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Diagnosis, please
#1
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Wat_Tyler
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I took Fred the Deluxe sedan out for a spin this afternoon. It was running happily. On the way home from our errand and to celebrate having made break-in status, I put my foot into it. Hard. To the floor. Second gear at 35MPH and pulling, maybe. It pulled for a couple of seconds and then gave it a big old stumble. It was hard to tell if it was fuel or fire, but after a few seconds, it resumed going and we got home. I never put in the clutch, and I took my foot off the throttle. We resumed after the second trial pat to assure it was back to running again.


Conditions:
outside air at the time: mid 80s and sunny. It had been parked in the sun for a few minutes, and it's black.
Operating temp: 195*F. That's where it operates.
Engine: rebuilt almost 600 miles ago.
Fuel system: stock/original. Think the tank and line were flushed when rebuilt or to get it to run after 35 years of sitting.
Fuel pump: stock, rebuilt with engine.
Carb: may need a rebuild - maybe. 512S. New carb awaiting - something.
Electric fuel pump: in the box awaiting installation
Ignition: seems fine, but could likely use a good going through (gaps and such). Pretty sure it was all new goodies when rebuilt.


Could this be an example of the dreaded Vapo(u)r Lock???

Posted on: 5/30 17:59
If you're not having fun, maybe it's your own damned fault.
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Re: Diagnosis, please
#2
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HH56
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It could be a sign of impending vapor lock but usually that will be evident even in normal driving.

When you mash the pedal is the accelerator pump pushing out a good squirt when the pedal floors? Possibly the leather plunger seal has been forced out of position or if the leather was dry at some point a split could have occurred in the seal. There is a ball check valve in the pump bore to keep gas in the chamber from returning to the reservoir bowl when the pump is needed. Perhaps that check valve is not working. The vacuum timing advance mechanism could also not be working as designed.

If it has overdrive, the ign cutout portion my be working and causing the engine to stumble for longer than desired because something mechanical prevented a kickdown.

Posted on: 5/30 18:13
Howard
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Re: Diagnosis, please
#3
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Wat_Tyler
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Nope, it's a boring 3-on-the-tree and no goodies. Needs a gear, really.


It pulled fine, until it didn't. Felt like it wanted to cut off. I think the main reason that it didn't was that I left the clutch engaged. It felt good for the 1.836 seconds after rapid accelerator depression, like it got its shot of fuel from the pump


It pulled this once before and died. I put the clutch in. Now that I think about it, I wanted to blame the coil (it was warm that afternoon), but maybe it was this condition. It started back after maybe 20-25 minutes.

Posted on: 5/30 18:37
If you're not having fun, maybe it's your own damned fault.
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Re: Diagnosis, please
#4
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Highlander160
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This is a lot like the old "Hold the phone closer to the car..." thing. But there's about 3 things to eliminate before you do forensic surgery. How is the condenser? Sparkling new, as in fresh...from Asia? You sense something in the coil (we know our cars like our bodies sometimes) so instinct may be kicking in. We say "vacuum advance" colloquially most times, but the reality is when vac drops (stab of the go pedal) timing retards. This is done by the point plate moving and its entirely possible it tweaks a wire outta contact momentarily. Could lose ground or primary input/output. If it's not getting proper current the coil can heat and so can the condenser. Too hot, either stops working. Rule those out before you dive into fuel. Vapor lock? I have hot summers and blended fuel (Michigan) and I haven't had vapor lock on anything since the mid 90s. There has to be a really screwed up fuel system to cause it. Random thoughts...

Posted on: 5/30 22:22
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Re: Diagnosis, please
#5
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Wat_Tyler
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So noted.


I have, in the past, when driving carburetor vehicles as a way of Life (one which seems to be returning), always found that it's 90+% ignition and only a few percent fuel related. I don't think I ever had any vapor lock stuff on those cars. And I have wanted to pull the plugs to check for gap and color anyway. So it looks like here's my chance to go through the entire ignition, just so's I know.


So who makes a decent distributor tune-up kit?

Posted on: 5/31 4:45
If you're not having fun, maybe it's your own damned fault.
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Re: Diagnosis, please
#6
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Fish'n Jim
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Not sure it's appropriate to respond to a one time incident. aka: "bog"
If it continues, then there's an issue. Might just have been the fuel level and pump hadn't caught up with the bowl level float or vacuum lag, etc. vs rpm. There's a couple "on-off" control systems working here and not unusual to find them out of sync on a sudden big set point change, like flooring it. Tuning parameters have to change for that but in this case can not. We tend to think they run perfect at all conditions or something's wrong. Not so.
If it didn't 'catch" and died, then I might be more inclined to address. Could be the timing's off slightly or something simple. In the wrong gear for the acceleration, etc. Combination of factors.

Posted on: 5/31 10:11
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Re: Diagnosis, please
#7
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Wat_Tyler
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Yeah, but it's not like Black Fred Sedan II was hitting 100% before The Bog Incident. It did conk out the one time, and whereas it did come back to life after a bit, I haven't forgotten about it. Maybe a good go-through under the distributor cap and installing this newer hotter coil I bought wouldn't be a bad place to start. And it'll give me a chance to look for possibly loose bits under the cap.


I ordered a tune-up kit including plugs. That's where we're going to start.

Posted on: 5/31 15:10
If you're not having fun, maybe it's your own damned fault.
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Re: Diagnosis, please
#8
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JWL
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Sounds like it may be fuel starvation. Check out the filters and flex line. Then the pump pressure and flow output.

Posted on: 6/1 11:27
We move toward
And make happen
What occupies our mind... (W. Scherer)
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Re: Diagnosis, please
#9
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HH56
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Quote:
Check out the filters and flex line.


Second that suggestion and especially the flex line. If it is the old original there is every chance it is hard and brittle to the point the interior bore lining is cracked. I had a 54 where a piece of the lining was loose and could be pulled out by pump suction and partially block the inner bore. This resulted in fuel starvation over a certain engine speed. If it is an old original line I would replace it just as a matter of practice. Napa might have fittings but If you have a hydraulic place nearby they can also make one with the proper fittings. If not, one of the PAC regions has repros. There are two styles.

Posted on: 6/1 12:08
Howard
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Re: Diagnosis, please
#10
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Wat_Tyler
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I haven't looked at it, but I can add that to the do-list


I reckon that I'll tie into it the week of the 12th. I'll have time and can be where Fred can supervise properly.

Posted on: 6/1 19:46
If you're not having fun, maybe it's your own damned fault.
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