Yeah, its made out of some type of crappy pot metal, same material for the coolant hose quick disconnect IIRC. Those things snap just looking at them funny, they actually make a specific extractor tool for that job.
'90s Chevy truck elusive engine knock. Rod/Main bearings, or what?
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Yeah, its made out of some type of crappy pot metal, same material for the coolant hose quick disconnect IIRC. Those things snap just looking at them funny, they actually make a specific extractor tool for that job.
Keep us posted on the updates! With the condition of those bearings I wouldn't be surprised if that was the source of the knock...it doesn't take much.
At this point the only thing left for a complete bottom end rebuild is piston rings, wrist pins and gaskets/seals. Maybe cam bearings too. If it's fixed...great! If not, you'll have to ask yourself how far you want to go. The intake and heads will have to come off for the rest of the repairs. At that point it makes sense to go through the heads too...but financially it might not be worth it.
Low-buck performance aftermarket heads are probably going to be close to the same cost as a complete rebuild of your existing heads. It would make sense to put in a new Torque/RV style camshaft too with a new roller timing chain, pushrods and rocker arms too if you want a bit more power. It doesn't take much before a cheap crate engine becomes more economical (and easier).
At this point the only thing left for a complete bottom end rebuild is piston rings, wrist pins and gaskets/seals. Maybe cam bearings too. If it's fixed...great! If not, you'll have to ask yourself how far you want to go. The intake and heads will have to come off for the rest of the repairs. At that point it makes sense to go through the heads too...but financially it might not be worth it.
Low-buck performance aftermarket heads are probably going to be close to the same cost as a complete rebuild of your existing heads. It would make sense to put in a new Torque/RV style camshaft too with a new roller timing chain, pushrods and rocker arms too if you want a bit more power. It doesn't take much before a cheap crate engine becomes more economical (and easier).
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Thanks. Hopefully, in a few days when I get it running I'll see what my next step is. There is one rebuilder local to me, but he's a small time operation, so it might take a couple months for a rebuild. If I end up doing a rebuild, or installing a crate motor, we'll probably keep the truck a while longer, as we've had it since new. If my repair works and the knock is gone, we may end up selling it.
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The agony of defeat? Engine spins but does not attempt to crank at all. I'm stumped as to what the problem is, as the truck has never had a starting issue (always cranks instantly). The only thing I can think of, is I didn't have TDC on cylinder #1 set properly, making the distributor installation totally off.
When I set TDC the other day, I spun the pulley/damper around while my wife held her finger to plug #1 hole. Told her to let me know when she felt air. Will the piston make air other than TDC stroke?
When I set TDC the other day, I spun the pulley/damper around while my wife held her finger to plug #1 hole. Told her to let me know when she felt air. Will the piston make air other than TDC stroke?
Pistons will be TDC on compression and exhaust strokes.
If your sure you dropped the distributor back down with #1 at TDC, the rotor is 180 degrees out. Don’t touch anything else, just pull the distributor back up and drop with the rotor spun exactly 180 from where it was.
Make sense?
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Yeah, that makes sense. Just saw in my Haynes manual about the exhaust stroke. No doubt that's what I did wrong. Will try to get things corrected tomorrow.
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180'd the distributor last evening, and no change. Today, I re-aligned pulley/damper, removed valve cover and both #1 valves were closed, re-oriented the distributor properly, still not starting. So I pulled two plug wires and they are not firing, no juice. So, I have an electrical issue that was not there when I started this repair. Will have to do some testing and see what's going on. This thing is really working me!
I’m pretty sure piston slap was common in this era. A friend had a nearly identical truck that would occasionally have a muffled knock or thump when it was running. His son is still driving it today
At least we have the distributor and timing confirmed
First things first, go back and double check all the connectors are plugged in correctly.
My memory is a little fuzzy on the TBI setups, last one I worked on was my 91 4.3 Blazer many years ago. Here is a excellent walk through on diagnosing the ignition module:
https://easyautodiagnostics.com/gm/4300-5000-5700/distributor-mounted-icm-tests
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I determined there is electrical spark by connecting a spare spark plug to wire #1. I'm at a loss as why it will not start. Can't believe I got this far with bearings/oil pump installation and then end up with a no start situation. I've checked and rechecked the distributor installation and its alignment with cylinder #1 compression cycle (both valves seated, timing marks on zero, rotor pointed in general direction of Cylinder #1), Either I'm off with the timing somehow, or maybe I screwed up tweaking/adjusting the valves?
