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DEEPNHOCK
03-29-2006, 07:13 PM
You might try your load test again with the gas cap loose.
Just a thought...
Jeff[8D]

LarkMark
03-29-2006, 07:44 PM
My '63 Lark has been driven a lot lately. It had some oil burning issues, but they seem to be getting better as time goes by. I recently installed an overdrive transmission that vastly improved the car. I've driven several hundred miles with little trouble. The other day, I decided to try the car out on the Interstate. The Lark was working great! I was blasting along at 65 to 70 MPH without any trouble for about ten miles. But then I came to a hill (not the first hill on the trip). It wasn't much of a grade, but it did slow the big trucks down. The Lark is only a 6 cylinder, but I thought it was doing OK. After a couple of minutes on this hill, pushing it pretty hard, the engine suddenly lost some power and starting backfiring out the carb. When I backed off the throttle, it stopped popping and ran well. If I pushed the throttle beyond a certain point, it started backfiring again. I had to slow down to 50 MPH and it was fine at that speed. I figured this was symptoms of fuel starvation due to a plugged fuel filter. I drove home, but at reduced speed.

When I got home, I tried to figure out the problem. The fuel pump is new. When I took the filter off, I was able to blow air through it (easily). When I tried blowing on the gas line back to the gas tank, I heard the air bubbling in the gas tank (eventually). There seems to be pressure at the carb and the fuel flow seemed OK when I took the gas line off and pumped gas into a pop bottle. This didn't necessarily rule out fuel line problems, because maybe there is a pin hole and it's sucking air into the line someplace (though I can't smell gasoline leaking anywhere.). So I really didn't see a problem with the fuel lines.
If I take the car and accelerate quickly in first gear at full throttle, it revs up just fine and has good power. It'll get past 4000 RPM no problem. As soon as it's been at full throttle for more than a few seconds, however, (like in second or third gear) it starts backfiring (like it's running out of fuel). I don't hear any tapping noises that would suggest a stuck intake vavle. Are there any other possibilities besides fuel delivery problems that would cause this. What about a leaking head gasket, for instance, or the dreaded OHV 6 head cracking problem??

Where do these OHV 6 heads crack anyway?

Thanks
LarkMark

MARC
Punxsutawney, PA

ROADRACELARK
03-29-2006, 08:14 PM
If you haven't already, check/replace the ignition points and condensor. Make sure the point gap is set to specs. Also make sure the vacuum advance unit is working.
Dan Miller

whacker
03-29-2006, 11:55 PM
I agree with ROADRACELARK. Backfire is usually caused by timing problems. Check your vacuum advance and your distributor weights. Also check the vacuum line going to the vacuum advance. Try a new set of points. It can also be a problem with spark plug wires, but that would most likely occur at all speeds. You might also take a look at the coil, see if there are any cracks, or if it is overheating.

curt
03-30-2006, 08:52 AM
The slow down at full gas feed or there about sounds like an intermitent pulg on the inlet inside the tank or a fuel starvation. The backfire sounds electrical. Good luck.

jcarmichael
03-30-2006, 12:49 PM
I found that the metal cable that operates the heater control valve was shorting out the kick down switch on my overdrive when I was at full throttle. Of course I found that out after replacing my complete ignition system.

1961 Lark

curt
03-30-2006, 05:46 PM
Are these cars 4000rpm engines? That seems to be the upper end. What is the "red line"?

GTtim
03-31-2006, 10:37 PM
I'll bet on a fuel supply issue. Crud in the tank, soft rubber hose collapsing, bad new fuel pump, pinhole in the fuel line, plugged tank vent tube. Take the gas cap off and see if still happens.

Tim K.
'64 R2 GT Hawk

LarkMark
03-31-2006, 11:46 PM
I still haven't figured it out, but then I haven't had much time off to look at it. I did discover that the wire to the condensor in the distributor was hitting the rotor. I fixed that, but the problem remains. It runs fine for 5 seconds or so, and then it losses power and starts to backfire. You have to be pushing it pretty hard for it to happen at all. I'm thinking it's fuel supply, though I can't figure out why. I didn't think of soft hose collapsing; I'll check that out. I once had a new defective fuel pump in my Chrysler that quit completely in 500 miles, so I'll check that out. I do think the tank is venting OK, and I believe it happens too quick for it to be that. I set the points, and checked the vacuum advance and the timing is at the same place it was before (slightly advanced from the mark. I checked the spark plug gap (set at .030). I purchased a clear fuel filter to check the fuel for bubbles coming through the line, but I haven't had time to install that yet. Maybe tomorrow I can find a few minutes to work on it,
Thanks for the suggestions!
LarkMark

MARC
Punxsutawney, PA

Roscomacaw
04-01-2006, 10:30 AM
DEEPNHOCK gave you a clue earlier that might be worth checking out. This could be a symptom of improper venting of the gas tank. When you reach a point where the fuel pump is drawing fuel faster than the hampered venting of the tank can allow for, a vacuum develops in the tank and the pump can't draw enough to meet demands. A starving engine is likely to backfire as it starts to run too lean.
Try duplicating your malady with the gas cap removed one time.:D
This can happen due to an improper cap OR the venting line of the tank. You noted that this started on a slight hill. This would send the gas in the tank rearward to where it would cover the vent line I would think. Either way - easy to check out.;) We've seen this sorta problem before, so it's not just wild speculation.

