Do I need a carb rebuild?

Post by **wesk** » Fri Jan 04, 2008 12:16 am

You can time these old girls the old fashion way with a piece of clean white paper and a bright flashlite (so you can see the timing marks on the flywheel). Clean the flywheel mark area so they are easily seen. Mark with white or yellow crayon if it helps.

Get #1 TDC on compression. Pull the distributor cap and verify the rotor is pointing near to #1 wire. Look at your flywheel timing mark. Move the TDC mark to the center of the window. Now back up the flywheel about twice the distance from TDC to 5 Deg BTDC. This should leave you advanced about 10 degrees. Now open the points and insert the piece of paper. Now very slowly rotate the flywheel forward towards TDC again while maintaining a very slight pull on the piece of paper. The instant the piece of paper pulls loose from the points is where you're timed. This is the point where the points just start to open. It's book 5 degrees on all the L134's and F134's. If you're running her hard and using 87 or higher octane gas you can bump it ahead a little more to 7 or 8 BTDC.

The only need for a timing light is to check for a loose shaft or bad governor action. A loose shaft will give you a noticeable fluctuation in timing and a lack of advance to 11 to 15 BTDC when punching the gas will indicate the governor (centrifugal advance) is stuck.

Now if you do not have the flywheel mark inspection window you have 3 options. Time it while observing the best vacuum reading, pull the head and accurately (dial indicator) find #1 TDC on compression and mark the crank pulley and cover your self, or pull the timing cover and align the chain sprockets on WWII engine or timing gears on post WWII engine with their valve timing marks then re-install the cover and mark your crank pulley and timing cover.

How are you working an aircraft shielded lead into mating your timing light to the jeep's shielded lead?

On the Allis it's the left rear hydraulic ram that I am missing. I have a second gas tank but it is rusty inside and I have been looking for an old cheap concrete mixer so I can load the tank with river stone and cleaner and let her tumble for a few days. Then I am going to fabricate a 1.5 inch standpipe in the bottom feed fitting.

Full size views are at: http://allisb.mypicgallery.com/

sergeantfirkus · Post by **sergeantfirkus** » Fri Jan 04, 2008 8:12 am

Wes:

I've got it timed now with the best vacuum reading.
I'm looking for that AHA! moment when you pull something apart and find what is actually causing the problem. I've went thru diagnostic $&% over a condenser before.
Starts good, idles decent. I only drove the jeep for about 75 miles before the gas tank, and it was warmer but I don't recall needing the choke then.

The aircraft lead: it was a jury rig but it worked, 8" piece, had to cut the shielding off, strip the end wire and wrap it around the end of the plug wire. Then the silicone insulator had to come off since it wouldn't slip into the spark plug. But it worked.

Greg

sergeantfirkus · Post by **sergeantfirkus** » Fri Jan 04, 2008 9:53 pm

I'm running out of tricks.

Removed the carb. Dismantled, inspected, cleaned (it was already clean) nothing appeared out of order or damaged. Check balls in place. Diaphragms good. All ports and passages clear.

Reinstalled and drove, runs the same. As suspected since I didn't find anything wrong.

There is no inspection hole for timing above the starter. So I left the timing alone.

The distributer mechanical advance is working.

Grasping,
Greg

sergeantfirkus · Post by **sergeantfirkus** » Sat Jan 05, 2008 7:03 pm

It's running fine now? Why?

Here's what I did today:
Closed the vent on the cap and put put 3 psi of air pressure thru the vent line that goes from the tank to the air filter. Used gas leak detector soap at all the fittings. No leaks. Removed the air line. Awhile later I removed the cap to open the vent in it and got a good woosh of air out. So everything must be tight.
Removed the gas line and put a line leading to a 5 gallon can on the fender, took it out for a drive, ran great. Removed the gas can. Took the line from the tank and opened the valve and watched fuel drain out steady until a quart was poured. No lack of fuel flow. Hooked the line back to the fuel pump and drove it again and it still ran great.

What else changed: Warmer today about 45º, put 5 more gallons of fuel in the tank for a total of 10 now. The other gas in the tank had Valve Guard added to for using unleaded fuel in old engines. The new gas I added I didn't put any in.

I wish I knew the cause.

