Baffling engine problem - looking for advice

jhjacobs

jhjacobs

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My baby, Amelie, made it through the winter with a few "nice day" drives. She is running perfectly: smooth idle, full performance and generally no major issues. However, if she sits for a day or two she doesn't want to start without cranking the engine over for about 10 seconds. If she is warm or only sits for a few hours she starts immediately. The other symptom is white smoke that come out for about 2-4 minutes of running if she was totally cold or for about 1 minute if a bit warm; after this the smoke is gone. She isn't losing oil or antifreeze and the run temperature is spot on. I also haven't noticed anything funny with reduced mileage either.

I decided the likely cause was that the carburetors are leaking the float bowl fuel slowly into the intake manifolds. This afternoon I decided to pull the air cleaner assembly to look at the carbs (webers) to take a peak. What I saw was excessing oil blow-by from the PCV valve cover feed - the top of the forward carb had a layer of oil film all over the top. I pulled the plugs and they are all text book - dry and pinkish grey.

So anyone seen this before? I am still thinking my initial guess about carbs may be right. If fuel is running leaking out of the float bowls it would drip down the manifolds into the cylinders and then leak down into the oil a bit. As the engine runs it would vaporize and create excess vapor pressure in the crank case and that which stayed in the cylinders would burn extra rich and produce smoke. What I can't figure is why it needs to crank for so long to start when several days cold. I figured it needed to run the mechanical fuel pump a bit to recharge the carbs; if this is the case then both carbs are probably doing the same thing and this seems unlikely (if it is a failure mechanism). If only one carb leaked then half the cylinders should catch and it should start and run badly for a bit...

Stumped,
 
My baby, Amelie, made it through the winter with a few "nice day" drives. She is running perfectly: smooth idle, full performance and generally no major issues. However, if she sits for a day or two she doesn't want to start without cranking the engine over for about 10 seconds. If she is warm or only sits for a few hours she starts immediately. The other symptom is white smoke that come out for about 2-4 minutes of running if she was totally cold or for about 1 minute if a bit warm; after this the smoke is gone. She isn't losing oil or antifreeze and the run temperature is spot on. I also haven't noticed anything funny with reduced mileage either.

I decided the likely cause was that the carburetors are leaking the float bowl fuel slowly into the intake manifolds. This afternoon I decided to pull the air cleaner assembly to look at the carbs (webers) to take a peak. What I saw was excessing oil blow-by from the PCV valve cover feed - the top of the forward carb had a layer of oil film all over the top. I pulled the plugs and they are all text book - dry and pinkish grey.

So anyone seen this before? I am still thinking my initial guess about carbs may be right. If fuel is running leaking out of the float bowls it would drip down the manifolds into the cylinders and then leak down into the oil a bit. As the engine runs it would vaporize and create excess vapor pressure in the crank case and that which stayed in the cylinders would burn extra rich and produce smoke. What I can't figure is why it needs to crank for so long to start when several days cold. I figured it needed to run the mechanical fuel pump a bit to recharge the carbs; if this is the case then both carbs are probably doing the same thing and this seems unlikely (if it is a failure mechanism). If only one carb leaked then half the cylinders should catch and it should start and run badly for a bit...

Stumped,
 
Random thoughts.

The erratic cold vs. hot starting can be attributed to a lot of things, but I would focus my direction towards fuel delivery, as you have done. Is it possible the carb chokes are not synched so that the choke flaps are opening or closing differently?

I find your observation of white smoke potentially more troublesome - especially if you are using a stock pre-1980 head. As you know, white smoke is typically not an indication of a rich mixture. Depending upon your ambient humidity, much of the exhaust could hopefully attributed to water vapor. You mentioned excessive blowby, which you are evidently venting to the airfilter housing and the carbs. This would show up more as blueish "oil" exhaust, which is not what you describe. Of course, you might also have, for some unknown reason, condensation building up under the valve cover and this might be subsequently sent into the intake along with the "blowby." You might pull the valve cover to take a quick look at what, if anything, is developing there, but I doubt you'll find anything - especially if you are driving the car long enough to burn off these combustion byproducts.

