idles/runs super rough, no power.. fuel pump?

[column_shift]

So I have a 1991 (i think its a 1991, 1990? i always mix it up) K1500 4x4 Silverado with a 350tbi, automatic, and 23,000 miles on it. (yes 23, not 123 or 223) Sees very little use normally but last fall just as I was starting college it went from running great to insta-crap. Couldn't barely hold 55mph, no power to accelerate, even idle was bad. I replaced the fuel filter wondering if that was it, but there was no change in how the truck was running. Since I was just starting a heavy class load and didn't have time or handy tools to mess with it, I put Pri-G in the tank (it's like Stabil) and parked it in the garage for the winter.

Unless I did something wrong in swapping the fuel filter (like was it supposed to not just be a swap, was I supposed to bleed the lines or fear of air bubbles) it didn't improve anything, so I assume the next guess would be the fuel pump... which i've heard is up top the tank or something in these trucks. (didn't have a manual handy to check) I was just wondering if this is correct/whats the next process to check.

It wasn't a slow degradation, just an instant "it was running fine now it's not" scenario. How do I narrow down what's causing my problem better?

 

[pro17]

Check the fuel pressure before buying a pump. Also check back pressure in case the cat is clogged.

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[Loydw]

old wires can break. look for loose wire, battery grounds, sparkplug wires if not replaced, if it had been park critters may have worked on it. do a really close inspection of wiring looking for chewed, worn, rubbed areas. the fuel maybe a problem check for spray in the tbi. good luck

 

[94burbk1500]

I'd definitely do some more troubleshooting before throwing expensive, labor intensive parts at it. When's the last time this thing had a tune up?

Low miles doesn't mean it is in perfect running order, in fact it can lead to all sorts of problems on old vehicles you don't see with daily drivers.

 

[column_shift]

I'd definitely do some more troubleshooting before throwing expensive, labor intensive parts at it. When's the last time this thing had a tune up?

Low miles doesn't mean it is in perfect running order, in fact it can lead to all sorts of problems on old vehicles you don't see with daily drivers.

I'm fine for troubleshooting, i'm just not sure what to check for or what the followup questions are. Like if I have low fuel pressure, is there likely to be another (easier to fix or check) cause that could have happened out of the blue when it was running just fine literally an hour before?

I'm okay and replacing broken parts, I mean I can put in a clutch for instance, but figuring out whats broke if I don't know I freely admit i'm not broke at. Is there a suggested list of things you'd say to check on an "old but low miles vehicle?" I'm sure it's been awhile since a tuneup but I couldn't imagine going firing on all 8 to stumbling on 5 (about how bad it feels,part throttle is horrible, worse than full throttle actually) from an older spark plug or wire deciding to randomly konk out.


This will be a slow (summerlong?) process as I can't get to my tools (garage became emergency storage when brother evicted illegally) but i'm trying to plan out a strategy of what to try to make my way to (for tools) or borrow elsewhere in the meanwhile maybe if it's a simple fix, or to rule out at least the simpler possible causes. Just help me figure out/plan out the "check A, if it's not A look to B, if it's not B then it must be C" strategies so I can hopefully get thru as many as possible in a row/in the same day the moment I have tools ready to do so.

 

[94burbk1500]

I'm fine for troubleshooting, i'm just not sure what to check for or what the followup questions are. Like if I have low fuel pressure, is there likely to be another (easier to fix or check) cause that could have happened out of the blue when it was running just fine literally an hour before?

I'm okay and replacing broken parts, I mean I can put in a clutch for instance, but figuring out whats broke if I don't know I freely admit i'm not broke at. Is there a suggested list of things you'd say to check on an "old but low miles vehicle?" I'm sure it's been awhile since a tuneup but I couldn't imagine going firing on all 8 to stumbling on 5 (about how bad it feels,part throttle is horrible, worse than full throttle actually) from an older spark plug or wire deciding to randomly konk out.


This will be a slow (summerlong?) process as I can't get to my tools (garage became emergency storage when brother evicted illegally) but i'm trying to plan out a strategy of what to try to make my way to (for tools) or borrow elsewhere in the meanwhile maybe if it's a simple fix, or to rule out at least the simpler possible causes. Just help me figure out/plan out the "check A, if it's not A look to B, if it's not B then it must be C" strategies so I can hopefully get thru as many as possible in a row/in the same day the moment I have tools ready to do so.

Honestly, start with routine maintenance, if you can't remember the last time it was done, it's probably time to do it. I'd check the fuel pressure, if it's within range, it's not your pump. How long did this sit with fuel in the tank? I'm wondering if you could have bad gas, even with the stabilizer in it. Siphon some out and make sure it doesn't smell like varnish and that it looks clean. From there, pull the plugs and inspect them, you can learn a lot from plug condition, compare them to here:
http://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/how-do-i-read-a-spark-plug
If they are good, take a look at the distributor cap, see if the inside of the cap has corrosion. You can get a pretty good tune up kit (cap, rotor, wires) from United Motor Products on Rockauto.com for cheap https://www.rockauto.com/en/moreinfo.php?pk=1144949&cc=1050882&jsn=1809 replace the plugs if you go this route, I like NGK plugs. Try cleaning up the injectors and throttle body. If you still don't know what's going on, take a look at the oil and at the coolant, make sure they aren't contaminated. Do a compression check.

A few years back I bought my 2000 s10 with 40k miles on it and it ran great for about 3 months, then it started chewing up electrical and ignition components. Every time I found a bad component, I thought it was fixed, but then something else would go. I replaced plugs, wires, coils, battery, starter, alternator, abs controller, then it finally clicked. I started tracing every wire I could find and then ohm'ed them out. I had a frayed (seemingly nicked) positive wire going to the main fuse block that would occasionally short to ground as well as a negative battery cable that looked good, but the inside of it was corroded all to hell. I can almost guarantee you that this truck would've been a lot better off being driven regularly.

 

[ram1220]

My bet is on the distributor cap. My 90 was running great one day and the next it would fall flat on it's face. A new cap fixed the issue. The dist caps in these trucks are known to corrode. One day the truck runs fine and the next it doesn't.