over time.
Hmm. I know on many of the old GM OBD-I type cars, the fuel pump is normally powered through the oil pressure switch with the relay only supplying power when starting. But I thought on all the OBD-II ones (which your '96 should be) the pump is usually powered by the relay (and controlled by the computer) and the oil pressure switch only serves as a cutoff. Looks like on those forum posts, maybe some of the early OBD-II trucks were wired the old way, though.
So if that’s true, have you checked if there’s a fuse you can pull instead? This is really blowing the cobwebs out of my brain, but I think on those vintage GM’s the fuel pump was sometimes on the same fuse as the ECU and so if you pull it the injectors won’t fire either, so you might not be able to relieve the pressure that way. You might need to actually unplug the oil pressure switch, or else like I said, just letting it sit for a few hours (ideally overnight) and carefully opening the fuel line should work okay.
Definitely worth diagnosing, since it should be fairly obvious where it’s leaking from. Most likely, it’s either a rubber hose or a hydraulic component that’s leaking and those are generally pretty straightforward to replace. If it is actually a hard metal line that’s broken or rusted through, those can be a pain in the butt and may be worth leaving to the pros.
Finally got the fuel filter replaced. The engine definitely runs better, but still a bit rough.
I looked at the brake issue a bit more and it looks like I have fluid leaking from the booster behind the master cylinder.
I took a video of it and put it on youtube. Take a look and let me know what you think.
I’m thinking the seal between the master cylinder and booster failed and brake fluid is leaking into the booster. Which worries me because that means brake fluid might have entered the engine via the vacuum hose. I can’t figure out where else all of that air and brake fluid would be coming from.
You have brake fluid leaking from the rear of the brake master cylinder. This means the master cylinder is faulty and needs to be replaced. Brake fluid sucked into the engine through the booster’s vacuum hose isn’t going to hurt anything. If a huge amount is being sucked in, it will produce exhaust smoke similar to burning oil.
Note that brake fluid dissolves paint rather quickly; be careful with it.
