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. . . engine will crank, like normal . . . but won't turn over . . .

Good. That's what I meant about using the term "turn over" differently. To many people, "turn over" means the engine turns, or cranks.


To answer your previous question, yes. As long as the starter is spinning the engine round and round, you can measure the compression. That's a good thing to do. You might Google and read up on "dry" and "wet" compression and measure both.


The fundamental rule of engines is that if it has compression, fuel and spark (timed correctly), it will run. Once you show you have good compression, it's time to check the spark.


People have a tendency to check the spark by pulling a wire and holding it 1/4" or so from a grounded engine part. I believe this is a bad idea and sometimes damages a perfectly good spark coil. For a spark to jump farther than .035" takes proportionally higher voltage, and excessive voltage leads to internal arcing in the coil. I prefer to connect a spare spark plug to the wires, and tie it securely to ground with a wire.


Once you have compression and spark, it's time to spray starting fluid into the carb. If the engine fires on starting fluid, that suggests you may have a fuel system problem.
 

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Discussion Starter #22
One more question since I’ve got all your attention... if you look back at the points photos, that wire is pretty frayed, could this play any part? Looks like that part is pretty cheap on eBay but would messing with the screws cause any more issues?
 

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. . . points . . . wire is pretty frayed, could this play any part? Looks like that part is pretty cheap on eBay but would messing with the screws cause any more issues?
If the points wire is shorted to ground, you will have no spark. If the wire is flopping around and shorting when you break, that could cause you to stall. If shorted points were preventing you from restarting, it would be obvious that you have no spark, and the voltage at the coil (-) would be zero.


New points are always good. Set the gap to spec readjust the timing after changing points.
 

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Discussion Starter #24
Hi guys, thanks for all your help throughout this process; I would have been ost without this wisdom! So I took out the spark plugs and tested the compression in each cylinder. They were all 126 or 127, which is a good sign, correct. I also tested for a spark and got that too. Also picked up some starter fluid and shot it in the carburetor and the thing started right up and ran for about 10 seconds!! So I’m thinking it’s gotta be the fuel pump?

I removed it to check it out and ordered a new one off eBay. Hopefully this is the fix I’ve been looking for! I’ll keep you posted , you’re on the journey now too!
 

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. . . So I’m thinking it’s gotta be the fuel pump? . . .
I think you're jumping to conclusions about the fuel pump. If the fuel pump is the problem, then the engine should run with a steady fuel supply, right? I like to hang a pop bottle of gas from the hood latch and run a fuel line from the bottle directly to the carb - kind of like an IV bottle. It's an instant fuel system.

If the engine runs on the pop bottle, then you know the carb is OK. With the engine running, you can test the fuel pump. Route the inlet to a jar of fuel, and the outlet back into the same jar. See if it will pump fuel.

Other fuel system problems include clogged fuel lines, lines sucking air, clogged fuel filter.
 

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Take a short piece of fuel line and an old pump oil can, fill the oil can with gas and clamp it to the line, pump the carb bowl full of gas, start the engine. Keep pumping and it will keep running, get to crazy and you will overfill the bowl and the gas will run out the top, fire hazard.

Take a portable air tank and a gas cap, drill a hole in the top of the gas cap (preferably one you know is fubar'ed) and install a gauge and air fitting in a line connected to the cap with a one way valve put 2 pounds of air pressure in the tank and you have a fuel pump as long as you keep the air pressure at 2 psi.

The IV idea posted above is a good one since you get pressure supplied by gravity as long as it is enough to get the valve in the float chamber to let the gas in.

Another suggestion, when you get it running take a timing light and point if down the carb and watch the fuel using the timing light for it's strobe effect, if you see any fuel dribbling out instead of being atomized, the carb is not working properly. Only exception is the power valve, which should not dribble but give you a forceful stream.
learned that in the late 1960s.

We used to use air pressure to pop out dents in fuel tanks, back when they were metal.
 

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(Just interjecting this - nothing to do with fuel pump tests and the great ideas for testing in the previous posts.)

.... compression in each cylinder. They were all 126 or 127, which is a good sign, correct....
Absolutely. Very healthy compression numbers.
 

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Discussion Starter #28
Great things to try, might be a little over my head though. I’ve already ordered a new fuel pump, on $40, so I’ll give that a try. I was also lucky enough to find a factory restored carburetor on eBay, if they fuel pump doesn’t work maybe that will.

