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Had time to try a few tests today after remounting the original carb:

1. Tested the Bendix electric fuel pump pressure with and without its built-in fuel filter, and got readings of 4.5 psig both times. That seems to be very good.

2. Checked fuel flow with and without the fuel filter, and both times got 3/4 cup of gas in 60 seconds. Anybody know if this is good or bad? One book I read mentioned one pint in 30 seconds. Isn't that high?

3. Warmed her up and checked the vacuum at the metal windshield wiper tube and got a steady 18 Hg at idle. When I revved the engine (without a tach) the gauge dropped to below 15 Hg...well within the red zone, suggesting late timing.

So, next up is a good timing check and looking to see if the centrifugal advance mechanism is sticking or not.

Edited by Phil 32DL6 (see edit history)
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OK glad to see a steady 18" on the vac guage; we really are clutching at straws now, back to fuel and ignition.

I know we discussed this before and it seemed too hard, but, what about leaving the air cleaner off the carb before you get on the road, taking your tools with you and lifting the top off the carb as soon as it begins to falter and check that there actually is fuel in the carb. This is the only way I can think of to determine if adequate fuel is getting to the carb, and, knowing that you changed carbs there is not much else to look at in the fuel department.

If you pass this test then back to spark, what about running a jumper lead direct from the non earth side of the battery to the ignition switch side of the coil; the terminal that doesnt go to the distributor, this should eliminate any issues with the low voltage side of the ignition.

Oh and by the way what are the distributor point gap and spark plug gaps ? and another, what are the colour of the plug tips immediately after it falters ??

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...lifting the top off the carb as soon as it begins to falter and check that there actually is fuel in the carb.??

Can't see how that's going to happen with an updraft carb.

Also, it's only faultering as long as I shift into third gear at about 30-35 mph and I'm still pushing her a bit. If I back off, she settles down and I can cruise home at 20-25 mph no problem.

I'm going to recheck the point gap, possibly put in a new set while I'm in there checking the advance, but the plugs have always held steady at .028 and looked perfect.

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Some old carbs have a drain valve at the bottom. If you could somehow fit a length of clear plastic tubing onto it you would have a very accurate gauge of fuel level.

My Carter BB1 has at least a hole on the bottom...to allow excess fuel to drip out. That happens sometimes while cold starting if I tromp a little too much on the peddle. I'm not sure if it's an actual valve or not...never look up in there.

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My book for my 1931 Dodge DH6 has these specs.....022 for the spark plug gap. I find it hard to believe that there is that much difference between the same two basic engines???!!! What does your book say?

John...As they say in the advertising trade: "Amazing, but true!"

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Ok I have been reading this post,and what I have read and what I feel would cause this problem is the vacumee advance on the distrubtor.

Vern.

Yes a good possibilty, but then why do you have to drive some distance before the fault occurs. I feel that if the advance / retard mechanism was at fault the problem would be there right from the get go.

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Yes a good possibilty, but then why do you have to drive some distance before the fault occurs. I feel that if the advance / retard mechanism was at fault the problem would be there right from the get go.

Malfunctioning advance has been high up there on my list of suspects for some time now (see post #6) for the very reason that the problem doesn't show up until the advance function starts to become needed. I've focused on fuel delivery first because that seemed like the logical place to start, given the starving symptoms.

That of course has included vacuum leaks which would effect the air/fuel mix, but wouldn't effect the timing since there is no vacuum advance on this distributor.

Edited by Phil 32DL6 (see edit history)
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So do you have an exchange distributor ?

What's that?

All I know is that there is no vacuum line attached to the distributor (like my later cars) and the manual doesn't describe or show anything vacuum related in the distributor's neighborhood...only the weights associated with a centrifugal advance mechanism.

Or am I missing something?

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What's that?

All I know is that there is no vacuum line attached to the distributor (like my later cars) and the manual doesn't describe or show anything vacuum related in the distributor's neighborhood...only the weights associated with a centrifugal advance mechanism.

Or am I missing something?

Sorry I meant do you have a distributor to swap over, failing that a timing light should show up issues with failed centrifugal mechanism.

The other thing you could try is loosen the distributor clamp bolt and rotate the distributor perhaps a 1/4" either left or right then tighten the clamp: what we are trying to establish here is that the distributor centrifugal advance is the culprit; moving it around a little may compensate for incorrect timing whilst you are at speed or it may have no effect at all.

To establish whether you are moving towards advance or retard, remove the distributor cap, turn the engine in correct rotation by hand and note the direction of rotor button rotation. Now having loosened the clamp bolt if you move the distributor base in the same direction as the rotor moves you will be retarding the timing, obviously going the other way advances it.

At this stage you may have to move the distributor back and forth to find the sweet spot, now take it for a drive and what we really want to know is does this have any effect on the symptoms at all ?