Greg

OKCM38CDN · Post by **OKCM38CDN** » Sat Jan 05, 2008 8:40 pm

Sounds like you had a plugged vent line. you blew out the obstruction or the valve in the pickup the vent hooks to was stuck...

Your problem if that was the cause is a vapor lock...

I have also found, that I do not need to run the fuel additive. Mine runs great without it. But then again I do not know if some PO has rebuilt the engine to accept the new fuels.

Good luck, hope it stays running...

Post by **wesk** » Sat Jan 05, 2008 9:11 pm

The unleaded fuel issue is not critical to low compression, low RPM engines like the L and F 134's. Over the last 30 years I have put a couple hundred thousand miles on my old engines with NOTHING added to the pump gas. Guess what. No burn't valves or seats. Those additives are like many other old wives tales. Just dump them and spend your money on real things that get real things done.

sergeantfirkus · Post by **sergeantfirkus** » Sun Jan 06, 2008 7:25 am

My cap has a on/off vent in it also, if the vent to the air breather or check valve was stuck it should have been able to draw enough air through the cap I believe?

Vapor Lock: usually associated with hot conditions, though in this instance from not having a sufficient prime of fuel through the lines leading to the fuel pump.

Wes:

I haven't spent much money on Valve Guard (snake oil) though it turns the gas a pretty red!

My MM R tractor augared all the corn on the farm for several years and burned the valves in it after a few years of unleaded gas thru it. I didn't use any snake oil's in it. I told my fuel guy and he gave me 2 quarts of the stuff. Each treats 300 gallons. I also had two straight grain trucks from the early 70's that ran on non treated gas and had no troubles.

I'm going to start another thread on snake oils!

Greg

artificer · Post by **artificer** » Sat Jan 19, 2008 4:36 am

Took the line from the tank and opened the valve and watched fuel drain out steady until a quart was poured. No lack of fuel flow

I don't understand how this can happen. There should be no flow except the little in the line if you disconnect the tank to fuel pump inlet line.
Have you a vacuum gauge and what does it tell you to look for?

sergeantfirkus · Post by **sergeantfirkus** » Sat Jan 19, 2008 7:30 am

To clarify:

I disconnected the supply hose coming from the fuel tank at the fuel pump. Routed it down past the tire into a pan, then turned the valve on near the firewall and watched the fuel flow smoothly without interruption.

I'm not sure about the your vacuum question. Fuel pressure is 5 psi. Vacuum on the engine is around 19 in.

Greg

artificer · Post by **artificer** » Sat Jan 19, 2008 7:45 am

Have you a vacuum gauge and what does it tell you to look for when the engine is running?
http://www.secondchancegarage.com/public/186.cfm
As the delivery from tank line to pump relies on pressure differential to lift fuel up and out from a pickup near the bottom of the tank I can't see how there can be free flow.... the pump creates a low pressure and atmospheric pushes the fuel up and along the pipe to get to the lower pressure (normally the operating fuel pump.... working like a siphon). When disconnected there is atmospheric at both ends and should be no flow....maybe I am missing something?

Post by **wesk** » Sat Jan 19, 2008 7:47 am

There are three kinds of fuel caps:
1-Un-vented -relies on other means to vent the tank
2-Vented - Has a permanently open vent installed
3-Controllable Vent - Has a lever to open or close vent manualy.

The quickest way to determine if the cap is impeding your fuel flow is to remove the cap and operate the jeep.

You vacuum readings should offer more info then just one reading.
You have the idle reading, you need to post needle behavior (IE fluctuating or steady) and then the acceleration check reading.

sergeantfirkus · Post by **sergeantfirkus** » Sun Jan 20, 2008 11:29 am

Artificer:
Nice article on reading the vacuum gauge.

My reading is steady at 19.

The fuel tank has a Midwest Military replacement cap with the movable valve in it for opening and closing the vent. I've got about 8 or 9 gallons of fuel in the tank, with the cap installed and the vent valve in the open position, fuel does indeed siphon or flow out when the line from the fuel pump is lowered to the floor.

The only other thing I might try (when the outside temperature is above zero!) is to see how much fuel is delivered by the pump over a set time. Doe's anybody have an idea what that figure might be?

Greg