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

LarkMark
04-02-2006, 10:43 PM
On my old Chryslers, the fuel filter is located between the fuel pump and the carb. On the Studebaker, it is in the line between the pump and the gas tank. Is this the normal place? I would think that it would be harder to suck the gas through the filter than to push it through.

LarkMark

MARC
Punxsutawney, PA

Roscomacaw
04-03-2006, 03:21 AM
Not true. Probably better to have it there as it protects the fuel pump's valves from being put out of action by a piece of crud.;)

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

LarkMark
04-03-2006, 07:42 AM
Somebody just told me that the fuel tank vent plugged in his Camaro. He said there was a bang and soon after, the engine shut off. The vacuum in the tank had crushed the tank flat!! So, I guess there's plenty of suction to bring fuel through a fuel filter!

I changed the filter to a clear filter to see what the fuel flow is like. I don't see any bubbles coming through that would indicate a leak. I didn't get a chance to drive it yet, however.

I took the fuel line off the carb and ran fuel into a container for about 8 seconds (at normal idle). I got over a cup of gasoline. The flow of fuel appeared to be good.

Checking the fuel line from the tank, I see somebody has replaced about 2/3 of it with rubber hose. I think I'll buy some metal line and some new rubber hose and replace the entire fuel line.

The other unknown, is the inlet in the carb. Maybe the fuel float valve is dirty and semi-plugged. It's a rebuilt Carter carb that is on the car.

MARC
Punxsutawney, PA

Roscomacaw
04-03-2006, 11:29 AM
Have you TRIED driving it with the gas cap loose yet?????????[?] Don't do it with a full tank of gas. If you charge up a hill, a full tank might slosh out the open filler neck.[:0]

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

N8N
04-03-2006, 01:17 PM
reminds me of a similar problem I had with my Daytona... what the problem ended up being was a small, hard, red cloth-like piece of something that was just big enough to get sucked up against the pickup in the tank. I fixed just about everything else on that car before I checked the tank, because I'd just cleaned the tank maybe 6 mos. earlier!

I still have no idea what it was or how it got in there, but there it was, and once I got it out of there and cleaned the inside of the tank again the car ran fine.

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel

Roscomacaw
04-03-2006, 01:26 PM
Boy, that tale brought back a memory I hadn't recalled is some time, Nate.[B)] I had a Stude some time ago (don't remember which one it was even!) that was giving me fits with it's unpredictable stalling.
Turned out there was a whole shop rag floating around in the damned gas tank. You might drive for some miles before it would get sucked against the pickup tube - and then you might not make it out of the driveway:(.
All I could figure was someone had used the rag as a temporary gas cap at one time or another and it either got sucked into the tank or someone pushed it in in a moment of devilry.[}:)]

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

55pres
04-03-2006, 09:14 PM
You don't think the problem could be a weak valve spring?

1955 President

Location: Central PA
Job: Student @ Penn State
Love of Studebakers?: High

Chicken Hawk
04-03-2006, 10:20 PM
You have had all kinds of suggestions so I'll throw in another one. Check the distributor wires inside the cap. It has been known to have a bare wire that would short out as the distributor advances and/or retards. Since it would be retarding as you start up a hill (or depress the accelerator)this is a possibility.

Ted

Lark Parker
04-03-2006, 10:33 PM
Had a 48 Champ once that would not rev past a certain point. The throttle linkage was pushing the coil wire out of the top of the coil. When the accelerator was let up, the wire would spring back and make contact again.

LarkMark
04-04-2006, 08:53 PM
I'm still trying to figure out the problem. It runs fine for about 8 seconds at full throttle ...and then it looses power and starts backfiring. I put a clear plastic fuel filter in the line. I think I got a clue when I saw a bubble come thru the line. There was more air in the filter after I ran around town than there was before I started. It very well could be a pin hole somewhere between the pump and the tank. It all looks like it should be replaced anyway, so that's the next project. Unfortunately, I might not have a day off to get the supplies and do the job for about three weeks .....so until then, I'll just have to drive around town.
LarkMark

MARC
Punxsutawney, PA

studebakerkid
04-05-2006, 04:21 AM
Once you get all the things looked at and still cant find what it wrong it may be simply that you dont have enough of an ignition system to fire of what is passing for gasoline these days. My 65 was driving me nuts about a year back and I went through everthing and it still was starving out When I got up around seventy and tried to pull a hill. Turns out that I had two problems. THem Carbs on the 6 cyllinder Chevy bakers have a vaccume plug in the carb that can fall out and when that happens you dont have much venturi vaccum. THat will not be your problem but the other could be. I installed a Pertronix unit inside the distributor and wow what a change. The old girl drives like she used to a hundred thousand miles ago....

If you car is ugly then it better be fast.....

65 2dr sedan
64 2dr sedan (Pinkie)
61 V8 Tcab
61 Tcab 20R powered
54 Champion Wagon