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Also, it's only faultering as long as I shift into third gear at about 30-35 mph and I'm still pushing her a bit. If I back off, she settles down and I can cruise home at 20-25 mph no problem.

This is some ignorance on my part, but is it normal to wait until you are going that fast to change into high gear?

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This is some ignorance on my part, but is it normal to wait until you are going that fast to change into high gear?

I normally shift at a bit slower speed, but for these tests I'm just trying to work the engine in a shorter distance. Plus the road is flat, so I figure the extra load simulates climbing a hill. Also, that 30-35 mph is a rough guess...I suppose I should quantify that number?

Edited by Phil 32DL6 (see edit history)
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My Carter BB1 has at least a hole on the bottom...to allow excess fuel to drip out. That happens sometimes while cold starting if I tromp a little too much on the peddle. I'm not sure if it's an actual valve or not...never look up in there.

I was talking about the float bowl. If you could attach a clear plastic tube to the bottom of the float bowl you could see exactly how high the fuel was.

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I was talking about the float bowl. If you could attach a clear plastic tube to the bottom of the float bowl you could see exactly how high the fuel was.

I haven't located a schematic for the Carter BB1, but I'm guessing this port would probably serve nicely for the test you propose. (This is a spare carb I bought at a flea market 40 years ago for $10.)

But here's the thing...by swapping out the two identical make/model carbs with absolutely NO effect on the stumbling, I feel that I've eliminated the carb as the cause. It seems unreasonable that BOTH would suffer exactly the same malady to exactly the same extent. If there were a low level of gas in the float bowl during acceleration, it would have to be the fuel pump. Slow down a little, use less gas, and the bowl would fill up again, right? That would be hard to observe on a road test. (My dad told me a story of a daring mechanic who rode along on the fender of their 28 Buick fiddling with carb settings!)

Sooooo...I'm still wondering if anybody else has actually measured the output of their fuel pump? I located that suggested figure (I quoted earlier) of one pint in 30 seconds in a 70s vintage Motor Trend Basic Auto Repair Manual, but by then cars were using higher pressure pumps, I believe. My 4.5 psi Bendix is pumping out 3/4 of a cup in 60 seconds, so that big a difference is worth questioning.

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Edited by Phil 32DL6 (see edit history)
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I'm familiar with Plymouths and the '32 Plymouth PBs,the last of the 4 cylinder Plymouths, also use the BB1 as their standard carb and I've never heard of ANY annoying,confusing,repetative faults with the BB1. They must be a good carb because there is an industrial version of it for stand-alone power units. I once had one and sold it to a guy wtih a PB. FWIW.

Edited by DodgeKCL (see edit history)
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The point of adding the clear tubing gauge was so you could check the level of fuel in the float bowl without taking anything apart. This is not only to check the carb, but to check that it is getting fuel at all times.

But since you know beyond a shadow of a doubt that your carburetor is perfect and your whole fuel system is perfect, we can cross them off the list.

That means the only thing left is the ignition. The type of failure you describe could be a bad condenser or a bad coil that fail when they get hot.

By the way this is too obvious but I hope the vent in the gas tank cap is not plugged? If your tank is not vented it will cause the problem you describe.

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Until a few days ago, I had always assumed that the BB1 came standard on 32 DLs. My first DL (an early DL) has one and my new one (a later DL) does too. That a brass-bottom Carter DRT-8 is shown in both owner's manuals I always thought was because that was what Dodge carried over from the 31s onto the early 32s...at least in the manuals anyway. But I was doing some Internet research on the BB1 the other day and read that it was very common to replace the original carbs on many contemporary cars with a BB1 because they were so reliable. So, it may be that DLs never came from the factory with BB1s?

Edited by Phil 32DL6 (see edit history)
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The point of adding the clear tubing gauge was so you could check the level of fuel in the float bowl without taking anything apart. This is not only to check the carb, but to check that it is getting fuel at all times.

But since you know beyond a shadow of a doubt that your carburetor is perfect and your whole fuel system is perfect, we can cross them off the list.

That means the only thing left is the ignition. The type of failure you describe could be a bad condenser or a bad coil that fail when they get hot.

By the way this is too obvious but I hope the vent in the gas tank cap is not plugged? If your tank is not vented it will cause the problem you describe.

I got the point of the clear tube and it would be an excellent test, it's just that it would be hard to check under road conditions and, if the problem IS a weak fuel pump (there's a shadow of doubt right there), then any low level in the tube would rise as soon as I slowed down and stopped to check it. That's why I'm interested in hearing if anyone has a normal fuel flow figure they can offer. 3/4 of a cup in 60 seconds may be weak?