Good to hear the compression numbers are in a good range, I was pretty excited to see that.
 

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. . . factory restored carburetor on eBay, if the fuel pump doesn’t work maybe that will . . .

It's totally your call, of course, but I would recommend you think the problem through to a diagnosis rather than changing parts. It's not always a part that's bad. You can waste a lot of money on parts and come to find the problem is a $5 clogged fuel filter, of even just a kink in the fuel line.


A big tip of the hat to Old Mechanic for his pressurized fuel tank idea. I just pressurized my tank to 2 psi last month for a different reason (smog test). On trucks with evap like my '84, you can pressurized the tank from the vent line. Not even any need to adapt a gas cap. I'm going to keep this tip in my bag of tricks. Thank you for sharing it.
 

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Discussion Starter #30
Hey guys

So I removed the fuel pump and cleaned it out, messed with the arm, etc and reinstalled it. I also disconnected the fuel line from the carb and put the end in a bottle and started it up, there was definitely gas shooting into the bottle so I reattached the cable and the truck began running well again!

I changed the oil and oil filter and the truck seemed to be running and idling pretty well. There was hesitation when I’d give it gas though, which kind of concerned me. Also, it seems to idle better when the air filter and housing are off of the carb. What line is supposed to connect to the air filter? The larger one coming off the engine housing?

When I tried the truck tonight it seemed to not be idling as well and would hesitate and almost stall when I’d give it gas, any ideas?

Thanks for the help, glad she’s running again, just want to get it road ready!

Thanks guys!
 

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The low speed circuits have emulsion tubes where the air and fuel mix, you can use a blow gun with a line that extends it's reach and place the air flow just over the orifices where the fuel enters the venturi and use them to "purge" those orifices and sometimes get lucky and fix low speed fuel mixture issues. Do this with the timing light strobing the area and it makes it easy to see the vaporized fuel flowing out of the carburetor int the intake.
 

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Discussion Starter #32
Hi old mechanic, sorry for the slow response. I’m not really getting what you mean. The issue still persists, seems to idle very low(too low) when I start it for the first time of the day. Then when I give it a little gas it nearly stalls if I take the clutch out as well. Is the idle adjustment too low? Could it be an issue with the fuel mixture screw? Carb?

Any more detail would be helpful, I feel like I’m close to getting it running well again. Could it still be a fuel pump issue?
 

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Hi old mechanic . . . not really getting what you mean . . . Is the idle adjustment too low? Could it be an issue with the fuel mixture screw? Carb? . . . Could it still be a fuel pump issue?
I think Old Mechanic was saying that clogged jets in the carb are a possibility, and he offered a (in my opinion) great tip on cleaning jets without having to remove and disassemble the carb. I wouldn't mess with the idle and mixture screws. They were set right, and changing them is not the way to deal with a clogged jet.

I apologize if we already covered this, but have you verified that your choke is working? A stuck choke would cause symptoms like you describe. Especially when the engine isn't fully warmed up.

As for the possibility of a bad fuel pump, i already outlined how to check for that using a pop bottle. As it happens, I needed to do this very thing on my Vespa last weekend, so I snapped this photo of my "IV Gas Bottle". Takes about ten minutes to make, and supplies gas to the carb independent of the fuel pump.



One thing that's not clear to me yet. Can you get this truck on the road at all? Driving a few miles - even performing badly - gets gas flowing through the carb. Sometimes that's enough to open a clogged jet.
 

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If it turns over but will not start it is 1 of 2 things: either no spark or no gas or both.



Looking at the photos I would say it has multiple issues and would do the following before chasing ghosts.


Pull the plugs. put new ones in, also, change the plug wires and rotor in distributor; leave one plug uninstalled so that you can now turn it over and check for a spark; if you now get a spark then check for the presence of fuel. The carb is equipped with a sight glass (located on the side of carb) clean the oil off of it and see if you see fuel; it should be about half way up the glass.


No fuel present means either float stuck or fuel pump not working or fuel line clogged.


Pull fuel line and blow compressed air into line running to fuel tank you should hear air going into tank if so,check fuel pump for operation; disconnect fuel line and turn engine over; if fuel is present it should shoot out (mechanical); if fuel shoots out; then suspect carb and either rebuilt it or have someone do it for you.


I suspect the carb is gummed up.


check ALL vacuum lines as well.
 
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