Carburetor, fuel, ignition.... HELP!

[arrowicons]

Help, I am stumped. I feel like I have tried everything but I am still missing something.

My 1943 GPW had a hard time starting. It has never run as it should since having the engine professionally rebuilt 10 years ago. It would crank and crank and after awhile, sometimes with starting fluid being necessary, would start. After driving, and hot, It would still crank and crank to start. Recently I starting to dig deeper into it. At first I thought that fuel was evaporating from the bowl so I made sure the manifold flap was working correctly. It needed a new spring, so I replaced it. No difference.

I checked the carb and fuel was getting to the bowl. I tested the fuel pressure and it seems good (4psi). After sitting, it likes. a hand prime at the. pump and always likes a little choke.

I went through the ignition system. New wires, plugs and coil. Newly rebuilt distributor. Points are within speck and have a nice arc. Next, I played with the timing. When retarded, the jeep would start right up. But then it would backfire and run rough, almost as if on three cylinders. Too advanced and it wouldn't start at all. Zeroed it in so it starts after a couple cranks once, with coke and luck, but still a runs a little rough.

Next I started looking at the carb. I took it (original) apart and rebuilt it. I adjusted all as specified. It was all very clean but I noticed that the metering rod was set as high as it could go, if any higher it would be impossible to tighten the nut. I adjusted the metering rod as per spec and re assembled. Jeep would start but then die right away. I raised the metering rod slightly and it acted like it was fuel starved so I gave it gas with the accelerator; this would make the engine die. I then set the metering rod as high as it would go. This allowed me to run the jeep without it dying. Thinking something must be wrong with the carb, I bough a new one from Ron. I had to adjust the float and rod. Installed. Jeep would die once out of the idle circuit. Adjusting the idle screw does nothing. It will not die when completely closed. Raising the metering rod as far as it would go would get the jeep to run again: basically same exact issues as with the original carb. I am convinced that the carb's whacky adjustment is masking the real issue and that the real issue is fuel related. But what else could I check?

Thank you!

[parker007]

check compression which is easy, if good then look for vacuum leaks a leaking intake valve will make lean.. and i would pull your distributer and clean it and check the counter weights for corect advancing also check the shaft play.

[Adam]

You say you have a nice are at the points? electric arc i guess, should not be that much there at all,, do spark plugs have a strong spark? is condencer bad or corrected right, if a 6 volt system is coil a 6 volt coil.

how is the valve timing compared to piston timing,, could timing be off a tooth or 2?

for sure the plug wires are on correct 1342 in a counter clockwise direction?

Adam

[arrowicons]

Thanks for the suggestions. Distributor advance has new springs; and the shaft is clean and tight. Wires are connected correctly. When I say Arc, i meant when testing the wires while removed from the plugs.

I will try a compression test, but am curious how I would go about testing valve leaks. I am handy, but no mechanic. Would I just remove the cover and make sure all seems as it should?

[Scoutpilot]

When the #1 piston is at Top Dead Center on the compression stroke where does the rotor in the distributor point? Imagine looking at a clock.

[dpcd67]

Three things that will work;
1. Send your carb to Scout Pilot and he will rebuild it and test run it.
2. Get a Vacuum gauge. (Those actually tell you about timing too)
3. Get a compression gauge.
Do what those three things tell you and it will run.
And really, to own, maintain and operate a WW2 jeep, you do have to be a mechanic, at least some of one. Or do like my friends here do who don't know points from wheels; call me.

[Scoutpilot]

And don't get in a hurry!

[dinof]

If you bought a new Carter repo carb from Ron, AND the idle adjustment screw still does not change anything, I would bet
your getting a vacuum leak from the carb base gasket or the intake manifold gasket. Did you tighten down the carb tight enough to crush those stupid copper rings?.

[savmag]

Also, try to check the fuel pump. I had a similar situation like yours a few years ago.

The jeep ran fine but it started acting oddly with the idle mixture screw not changing any responsiveness on the engine. After a while it was idling very rough and after some days it was dying almost instantly. Nothing could keep the engine idling. The problem was the fuel pump diaphragm which was almost eaten up, allowed oil to enter the fuel and vice versa, creating back pressure in the engine block and altering the fuel composition in the carb. After rebuilding the fuel pump, the problem went away and on the plus side, the engine was cleaned well internally.

You can check a faulty fuel pump if the engine smoke is blueish or by smelling the engine oil.

[dinof]

Also, try to check the fuel pump. I had a similar situation like yours a few years ago.

The jeep ran fine but it started acting oddly with the idle mixture screw not changing any responsiveness on the engine. After a while it was idling very rough and after some days it was dying almost instantly. Nothing could keep the engine idling. The problem was the fuel pump diaphragm which was almost eaten up, allowed oil to enter the fuel and vice versa, creating back pressure in the engine block and altering the fuel composition in the carb. After rebuilding the fuel pump, the problem went away and on the plus side, the engine was cleaned well internally.

You can check a faulty fuel pump if the engine smoke is blueish or by smelling the engine oil.

Your oil pressure will be lower, more noticeable at idle when hot. The gas will dilute the oil and then you get this. Don't ask me how I
know this.

[Wolfman]

How often do you start and run the jeep ??
What type of fuel are you running ??
E-10 or non-ethanol ??
Where I am headed.
My neighbor called me yesterday.
His antique Minneapolis-Moline tractor would not start. Help!
The tractor was running & parked in a tool shed back early summer. Not again run until now. Or at least try to get started.
It had good spark but not a putt.
This tractor had a Zenith up-draft carb with a bowl drain. Gravity feed fuel system.
I took the bowl drain out, actually to see if there was fuel in the bowl. Maybe a stuck carb. needle valve.
What came out was a blue-green sweet-smelling liquid that hit the shop floor like water.
Separated ethanol.
I let the bowl drain a bit and put the drain plug back in. The farmer hit the starter button and the tractor fired right up.
Foot note: the blue green stuff that settles to the bottom of the carb, fuel tank, etc. is separated ethanol.
The tan fuel above is good fuel with the ethanol gone.
No need to drain the entire fuel system. Just get rid of the separated ethanol.

[thomas19221]

I had a similar problem that I had trouble diagnosing. I did all that you tried and ended up taking it to a mechanic. I found a typical old man mechanic that had been working on cars his whole life and seen it all. He had the problem diagnosed in less than 2 minutes. Here's how...

Once I got it running, I off loaded from the trailer and pulled it up to the bay door. He walked out with a propane bottle like you would use for a lantern or small campsite burner except it had a rubber hose coming out of it. He turned on the flow of propane and held the rubber hose close to the joint between the intake manifold and block. When he got to cylinder 3 the engine rpms increased slightly. He said, "there you go, intake manifold leak."

I had him make the repair and it ran fine after that.