1941 Special engine dies when warmed up

[Grimy]

There was a recent thread which in part addressed the correct routing of the fuel line on a 1941--may have been on the big 320 engine.  A photo was provided.

[Lare]

Thanks a lot, I'll hunt up that thread.  It's pretty much the stock layout, coming up the side of the engine from the pump and going across in front of the valve cover, using the stock bracket that is there, but where it rounds the manifolds I might have cut the corner too close.  Dumb.  But, we'll see, maybe I'm just running too hot right now.  Hope that's it (and that I can solve that).  Thanks again.

[MCHinson]

The recent discussion was about a 1938 320 in a Century. I would suspect the routing to be similar but I have no idea if it is the same. 

 

http://forums.aaca.org/topic/310767-1938-buick-century-carburetorfuel-line-routing/

 

[Terry Stock]

I hesitate to chip in.  But do you have the original style filler cap that lets air in as fuel is drawn by the motor?  If the fuel cap seals the tank, cars have been known to be starved of fuel.

[Morgan Wright]

3 hours ago, Terry Stock said:

I hesitate to chip in.  But do you have the original style filler cap that lets air in as fuel is drawn by the motor?  If the fuel cap seals the tank, cars have been known to be starved of fuel.

 

Good point. Make sure the hole is open too.

[Lare]

That's interesting, I hadn't given any thought to the gas cap.  It's a vintage key-locked cap that came with the car.  But I have a vented one that I can try instead.

Also, waiting for the fuel pump kit and the Thermocure cooling system cleaner.  I'll do those things next and we'll see.  Thanks again for the posts!

[Ben Bruce aka First Born]

On 6/18/2018 at 2:13 PM, Lare said:

Also-  If I'm right about this problem, does that indicate a faulty stock fuel pump, and I should rebuild it?  I would think so.  Or, my engine simply runs way hotter than it should.  The stock temp gauge works and it stays below 200, so I thought that was acceptable.  It doesn't climb into the hot (220+) zone until I switch the engine off.  But it seems to me that the fuel lines and the carbs shouldn't get so hot you can't touch them, right?  Or is that normal?

 

   Larry 

 

 Larry, the under hood temp is probably the same temp as the air coming through the radiator. Probably near 200. A handy tool to have is an infrared "point and shoot" thermometer. Not expensive. Now one can have real temp readings. 

 Be neat to have a pressure gauge in that fuel line.  

 

  Ben

[kgreen]

I just found this thread and think you have received good advice.  A point to remember regarding engine temps is that the engine temperature gauge only indicates the temperature of the engine cooling water leaving the engine.  Other component temps within the engine compartment vary such as the exhaust manifold which at idle can get to around 800 degF and under heavy or high speed load over 1000 degF.  The point is, your temperature gauge is only useful for coolant water temps, other heat sources in your engine compartment exist that can also affect your fuel system.  

 

Another potential problem is the winter gasoline blend that may be in your fuel tank at the start of the hot summer driving season.  Winter gas is blended to have a lower boiling point for faster vaporization in cold temps.  Summer gas blends have a higher boiling point to compensate for the higher ambient temps.  If you have any winter gas blend left in your tank either from a full fill the previous fall or a fill just before the seasonal blend change, you could have a problem that would seem to disappear after the next fill up in the summer with the summer-mix fuel.  Also know that E10 has a shelf life of about three months.  Ethanol is hygroscopic (attracts moisture similar to salt), and as the ethanol becomes saturated with moisture, it will separate, (visibly noted in a clear container I might add!) into an ethanol rich layer on the bottom of your tank (lower boiling point) and an ethanol deficient (low octane) layer on the top of your tank.  Beware of fuel enhancer additives as well, they are often rich in highly volatile alcohols that just add to your problem.

