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Engine Issues or Fuel Issues

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Fall_Guy

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Hello people, I hope you are all having a great day.

I'm having trouble with my 1974 K5. It has a 1995 Tahoe engine, that has been converted to carbureted.

It is making tapping or knocking or banging sound. I assume it's from the engine, as I don't think there is a fan blade hitting anything.

In the past, this truck has had a few problems, and I suspect they have been due to fuel not getting to the engine. Two weeks ago, I was driving up hill (a drive I do daily), and suddenly it felt as if I was driving on one cylinder, then when I got to flat ground, the truck engine essentially stopped working. I went to turn the engine back on, and it wouldn't start. I came back an hour later, and it started up just fine.

Prior to this issue, the truck has had a lag when I hit the accelerator, before getting going.

Also, sometimes, the truck will stall when I shift to reverse. It has automatic transmission.

About a year ago, the truck had a similar issue with the engine losing power and stopping. I had to use starter fluid to get it back to my driveway (thankfully it was only a block away), and I had a mechanic tell me the fuel pump went bad, and he replaced it. (Fuel pump connected to engine was replaced. I'm not sure if there is another in the tank. Does anyone know if there is a fuel pump in the tank?)

I wonder if there is some blockage not allowing enough fuel to get to the engine.

Or, I wonder if the carburetor is not calibrated properly. Which could be, because this is not supposed to be a carbuerated engine.

I'm doing as much work as I can, and I am still fairly new at working on cars, so any advice is greatly appreciated.

I also noticed the sound speeds up when I accelerate.

Here is a link to how the engine sounds now. Please help me figure out what this is, and what I can do to make the truck run again. It is a daily driver.

 
Yeah, check the easy stuff first. Take the belt off to isolate the fan or any accessory issues. Just don't run it very long like that because you won't have any water flow.

Have you dumped the oil to look at it?

At some point, the Vortecs weren't drilled for a mechanical fuel pump anymore, but I think that was later than1995. Because that's the only reason I can think of that the noise is related to a fuel issue - the pump is loose, it's the wrong rod or the fuel pump lobe of the cam is going flat (or it's just a junk rattly pump). You could probably verify that by checking the pump bolts, then loosening it to verify it's always under tension from the cam.

If you still haven't found anything, pull the torque converter bolts and push the converter back just enough to clear the flexplate. That will tell you if a cracked flexplate is the issue (or anything in the tranny).
 
Hi guys, thanks for the replies. I will check the torque converter to flex plate bolts.
I've never done this before.
Do I need to take the entire transmission out to do check this, and tighten them if necessary?
Or can I do it while it's still hooked up to the truck?
 
Just remove the inspection cover, which is sort of the bottom part of the bellhousing. Get a good light and something to turn the engine and look for cracks, if the bolts are already tight.
 
Hey everyone, I made a video investigating the flex plate to torque converter bolts. Please check it out. I don’t think that’s the problem. Maybe you can spot something I didn’t.

 
Fall_Guy said:
Hey everyone, I made a video investigating the flex plate to torque converter bolts. Please check it out. I don’t think that’s the problem. Maybe you can spot something I didn’t.

Click to expand...
There’s only three bolts… put a wrench on them not just your fingers.

you can isolate the engine from the transmission by removing all three bolts and push the converter back away from the flexplate. Also remove all the fan and accessory belts then start it up again.

were there any metal shavings in the cover you removed?
 
Check all the bellhousing bolts too, maybe they‘re loose and allowing the engine to not stay square to the transmission
 
Fall_Guy said:
Hey everyone, I made a video investigating the flex plate to torque converter bolts. Please check it out. I don’t think that’s the problem. Maybe you can spot something I didn’t.

Click to expand...
This sounds like a crack in the flex plate or it's just not loose enough to turn the bolts by hand but enough to wiggle in the hole
 
imiceman44 said:
This sounds like a crack in the flex plate or it's just not loose enough to turn the bolts by hand but enough to wiggle in the hole
Click to expand...
How can I tell if it's cracked? Do I need to remove it?

Should I loosen and then retighten the 3 flex plate bolts first, and then if the problem persists, remove the plate and check for cracks?
 
bradshawtech said:
There’s only three bolts… put a wrench on them not just your fingers.

you can isolate the engine from the transmission by removing all three bolts and push the converter back away from the flexplate. Also remove all the fan and accessory belts then start it up again.

were there any metal shavings in the cover you removed?
Click to expand...
Are you suggesting that I isolate the engine from the transmission to see if the noises persists when the transmission is disconnected?