Pursuing the white smoke phantom a bit further, is this something you normally notice in the past? I ask because I had a similar M30 cold start problem without any issue at hot starting. The plugs were all suspiciously spotless and the oil did not exhibit any milkshake properties, as might occur with a blown head gasket. Compression was also even across the board. But, I would get more condensation at cold startup than I could tolerate.

After the car sat at airport parking for several days, I cranked and cranked the engine - without the usual immediate starting success. I pulled a few of the plugs and thought I noticed some water beads along with the gas. I pulled each plug and blew them dry. The car started and I drove it home. I pulled the head and it wasn't until I examined the water jacket area nos. 2 and 3 and followed the corrosion that I found a crack. I theorized that when cool, the crack or cracks permitted coolant into the combustion chamber/s. As soon as things reached operating temp, the aluminum head expanded, in effect, sealing the crack or cracks. I never noticed a drop in coolant level, but that does not mean it wasn't happening. At the time, I was fortunate to have a used head on the garage shelf saved for a different purpose. I rechecked it for warpage and bolted everything up with a new head gasket. No more white exhaust.

I certainly hope your situation is nothing more than a byproduct of high humidity or even water in the fuel. I can't think of anything else that would cause the white, unless you are also running water injection.

Good luck!
 
Random thoughts.

The erratic cold vs. hot starting can be attributed to a lot of things, but I would focus my direction towards fuel delivery, as you have done. Is it possible the carb chokes are not synched so that the choke flaps are opening or closing differently?

I find your observation of white smoke potentially more troublesome - especially if you are using a stock pre-1980 head. As you know, white smoke is typically not an indication of a rich mixture. Depending upon your ambient humidity, much of the exhaust could hopefully attributed to water vapor. You mentioned excessive blowby, which you are evidently venting to the airfilter housing and the carbs. This would show up more as blueish "oil" exhaust, which is not what you describe. Of course, you might also have, for some unknown reason, condensation building up under the valve cover and this might be subsequently sent into the intake along with the "blowby." You might pull the valve cover to take a quick look at what, if anything, is developing there, but I doubt you'll find anything - especially if you are driving the car long enough to burn off these combustion byproducts.

Pursuing the white smoke phantom a bit further, is this something you normally notice in the past? I ask because I had a similar M30 cold start problem without any issue at hot starting. The plugs were all suspiciously spotless and the oil did not exhibit any milkshake properties, as might occur with a blown head gasket. Compression was also even across the board. But, I would get more condensation at cold startup than I could tolerate.

After the car sat at airport parking for several days, I cranked and cranked the engine - without the usual immediate starting success. I pulled a few of the plugs and thought I noticed some water beads along with the gas. I pulled each plug and blew them dry. The car started and I drove it home. I pulled the head and it wasn't until I examined the water jacket area nos. 2 and 3 and followed the corrosion that I found a crack. I theorized that when cool, the crack or cracks permitted coolant into the combustion chamber/s. As soon as things reached operating temp, the aluminum head expanded, in effect, sealing the crack or cracks. I never noticed a drop in coolant level, but that does not mean it wasn't happening. At the time, I was fortunate to have a used head on the garage shelf saved for a different purpose. I rechecked it for warpage and bolted everything up with a new head gasket. No more white exhaust.

I certainly hope your situation is nothing more than a byproduct of high humidity or even water in the fuel. I can't think of anything else that would cause the white, unless you are also running water injection.

Good luck!
 
I tend to start out blaming symptoms like these on present day "gasoline" formulations. Apparently the 10% added ethanol is a bare minimum and most gas you buy is more like 15% or more. That is a source for a lot more moisture in the engine and exhaust. Have you been able to drive your car long enough to get it thoroughly warmed up?