 

The suggestions about adding an auxiliary fuel pump are excellent.  The factory mechanical pump suction is not as efficient as electric operated mechanical auxiliary pump that pushes fuel when installed at or near your fuel tank.  By pressurizing the fuel, you also increase the boiling point of the fuel, reducing fuel starvation through vaporization when hot.  As for pressure, most carbureted engines require 4 to 6 psi fuel pressure.  When running at high fuel flows the engine may require upwards of 9 psi.  A preliminary indication of failure on the engine mounted mechanical fuel pump is reduced pressure caused by leaking, noticed when driving at higher speed.  The leaks can be at the one-way valves or within the diaphragm.  If your last fuel pump rebuild was in the 70's as I think you suggest, you should take a look at that unit. 

[kgreen]

Another comment that I just thought of.  If you use higher octane gas which has a lower vapor pressure, you can suffer vapor lock more readily.  Higher octane gas is designed to reduce pre-ignition within the cylinder when under compression.  The typical additive for making the higher octane gas is alcohol, lower vapor pressure means it boils at lower temperatures.  

 

Don't use high octane gas in low compression engines typically found in older cars.

[Lare]

Thanks a lot for the info.  Hmm, yeah, I've been getting the high octane thinking that would be better, but I'll try using the lower octane.  I like to get whatever has no ethanol in it, when I can find it.  But I can't remember if when I do find it, it's the high or low octane gas.  Sure wish plain old gas wasn't so hard to find.

And yes, I'm rebuilding the fuel pump this week.  The 41 has a weird strainer in the bowl, and it was all gunked up. 

At any rate, we'll see what the new pump build brings.  Thanks again all for the help.

[kgreen]

The strainer could be yet anther problem.  I see smooth sailing after you rebuild the pump.  Good luck!

[Morgan Wright]

11 hours ago, kgreen said:

 ……… lower vapor pressure means it boils at lower temperatures.  

 

Lower vapor pressure boils at higher temperatures.

[kgreen]

I stand corrected.

[Lare]

Late in coming but here's an update to this issue.  It seems I had three problems-  the coil, fuel supply, and insufficient cooling.  I changed the coil first and that changed things a lot, to where the failures at warm up changed to a softer stalling that I could overcome with the electric fuel pump.  The engine ran kind of hot, like 190, and the pump was clogged and old, so I rebuilt it (fuel was percolating with flow being too sluggish).  That basically made the problem go away, but not entirely when really hot.  So I next did the Evaporust Thermocure flush and installed a 160 degree thermostat, and that lowered my engine temp by about ten degrees. 

 

I can pretty much drive it around now without the stalling when hot, which was the original problem I brought to the forum.  The temp gauge stays on 180 now as long as I don't sit too long at a light idling.  It goes up to 190 then, which is probably actually hotter than that.  when it hits 190 like that my 7lb radiator cap starts to release coolant through the overflow tube.  So my guess is it's more like 200-220 when my gauge says 190.  I'm close to vapor locking/fuel percolation again when it gets like that, I can tell.  So, although I can drive it now as I described, I'm still not satisfied with cooling.  It should be able to sit at idle and stay at 180, shouldn't it?  At any rate, perhaps it's time for rodding out the radiator.

Thanks loads again for all the replies, it's why I'm out from under the problem now.

[Spinneyhill]

On 7/21/2018 at 4:04 AM, Lare said:

perhaps it's time for rodding out the radiator.

Use your infrared thermometer on the radiator when it is running and hot. Shoot at an angle so you don't register the temperature of the engine or whatever behind. If it is blocked, you will have a cooler area. Mine was blocked in a triangle reaching up into the middle from the bottom. The radiator shop showed it by wetting it all over, then filling with hot water. The clear areas dried quickly, the blocked areas did not.

[Spinneyhill]

You can probably do this in the car. Get it hot, shut down and wet the radiator. Blocked areas will dry last.

