Motorcraft 2150--Cleaned parts and now 351M doesn't start well?
Well, I got an itch to do something to my truck this weekend and had been toying with the idea of rebuilding my Motorcraft 2150 2V carb. I decided that I would start by simply removing the air-horn and cleaning whatever parts I could get to from there. So, I removed the air-horn, the float assembly, the jets, and the high-speed pullover system (I think that's what it's called). I proceeded to spray things down with a little carb cleaner and then blew a little air through things to clear them out. Everything looked pretty good to my relatively untrained eye, so I put it all back together. Here is my problem...Before I did this "repair", my truck started right up with one or two tries if I set the choke. Now I have to pump the pedal 7-10 times to get a good shot of gas in there to start the truck. I took it apart again to make sure all the parts were accounted for and that I put it together right. They are, and I did. The choke will set like it's supposed to, but it seems like the carb is starved for gas at startup. Once I get it started and running, it runs fine. What might have I done to cause this "starved" situation at start up?
Can the jets be flipped from one side to the other incorrectly?
Does the high speed pullover assembly need to set un-equally? (I straightened out the alignment when I had it apart so both metering valves were even).
Any help is appreciated. In the meantime I'll just have to stick with the new start up routine. Thanks.
HMMM, Sounds odd. What does the fuel level look like when you remove the top before starting it cold? Any fuel in the bowl? Also, after it has been running, how does the fuel level look then?
Checking the bowl before I start it up is going be my next check. I was only iterested in getting the thing started the first couple of times so by the time I stopped and took it apart again the fuel bowl was full. I pushed the float down a little and gas squirts out of the valve under the float so it seems like that is working okay. I don't see any signs of a gas leak around the carb so, assuming the bowl is empty prior to startup, where cold the gas be going? I also double checked that I didn't knock any vaccuum lines loose, and that the fuel line itself is hooked up okay. Like you said, it seems odd. Thanks again for any help out there.
I know earlier you said that everything looks to be put back together right, but it takes experiences like this to teach you that you can't assume anything.
On my carb, I left a c-clip off the choke linkage so that I can actually remove the air horn rather than rotating it out of the way. However, because I've done this, I have to be espeically careful when I put the air horn back on because I have to make sure the choke linkage is back together. I know you said the choke seems to be setting right, but "starved for gas at startup" just screams choke, so it can't hurt to just check over the linkage.
Since you mentioned that you have to pump the pedal several times to get a good shot of gas, I would look at the booster venturi assembly as well. Take the air cleaner off, and hold the choke open so you can see down in there. Pull the throttle back, and you should see two nice little streams of gas spray onto those venturis. It is possible that the ball check and weight weren't installed properly.
Well, I came home from work today and popped the hood to take another look at my carb. The truck had been sitting since last night so it was a typical cold start situtation. I pulled the air horn off and took a look at the float and fuel bowl level. There was fuel in the bowl but I don't know how much is correct/typical.
Here's what I saw: There was about a 1/2 inch or so of fuel in the bowl and the float was tipped down far enough that it was not sitting against the needle valve that it meters.
I'm guessing that with the truck turned off and sitting for a period of time there is no pressure in the fuel line to speak of because if there was, gas would come up through that needle and fill the bowl until the float shut it off. Is that a correct assumption? And if the bowl is full when I shut the truck off, there is no reason that the fuel bowl should be as low as it was when I took the carb apart today.
So I guess I'm back to the same question...How is it that the fuel level in the bowl is dropping that far overnight? I think this is a big clue...I wasn't smart enough to replace the gaskets when I put things back together. Duh. Is it possible that without a good seal the fuel is evaporating overnight to a level that can't support a start up? I appreciate the help.
I had a similar problem with my 84, what it sounds like to me is that your needle seat is not making a good seal and is allowing gas to flow back down the fuel line, you could also check to make sure the clip that holds the needle is back in its place, another possible option is that the carb starter has messed up a diaphragm or rubber seal.
Also did your gasket fall apart? if so it needs to be replaced.
You didn't by chance install the accelerator pump spring on the wrong side of the diaphragm. If not mistaken, been a while, the spring goes between the diaphragm and the carb. body so it will pull fuel from the bowl. There is a ball bearing in the body behind the spring that prevent the gas from going back into the bowl when the pump is operated. You should see gas squirt out of the the acc jet when you operate the throttle.
Most hesitation and starting problems can usually be trace back to the acc. pump. Good luck. Alan
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