52 Mercury engine

[oldford2]

I am stumped. Fresh engine up on the test stand. It starts first turn and idles smooth and quiet. Then as I slowly give it throttle it runs great up to a fast idle. Will run at a fast idle smooth forever. Then as I give it more throttle the accelerator jets squirt properly and the engine dies immediately even though the jets have provided the extra fuel. So I don't think it is fuel starved? I don't understand how it could die so quickly. If I let off on the throttle before it dies, it returns to a nice smooth idle. It has a Holley 9510 teapot carb which I know nothing about. I have the manual and compared to the simple 94 it is a complicated carb. Timing is right on. I only took the top off and everything is clean. Put a fine wire down what tubes I could access up top. Carb had sat on a shelf for 20 years so I could understand if it ran poorly. But the fact that it starts and idles great has me stumped. Any suggestions from folks that are familiar with the teapot?
Thanks

[keith oh]

Sounds more like a ignition problem. See if you still have spark at plugs as it stops running.

[Ross F-1]

Check the wire that goes from the coil, under the points plate, to the points. A lot of times they get chafed and short out in certain points plate positions. I had a car that did just what you said, the wire was shorting against the bottom of the screw holding the points down. It would only touch when vac advance got to a certain point.

[38 coupe]

I chased an identical sounding problem recently on a 1953 Mercury. In that situation I rebuilt the carburetor. The car idled great, but ran like crap and would die at anything past fast idle. Our problem turned out to be the ignition timing way too far advanced, something like 30 degrees at idle.

The main jets and main wells are the only parts of the supply common to both the idle and main fuel circuits in the carburetor. There are fuel to air mixture parts in the main fuel circuits that have to be clean or nothing works properly (the "main well tube" and the "aspirating nozzle"). Also, the carburetor top has air metering holes that line up over all this stuff. These holes have to be clean. These can be seen in the "main metering system" diagram in the manual.

One other thing to note: the carburetor is a Holley 1901. The 9510 is Ford's part number, not the true carburetor identification from Holley.

[51 MERC-CT]

Sounds like the idle side of the circuit is working properly.
This is what the main jets look like on a carb that has been sitting a long time.

[ford3]

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hook a timing lite to the coil wire or a spark plug wire, watch the lite as it flashes and see if the flashes stop as engine dies, if it does you have an electrical problem with the dist, shorted wire as was said in an earlier post

[oldford2]

Originally Posted by Ross F-1

Check the wire that goes from the coil, under the points plate, to the points. A lot of times they get chafed and short out in certain points plate positions. I had a car that did just what you said, the wire was shorting against the bottom of the screw holding the points down. It would only touch when vac advance got to a certain point.

Ross F-1,
You got it. Chafed wire under the plate. Fortunately I had a spare. So that solved the sudden shutdown of the ignition. BUT, now when it is revved up it starts to stumble like not enough fuel. Looks like I have to venture into a teardown and check out the main jets. Thanks all of you for your help but don't go away. I am sure I will be back.
John

[VeryTangled]

Great thread! Good catch Ross-F1!

-VT/JeffH

[oldford2]

Hey Fella's
Regarding this chafed wire thing, I got thinking (yes, sometimes I think) that a few years ago I sent an 8BA distributor to a good rebuilder. When I installed it the vacuum advance did not advance. So, I found out that the rebuilder found that chafed wire and instead of replacing it they put a piece of shrink wrap on it. Since both ends have terminals they had to use large size shrink wrap to get over the terminals. When they shrunk it, it became so rigid that it could not flex and restrained the plate from moving. So, this was the second time I got hit with the dreaded chafed wire syndrome .
John