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25 Buick fuel problems


carmover
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There are several items to consider concerning the amount of fuel pressure the carburetor will handle:

 

(1) Orifice of the fuel valve seat

(2) Effective pressure exerted by the float

(2A) Buoyancy of the float (material, and fuel volume displaced)

(2B) Mechanical advantage of the float (position of float arm, and type of float fulcrum).

 

While we have brass floats available for the early Marvels, the brass float does virtually nothing for buoyance (maybe a few percent). The brass float does have much better reliability than the original cork or the modern polynitraphyll (sp) closed cellular foam. Since the fulcrum position and style are unchanged, the float will exert only marginally more pressure.

 

Even if you are using the brass float, and have significantly reduced the fuel orifice; being from Missouri, I would have to be shown that this carburetor is capable of 3 psi, because of the fulcrum design and placement. However, not certain this is all of your problem.

 

As mentioned by others in this thread, ignition systems are less reliable than carburetors (even Marvel carburetors ;) )

 

Generally, a carburetor has very little personality. It will behave the same under similar conditions. The fact that the engine will idle, sometimes run, and then act weird to me indicates ignition issues. If the ignition is insufficient to fire the available fuel, then the plugs will be sooty just as if the carburetor was malfunctioning.

 

Unsure what tools you may have available to you. Readings from a clamp-on volt-meter on the plug wires when the engine is behaving, compared to when it is misbehaving would be interesting.

 

But just because some of us feel your coil may be suspect is not a REASON to change it! Ignition systems CAN be tested. Find a local friend or shop with an older Sun or Allen diagnostic oscilloscope (and knows how to use it) to hook up to the engine.

 

Jon

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3 hours ago, carbking said:

There are several items to consider concerning the amount of fuel pressure the carburetor will handle:

 

(1) Orifice of the fuel valve seat

(2) Effective pressure exerted by the float

(2A) Buoyancy of the float (material, and fuel volume displaced)

(2B) Mechanical advantage of the float (position of float arm, and type of float fulcrum).

 

While we have brass floats available for the early Marvels, the brass float does virtually nothing for buoyance (maybe a few percent). The brass float does have much better reliability than the original cork or the modern polynitraphyll (sp) closed cellular foam. Since the fulcrum position and style are unchanged, the float will exert only marginally more pressure.

 

Even if you are using the brass float, and have significantly reduced the fuel orifice; being from Missouri, I would have to be shown that this carburetor is capable of 3 psi, because of the fulcrum design and placement. However, not certain this is all of your problem.

 

As mentioned by others in this thread, ignition systems are less reliable than carburetors (even Marvel carburetors ;) )

 

Generally, a carburetor has very little personality. It will behave the same under similar conditions. The fact that the engine will idle, sometimes run, and then act weird to me indicates ignition issues. If the ignition is insufficient to fire the available fuel, then the plugs will be sooty just as if the carburetor was malfunctioning.

 

Unsure what tools you may have available to you. Readings from a clamp-on volt-meter on the plug wires when the engine is behaving, compared to when it is misbehaving would be interesting.

 

But just because some of us feel your coil may be suspect is not a REASON to change it! Ignition systems CAN be tested. Find a local friend or shop with an older Sun or Allen diagnostic oscilloscope (and knows how to use it) to hook up to the engine.

 

Jon

Jon,when I originally contacted Jeff Drybus [The old carb Doc] He asked if I was going to use the original vacuum tank or an electric pump.I told him that many had said that the marvel carb could not work with an electric pump and he assured me that he could modify the carb to handle the pressure.When I got the carb back and installed it and the new electric pump and regulator and filter and set the pressure at around 1 pound the engine cranked right up and ran perfectly.I could now finally enjoy driving the car any where I wanted to.It ran perfectly for years until I had to rebuild the engine.For several months the fuel system set dormant and the carb was on a shelf.Now the engine has been completely rebuilt and  all of the ignition system is brand new except the coil.As I have said before I can actually see it flooding and the engine cranks and runs perfectly as long as the fuel level is right but starts to run bad when the fuel starts covering up the float.I have tested the spark while this is going on and it still has a strong spark.I put a guage on the regulator last night and it is backed all the way out and is still registering nearly three pounds.It used to easily set to 1 pound so I think that is my problem.