Edited July 22, 2018 by Spinneyhill (see edit history)

[Greenfield]

One idea is to make sure the fuel mixture isn't too lean.  That could cause the engine to run hot.  Try opening up the mixture screw and run it slightly rich and see if you get better results.  Also, beware the dreaded effect of ethanol on rubber parts in the fuel system.  I once put a fuel pressure regulator on my TR3 and the car ran great for a day, then the next day it wouldn't start.  I removed it and let it sit, reinstalled, and same thing -- the car ran great for a day then wouldn't start.  The problem was the ethanol was causing the rubber in the regulator to swell, choking off the fuel supply.  I'd definitely would address the cleanliness of the cooling system as you are planning.

[rjengelhart]

Lots of great responses...some of them should do the trick.  Believe one of the last post was the condenser.  I had a bad one a few years back, and I'm having a problem w the condenser on my MG...notoriously a problem w after market stuff.

 

Easy to chek the coil when hot, condensor nedds a multimeter.

 

Good luck.  Btw, beautiful job on the fuel delivery and manifold  systems.

[Lare]

I'm back.  This thread from last summer had to do with my engine cutting out above a certain RPM when hot.  Runs fine at all rpm's when NOT hot, but I can only drive it slowly when it's at full temperature.  As long as I don't step on it, it runs fine when hot, I just can't go fast or the motor starts to stall out.  In a nutshell, I've done everything talked about in the thread.  All of it.  And it's much better now, runs cooler, stalls less severely, etc.  But it still stumbles above a certain speed when it's hot.  My only question now is whether the carburetor could have anything to do with it.  It's the one and only thing I haven't done anything with.  I rebuilt it some years ago from a really terrible core that needed new floats.  All in all the rebuild job seemed to go fine.  And the car idles and runs beautifully with this carburetor.  Until it's at full temperature, and then I start to have the problem.  So, not to beat this to death any more than I have to, but does anyone have any thoughts as to whether I should try a different carb?  I have three other rebuilt AAV-16 front carbs sitting on my bench, so I'm all set for trying another one.  I just don't want to go to all the trouble if I'm being foolish and the fact that it runs fine till hot means it can't be the carb.  Thanks loads again for the help.

    -Larry

[Matt Harwood]

Glad it's better, but it sounds like you might still have some tuning to do. You have Strombergs, so that helps with carb tuning--they're easier than the Carters. It might be a little too lean, even though it idles nicely. The low-speed jets can be enriched by turning the screws counter-clockwise and they work up to about 30 MPH, so it might help with your condition. Most of the time, I adjust them by closing them all the way (turn clockwise) until they're lightly seated, then back them off about 2.5 turns each. From there you can adjust in small increments (1/4 turn at a time, either direction) to see if things improve. My Limited seems to like about 1.75 turns, but the manual I have says that 2.5 to 2.75 turns is typical. You'll just have to experiment. 

 

My concern, however, is that you're only having the problem when it's warm and at high speeds. At higher speeds, those idle screws aren't doing anything and the primary jets have taken over. It's possible that they're too small (or too big) but unlikely. Have you pulled plugs to have a look? They should be tan-brown. Black is too rich and white is too lean. Do a little diagnosing before messing around with the carbs.

 

Also, how are your plug wires? Could you be having some cross-firing?

 

We'll keep working through this. There's a solution.

[Lare]

Thanks a lot for the note.  The plug wires are from the original restoration back in the early 70's.  I guess I didn't think to question those because of how smooth the engine runs, when it's not having the problem.  I could just change those, it's about time anyway I suppose.  I can't recall how a plug looks; tan, black or white.  I'll look at those.  And I'll start experimenting with the idle screws, nothing to lose by trying that.  I had them set for the smoothest idle and left it at that.  But I'd be happy to have a bit rougher idle if it solves the bigger problem. 
Thanks again, and I'll get back with my results.

