[lt1silverhawk]

Thursday morning, I added more oil and some Lucas to the engine. I used 20w-50 this time. I used 10w-40 during the previous oil change. I also check the cool ant level, which wasn't quite at full. There was also some crud under the oil filler cap. Visually checked the fuel filter before the carb and it looked clean and free of any debris. There was not starting up of the the truck this day.







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Started up the truck this evening and let it warm up on its own for a good twenty minutes. It reached operating temperature (about 195 degrees F) and then I took it for a spin. The truck ran pretty good again. No hesitations. No bogging.


This is the second time since the problem began that somethings were removed or adjusted and brought back to the same settings and the truck began working. The first time was replacing the coil.The second time was moving the distributor back and forth and closing up and turning out the idle mixture screws on the carb to 6 full turns. Both the distributor and the screws are at the position as before. No change in position.


The fuel was low so I added about five gallons to the tank.


I decided to take off the carburetor and remove the airhorn to see if there was any debris in the fuel bowl. I also removed the fuel filter for inspection and it came out clean.


Once the airhorn was removed, it was obvious that there was debris at the bottom of the fuel bowl.







I briefly looked at the idle tubes that cobalt mentioned, and they did not appear to be clogged. However, I did notice that the main well bleed tubes in the airhorn appeared clogged. Something to be concerned about?







I also checked the jets using the "light test", and they appear to be fine.


I removed the throttle body from the float bowl/main body, and discovered that the epoxy used during last rebuild was coming off. However, I cannot tell if it is even needed and if leaking is occurring.






Slightly off topic, but does anyone feel this info also should be added to the carburetor rebuild thread for a follow up?


Does anyone feel a complete tear down and rebuild is needed? Or can I just clean it all up using carb spray and bolt it back up? Can the same gasket between the fuel bowl and the airhorn be used? If yes, then i want to get this bolted up tomorrow and move onto timing. I've already begun work on the timing tape.

[123pugsy]

Clean it up and reuse the same gasket is OK as long as no chunks came off of it and its not torn anywhere.

Does the debris look like the stuff from the fuel filter?

If so, it may be time to replace your fuel line and possibly the tank.

[lt1silverhawk]

Hey Pugsy,

Originally Posted by 123pugsy

Clean it up and reuse the same gasket is OK as long as no chunks came off of it and its not torn anywhere.

Yes, the gasket appeared to be very solid.

Originally Posted by 123pugsy

Does the debris look like the stuff from the fuel filter?

If so, it may be time to replace your fuel line and possibly the tank.

It was similar. There were some red particles that resembled those found in the fuel filter. Also found a small stone which is in the pictures below.




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I went ahead and cleaned up the carburetor using carb and brake cleaners and put it back together. I removed some of the epoxy that was coming lose. Where it was still hard, I left it alone, mainly over the plugs. I also did a "light check" on the orifice in the fuel bowl and they looked nice and open.


As always, I forgot a few things here and there and had to redo them, and no project is every complete without me dropping or losing something.On the plus side, I think I can now install the choke pull-off assembly in my sleep.


I also installed a fuel filter in the carb.







Got everything bolted up, closed and then turned out the idle mixture screws to six full turns, and started the truck. Let it run for quite a while as it approached operating temperature. The idle sounded very strong the entire time and never dropped below 1,500 rpm. I temporarily turned it off and it kept it running - dieseling - for a few seconds before stopping with a small bang.


I took the truck for a spin, and ran it well. The temperature stayed at 195 degrees F at all times. No fluctuations. The engine speed in Drive when at stop hovered at 7,50 rpm.


When I finally parked, the temperature was still at 195 degrees, but rising. In park, the idle was still 1,500 rpm. When i killed the ignition, the truck kept going for a good fifteen seconds before stopping with a bang and some smoke from the engine bay. From what I have read, this is very much a timing issue.

[123pugsy]

I guess you're driving around without an air filter?

A stone can't get past a fuel filter.

The run on is from the high idle.
800 in park is high enough.

[lt1silverhawk]

Originally Posted by 123pugsy

I guess you're driving around without an air filter?

A stone can't get past a fuel filter.

Yes, I had the air filter off while making adjustments. Lesson learned.

Originally Posted by 123pugsy

The run on is from the high idle.
800 in park is high enough.

Ok, I will try to temporarily lower it to 800 rpm before getting to the distributor and hooking up the timing light.


Slightly off topic, but what are the chances a cheap-looking after-market tach can be off by a few hundred rpm? I ask because when I hooked up the timing light last time, the light was showing about 200 rpm more than what the tach was showing.

[123pugsy]

Originally Posted by lt1silverhawk

Slightly off topic, but what are the chances a cheap-looking after-market tach can be off by a few hundred rpm? I ask because when I hooked up the timing light last time, the light was showing about 200 rpm more than what the tach was showing.

