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No fuel pressure and Dry Primary bowl |
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390spirit 
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Joined: Jun/28/2008 Location: U.S.A. Status: Offline Points: 1426 |
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 Posted: Jul/08/2012 at 12:04pm |
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ya if it backfires threw the carb and it don't have the check ball for protection it will 90% of the time blow the PV.
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FuzzFace2
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Joined: Jul/05/2007 Location: Connecticut Status: Offline Points: 6374 |
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Posted: Jul/08/2012 at 1:22pm |
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Good to hear you got it to fire up but sorry to hear it still runs ruff. I dont see the PV causing it to run ruff unless it has a big hole in it. When it was running did you get to check the bowl(s) level? Too high will make it run rich and ruff, too low just ruff or not run at all. Now if it was running right then just out of the blue started running bad then could be dirt in the carb or if running points/condenser could be them. Check the points or replace them if you dont know how long they have been in. Even new poins/cond. can be bad so maybe try another set if you have them. Once the poins check out good set the timing then you can move on to the carb.
If it still runs ruff I think I would pull the carb apart to make sure it is clean by blowing out all the passages & replace the PV to be safe. Before you pull it apart I would count how many turns each idle mix screw is so they can be put back there as a starting point. When running good again adjust the screws 1/4 turn each till it runs better. They may need to go in or out but should be the same turns for both. Just so you know the carb adjustments should be done with the motr up to temp.
BTW what do the plugs look like with the short run it has had?
Dave ----
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75 GremlinX v8
76 GremlinX i6 (sons) 70 Javelin SST 390/4sp (360/5sp now) 70 Javelin 1/4 Drag car 360/auto |
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tmancusi
AMC Nut
Joined: Apr/25/2009 Location: WI Status: Offline Points: 395 |
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Posted: Jul/08/2012 at 11:06pm |
Thanks Dave. It has an MSD ready to run distributor so I don't have to worry about points. It's running rich, the float bowl his too high with gas. I fired it up again, she started right up without pumping the gas. Idled terribly but managed to keep it alive for a couple minutes and then gave it some gas. Got the R's up to 5K a few times with a few good rev's. Seems to do so much better above 2 grand. Would not hold an idle though. Once the R's dropped under 1500, she died. Pulled a brand new plug after a total of about 3 minutes of running. Already black and smelling like gas...  Edited by tmancusi - Jul/08/2012 at 11:08pm |
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'68 AMX 390 4-Speed
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FuzzFace2
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Joined: Jul/05/2007 Location: Connecticut Status: Offline Points: 6374 |
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Posted: Jul/09/2012 at 10:25am |
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You will need to lower the float as it can not be helping any. Also as said could be the power valve leaking but I would try the float first.
Dave ----
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75 GremlinX v8
76 GremlinX i6 (sons) 70 Javelin SST 390/4sp (360/5sp now) 70 Javelin 1/4 Drag car 360/auto |
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PHAT69AMX
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Joined: Jul/07/2007 Location: SW Ohio Status: Offline Points: 2810 |
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Posted: Jul/09/2012 at 4:14pm |
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The primary float could be lowered by loosening the primary needle Screw
and turning the needle nut clockwise maybe 1/2 or so turns while holding the screw.
On the needles the Screw is just a "lock" and the Nut screws the Needle in and out of the bowl
to adjust the float level and resulting fuel level in the fuel bowl.
Then remove the float level site screw and see if gas still runs out.
Other than the float level itself, it could also maybe be the O-Ring on the Needle & Seat.
If the spirit moves ya, could remove the front bowl from the carb.
Unscrew the Needle & Seat from the Bowl to inspect or replace the O-Ring.
I lube the O-Ring with wd-40 before putting the needle back in the bowl.
They make Nylon Needle & Seat gaskets now that a lot better than the blacl paper ones.
If using black paper ones, I soak those with wd-40 also.
A bowl screw head flange can be use to dry-set the float level.