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1 psi I can easily believe; really had an issue believing 3.

 

I think you have now found your problem.

 

I brought up the oscilloscope because of the 3 psi. I inferred from your post that the carb would stand 3. Wasn't convinced, but also didn't wish to argue. So the next logical place was voltage.

 

I am a firm believer in testing.

 

There are some incredibly knowledgeable helpful folks here that will try to help; but all of us are trying to "diagnose an upset stomach by telephone!". The more testing information which is provided helps reduce the number of possibilities.

 

Happy that you found the regulator issue. Enjoy that Buick!

 

Jon.

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Ronnie,

I am kinda disappointed that you still want to have an electric pump in your car's fuel system.  I have had good luck with the simple vacuum system on several cars over a 45 year period.  If one gets everything set right they will run great.  You have to do what you feel is best for you.  We will wish you good luck with this Buick.

 

Terry Wiegand

South Hutchinson, Kansas

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Terry ,If you want to use the Vacuum Tank in your cars and it works for you then it is fine! As for me I struggled with the tank for years and spent a lot of money on it and could never get it to shut off.When I put the electric pump set up on it I drove the car 45 miles up and down hills and it never gave any problems and never flooded and you didn't have to open the hood and turn off the fuel supply every time you stopped.Up until I up graded it I drove the car 4 miles in 12 years.This 25 Buick has been nothing but trouble since I bought it But the electric pump gave me some enjoyment for a while.I do not have any patients left for that vacuum canister any more! If this doesn't fix it I am going to put it in my warehouse and rope it off and it will be a piece of stationary art untill they put me in the ground!

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On 5/31/2018 at 12:52 AM, Tinindian said:

Patience, patience, patience.

I have stayed away long enough from the 25 Buick to calm down and gathered enough patience to take another look at it .I removed the carb and cleaned it and blew out all of the ports.There was some trash in the fuel bowl under the seat.I also found that the needle was not attatched to the float arm which was likely why the fuel wasn't shutting off.I also cleaned the regulator and readjusted it also.When I turned on the switch the carb filled right up and shut off like it is supposed to.The engine cranked right up but started running like crap.I have the plugs gapped at 040 like everyone on this site was doing years ago.I have a set of Bob's plug wires that are pretty discolored and are possibly oil soaked.I also noticed a small chip on the dist cap close to where the hold down clip snaps on.Points are properly gapped and seam to have decent spark.I am thinking of ordering all of the ignition parts replacing everything new.

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6 minutes ago, Fred Rawling said:

If the portable tank indicates it is not the fuel feed, I would change the condenser and if the problem still persists, buy a new coil and try that.

Fred, I am thinking the same thing,The coil and condenser have never been replaced and as I said before the plug wire set and cap got pretty oily while I was running the engine with the valve cover off adjusting valves.I cleaned the cap but the wires appear to be oily and discolored.I am using Bob's yellow wires.The cap has a small chip on the lower edge not close to the firing parts.It won't stay running long enough to check and see if it is arking fire around the cap or wires.

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If the portable tank indicates it is not the fuel feed, I would change the condenser and if the problem still persists, buy a new coil and try that.  

 

One of the BCA members near me uses a 1972 El Camino condenser in his 1923 6 cyl. .  he says he has no problems.   That may bve a good place to start for ease of finding a replacement.

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A crude but easy way to check for "leaky" plug wires is to start engine in total darkness and move plug wires around with an insulated object. I have done this numerous times to help locate voltage loss in ignition wires and caps.

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2 minutes ago, raydurr said:

A crude but easy way to check for "leaky" plug wires is to start engine in total darkness and move plug wires around with an insulated object. I have done this numerous times to help locate voltage loss in ignition wires and caps.

