Starting Problems & Rough Idle - 1949 Roadmaster

[Dan O]

I cranked up my '49 Roadmaster yesterday after sitting 3 weeks and she started and ran fine. I'd had a nice 20 mile run around Houston with no problems.  But last short drive It had been stalling on me for some reason so I let it warm up in the garage to observe.  After 5-10 minutes the idle descended as it should but kept going until it just stalled out.  Tried to start again to no avail so I just left it to come back to the next morning.  Next morning I went back to storage with the idea of cranking her up and driving 5 minutes to my house - ran well, drove home and right before the driveway she died and coasted into the drive (whew).  I got out, raised the hood, shot in some starting fluid, engaged the pedal/ignition and got nothing at all.  It was like the switch was off.  Let cool down 20 minutes and it cranked up enough to get all the way in the drive but now it runs really rough.  Any ideas?

 

It has had a carb rebuild by a pro, new plugs and wires, points, condenser, good tested voltage regulator, tested generator;  The fuel filter at tank I added is clear, fuel filter bowl at carb is clean and shows gas flow, fuel should be no more than three weeks old.

 

It does have the original wiring harness but the generator, voltage regulator wires are testing good for continuity and not shorting. 

 

It does have a leak around the next to rear exhaust manifold port and a crack in the center section of the exhaust manifold.  And some of the nuts were loose.  I tightened them up this morning,  started and it still ran rough, shot starting fluid on the intake manifold ports while idling (roughly) and heard no difference in idle so I don't think there is an intake leak but I may be wrong.  I am going to loosen the manifold nuts and re-torque tomorrow if the weather holds.

 

Any ideas, thoughts besides tow it to a good shop?  Magic tricks? 

Edited April 29, 2017 by Dan O (see edit history)

[Aaron65]

The first two things I'd check: 1. Points...make sure they're still gapped correctly and they're clean.  My '53 all of a sudden didn't start one day after running fine the previous day because the points were slightly corroded.  Sitting over the winter can cause them to form a thin film of corrosion that a piece of emery paper will clean.  2. Idle passages...pull out the idle mixture screws (noting how many turns out they are first) and spray some carb cleaner in there.  If you have access to an air compressor, blow out the passages.

 

Report back after that!   

 

Of course, the fact that it sometimes runs well cold and not hot could be any number of things, but I always start with the easiest stuff and work my way up.

[JohnO]

It sounds more like gas than electrical. In my experience electrical problems result in a sharp miss or immediate stall with no in between. It does not hurt to have a spare carburetor. Even though they are usually reliable, I've had driveability issues on my 58 and 61 which I attributed to carburation. Both had Rochester 4GCs. I found some Carters on ebay and had success. Since you replaced the ignition system components it is unlikely that the problem resides there.

[JohnD1956]

Sounds like a coil issue to me.  Check the wires going from the coil to the distributor, and the wires inside the distributor, in case the insulation on them has crumbled and broken away, causing the wire to ground out.

[Roadmaster75]

Quick kill.......

replace condenser.

 

have had 2 fail out of the box over the years.

if you have a known good one....try it.

falied condensers can exhibit the intermittent symptoms you

are having.

 

[NTX5467]

This might sound different, but use a digital meter and check the voltage between the battery and various parts of the engine/body.  Both cold and when it stalls (checking immediately after it stalls and you're in a safe place.

 

Here's what I had once on my '77 Camaro.  For no apparent reason, at a stop light, for example, I'd notice the engine rpm start to drop gradually.  I could usually pump the gas to get it back.  Other times, I'd hear the radio make a "motorboat" sound when this happened, after which it lost its station memory.  Other times, after sitting a while, when trying to restart, "nothing", until it had cooled off to "cold", at which time it would start normally.

 

I traced and checked everything I could think to check.  Ignition switch, neutral safety switch, everything.  I began to notice that one day on the way to home for lunch, the a/c fan stopped working and the radio quit.  When I got home, I got the meter and checked voltages.  What I found was a 1/2 volt loss in checking voltages between the battery and various body/engine points.  Then, as I was doing thing, the fan relay clicked and what wasn't working, began working again, AND the voltage loss disappeared.