Can the carbs really leak into the intake when just sitting there? I'll have to think about that some. I can say from experience that if you have much gas in your oil, you can smell it on the dipstick.

I've had the slow starting after sitting experience for years on cars that weren't driven often. I always assumed it was because the gas in the float bowls was evaporating. Probably wishful thinking on my part...
 
I tend to start out blaming symptoms like these on present day "gasoline" formulations. Apparently the 10% added ethanol is a bare minimum and most gas you buy is more like 15% or more. That is a source for a lot more moisture in the engine and exhaust. Have you been able to drive your car long enough to get it thoroughly warmed up?

Can the carbs really leak into the intake when just sitting there? I'll have to think about that some. I can say from experience that if you have much gas in your oil, you can smell it on the dipstick.

I've had the slow starting after sitting experience for years on cars that weren't driven often. I always assumed it was because the gas in the float bowls was evaporating. Probably wishful thinking on my part...
 
Bill Riblett said:
Can the carbs really leak into the intake when just sitting there?

I've had the slow starting after sitting experience for years on cars that weren't driven often. I always assumed it was because the gas in the float bowls was evaporating. Probably wishful thinking on my part...
Click to expand...

Although they are pretty reliable, a little crap mixed with the needle and seat of one or both carbs can result in a slight flooding. Of course, flooding can occur if the floats develop a leak or even a partial leak. It is also possible to induce a quasi flooding condition if you pump the throttle enough and get the accelerator pumps "apumping." (3 turtle doves?)

On one hot summer day, I watched in horror once when someone at a shopping center was trying to douse the flames coming from the carbs on a 3.0. The car was in a packed parking lot with a car full of passengers.

He was very lucky. With the filter housing removed, it was obvious neither choke was operative. To get around this he was hitting each carb with starter fluid. There were three or four cans in the trunk. The owner showed me a repair estimate that stated each accelerator pump needed a new diaphragm too. He said it was too expensive and unnecessary because up until that day, the car ran "like a watch." I'll bet this watch did not keep the best time, but I did not stick around.
 
Bill Riblett said:
Can the carbs really leak into the intake when just sitting there?

I've had the slow starting after sitting experience for years on cars that weren't driven often. I always assumed it was because the gas in the float bowls was evaporating. Probably wishful thinking on my part...
Click to expand...

Although they are pretty reliable, a little crap mixed with the needle and seat of one or both carbs can result in a slight flooding. Of course, flooding can occur if the floats develop a leak or even a partial leak. It is also possible to induce a quasi flooding condition if you pump the throttle enough and get the accelerator pumps "apumping." (3 turtle doves?)

On one hot summer day, I watched in horror once when someone at a shopping center was trying to douse the flames coming from the carbs on a 3.0. The car was in a packed parking lot with a car full of passengers.

He was very lucky. With the filter housing removed, it was obvious neither choke was operative. To get around this he was hitting each carb with starter fluid. There were three or four cans in the trunk. The owner showed me a repair estimate that stated each accelerator pump needed a new diaphragm too. He said it was too expensive and unnecessary because up until that day, the car ran "like a watch." I'll bet this watch did not keep the best time, but I did not stick around.
 
A bit more on this... my chokes are perfectly synced and at 80F they are about 70% engaged.

When cranking, if I pump the accelerator to move a bit of extra fuel it seems to help.

The smoke is definitely not bluish which would indicate oil burn. It also does not have an odor which pretty much implies water or fuel issues.

A water in fuel problem hadn't occurred to me to consider. Back in the days when I knew what I was doing, a problem with water would always manifest as missing, stalling, and such. This was especially try with an empty tank. However, with the high ethanol content of todays fuel water will be uniformly absorbed. I think I will try a can of gas dryer for good measure and then run the tank empty and refuel (a good excuse for an extended drive). 8) I must admit that I probably haven't fueled up since last fall when I put her away for the winter and over such an extended period water condensate could easily form.

