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ugh. problems getting the truck to run after putting my old engine back in -Timing? Valve lash??

500$k5 said:
I have always assumed that the tube was used as a jig for the factory to set timing, without physically holding a timing light. Don't know for sure though.
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I saw mention of analyzers having a "wand" with some kind of timing device that would holster there... not sure if its true, but I could see that.
Thinks its just a coincidence that the slot in the crank seems to point straight through that tube when #1 and #6 are all the way up???
 
On many oscilloscope, readengine diagnosis tool,
There was a magnetic probe that went in that tube, to measure timing. I very rarely used it.
If your shop had an Allen Smart Scope, super pita, and $30k + in 1980s $, you would have to hook everything up in order to get any info at all.
It could have been a fantastic tool. But why have spark and timing information when you only needed charging system
 
scouthead said:
what would kill fuel instantly? oil pressure sender fault?
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Oil pressure switch? Only if the fuel pump relay is dead too.

If the fuel pump primes when you turn the key from off to run, then the fuel pump relay is fine and your oil pressure switch is irrelevant to this problem, whether it works or not. It's redundant to the relay.
 
dyeager535 said:
Oil pressure switch? Only if the fuel pump relay is dead too.

If the fuel pump primes when you turn the key from off to run, then the fuel pump relay is fine and your oil pressure switch is irrelevant to this problem, whether it works or not. It's redundant to the relay.
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got it. that sounds correct. fuel pump seems to be working just fine. primes as normal. oil pressure displays on the gauge and seems to be correct for this engine... same range on the scale as I remember from the last time I ran "engine #1". depending on engine temp and rpm, always between high 20s and high 40s (assuming that little gauge on the dash is even calibrated correctly anymore)

Im still trying to button up the grunt work/ caveman mechanical- almost time to put my thinking cap on and try to outsmart this TBI system. I USED to think i knew my way around it pretty well...
 
I have not been able to put many miles on it since getting the timing thing figured out with the damper. while fixing that, i sat on the radiator one too many times (and/or I'm a little heavier than i was back when I crawled under the hood more often) -anyway i broke the radiator. ohhhhhh the collateral damage is always fun!
a tube cracked right where it goes into the core.

It was already weepy, and covered in green patina and all my repairs - soldering of the filler neck years ago. time to retire it.


Im hoping I get my spare radiator back from the shop today (a bent filler is neck getting replaced)... should be able to drop that thing in this afternoon or tomorrow, and start cruising around town putting the miles on it.


I DID get something important done this weekend though - the exhaust was a mess. it was leaking and stinking, and in general sounded like a boat. while swapping motors, one of the donut gaskets fell off a manifold, and i dont think we got it indexed the way it had been. major leak there.

-put new donut gaskets on the manifolds
-put a spare set of springs on the collector studs- old ones were very tired and squashed
-fixed a few of the exhaust hangers
-welded both the broken front and rear of the muffler where the pipe goes in and out of the can

This thing hasn't been this quiet in YEARS. Also- the last few test drives made my eyes water- only about 40 percent of the donut on the driver side manifold was sealing. the entire bottom of the blazer was a cloud of Pre catalytic dream sauce
now that all the exhaust goes through the cat, and 99 percent of THAT actually makes it through the muffler? so nice. sooooo nice.
 
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You can't ever rule out the potentisl for an intermittent failure of components, but its fairly unlikely for those two components.

You can try various things like starting without the relay hooked up, or running with no oil pressure switch, but that's only going to prove both components work at that time. Good idea to check wires/connectors though.
 
I'm actually kind of curious what the exhaust leak at the driver side manifold may have been doing? any issue with the leak being 2 inches behind the O2 sensor? Ive never tried to run a TBI engine open manifold / open header... would it run correctly?

I stuck my hand up between the manifold and the block on Saturday and there was a giant fan of exhaust puff puff puffing about once per second.

when I popped the donut out, literally 60 percent of the gasket had carbon/ exhaust streak showing where the gas had been blowing out.
 
well my spare radiator had a core that was thicker than the origional. mounts, pads, brackets, and shroud are all funky and barely working after a night of grinding and snipping.

im pretty sure the radiator was one of summits "premium" one size fits all chevy trucks models...

my old radiator was a 3 core with 45 rows of little tiny tubes and fins.... the replacement seems to be a 3 core with 34 rows of larger tubes and fins? its the correct height and width, but the tanks are a full 3inches wide. therefore it does not fit like the factory 2.5 inch wide. uuuuuuuuuggh. i cant remember what a big block or diesel radiator look like... this is probably just a summit/ china problem?