Odds are good.
My cheap piece of junk fluctuates and only works part time.

When you set your timing , you will have to reset your idle again.

[lt1silverhawk]

Originally Posted by 123pugsy

Odds are good.
My cheap piece of junk fluctuates and only works part time.

When you set your timing , you will have to reset your idle again.

Good to know. I will have to check on this and verify, but I wana say it was cobalt who said in another thread that usually the idle mixture screws on a Q-jet are turned out 4 full turns.

Thanks for the continued help!

[123pugsy]

Originally Posted by lt1silverhawk

Good to know. I will have to check on this and verify, but I wana say it was cobalt who said in another thread that usually the idle mixture screws on a Q-jet are turned out 4 full turns.

Thanks for the continued help!

Idle mixture screws have nothing to do with setting idle speed.

Idle speed may change however when using your vacuum guage to set the idle mixture screws.

[lt1silverhawk]

Originally Posted by 123pugsy

Idle mixture screws have nothing to do with setting idle speed.

Idle speed may change however when using your vacuum guage to set the idle mixture screws.

Oh, so its strictly a timing issue then.


Btw, I just tried adjusting the idle screws down to 5 full turns ,and then 4 full turns. Both times, the truck started up and revved with no issues and immediately shut off when the ignition was cut. So I am hoping that, at least for the time being, the engine is in an acceptable operating zone in case i need to move it before getting to the timing.




And I also wanted to ask about a part that fell out of the carburetor today while cleaning it. I never saw this part when I did the rebuild. But it seems like fell out where the the key and the rod for the choke plate. Any ideas what it is?

[123pugsy]

Originally Posted by lt1silverhawk

Oh, so its strictly a timing issue then.


Btw, I just tried adjusting the idle screws down to 5 full turns ,and then 4 full turns. Both times, the truck started up and revved with no issues and immediately shut off when the ignition was cut. So I am hoping that, at least for the time being, the engine is in an acceptable operating zone in case i need to move it before getting to the timing.
]

If its idling too high, do not adjust the mixture screws.
Idle speed is set by the idle speed screw on the driver's side of the carb.

[123pugsy]

Originally Posted by lt1silverhawk

And I also wanted to ask about a part that fell out of the carburetor today while cleaning it. I never saw this part when I did the rebuild. But it seems like fell out where the the key and the rod for the choke plate. Any ideas what it is?

KRYPTONITE?

[lt1silverhawk]

Originally Posted by 123pugsy

If its idling too high, do not adjust the mixture screws.
Idle speed is set by the idle speed screw on the driver's side of the carb.

So that screw doesn't have anything to the do with throttle linkage then? Because I noticed that if screwed in all the way, pushes the throttle lever back. This would be my error when adjusting the idle speed and timing by ear last summer. I was messing the idle mixture screws more than the idle speed screw. I will mess with this next then.

Originally Posted by 123pugsy

KRYPTONITE?

Lol! Considering how strong the truck runs and idles, that may very well be it!

[dogwater]

Im impressed with your closeup photography.looks pretty good.I used to do alot of photo work.

[lt1silverhawk]

Originally Posted by dogwater

Im impressed with your closeup photography.looks pretty good.I used to do alot of photo work.

Thanks man! Not bad for a 12 megapixel Sony point-n-shot, huh? I've been shooting away at car parts for over a year now and also do some amateur photography. I gotta say that practice does make perfect. Hopefully these pictures will come in handy for someone else. What kind of photography did you do?

[cobalt327]

The red cam-shaped plastic piece is the eccentric that lifts the secondary hangar/secondary metering rods in relation to the air valve opening. It has to be replaced, Ruggles has the kit, $12 to your door.

I noticed in one of the earlier photos the little anti rattle spring on the power piston that keeps the primary metering rods from vibrating (thus wearing) inside the jets was out of position. Later photos show it back in correctly, so that should be OK. That spring can be omitted if there's any question as to the condition of it, it's there to insure 100K mile service life under all conditions and many guys leave it- and the small clip I'll talk about next- off the carb altogether. I use them FWIW.

On thing that you have got to fix is the small hook that clips to the needle part of the needle and seat assembly. The hook does not go through the hole in the float arm. This is a common mistake, but it can cause the needle to hang up and the float level can be all over the map. So, hook it over the cross piece closest to the power piston.

I'd remove the epoxy. It's not doing any good and even though it can't fall into the float bowl, no reason to have it going through the engine. I'm guessing it was there for prevention's sake. If the well plugs ARE leaking get back to the forum and we can get into it further.

EDIT- The air bleed that's damaged needs to be opened back up to the same diameter as the undamaged one. You can use a small pick or smooth nail if small enough to resize the opening to match the other one. Dress the air bleed tip so there's no ragged edges, just don't shorten it excessively (excessive would be more than say 0.015").