 

I'd already cleaned the battery terminals and there were not acid leaks at these terminals.  The cables looked good too, as they were the originals with no outer signs if issues.  Replacing the ground cable fixed it, although it looked fine on the outside.

 

Another neglected area is the bulkhead connector on the firewall.  On another car, how well the terminals contact on both sides of it are important, as that's where the ignition switch feed comes through.  After years, gunk can accumulate unseen . . . out of sight, out of mind  . . . which can limit amps and not voltage.

 

On the same car, after I put an electronic ignition on it, I did five starts to check it.  On the fifth attempt, nothing.  Voltage was "everywhere", but not start.  I didn't worry about the battery terminals as they looked good, but further investigation found the edges of a thin layer of corrosion between the terminal and the post.  Didn't look bad, but when I removed the terminal, it was worse than suspected.  I found a wire brush for battery terminals I'd won at a road rally years before and chunked into my tool box.  Cleaned the terminal and battery post and end of that problem.

 

One other thing, when the engine dies, you're using starting fluid to restart it, BUT how does the accel pump shot in the carb look when it stops like that?  When I got my '68 5467, it ran decently good, but for good measure, I changed the plugs and plug wires and adjusted the carb better.  Even so, after about 20 minutes of run time, whether idling or driving, it would start to die out, usually, I could start rapidly pumping the accel pedal (while running or after it died) to get it back.  Sometimes, I'd end up coasting to the side of the road, getting it restarted, but it wouldn't idle well, so I found out how solidly the THM400 engaged a little above fast idle!  I did manage to get it to my shop and parked it that night.  Later, I discovered that the cigarette lighter socked didn't work with my old bag phone!

 

I had noticed that the prior owner had sliced the fuel line between the carb and fuel pump.  As I'd already done the ignition stuff, I ordered a fuel pump.  I also determined why there were TWO type of bolts that held the fuel pump (different from back hole to front hole!).  A new fuel pump and it sounded stronger than ever.

 

Sorry for the length, but sometimes ignition issues can act like fuel issues, and vice versa.  More things to check.

 

NTX5467

Edited April 30, 2017 by NTX5467 (see edit history)

[old-tank]

 If starting fluid will not work, then I suspect it is electrical (points,condenser, coil).  Check for spark and fuel when in the no run or no start situation.  

[Ben Bruce aka First Born]

LISTEN TO WILLIE AND WILLIS!

 

  Ben

[Dan O]

Gentlemen - THANKS for all your generous input!

 

This morning I: cleaned the points, checked the gap, checked integrity of all wires from the new coil to the distributor as well as inside, plus the plug wires.  Cranked it up with three pumps of the gas pedal and she cranked up.  That's what she usually does when cold.  Idled smoothly as my hopes rose then started running rough again.  I can keep it running if I keep the gas coming at high idle and goose it around when needed.  Crap.  So, I closed the hood and went around to open it from the other side where I cleaned the idle adjustment screw passages and replaced with the same settings as before.  I also tightened all the carb screws as I see it's been leaking when running.  This has a new Bob's Automobilia kit put in by a pro mechanic.  I then restart and get the same results as before.  BUT I can watch the carb better from driver's side and notice as she starts to stall out, gasoline starts pushing out from the gasket between the air horn and the bowl cover.  It pushes/seeps out so much it runs off the bowl cover and down the sides.  I killed it, checked the screws (all tight) and tried starting again and watched gasoline come out of the gasket as well as the pivot hole. 

 

I think the carb needs to go back to the mechanic at this point myself as I am not any kind of a carb mechanic.  Any ideas on the cause of the gas gush?  Is this my problem?  No one has commented on the intake manifold leak idea.

 

Here's a video attached with sound of the final crank up!

 

 

IMG_8130.MOV

Edited April 30, 2017 by Dan O (see edit history)

[Aaron65]

If the carburetor is overflowing, then you have a problem with the needle in seat in the carburetor OR an improper float level setting.  You can lightly tap the top of the carb when it starts doing this with a small rubber or plastic hammer, or the plastic handle of a screwdriver to see if the needle and seat will unstick.  Do NOT hit the carburetor hard.  Tap on the float bowl.  Most likely, however, the carb will need to come apart again.  At this point, I would also be doing a fuel pressure check to see how much pressure my fuel pump was producing.