I have 2 weeks to make this truck right. supposed to put about 1000 miles mixed highway/ offroad in 2 weeks!
 
I drove it home again just to get some miles on the motor. about 10 miles each way. staying off the freeway and trying to keep the RPMs inconsistent while not lugging or loading the engine.

on the way home:
-started running rough while idling at a light. like someone flipped a switch. timing was off- felt like it was retarded. truck kept running, but VERY underpowered and i had a SES light on. I pulled into a parking lot and was going to shut the engine off, but then the SES light went out and BOOM! truck ran fantastic again.
no further issues on the way home.

-on the way back to the office this morning:
-felt a little underpowered, but running and idling smoothly at first.
-then started accelerating sort of roughly with some surging (this was all very minor, but noticeable). shortly after this, im assuming i lost the spark again momentarily, because while accelerating gently, all power cut out and the truck bucked really hard once (gotta love the harshness of a manual trans sometimes). did not stall- just cut out - then i resumed accelerating gently after a minor dose of whiplash

have not had time to check yet, but I have at least one SES light that should have stored a code i can check later today.
 
So the exhaust leak B4 the o2s definitely has an effect. The computer is getting inaccurate info.
You need to do the wiggle test.
You put your left foot in you.....
Kidding. While running get in the and wiggle wires, individual is best. Prime spots tbi injectors where air cleaner meets, distributor, coil, iac and TPS.
When the power went away the computer went into limp mode. There are only a few systems that go into limp mode. I don't remember which. Hopefully someone will chime in with those to help narrow down.
 
Well that sucks- hooked up the Aldl cable and jumpered A to B…

I get the repeating flash code 12 for the data diagnostic deal, but no stored codes.

So whatever caused the SES light to come on last night made the engine run like crap for a minute, then fixed itself, and did all that without leaving a stored code in the memory.

Also the hiccup in the power this morning (never saw an ses for that) left no codes behind either.
 
Wes Harden said:
So the exhaust leak B4 the o2s definitely has an effect. The computer is getting inaccurate info.
You need to do the wiggle test.
You put your left foot in you.....
Kidding. While running get in the and wiggle wires, individual is best. Prime spots tbi injectors where air cleaner meets, distributor, coil, iac and TPS.
When the power went away the computer went into limp mode. There are only a few systems that go into limp mode. I don't remember which. Hopefully someone will chime in with those to help narrow down.
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the o2 sensor is in the manifold... exhaust leak was 3 inches behind / after it, at the collector/gasket/start of the exhaust piping.
 
Replaced some vacuum line last night. Afterwards, I let the truck run and idle a while. I hooked a vacuum gauge up to the back of the manifold, and the needle was vibrating across roughly 4 psi… From a high of 22, to around 18…
And every once in a while just for the slightest fraction of a second it would dip down to almost 16 and then back up into the 22 to 18 range
this smoothed out a little bit as the engine warmed up, but I never saw a steady needle on the gauge

Not long after going into closed loop, the idle speed dropped and the engine began running rough.
I was wiggling vacuum lines and wires… Didn’t notice that the check engine light was on.

I was able to retrieve a code this time. I got a code 42 repeated three times in a row.
 
So although it’s great to now have a code to chase…I have to chase this damn code now.

I saw a flow chart somewhere for this code. I will try to find it and test wiring before declaring my ICM broken.
 
Blue85 said:
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hmmmm HOPE i dont need to rebuild the heads- they had about 60K on them, and i just replaced the valve stem seals. valve stems were not super tight, but not so loose that I was worried about it. Also, Ive had the roller tipped rockers on them since they were assembled -I had hoped that might extend valve life a little bit.
 
also, I only had time last night to get the vacuum gauge attached to the rear manifold port... Ive seen some things on the interweb claiming this may be common on a dual plane intake... and that I should expect to see more steady readings from ported vacuum on the throttle body? will check that out asap as well.
 
ported vacuum is not what you want to see. only manifold vacuum.

put a ac delco icm in it, before loosing all hair trying to chase the code 42. Check the the dist 4 wire loom is as far away from spark plug cables as can be.
 
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