Are you also suggesting that I remove the belts to see if the sound is coming from the engine first. If it's not, then reattach the fans and see if it's coming from there? And if not, then that basically says it would be somewhere transmission related?

When I tighten the bolts to the flex plate, how tight should it be? Snug? Extreme? Is there a specific newton meter or lbs per foot that is necessary, or just regular tightness that it's solid but won't strip?

There were not any metal shavings in the cover.

Thank you for the guidance. It's very appreciated and really helps so much.
 
Fall_Guy said:
Are you suggesting that I isolate the engine from the transmission to see if the noises persists when the transmission is disconnected?
Click to expand...
Yes, but you're also taking load off of the flexplate, so if the noise goes away, it could be tranny or flexplate.
Fall_Guy said:
Are you also suggesting that I remove the belts to see if the sound is coming from the engine first. If it's not, then reattach the fans and see if it's coming from there? And if not, then that basically says it would be somewhere transmission related?
Click to expand...
Yes, the point is to see if the problem is with the alternator, fan, water pump, etc. Also, I have gotten noises like this from the bolts on the front crank pulley getting loose. Scary until you figure it out!
Fall_Guy said:
When I tighten the bolts to the flex plate, how tight should it be? Snug? Extreme? Is there a specific newton meter or lbs per foot that is necessary, or just regular tightness that it's solid but won't strip?
Click to expand...
You probably can't get a torque wrench up there, but it should be about 1 grunt with a box wrench. But note if it's easy to back them off or not - so you know if looseness could have been the problem.
 
If you remove the 3 flex plate to torque converter bolts, you can push the torque converter back into the trans front pump @1/4-1/2". This will allow you to see the flex plate near the crank bolts, a frequent failure point. Turn the flex 360° to inspect. Mark the converter flex alignment before turning, shouldn't matter but always good to put back together the same. Give the flex a light rap with a small ball peen hammer listen dull like thud. Should have a clear metal ring. Hard to put into words what crack plate sounds like.
If the flex plate has no visible cracks, push the crank towards the front of the engine, then pry rear ward, there should be very little movement, in fact you shouldn't really see any. Crankshaft thrust is measured with a dial indicator, .004-.008". Next start the engine, listen for noise if it is gone then the torque converter or trans are suspect, possible still the flex plate/crank bolts, Would be difficult to check with trans still attached. If the noise is still there, then re attach torque converter 45 ft pd, blue lock tite is optional.
Check the front crank pulley as suggested above, center balancer bolt is 60 ft pd, the 3 pulley bolts are 30ft pd. Also check the water pump fan/pulley nuts for tightness you will be using a wrench to this, the fan belt should be on and hold against your efforts, if not your belts are loose are worn out. After doing these steps check again for noise. I gone your good to go. If not remove the belts and check again. If gone then an accessory is responsible, Alt water pump, air pump, ps pump, ac comp, turn ea by hand feeling for roughness\ looseness. check mounting brackets for cracks and loose bolts. If noise is still there then you may have an internal engine issue.
Let us know the results
 
Sure sounds like a cracked flex plate to me.
 
If the flex plate is cracked, will I be able to replace it without pulling out the transmission?
 
No. But if get 4 or 5" 3/8" 16 tpi bolts you can exchange them for the lower 2 bell housing bolts remove the rest. Unbolt torque converter, drop both driveshafts, undo cooler lines shift linkage. Jack under t case, remove skid and rear crossmember, drop adapter bolts, jack up t case and slide the whole trans and t case assembly back to end of longer bolts.
This will give room to swap out a flex plate
 
Fall_Guy said:
How can I tell if it's cracked? Do I need to remove it?

Should I loosen and then retighten the 3 flex plate bolts first, and then if the problem persists, remove the plate and check for cracks?
Click to expand...
You can pry on the flex plate and you will see movement.
 
Here's what I have done so far. I listened to other videos of broken flex plates and I agree, it does sound like it's cracked.

So I took the cover off, checked bolts again, this time with a ratchet wrench, and they are all tight.

I made a video looking for cracks. I don't see any. But I'm a novice. Maybe you might see something I didn't. Here's a video searching for cracks in the flexplate. Please lmk if you see anything that might be a crack.

Thank you for helping!

 
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