With the fuel bowl inverted, adjust the needle and seat in and out
so that the bowl screw head flange just slides between the top of the float
and the inside top wall of the fuel bowl, this is usually a pretty close dry float setting.
On the needle & seat, the Screw is the "Lock" and the Nut adjust the needle in the bowl.
Once adjusted, tighten the screw to lock the needle in place in the bowl.
Avoid screwing the needle too far into the bowl because if ya do
the flats inside the nut will no longer have contact on the flats on the needle
and it will no longer be able to adjust the needle in and out of the bowl.
If this happens remove the gasket from the Nut and it may then be able
to once again contact the flats on the needle and back it out of the bowl.
Beyond that sometimes the Float Arm needs tweaked to midrange the
needle and seat adjustment in the tapped hole in the bowl
but that is seldom the case.
Once the float is adjusted, one way to "test" for a blown Power Valve diaphram
is while running at idle, screw in the mixture screws all the way.
If the PV is good this should kill the engine at idle.
If the PV is ruptured, it will keep idling with the mixture screws in all the way. Edited by PHAT69AMX - Jul/09/2012 at 4:17pm |
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tmancusi
AMC Nut
Joined: Apr/25/2009 Location: WI Status: Offline Points: 395 |
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Posted: Jul/09/2012 at 5:57pm |
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So got home from work, tried to adjust the primary float without the car running, 'cause it won't hold an idle. After making an adjustment I start it up and holy crap it idles beautifully!!!......for about 45 seconds, then stalls and won't start again. I'm sure it's flooded now. Question is why did it stall?
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'68 AMX 390 4-Speed
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Lucas660
AMC Nut
Joined: Apr/16/2012 Location: Vic, Australia Status: Offline Points: 368 |
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Posted: Jul/09/2012 at 6:25pm |
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Float is most likely too high now. Adjust it back down 1/4 of a turn at a time and remove the sight plug to check when it is running, the fuel should be just licking the bottom of the threads.
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tmancusi
AMC Nut
Joined: Apr/25/2009 Location: WI Status: Offline Points: 395 |
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Posted: Jul/09/2012 at 8:34pm |
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I'm really confused. No matter how I adjust the float, whether I set it visibly higher or lower in the sight plug, the gas level never gets below covering the 3/4 of the sight bowl. Even after I get it to run for a minute or 2. It almost seems to run better with the float visibly almost to the top. Isn't that too much gas? Maybe the PV did go bad from the flame spit the other day?
If all this isn't bad enough, my new alternator has stopped charging  . Sounds like the belt is slipping. Hopefully I just need to tighten. I have a headache. Thanks again for all the help guys.....I'll get it eventually.
Edited by tmancusi - Jul/09/2012 at 8:36pm |
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'68 AMX 390 4-Speed
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Lucas660
AMC Nut
Joined: Apr/16/2012 Location: Vic, Australia Status: Offline Points: 368 |
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Posted: Jul/10/2012 at 7:16pm |
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The float adjustment won't make any difference if the needle and seat has worn, I would remove the bowl, replace the power valve, needle and seat and check that the float does not have a hole in it by dropping it in a jar of fuel. Replace the fuel filter upon re-assembly.
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tmancusi
AMC Nut
Joined: Apr/25/2009 Location: WI Status: Offline Points: 395 |
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Posted: Jul/15/2012 at 12:38pm |
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Well, did a little more investigation today. There was a small piece of plastic in the float adjustment screw, kind of like some plastic wrap. I'm guessing this shouldn't be in there?
 I'm also having a problem understanding how the needle and seat work. No matter how much I adjust the float screw, the float bowl has full movement. It wasn't like this a couple of weeks ago. New one from the rebuild kit does the same thing. These pics are with the screw adjusted all the way down so the float shouldn't move. What am I missing?   Here's the original adjustment screw:  Thanks.
Edited by tmancusi - Jul/15/2012 at 12:40pm |
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'68 AMX 390 4-Speed
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FuzzFace2 wrote: