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First thing I did this morning was slip a gas can on the passenger seat, crack open the windshield, and run a siphon directly to the inlet on the carb to check out the whole fuel delivery system up to the carb. Then I warmed her up and headed up the street, roared by "that" house with nary a stumble. Took her about four miles up and down hilly terrain and got her up to about 45.

Back home, I unhitched the output line from the Bendix electric pump that's mounted just in front of the gas tank, stuck it in a liter soda bottle, and had my wife flip the toggle switch under the dash. One minute later, there was the same 1/3 cup of gas in the bottle as in previous tests. So, I figured, it could still be the pump, but the line to the carb was probably OK.

Next, I siphoned off some gas from the tank, then removed the tank's output fitting. I pulled my Voyager alongside so I could plug my portable air compressor into its 12V lighter outlet, put on the beachball inflator tip, and pumped air into the gas tank, listening to the gas bubble for maybe 15 seconds. Much to my surprise, when I removed the inflator, a small stream of gas squirted out.

"That shouldn't be happening," I said to myself. After all, I had drilled out the venting mechanism in the gas cap that came on the car, soon after I got her in May, because I was experiencing positive pressure buildup in the tank on ever hotter summer days. That had been working fine ever since: no burps when removing the cap.

The only way gas could be blown out now was if the tank were still becoming pressurized, and that could only happen if the cap hadn't been drilled out enough to vent anything beyond a very gradual pressure buildup. I removed the cap, reinserted the inflator, ran it for 20 seconds, pulled it out, and voila...no gas came out. If air can't get OUT fast enough, maybe it can't get IN fast enough, either? So, back to the drill press went the cap for a better reaming.

With the cap back in place, I hitched up the lines, stuck the hose back into the liter bottle, and told my wife, "Flip the switch." Only 30 seconds later, I yelled, "Turn it OFF!" The bottle was FULL. This time the pump hadn't had to fight the vacuum it had caused in the tank earlier, so gas gushed into the bottle.

Evidently, under identical test driving conditions, by the time I reached "that" house every time, there was just enough vacuum in the tank to prevent sufficient gas from flowing though the system, starving the engine. Back off a bit, lowering the demand to meet the restricted supply, and the engine smoothed out.

I tell ya, the 10 mile test that followed towards dusk after an unusually warm, sunny, late-November day here in New England was one of the sweetest drives yet!

...and a hearty THANKS to everyone for all the support and suggestions. Perhaps the most apt (in this case, anyway) was Nearchocolatetown's, "Look in STUPID places for the problem!!"

Edited by Phil 32DL6 (see edit history)
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Rusty...Back when I headed up a department, I'd tell my staff that I'd rather insult someone's intelligence in explaining what needed to be done, than assume they knew, and have the job done wrong. So I never feel insulted by hearing the obvious myself.

To my credit, I had recognized soon after I got the car that the previous owner had put on a replacement gas cap of the wrong kind, because the heat from the sun was causing pressure to build up in the tank resulting in a messy burp when I opened the cap.

What I DIDN'T recognize (loss of credit) was that my fix wasn't a complete fix.

What I really should do is pick up a proper cap. I see Andy Bernbaum has 'em for my '32 for about 8 bucks.

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So thats it, bad gas cap??? I was really expecting something marvelous, I guess its sorta like that movie that everyone said was so spectacular and your expectations became too high. Phil couldnt you have just lied?

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Whatever it takes to get a car running and driving, 1 post or 125.

Thats great and your right Doug, now hows about properly/correctly restored which is where Im at with mine, I need help with some curtain hardware as per one of my recent posts, you have a very nice very original ( for the most part ) DA, how about offering me some assistance???? It sure would be appreciated, Im losing alot of sleep over this!!!

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There is a person selling gas caps on e-bay from time to time that are advertised to suit 1928 onwards Dodge Bros cars. Please check your caps. These caps are vented but only one way allowing pressure to build up in the fuel tank. As I found out the other day with fuel overflowing the vac tank onto the hot exhaust manifold. Thanks for sharing the stumbling engine story.

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So thats it, bad gas cap??? I was really expecting something marvelous, I guess its sorta like that movie that everyone said was so spectacular and your expectations became too high. Phil couldnt you have just lied?

Think of it as a comedy not a thriller ha ha

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But...WAIT! There's a footnote to this Neverending Story.

While I've been fooling around with the fuel delivery system, I've purposely kept the tank level low so I could open up the outlet without spilling gas. Today, with the stumbling problem FINALLY solved, I figured I'd go gas up the buggy in anticipation of Old Man Winter.

After doing so, I went on a little joy ride around town. Three miles down the road I came to a stop sign. Starting up, the engine suddenly died. No warning...just died. I pushed in the clutch, coasted through the intersection, and headed for the curb. Each time I cranked it, I could sense maybe one cylinder firing weakly, but it wouldn't catch.

Naturally suspecting recurring fuel problems, I figured I'd walk home, load some tools and parts in my van and return. To my rescue came a retired Packard man who offered me a ride.

Back to the scene, I tried removing the gas cap just in case that was still providing "iffy" venting. Then came the old gas can/siphon-feeds-the-carb routine, but that didn't work, either. Neither did swapping carbs (just in case some dislodged dirt was causing a blocked needle valve).

The Packard guy returned, so now I had a handy helper to test the electrical components. After removing a plug wire while I cranked the engine, he announced, "You've got no spark!" A quick inspection of the points showed pitting, so I grabbed my point file and touched them up.

"Now you've got spark," he exclaimed, and sure enough, with the fuel pump switched on, she immediately fired up and purred steadily.

"Now, I'll follow you home, drop off the Dodge, and bring you back to your van," my new friend announced. After arriving home, he asked me, "Do you have your tank overly filled? You were spilling some gas as you rounded the corner."

Uh, oh...Guess what? In the scramble, I had forgotten to replace the gas cap after that early pressure check. I'd set it down next to the open filler pipe, and so, somewhere on the way home, that infamous gas cap got ditched...literally!

Anybody, enjoying this ironic ending with me?

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If it makes you feel any better, a friend of mine did that same thing in his '31 Dodge sedan. We filled up. He left the cap right where you did. We drove off. Got to the motel 1/2 block away and smelled gas really strong. Oops...no cap. Got in and went back to the gas station. I found it in the street all mashed. I have extras so I gave him one of mine.

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  • 7 months later...

Unfortunately, I have to rejuvenate this topic.

I've been scratching my noggin since last March over another lingering engine stumbling problem with the DL, but the cause would seem to be something different this time around.

It ONLY stumbles after I've been driving her around for a half hour or so, especially on warmer days, but not always. Generally it begins on longer hills in 3rd gear. She'll start to suddenly falter and slow down, and, if I back off on the gas, maybe feather the gas with the clutch in, or pull over for a moment, she'll keep going on normally for a short while then begin the cycle all over again. Usually I can limp home with a lot of babying. It can occur with the water temp gauge reading anywhere between 145 to 165 degrees.

I've cleaned/replaced all of the distributor components and retimed it. (It was set to only 5 degrees BTDC...in effect retarded by 5 degrees. She's peppier now.) I've also reset the idle and adjusted the mixture screw for max revs, but haven't rechecked with a vacuum gauge yet. Since she runs flawlessly most of the time, I can't believe it's the electric fuel pump or, or the pump's filter, a clogged jet, etc. But, the effect is fuel starvation. The plugs run clean, so I don't suspect too rich a mixture.

She's always had some clicking at the valve tappets, but the clicking seems a little louder when the engine's fully warmed. I do need to pull the valve covers and check/adjust the clearance.

She's begun to use a little more oil lately. The rear main seal is leaking ever so slightly, but I've also see some whiffs of blue smoke out the tailpipe...especially when warmed up. I'm using 30W ND oil, and keep it changed every 300 miles or so, but I'm wondering if maybe that's too light and I'm losing compression when the engine's hot.

Anybody ever experience anything like that? Just a theory on the oil weight...but I'm trying to figure what could cause the problem only when it's warm. Any ideas?

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I did change the condenser, but I have another I can swap out as an easy test.

Someone else I spoke with thinks that it might be vapor lock caused by the alcohol in today's gas. Having installed an electric fuel pump to solve that problem a year ago, I'm having trouble believing that. Anybody else have vapor lock with an electric pump?

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How about the vent in the gas cap.

Oh, no...not gas caps again!

Actually, I HAVE been experiencing as issue with the new (and supposedly correct) cap I got to replace the one that caused the birth of this thread. This new cap vents INWARD just fine, but allows pressure to build up in the tank on hot days. It's most noticeable after I've just tanked up: the cool gas from the gas station's underground tank expands faster than the OUTWARD vent can dissipate the pressure caused by the expanding gas & air.

But, I can't imagine why moderate positive pressure in the tank would cause the stumbling problem. Wouldn't it just act as a "booster" for the electric pump? Doesn't the pump determine the pressure delivered to the carb? Usually, I just pull over after a bit and "burp" the tank as a precaution.

What's funny, though, is blowing and sucking on the cap's vent hole indicates good venting both ways.

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Could also be the coil.

I replaced the coil a year ago when I was trying to solve the original stumbling situation. I suppose there's a slim chance that the new one could be defective under certain heated up conditions? Maybe I should put back the original one as a test...or pick up another new one to at least have a spare...

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Have you tried checking the wiring to the coil yet? When the wiring gets warm you could be getting a weak connection. You wold be getting good voltage but not enough amps for a good spark. I personally would run a temporary set of wires to the coil with modern wire to test this. Just a thought, good luck.

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Well...I still haven't solved the stumbling problem yet, but, if eliminating likely causes is progress, I'm making GREAT progress!

I still sense that it's a fuel delivery/use problem because when I approach one of the steepest hills in town at a steady 40-45 mph she cruises along just fine, but, as soon as I start up the hill the engine suddenly starts losing power and then it will start to stumble and pop like it's running lean. Pushing in the clutch and pumping the gas helps a little sometimes, but the best solution is to pull over to the curb...wait 20-30 seconds with the engine idling...then put her in first and finish the climb without any problem. I can smoothly cruise home on the flat road along the ridge top.