 

 

[Dan O]

Knocked it around prior to starting.  No change.  Tapped it more all around while running.  No change.  Back to the mechanic tomorrow.  I hate old cars sometimes.

[carbking]

Dan - reference your post #9.

 

The issue is that the float is not shutting off fuel to the carburetor. WHY?

 

Possible causes:

 

(1) dirt under fuel valve (not probable, as you have tapped on the carburetor)

(2) incorrect orifice fuel valve

(3) defective fuel valve

(4) defective float

(5) incorrect float setting

(6) too much fuel pressure

 

I would check number (6) above first, especially if you have put on either a new mechanical or an electric fuel pump recently. I have tested some of the newer, made on the opposite side of the planet and boxed in American boxes fuel pumps that put out as much as 18 psi. Your carburetor probably would be very happy with 4 psi. If the fuel pressure is not too high, then I would disassemble the carburetor.

 

Jon.

[Beemon]

Dan, if it's just the float or needle and seat, you can probably do that yourself by taking the top off the carb and checking float drop, rest and needle and seat. If your mechanic didn't get it right the first time, I doubt he will the second time.

[avgwarhawk]

For me, since the carb was working fine three weeks prior,   I would pull the carb and clean what I could with carb cleaner.  It is probably some dirt found it's way in.   Do your best to drain what gas is in the bowl in hopes to remove the offending particle.  Install again and test.      

[Joseph P. Indusi]

I use carburetor cleaner in the spray can instead of starting fluid whenever I have to start a car that has not been run for a month or so.   I have been told that starting fluid can, if overused or in certain engines,  can cause mechanical damage.   This is pretty powerful stuff!

Joe, BCA 33493

[NTX5467]

Might it be possible that IF the fuel pump has too much pressure, it would have enough pressure/flow to clean the gunk from the needle and seat too? 

 

A Holley rep once said that the fuel pump will do max flow when unrestricted by the needle and seat valve.  If, perhaps, the car sat long enough once for the float to drop (not a full float bowl), that initial max flow dislodged something in the fuel line that got hung up at the needle and seat, then it wouldn't seal enough to prevent flooding?

 

Over the years, the brass "seat" castings were off-center but machined correctly . . . quality control issues, but worked fine as everything indexed when assembled.  Just the hole in the seat was not centered.

 

At this point in time, a new air horn/float bowl gasket is needed as the present one will continue to wick fuel through it, I suspect.  That means partial disassembly for a new gasket and needle/seat/float inspection.  Whatever was caught by the needle/seat or went through it should be still stuck in the needle or in the bottom of the float bowl.

 

Please keep us posted.

NTX5467

[buick man]

… some thoughts here … If you are running corn-a-hol this as all know, will erode your non brass components be it float, jets, seats and valves in the carb etc and it will eat up components in the both the filter and fuel pump if those components even if the gaskets, rubbers etc are supposedly ethanol resistant.  Also remember that the spec float setting in the carb is calibrated as stated in the manual for Real Gas ( R-CH3) and not alcohol ( R-OH) which has very different coefficients in regards to temperature operative ranges, water vapor, air density to fuel ratio etc… all of which will effect that float OEM back in the day, setting spec so when rebuilding the carb and setting the float take this into consideration which usually results in an increase float drop.  Also since R-OH needs more atmosphere and is more dense then R-CH3 Gas, increasing the orifice size of jetting and recurving your distributor can solve many problems caused by R-OH fuels … oh, and we would recommend contacting Daytona Carbs and get a proper set of bullet proof gaskets and also check to see if the matting surfaces of the carb horn to the fuel bowl is completely flat and true not warped as this can be caused by repetitive over torque conditions thus causing a leaking condition regardless of the amount of gorilla tightening one applies ….