[Lawrence Helfand]

May I suggest that your accelerator pump plunger is not doing the job. If it is not sealing well it will not squirt enough gas into carb off idle it will stumble under load. Check by looking into carb and opening throttle to see how strongly its injecting fuel. There are 3 positions on the pump linkage that determine volume by limiting or increasing stroke. If it is in the shortest throw try a longer stroke position and see if that helps. The Buick does have high heat under that hood and not the best venting so shielding your fuel lines with heat wrap does help. Buy the Velcro type so you dont have to take anything apart. Never use high octane gas! Your best bet is non ethanol low octane not available everywhere but you can go to the website Puregas.com and locate stations that sell it nationwide. Also 6 lbs of fuel pressure will overwhelm your float valves and installing a pressure regulator is a good idea if you plan on using an electric pump full time. It does sound like you require a pump rebuild as they marginal at best and are compromised by poor vacuum. If your wipers run slow your vacuum is too low. Regarding ignition I run Petronix  pickup and flame thrower coil with slightly hotter plugs and of course fresh plug wires which are Packard Bell nothing fancy. A slightly advanced timing over stock which was meant for mid 70's octane fuels of the period also improves performance economy and cooler running. For cooler running in traffic I fitted a Summit racing fan with more blades that pushs alot more air at idle. In hot weather its always a good idea to crack the hood after its parked as engine heat will really soar when motor has stopped, Good luck! 

[Spinneyhill]

8 hours ago, Lawrence Helfand said:

If your wipers run slow your vacuum is too low.

Or the wiper motor needs lubrication.

[Lawrence Helfand]

Actually in regard to the wiper motor the factory does not suggest any lubrication is ever required. Only occasionally putting a few drops of light oil on the cables where they contact the cable pulleys is suggested in the workshop manual. In general the action of the wipers is a good indicator of vacuum and the state of intake manifold gasket gasket  integrity which is usually the culprit outside of a bad vacuum line or low compression. 

[Lare]

I did rebuild the fuel pump, it was pretty tired but is great now.  I won't plan on running the electric pump full time, no.  I think the accelerator pump on the carb is ok, it squirts like heck when you look into the carb and open the throttle.  Good tip about the gas too; I was getting higher octane gas only because that's what is common for no-ethanol gas.  But I used your web site suggestion (pure-gas.org) and found some places that sell 87 octane with no ethanol, so I'll try going with that.  Regarding the summit Racing fan-  do you mean an electric fan, or did you literally replace your original steel fan with a new one that just bolts right up to the stock pulley?

It is a weird problem alright.  When hot, if I hit the gas above say, thirty miles an hour the engine dies, and I have to stay light on the gas pedal and keep it below thirty five miles an hour, and it runs fine then.  But when I try to accelerate up to 55, the engine dies.  You can feel it just completely lose power when you step on it.  Not just hesitate, it quits and would totally shut off if I don't let off the gas.

Aaanyways, I'll try all of these suggestions I've gotten so far and see what happens.  Thanks again for all the help, hopefully I can soon stop bothering people about this 'danged' problem....

 

[Spinneyhill]

OK, a dumb question. If you run the revs up in a lower gear does it do the same thing? I am thinking of breakdown in ignition at higher revs.

[Lawrence Helfand]

2 hours ago, Lare said:

I did rebuild the fuel pump, it was pretty tired but is great now.  I won't plan on running the electric pump full time, no.  I think the accelerator pump on the carb is ok, it squirts like heck when you look into the carb and open the throttle.  Good tip about the gas too; I was getting higher octane gas only because that's what is common for no-ethanol gas.  But I used your web site suggestion (pure-gas.org) and found some places that sell 87 octane with no ethanol, so I'll try going with that.  Regarding the summit Racing fan-  do you mean an electric fan, or did you literally replace your original steel fan with a new one that just bolts right up to the stock pulley?

It is a weird problem alright.  When hot, if I hit the gas above say, thirty miles an hour the engine dies, and I have to stay light on the gas pedal and keep it below thirty five miles an hour, and it runs fine then.  But when I try to accelerate up to 55, the engine dies.  You can feel it just completely lose power when you step on it.  Not just hesitate, it quits and would totally shut off if I don't let off the gas.

Aaanyways, I'll try all of these suggestions I've gotten so far and see what happens.  Thanks again for all the help, hopefully I can soon stop bothering people about this 'danged' problem....

