1994 GMC 1500 Engine Knock

[Rwatkinstx]

1994 GMC 1500 that belonged to my Father. It's been sitting in my mother's driveway for a year (with 1/2 tank of Gas). Charged the battery and started it up- after running for a few minutes, it developed a loud knocking sound in the engine- could this be fuel related since it sat for so long without running? The last time it was driven, this was not a problem -has 200,000 miles on it, but it was very dependable - he changed oil regularly (checked oil level, it is full).

[barry G]

sensitive time for an engine.. sitting awhile.

you might have spun something.

 

I like these older mains for the drain back, you get fresh shots of oil on stress.. with a noise that goes away.

the only problem is a scenario like yours.

risky time.

[Motor City Rick]

Is it a "hard knock" or more like a lifter click??? Does it sound the same cold as warm??? Does the knock stay through the rpm range??? If yes, stop running the motor and get ready for major motor work.

[Rwatkinstx]

It is somewhere between a hard knock and lifter click. Oil is full, but since it sat for a year, not sure if everything drained out, (maybe oil pump gone bad.) It has only run for a little bit in the driveway (less than a minute at a time), don't want to drive it til I figure out if it's the lifters, or something more internal. I'm afraid it's more than a lifter- sounds more like "tika-tika-tika" (or thumpa-thump a-thumpa) rather than a click. It started out okay just idling after startup, but suddenly the knocking started (while idling)- haven't revved up the RPM yet.

Thanks for replying- trying to give my mother advice on what to do with it.

[Motor City Rick]

Is your Father available to answer why he parked the truck for a year???

 

Get a mechanic that knows motors to hear the sound. Tell him to bring an oil pressure gauge (if you have an idiot light) or look at the oil pressure gauge on the dash.. Oil pressure should shoot up to 60 psi. cold. 25 to 35 warm at idle. 45 around 2500 rpm's.

 

A piece of carbon that fell off an intake valve can cause a hard knock, along with something dropped through the throttle body.

 

Don't run the motor anymore except for noise diagnosis.

 

Your describing a bearing issue.

[bigblok]

Dun d dun dun... Hope you can get it pinpointed to one side or the other. Try to get a good listen while it's running. Good luck.

 

Sent from my VS995 using Tapatalk

[Supreme Pizza]

Ideally you would pickle the motor before storage, and prime it before you fire it up.

 

Pickle:

 

Change the oil

Add fuel stabilizer to the fuel tank, drive it around a little.

Pull the spark plugs out and squirt oil into the cylinders, crank engine for 5 seconds. (or fog it)

Loosely replace the spark plugs.

Put a rag into the exhaust pipe.

Put it on a "floating" battery tender.

Cover vehicle.

 

Prime:

 

Pull the spark plugs, squirt some oil into the cylinders and crank for 5 seconds. (or fog it)

Change the oil

Crank the engine for 10 seconds, wait 1 minute, repeat several times (to bring oil pressure up).

Replace the spark plugs.

Check all fluids.

Start the engine, and idle for 5-10 minutes (dont rev it up).

Check the tire pressure, and your good to go.

 

 

Did I forget anything?

[thx1138v2]

You can buy an engine stethoscope to better locate the knock. I usually just use a small diameter steel rod and cup my hand around one end and hold to my ear and place the other end on different locations around the manifold, heads, and block. If it gets louder or more pronounced the lower you go its probably a problem in the block. If it's in the heads or above you can move from side to side to better identify its location.