I have seen cracked float bowls and leaking idle solenoids cause carbs to slowly drain down. A cracked carb is pretty rare and usually happens only after a thermal sock; one that would also crack a head. Since I currently have webbers installed, the idle solenoid most likely can leak since it is too high up (this isn't true for the stock Zenith).

My head is a '77. My compression is good and uniform. I will sniff my dipstick next. If I like what I smell I may do it twice or even form a habit. :shock:

When driving I usually go out for at least 15-20 miles so the car is getting up to temperature. Once it is warms the smoke is gone. I guess another thing I need to try is an Italian turn up; I am always looking for a reason. :twisted:
 
A bit more on this... my chokes are perfectly synced and at 80F they are about 70% engaged.

When cranking, if I pump the accelerator to move a bit of extra fuel it seems to help.

The smoke is definitely not bluish which would indicate oil burn. It also does not have an odor which pretty much implies water or fuel issues.

A water in fuel problem hadn't occurred to me to consider. Back in the days when I knew what I was doing, a problem with water would always manifest as missing, stalling, and such. This was especially try with an empty tank. However, with the high ethanol content of todays fuel water will be uniformly absorbed. I think I will try a can of gas dryer for good measure and then run the tank empty and refuel (a good excuse for an extended drive). 8) I must admit that I probably haven't fueled up since last fall when I put her away for the winter and over such an extended period water condensate could easily form.

I have seen cracked float bowls and leaking idle solenoids cause carbs to slowly drain down. A cracked carb is pretty rare and usually happens only after a thermal sock; one that would also crack a head. Since I currently have webbers installed, the idle solenoid most likely can leak since it is too high up (this isn't true for the stock Zenith).

My head is a '77. My compression is good and uniform. I will sniff my dipstick next. If I like what I smell I may do it twice or even form a habit. :shock:

When driving I usually go out for at least 15-20 miles so the car is getting up to temperature. Once it is warms the smoke is gone. I guess another thing I need to try is an Italian turn up; I am always looking for a reason. :twisted:
 
Another possible cause of Amelie's slow starting is that the fuel pump is sucking air. To test, disconnect the fuel pump output and redirect it to a clean two litre soda bottle. Correctly defeat the ignition and then crank to see how long it takes to have fuel output.
If there is a significant delay, you can diagnose the failure with a vacuum/pressure gauge, a couple lengths of fuel line and a tee. A hand operated vacuum pump is handy, but use the brake bleeder bottle so you don't suck fuel through the pump and damage it's seals.
 
Another possible cause of Amelie's slow starting is that the fuel pump is sucking air. To test, disconnect the fuel pump output and redirect it to a clean two litre soda bottle. Correctly defeat the ignition and then crank to see how long it takes to have fuel output.
If there is a significant delay, you can diagnose the failure with a vacuum/pressure gauge, a couple lengths of fuel line and a tee. A hand operated vacuum pump is handy, but use the brake bleeder bottle so you don't suck fuel through the pump and damage it's seals.
 
Tom - good suggestion. I actually have a fuel pressure gauge. I also have an electric pump and adjustable pressure regulator I've been planning to install for a long time. This may be a good time. I've even pre-wired the trunk with a direct battery (fused) link and a relay drive feed. If the starting delay is related to filling the floats this will certainly cure the problem. If it does solve this problem it would also indicate that the floats are leaking for some reason.

I'm going out to snif my dipstick now and then I'm taking my dogs out for and Italian tune up. :twisted:
 
Tom - good suggestion. I actually have a fuel pressure gauge. I also have an electric pump and adjustable pressure regulator I've been planning to install for a long time. This may be a good time. I've even pre-wired the trunk with a direct battery (fused) link and a relay drive feed. If the starting delay is related to filling the floats this will certainly cure the problem. If it does solve this problem it would also indicate that the floats are leaking for some reason.