 

The summit fan replaces the original on the fan pulley. I cannot imagine what might be wrong with your engine and have never heard of anyone experiencing these symptoms with their Buick eight. Guessing you already checked the rear carb intake counter weighted butterfly to make sure its moving freely  and not opening prematurely which might lean out the mixture by sucking air through the rear carb before secondary linkage opens up the main jet. It does sound like your problem is with  carburetion. 

[valk]

Late to the party; did you guys already point to the vacuum advance unit? 

[Lare]

A couple of responses to the latest suggestions:

Regarding spark at higher revs-  I'm not sure what to think about that actually.  I'll add that to the things I need to test out the next time I'm able to drive it. 

I did install a rebuilt (from that place in Texas) vacuum advance unit onto the distributor.  The old one was shot and the new one does hold vacuum when I test with my vacuum gauge.  And the line from the carb is new, so I think I'm ok with the advance.  The plate in the distributor moves freely too.

Yup, the weighted butterflies on the rear card do move freely.

I'll be testing all these suggestions the week after next and will report back.  I also need to verify my earlier claim that the problem goes away when I turn on the electric pump.  I'm not so certain of that right now, but I did say that last summer in the old thread.  That would of course point to a fuel issue and not ignition.  So yeah, let me try all this out, and make sure I'm correct in the things I'm saying, and report back.  Thanks all again.

[MCHinson]

In my experience, when you attempt heavy acceleration when hot and have problems, switching the electric fuel pump on will usually solve the problem. If that happens, it indicates a vapor lock situation due to the heat of the engine boiling the fuel in the lines or in the carb bowl.  Does this car have a thick aftermarket gasket between the carburetor and the manifold to thermally isolate the carburetor from the engine? If not, I recommend adding one.

 

Another remote possibility is if the exhaust manifold valve is stuck in the wrong position, it would cause excess heat to be diverted from the exhaust stream to the carburetor.

[FLYER15015]

Having read all the posts here, I'll add my two cents.

Since my '40 LTD is a driver, and I'll never get to the "badging level", I did the farmer's fix.

As you look at where your, and all other Buick straight 8's fuel lines are routed over the head and RIGHT BEHIND the thermostat housing, the hottest part of the engine, no wonder the crap we now are forced to buy boils.

My fix was to reroute the fuel line back along the inside of the right fender, turn right under the coil and up over the valve cover (with about 5" clearance) turn right and come to the carb from the back.

All of this is 5/16" copper tube. I also slipped 1/2" rubber heater hose over the whole length.

Here in the mountains at 8500 ft, we do not have any flat roads, and you are either going up or down all the time, so on a long pull, "vapor lock" is a way of life.

I keep my finger on the electric fuel pump toggle switch all the time. Saves my bacon 100% of the time.

 

Mike in Colorado

[Marty Roth]

I did something similar to what FLYER15015 did, but on my 1937 Roadmaster 80C. I routed the gas line from the passenger side up to near the top of the firewall and across the valve cover with as much clearance as possible, and then forward to the carburetor, again with maximum clearance from hot surfaces. I also added an inline fuel filter with a 3rd fitting for a bypass, allowing for fuel to return all the way back to a nipple on the gas tank's filler neck. This way, the fuel doesn't stand in the line absorbing as much heat, and is typically flowing so as not to boil. We here in the Deep South also have vapor lock issues and this is one of the "FIX" attempts which really seems to work - especially in conjunction with an accessory electric fuel pump to prime the system if we've had long-term storage while driving other cars on multi-week tours.

 

Good luck, and let us know of your success,

and some pictures of your car!

[rodneybeauchamp]

Just my two cents worth.

 

is the carburettor correct for your Buick. Or is it from something else or an earlier model or smaller engine.

 

I swapped the Stromberg on a 40 Pontiac and idle and low speed were fine but it had no power or high speed. Sure it fitted the manifold but it was off a much smaller engine and the jets and the throat size were way too small.

 

Going back to the original carby was an amazing difference on overall performance.

Rodney 😀😀😀😀😀😀