So, first thing I did was swap carbs with my other DL6 which has the same Carter BB-1 and has never had the stumbling problem in the past. I figured, even though it had been professionally rebuilt about two years ago, if my newer DL's carb had float problems or a clogged needle valve, swapping carbs would at the very worst, show some other behavior. Nope, exact same stumbling behavior.

Since I by-passed the mechanical fuel pump (also professionally rebuilt) and installed a Bendix electric fuel pump last fall I can't believe the problem is vapor lock. I've tested the electric pump's pressure with a gauge and also observed the flow into a 2 liter soda can. Both were normal. But, just in case, I removed the built-in fuel filter from the bottom of the Bendix (in case it was clogged) and put an in-line paper filter upstream of the pump. Back on the road she stumbled as before.

To keep you electrical-side guys happy, I cleaned and checked the distributor components, changed the condenser, and checked the connections. The idle speed and mixture were adjusted before the timing was checked with a scope and adjusted. I then replaced the wiring from the ammeter to the ignition switch, and from the ignition switch to the coil with modern 12 gauge braided primary wire, and then the wire from the coil to the distributor with modern 10 gauge braided primary wire. I also tried swapping coils. No change in the stumbling during any and all road tests...which BTW I do after EACH change so, if something finally works, I'll know exactly what the fix was.

I've got good vacuum pressure at idle (about 16-17 psi), but really need to do a compression check since it's been awhile. The valve tappets are a little noisy to my ears, so a valve adjustment is on my to-do list. (Could too large a valve clearance cause such behavior?) One thing I suddenly just realized is that I've checked the fuel flow and pressure at the pump which is just in front of the tank. Tomorrow I need to check pressure and flow from the line just before the carb to eliminate the possibility of a restriction in the metal fuel line. (Yeah, yeah, I know brain f*rt.)

Oh, and for you bad gas cap theorists, I rechecked the vent valve by sucking both in and out: tasty but normal unrestricted venting.

So...who wants to suggest anything else? If nothing else, there's a ton of preventive maintenance happening under the hood!

Edited by Phil 32DL6 (see edit history)
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We had a truck from the 50's some 30 years or so ago now and it would act like that once in awhile and it turned out the gas line going into the tank was either loose or sitting in the tank wrong. I forget which now as I was a kid. But the line would get against the bottom of the tank and starve the truck for fuel and act like that at random. I suppose you might as well agonize over that theory as well.... I know how maddening these things can be at times and they often turn out to be something simple.

I couldn't get my '41 Buick to idle right for about 8 months and finally found out by accident that the intake/exhaust manifold bolts were all loose. After I tightened them it began to run like it should. I would have never thought they would be loose, but someone must have done something there and they didn't get re-tightened. Good luck with it now, Earl.

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  • 2 weeks later...

By gosh & by golly...I DO believe I've cracked the case!

All along she's been acting like she's running out of gas whenever I put extra demands on the engine, like climbing a long, steep hill, or accelerating crisply. If I hadn't installed an electric pump, I'd guess it was mild vapor lock.

The carb had already checked out (by swapping an identical one with no change in stumbling), so I decided to recheck the pump output. When I put it in last Fall, I got a gauge reading of 4psi and the flow was excellent. So, yesterday I started at the carb input and got a reading of 4psi, BUT...the flow rate was about 3 to 4 times less! YIKES!

Working backwards to test each segment of the system, I sampled the flow at the pump outlet without any increase. Steel fuel line must be OK.

I took off the gas cap to check venting without any change to the flow rate. Cap was OK.

I removed the pump's input line from the tank and set up a gas can with a siphon to the pump. No change in the flow. Tank output was OK.

Pump must be clogged, right. I opened up the bottom of the pump then took my little tire inflator/compressor and blew some air into both ports on the pump. Not much went in, of course, but when I hitched everything back up and retested the flow...voila! Flow was strong and steady.

Out on the road, she stormed up the longest, steepest road in town...in 3rd gear...3 times without a falter. Today, my wife and I took her for a 24 mile spin, including cruising on a highway up and over a long bridge at 50mph.

My best guess is that either some crud got lodged in the pump, or the new gas has been working on the innards of the old Bendix pump. Figuring that the pump was used (how much I haven't a clue, since it tagged along with the car) it could fail again at any time, so I've ordered a new 6V pump which claims to be able to handle today's gas.

Whew!

Thanks for all the help and suggestions, everyone! No steps were a waste since a lot of routine maintenance got done in the process.

P.S. Today's test ride took us across the Connecticut River aboard the oldest continuously-operating ferry in America. It was a good day!

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Edited by Phil 32DL6 (see edit history)
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It actually ate the paint off my DA fender, and it was only there about 3 seconds.

Hey...mine, too. Once when I was having gas cap venting problems, the sun heated up the cool gas from the station's underground tank building up pressure in the tank. When I opened the cap, gas burped out and across the skirt above the tank and instantly ate away the paint. :eek:

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