I'm going out to snif my dipstick now and then I'm taking my dogs out for and Italian tune up. :twisted:
 
JJ

Don't forget the short piece of hose that connects the hard line to the fuel pickup/ gauge sender at the tank.

Tom
 
JJ

Don't forget the short piece of hose that connects the hard line to the fuel pickup/ gauge sender at the tank.

Tom
 
I have replaced all of the hoses - I don't think there are any leaks; no fuel aroma anywhere. There is also no smoke when warm and running at at high RPM. My suspicions are leaning toward old, ethanol and water laced fuel. The starting thing may or may not be related. I drove it a bit yesterday and this afternoon it started on the first stroke; it smoked minimally to the top of the street and then stopped. I also confirmed that my idle solenoids are working - I used a clip lead to the battery and listened for clicking. I also disconnected them and it would not idle; this means that they are opening and shutting properly. It doesn't mean that they are closing 100% though when off but since they are mounted high relative to the float level I don't think they are the culprit unless there is a siphon effect.

If Mama lets me play with it this evening I may start installing the electric pump and pressure regulator. I plan to install it in the trunk for an improved chance of vapor locking. Does anyone have any opinion about the location of a pressure regulator: in trunk with pump or in the engine compartment near the carbs? I am planning to set the pressure around 2.5psi (Webbers) unless someone has a better number to offer.
 
I have replaced all of the hoses - I don't think there are any leaks; no fuel aroma anywhere. There is also no smoke when warm and running at at high RPM. My suspicions are leaning toward old, ethanol and water laced fuel. The starting thing may or may not be related. I drove it a bit yesterday and this afternoon it started on the first stroke; it smoked minimally to the top of the street and then stopped. I also confirmed that my idle solenoids are working - I used a clip lead to the battery and listened for clicking. I also disconnected them and it would not idle; this means that they are opening and shutting properly. It doesn't mean that they are closing 100% though when off but since they are mounted high relative to the float level I don't think they are the culprit unless there is a siphon effect.

If Mama lets me play with it this evening I may start installing the electric pump and pressure regulator. I plan to install it in the trunk for an improved chance of vapor locking. Does anyone have any opinion about the location of a pressure regulator: in trunk with pump or in the engine compartment near the carbs? I am planning to set the pressure around 2.5psi (Webbers) unless someone has a better number to offer.
 
Jim and Spence at Mesa Performance told me to set my regulator to 3.5 when I purchased my new pump. I mounted the regulator just after the pump next to the fuel tank. At 3.5 the carbs starve on hard acceleration. I eventually removed the regulator and have had no problems. I believe my pump runs at 6.5. I also think that placing the regulator in the trunk near the tank will result in pressure drop once the fuel gets up to the engine compartment and that is why setting the regulator at 3.5 did not work for me. I am running freshly rebuilt Weber 38/38's with the largest float needles available.

Just a note, mounting the pump on rubber bushings will help reduce the pulsating noise coming from the pump, it is also a good idea to use an additional glass inline fuel filter so that you can check for rust in the tank. This is how I discovered that my tank was rusty.
 
Jim and Spence at Mesa Performance told me to set my regulator to 3.5 when I purchased my new pump. I mounted the regulator just after the pump next to the fuel tank. At 3.5 the carbs starve on hard acceleration. I eventually removed the regulator and have had no problems. I believe my pump runs at 6.5. I also think that placing the regulator in the trunk near the tank will result in pressure drop once the fuel gets up to the engine compartment and that is why setting the regulator at 3.5 did not work for me. I am running freshly rebuilt Weber 38/38's with the largest float needles available.

Just a note, mounting the pump on rubber bushings will help reduce the pulsating noise coming from the pump, it is also a good idea to use an additional glass inline fuel filter so that you can check for rust in the tank. This is how I discovered that my tank was rusty.
 
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