Have you verified that both TBI injectors are spraying when its cranking?
Does it make any indication of trying to start(popping slightly or erratically) or just cranking with no sign of ignition whatsoever?
You mentioned prior that you pulled two plug wires and there was no spark, was #1 one of those or no?
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I'm pretty sure I smell gas, but have not verified any spray. There has been a misfire/poof sound a coupe of times. When I pulled the wires earlier today, it was #1 and then # 2. Just let them dangle near a ground source. Later, I took a spare plug and clamped it to engine ground point and had a spark with #1 plug wire attached.
Did you pull the wires off the cap when you pulled the distributor or leave them all connected? If you pulled them off, wondering if they are out of order...?
If you have spark at the end of each wire/plug, we are back to either a timing or fuel issue. If plug wires are verified correct, wondering if you are off a tooth on the distributor gear...
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Yes, my wires are correct at cap, have them numbered with tape. I will trace them back to the plugs to make sure though. I may try to reset the distributor another notch over tomorrow. Thanks.
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I've spent two days trying to to get it to start, and it simply isn't happening. I set and reset the distributor 15-20 times. It's getting gas. I installed a small hose in cylinder #1 and had my wife crank the engine. The compression did not seem all that strong to me, not like what I've see on videos. I'm not an expert on engines, but I've done virtually all the repair and maintenance on my cars for over 50 years, and can't explain this issue. I adjusted some of the slop out of the valves, and then tightened them 1/2 turn each. Is there anyway this would cause a non-starting issue?
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I know its frustrating, I've been there, but we'll get it figured out.
Just to verify for the troubleshooting process:
- You are getting spark at all 8 plugs or no?
- You are getting spray from both injectors or no?
- Oil pressure sensor is screwed back in and connected?
Since the engine was running normally(minus the knock stuff) before disturbing the distributor/ignition components, I'm still thinking that's the root of the issue.
I hate to pull out the parts cannon too early, but would you be willing to replace the ignition control module on the distributor? I assume yours is original or no? With electronic components, even if they look perfect on the outside, leads can crack or break internally from handling it or heat flex, especially on 32 year old stuff. Its possible the pickup coil(little disk with two leads that plugs into ICM under the reluctor wheel) is bad leading to erratic signal, but the ICM seems to be the more common cause of crank/no start issues.
The TBI trucks are fairly simple in some regards but a bit wonky in design with some of the ECM stuff.
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Standard SBC hydraulic lifter stuff. On a closed valve, tighten the nut till you cant spin the pushrod and then go another 1/4 - 1/2 turn.
If that's what you did, its not the source of the issue.
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Lawnman: Yes on the valves, just snugged up until pushrods had slight resistance, and when I had done several cycles with engine, I tightened all 1/2 turn.
I replaced the Ignition module in May '24. MSD billet distributor. I'll still have to test at some point to make sure it's not the problem, as they have a reputation of being flakey.
Will check firing on other plugs this afternoon.
When I can crank the engine again, I'll check on the injectors.
Yes, Oil sensor is plugged in and is a good unit.
I'm still rechecking to make sure my distributor is in the right spot this afternoon.
I replaced the Ignition module in May '24. MSD billet distributor. I'll still have to test at some point to make sure it's not the problem, as they have a reputation of being flakey.
Will check firing on other plugs this afternoon.
When I can crank the engine again, I'll check on the injectors.
Yes, Oil sensor is plugged in and is a good unit.
I'm still rechecking to make sure my distributor is in the right spot this afternoon.
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Found a pic from 2011 after I did the intake manifold gaskets (see below). As you can see, distributor#1 terminal is lined up with the coil terminal, and the rotor inside is pointing towards cylinder #1. Today, I reset the distributor in the exact same spot as in the 2011 pic. Damper in line with zero on timing marker.
All plug wires have spark.
Still not starting. I poured a pinch of gas in the TB, and not a sputter.
What is the procedure to check the injectors to see if they are functioning properly?
All plug wires have spark.
Still not starting. I poured a pinch of gas in the TB, and not a sputter.
What is the procedure to check the injectors to see if they are functioning properly?
We used a noid light to test for signal at the injector,
However you should be able to have someone crank it over and watch the injectors for spray. if they spry you're good if not more in depth diagnosis is in order.
I might back of the valves 1/4 turn just to make sure they aren't staying open.
As you know, you need fuel air spark and compression - and at the right time - to run, so if it wont run you're missing one of those things.