| JayChicago | -- 11-04-2016 @ 3:46 PM |
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40 Ford all stock 85 H.P. Won't idle without choke plate half closed or palm of hand over the air horn. This makes me think I have a vacuum leak. But if there are other things I should look for, please let me know. Vacuum gauge on the wiper port reads 15.5 in. at idle. I sprayed starter fluid all around the intake manifold and distributor vacuum port....no engine response, no leak showed itself. I have two different carburetors that I believe are good, same symptoms with either on the car. I need ideas on how to continue the trouble shooting hunt. Thanks.
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| stickshift | -- 11-04-2016 @ 4:12 PM |
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Maybe the idle circuits are dirty or lean, and the extra vacuum you get by choking it pulls fuel through the main jets. Try opening the idle needle valve for a richer mix, or failing there, pull them out and shoot some carb cleaner through them with the plastic tube on the can. If it was working fine, and just flubbed up I would guess dirt. Seems I remember winding up a running motor, then choking it down to almost a stall, then opening it up (the choke) to clear the fuel out of the engine. This was all done at full throttle (not over revving) and using the choke to shut down the engine, and the opening it up again. ( to clear the flooding combustion chambers) This easy try can suck the dirt through if your lucky. Has worked for me in the past. Good luck. Opps just read about the two carbs same symptoms. Now it is getting tough. How is the compression? At what speed will it run okay? Just a idle issue only? I have seen carbon behind the valves (intake) so built up the motor would only idle because of the restriction, just the opposite of your situation. Need to pine on this one. This message was edited by stickshift on 11-4-16 @ 4:22 PM
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| JayChicago | -- 11-04-2016 @ 5:30 PM |
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Compression is low: Five cylinders @ 80 psi, one @ 88, two @ 70. (the two very low cylinders are not adjacent, in opposite banks) It seems to run OK at around 800-1000 RPM and above.
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| stickshift | -- 11-04-2016 @ 9:45 PM |
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After some consideration, I suspect the compression might be the issue. Is it hard to start after sitting for a week or so? My SBC ran ok when you got it to run, and if you used it regularly, but if it sat a while, I had to prime it to get it to run. It had low compression and burned no oil. My guess was the oil ran off the rings after it sat for some time, and did not suck enough to pull fuel from the carburetor. Good luck. Maybe a can of STP to up the compression (seal the rings) might help for a bit?
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| TomO | -- 11-05-2016 @ 9:18 AM |
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Jay, I thought that you had it running OK in Sept. What has changed since then? My guess is that you have some cylinders that are not firing correctly. Try shorting out one plug at a time to find out if all cylinders are providing full power. Tom
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| JayChicago | -- 11-07-2016 @ 9:08 PM |
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Follow-up: I am embarrassed to tell you that the problem was just an empty gas tank. The engine ran at idle, poorly and only with a lot of choke, for a very long time before it finally quit abruptly and I figured-out what was happening. I guess it had been running on moisture-laden gas from the bottom of the tank. The fuel gauge was showing about 1/8th full, but I should have known better than to trust the gauge on an old car. Sorry I caused you guys some head-scratching over something that was just my dumb mistake.
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| TomO | -- 11-08-2016 @ 6:47 AM |
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Jay, do you have an aftermarket sending unit? They are not as reliable as the original King-Selley units and have to be adjusted by bending the arm to give you decent readings. The arm must be bent so that it does not touch the bottom of the tank when the tank is empty and does not hit the top of the tank when the tank is full. You may want to check with Baxter Ford Parts in KS to see if he has the correct sending unit for your tank. Tom
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| ken ct. | -- 11-08-2016 @ 7:05 AM |
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Jay I'm glad you found the problem LOL. You had me scratching my head on this one, thanks for the update. ken ct.
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| JayChicago | -- 11-08-2016 @ 8:08 AM |
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Tom Thanks for that advice. I have pulled the inspection cover over the tank sending unit and can see that it is a fairly recent replacement. Probably an aftermarket unit. And what you are saying makes sense; the gauge needle stays pegged on the FULL line until the tank is down to about 3/4 full. I will put that on my to-do list, to pull the sender and bend the arm up a tad.
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| Drbrown | -- 11-10-2016 @ 11:14 PM |
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JayChicago .... Bought a Bob Drake 6-12 volt sender unit. Went to change mine and found the OE sender unit was still functional except the cork float on the sender unit arm had become saturated with gas and sunk to the tank bottom giving me a near-empty reading. So I just replaced the float and didn't install the new Drake sender unit. I did test the Drake unit and it worked as it should. As TomO recommended, you could try bending the arm to correct the gauge reading. The float arm provided with retro units is also typically adjustable in its length. If so, that might give you so more latitude in adjusting it. PS: The float provided in Drakes sender kit is plastic. Mine began to leak after a years time. I replaced it with a brass float from Mid West Auto, ironically also made by Drake. Both floats fit the OE sender arm. This message was edited by Drbrown on 11-10-16 @ 11:17 PM
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