[Dan O]

Update - I checked the fuel pressure thru the glass bowl filter and it is 3.75psi so that is ok.  My carb rebuilder opened it up again to check his work and found no foreign particles in the carburetor and settings to specs..  He also says he pressured it up to 6psi with an electric pump and did not see any leakage so I will put it back on and see what happens.  This is a new kit put on  in the last two months and a low mileage car (believe it or not).  The mechanic has a good reputation for rebuilding early engines - that's his specialty and all does in his shop but he could be overlooking something.  I want to see what the leak does after the carb goes back on.  He has offered to look at the whole car if I tow it across Houston to him.

Edited May 2, 2017 by Dan O (see edit history)

[avgwarhawk]

Since the carb checked out ok start looking for a potential a vacuum leak.  Sometimes a vacuum leak will pull gas from the bowl(dripping).  I have seen this with Holley carbs on Chrysler products.  I have seen this with a bent valve in another vehicle. On this vehicle I was chasing down the carb as the issue.  Gas was dripping down the throat.  Replaced carb. Same result.  Compression test done.  Found bent valve.        

Edited May 2, 2017 by avgwarhawk (see edit history)

[old-tank]

Maybe all it needs is a new fill up with the currently available summer blend fuel.  If it still has fuel from a few months ago (boils at only 100* F) it may be boiling (percolating) in the carburetor and then slobbering down the throat and out the sides.

[Beemon]

Buickman, my car has only ever seen ethanol fuel and I have never had issue with using the original float setting. What I've found out is that the Ethanol will creep up the sides of the bowl, for whatever reason, and just wick through the gasket. That, and also sink lead plugs on 4GCs....

[NTX5467]

One of our late chapter members mentioned the lead plug issue several years ago.  Even helped put out a fire on a '55 Cadillac that had just pulled into a weekend cruise venue, from the lead plug falling out and raw fuel on the intake manifold.  It's the seal solder that is degraded by the ethanol in the fuels.  The plug can then move around in its seat and then degrade or fall out.

 

We've had ethanol in gasoline since the first Reforumuated Gasoline about 20 years ago, and the "high altitude" gasoline in the Denver, CO area.  Even back then, there were mentions of the "new fuel" not working well in some engines.  Ethanol was an octane enhancer, typically, but was at about 50-50 in the approx. 10% oxygenate when MTBE was being used with it.  Now, we have up to 10% ethanol, unless some regional stations sell higher blend levels . . . as other regional chains have E0 fuels.

 

With time, even the older leaded fuels of the 1960s would wick through bowl gaskets (as evidenced by the accumulation on the exposed edges of those gaskets), but never a leak-through situation.

 

The casting warpage issue is a valid point, from my own experiences, but I haven't found that on the outside edges, myself.  In tightening carb bolts, no matter which castings are involved, I ALWAYS use the circular or diagonal bolt torque sequence in several torque levels.  Locate/snug to a little tighter when pleased with the positionings of the gaskets, then the final torque.  SAME with the carb-to-manifold retainers!  AND, or course, only just enough wing nut torque to snug things up . . . and NO more than that, which keeps the airhorn from warping upward in the air cleaner stud area, from experience.

 

Please keep us posted . . .

NTX5467

 

 

[Dan O]

I got the carb back on the car after acquiring a new glass fuel filter bowl from Bob's -  I dropped mine.  So, I ran fuel into the line and carb with my handy dandy electric priming pump, gave it a crank, wouldn't go right away, so I shot in some starting fluid and she started running.  Smoothly!  Turned it off after a five minutes and she cranked back up with no problem.  I repeated that as I messed with the filter bowl drips and she kept firing up and running smooth.  Did not need to depress the throttle first even.  The carb no longer overflows.  Runs at slow idle and sounds great.

 

Now I see the problem all along - needed a new glass filter bowl!!  (That's a joke).   The mechanic had said he saw no debris in the carb and all settings were fine.  Perhaps it was something small he did not see and it's gone.  Perhaps it will strike again after a short drive.  I have not had time to venture out.

 

Tomorrow is the Keels & Wheels boat and car show in Houston.  It is a really fine show and not to be missed so it will be a great day and old car driving will have to wait until Sunday.

 

Thanks for all the tips and discussion!

[avgwarhawk]

Sometimes we overanalyze the simplest of issue and resolution. Glad she is running again.