I've checked the gas cap vent for blockage (actually its a non-vented modern one which I drilled out this summer). And, to make sure, I removed the cap when I did the fuel pump flow tests.

Since I've replaced both the coil and condenser already with no effect, I'm going to check out the distributor first. If my wood splitting chore goes well, it may be this weekend...

Edited by Phil 32DL6 (see edit history)
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I have seen soooo many Chrysler products of the late 20s', early 30's with the BB-1. They are indeed replacements. The DRT-08 is a very tough carburetor to find and fix if the pot metal tube in the middle is broken off at the base. My '31 DB had the DRT-08 and now has a BB-1. Not my choice (because it stumbles), but the DRT-08 is scarce. I think that it may be a carb "outlet" / intake manifold "inlet" mis-match.

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My '31 DB had the DRT-08 and now has a BB-1. Not my choice (because it stumbles), but the DRT-08 is scarce. I think that it may be a carb "outlet" / intake manifold "inlet" mis-match.

John...Didn't know (or remember?) your '31 stumbles, too. What are your symptoms and conditions?

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John...Didn't know (or remember?) your '31 stumbles, too. What are your symptoms and conditions?

Pretty much the same as yours.....except I get a popping noise, too. I think that the previous owner ran the pi$$ out of the engine. It needs to be rebuilt.

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I still think that you should try to eliminate your fuel supply. Borrow your fishing buddies boat tank and put the fuel line directly onto the carb and manually pump the fuel with the primer bulb from the front seat. Dont worry if there is oil in the gas, it wont hurt a thing and you have just proved or dissproved gas tank, fuel pump, cloged lines and every other possible supply problem right up your the carb.

Backing off of the throttle to get home strongly suggests that you have a fuel supply problem.

Years ago I had an old Jeep that did a simalar thing. I foung that a pebble had made it into the hard line running from the tank to the engine. It got to a coupler that would not let it pass and it turned into an very effective valve when the mechanical pump tried to pull fuel from the tank.

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I still think that you should try to eliminate your fuel supply. Borrow your fishing buddies boat tank and put the fuel line directly onto the carb and manually pump the fuel with the primer bulb from the front seat. Dont worry if there is oil in the gas, it wont hurt a thing and you have just proved or dissproved gas tank, fuel pump, cloged lines and every other possible supply problem right up your the carb.

Backing off of the throttle to get home strongly suggests that you have a fuel supply problem.

Years ago I had an old Jeep that did a simalar thing. I foung that a pebble had made it into the hard line running from the tank to the engine. It got to a coupler that would not let it pass and it turned into an very effective valve when the mechanical pump tried to pull fuel from the tank.

My old '57 Chevy shortbed stepside with a 235 in it did that. It was a very small flake of rust that kept flipping closed in the line when I put my foot on the gas. It would idle and rev fine, but as soon as I was under a load, the rust would flip up, block the fuel line and cause the engine to stumble. It always seemed to do it about 2 miles from my house. Took me a very long time to figure it out.

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Borrow your fishing buddies boat tank and put the fuel line directly onto the carb and manually pump the fuel with the primer bulb from the front seat.

Excellent idea, Jack...will you be my fishing buddy? (I don't have any.) :)

I don't know why I haven't tried this yet. I used to run my old DL off a plastic emergency gas can using a siphon. Worked great (except for that one mouthful of gas early on) and by-passed the gunked-up tank and clogged Bendix pump.

This such a good wake-up call that I might by-pass a buddy and buy a boat tank.

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I would be your fishing buddy but you will have to get the thing all the way to Oregon. Record Coho in the Willamette this year. I mean RECORD, like double the last record from 30 years ago,,,When we had hatcheries.

There have been no operating Coho hatcheries up river for many years. This is truly Ma Nature doing her thing..

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NAILED IT! Mystery over...problem solved!

Wanna know what it was? Send 10 bucks and a SASE to...

Naaaah, can't do that. But, I'll give you one last chance to place your bets.

Big clue...my hunch about it being a fuel supply problem was right. And, Rusty-OToole asked the right question, but my answer, while true, ended up being only partly correct, and thus deflected my attention elsewhere.

More? It wasn't anything I had replaced or added or swapped from the other DL. Nothing was damaged, worn, rusty or out of adjustment.

So.....?

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NAILED IT! Mystery over...problem solved!

Wanna know what it was? Send 10 bucks and a SASE to...

Naaaah, can't do that. But, I'll give you one last chance to place your bets.

Big clue...my hunch about it being a fuel supply problem was right. And, Rusty-OToole asked the right question, but my answer, while true, ended up being only partly correct, and thus deflected my attention elsewhere.

More? It wasn't anything I had replaced or added or swapped from the other DL. Nothing was damaged, worn, rusty or out of adjustment.

So.....?

Wrong gas cap??

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