Two weeks ago I found a similar method in broad daylight while trying to diagnose a miss under load (OK at idle) in a 1919 Pierce dual ignition with old wires.  I attached a modern inductive timing light, powered by a 12V small sealed battery used for GPS, first just above the distributor cap towers and then near the spark plug terminals.  Near the cap, at idle, the idle noticeably slowed upon connection.  In this Dual Delco system, there are two 6-cyl caps, one with wires to the right side plugs, the other to the left.  Not surprisingly, the cap and wiring tray (insulated metal loom) closer to the exhaust manifold had the worse results.

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2 hours ago, Grimy said:

Two weeks ago I found a similar method in broad daylight while trying to diagnose a miss under load (OK at idle) in a 1919 Pierce dual ignition with old wires.  I attached a modern inductive timing light, powered by a 12V small sealed battery used for GPS, first just above the distributor cap towers and then near the spark plug terminals.  Near the cap, at idle, the idle noticeably slowed upon connection.  In this Dual Delco system, there are two 6-cyl caps, one with wires to the right side plugs, the other to the left.  Not surprisingly, the cap and wiring tray (insulated metal loom) closer to the exhaust manifold had the worse results.

 

Do you mean it slowed down when you put the inductive pickup on?

 

I could really use a battery powered timing light that doesn't freak out and lock up every time it encounters a prewar car with solid wires. What is it? Does it have dialback?

 

 

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43 minutes ago, Bloo said:

Do you mean it slowed down when you put the inductive pickup on?

 

I could really use a battery powered timing light that doesn't freak out and lock up every time it encounters a prewar car with solid wires. What is it? Does it have dialback?

Bloo, this is a late-1970s Craftsman inductive timing light with a plastic body. I've had issues with the metal-bodied light on older cars.  When the inductive pickup was attached just above the cap towers (to see if there was a steady spark being sent to the plugs), the idle faltered--not a dead short of that cylinder, and an irregular strobe resulted.  This was a hotel parking lot diagnosis on a 5-day tour based out of Sequim (generally your neck of the woods).  The intermittent short effect was minimal at the far end of the wires near the plugs, BUT this was a no-load test.  The owner is attending to replacing the plug wires before the Pierce-Arrow Society annual meet in Rohnert Park CA next month.

 

This light does NOT have dialback.  I'd used it on my 1930 roadster a week before in the same manner while diagnosing an occasional miss at idle.  In that case, one spark plug was at fault.

 

The 1919 Pierce in question had recently been acquired by a WA collector from a static collection, and the plug wires were decades old, smaller than 7 mm, and although not visibly broken were dried out in their high-heat location below the exhaust manifold.

 

I get a lot of use out of about three sealed 12V batteries which were designed as backup batteries for home alarms and for gate openers.  I run an 11-year old Garmin GPS off such a battery, connected by a Radio Shack cigar lighter intended to be connected directly to a 12V battery.  I cut off the alligator clips and soldered on female push-on connectors to fit the male push-on connectors on the battery.  The battery rides on the floor in a plastic Folger's coffee can.  This set-up is easily moved from car to car, and feeds the GPS for about five days without a recharge.  I prefer using my Sun 820 machine but (1) its timing light is not inductive, and (2) it's anything but portable. 

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5 hours ago, Grimy said:

Two weeks ago I found a similar method in broad daylight while trying to diagnose a miss under load (OK at idle) in a 1919 Pierce dual ignition with old wires.  I attached a modern inductive timing light, powered by a 12V small sealed battery used for GPS, first just above the distributor cap towers and then near the spark plug terminals.  Near the cap, at idle, the idle noticeably slowed upon connection.  In this Dual Delco system, there are two 6-cyl caps, one with wires to the right side plugs, the other to the left.  Not surprisingly, the cap and wiring tray (insulated metal loom) closer to the exhaust manifold had the worse results.

I checked it tonight in total darkness and it is jumping fire around the distributor cap.It is a pretty strong ark.I didn't see any arking around the plug wires.I am going to put my old cap back on and see what it does tomorrow..It looks like it may be arking where the chip is on the cap.

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Next time you do a darkness test , be sure to watch for arc where the wire come into contact with each other. The arc is hard to catch without separating and moving the wires around while running. Also remember plug wire covers can cause problems once installed. Good luck.

Edited by raydurr (see edit history)
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