Start-up problems after lay-off.

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Allan
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Start-up problems after lay-off.

Post by Allan » Wed Mar 06, 2019 8:21 am

I have been helping a mate to get his T running again after a five year lay-off. The car gave him lots of grief on a 5 day rally with gunk in the fuel system, so the tank was removed, thoroughly cleaned and given the three step POR 15 tank treatment. Because it has a custom made fuel tank fitted by Duncan and Fraser when they lowered the seating position, it has a drop section in the tank between the chassis rails, which in turn means it has a Stewart vaccuum tank for fuel delivery. The original tank float mechanism was found to be badly worn when dis-assembled for a cleanout, so was replaced with a sound unit. So we have a clean tank, clean vacuum tank, clean NH carburetor, and a problem!

With new petrol in the tank, the vacuum tank primed and fuel at the carburetor, she starts right up and will run for a couple of minutes before faltering and dying. We can wait 5 minutes and start up again, run and falter and die again. It is typical of fuel starvation, running well until the carby bowl is drained. So, we opened the drain cock on the tank outlet n fuel ran nicely. I dropped the fuel line at the tank, and still had a good flow, so no restriction in the sieve. I opened the carby drain and had good flow there, so fuel is getting to the carb. We took the carb off and removed the fuel bowl, the needle and the seat, the spray needle and the main jet and blew it all out. No trace of gunk anywhere. I put it all back together with a re-setting of the float level. After priming the vacuum tank again, we started her up again, she ran for a couple of minutes, faltered and died!!!!!

Before I tear into the vacuum tank I thought I'd ask here. I have not had a lot of experience with them. One last check to make is to run the car again until it falters and dies, and immediately crack the carb drain to see if it is empty. Perhaps the fuel is not getting from the vacuum tank at sufficient rate to sustain running.

Any other suggestions?

Allan from down under, and under.

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Henry K. Lee
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Re: Start-up problems after lay-off.

Post by Henry K. Lee » Wed Mar 06, 2019 8:35 am

Hey Mate Allan,

Those old vacuum pumps if there is any leaks at the diaphragm will give you a hair pulling experience. Is the pump getting warm where it is located? how about the routing of the fuel line? A quick test, old school witch hunt, take some wooden clothes pins to act as a heat shunt on the fuel line where any heat is noticeable to remedy a vapor lock. Depending on the length and levels those pumps do not have the greatest draft. Might want to attempt using a temporary electric pump set to 1 1/2 lbs regulator pressure. Hope this helps.

All the Best from Up Yonder,

Hank in Tin-A-See


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Re: Start-up problems after lay-off.

Post by Russ T Fender » Wed Mar 06, 2019 8:45 am

After fighting poor starting and performance on my 1930 Plymouth I finally put a small 6 volt fuel pump in the vacuum tank. No one knows it is there unless they hear the click when I turn the key on. No more issues!

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Re: Start-up problems after lay-off.

Post by TFan » Wed Mar 06, 2019 9:21 am

Does it have a vented cap on the fuel tank? It could be plugged with a bit of dirt or something creating a vacuum and stopping the flow after a few minutes. Jim
Back road kinda guy stuck on the freeway of life.

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Re: Start-up problems after lay-off.

Post by Henry K. Lee » Wed Mar 06, 2019 9:43 am

Good catch Jim!


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Re: Start-up problems after lay-off.

Post by Dallas Landers » Wed Mar 06, 2019 6:59 pm

Any vacume leak in the system will cause you trouble.


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Re: Start-up problems after lay-off.

Post by Allan » Wed Mar 06, 2019 7:29 pm

Thanks fellows. I had Jim's thought on the vented cap too. All clear there. I had checked the vacuum tank line for cracks. Held vacuum when I sucked on it, and we sealed it at the unions when refitting it.
Hank, the tank is high on the left of the wooden firewall,[car is RHD], so it is located well away from the exhaust manifold. The original tank worked OK when the car first hit the road 8 years ago, but all the pivot pins in the mechanism were found to be well worn when we came to clean it out, so we replaced it with a unit in much better condition.
Others with vacuum tank problems on other makes have gone the electronic pump route, even hiding the pump in a gutted vacuum tank. We may have to go that route too, to make the car reliable for the new owner, but I'd rather fix it. The system on my 1924 Tarrant special T tourer works well, and it has to draw fuel from a tank under the spare tyre carrier at the back of the car.

In frustration, Allan from down under.

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Re: Start-up problems after lay-off.

Post by Henry K. Lee » Wed Mar 06, 2019 7:51 pm

Glad to hear you are getting it narrowed down. Holler, (or contact me) if you need anything up yonder way.

All the Best,

Hank in Tin-A-See


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Re: Start-up problems after lay-off.

Post by Dan Haynes » Wed Mar 06, 2019 10:19 pm

I think if the vacuum tank is empty and is not remaining full and has to be re-primed, two things to check; first check that the line from the manifold to the vacuum tank is actually supplying a strong enough vacuum.

If the vacuum tank is full of gas (about a quart), the engine will run for a while and long enough for a few tests. You probably have (or should have) a petcock on the vacuum line at the intake manifold. Turn off the valve and disconnect the vacuum line to the vacuum tank. Put a small diameter vacuum tube extension on the petcock on the intake manifold and dip the tip of the other end of the tube into a can with some gas on the ground under the carburetor. With the engine running, open the vacuum petcock and the engine's vacuum should slurp gas up the tube from the can on the ground. I say use small tubing because even sufficient vacuum to operate the system may not be enough to lift the weight of a solid column of liquid gas in a big diameter tubing. But if the gas is sucked into the manifold, the vacuum is sufficient. If not, you have a vacuum leak somewhere. You can spray WD-40 or motor oil from a squirt can around the various intake manifold connections, including the carburetor flange and watch and listen for smoke or motor stumbles. A four cylinder engine will make enough vacuum for a vacuum tank system, but it doesn't have one bit of vacuum to spare and a leak will kill it. Even when it's running good, driving fast with wide-open throttle will often not provide enough vacuum to sustain it.

Once the vacuum has been proven, partially or completely drain the vacuum tank and put a rubber extension on the vacuum connection on the vacuum tank and suck on it. There must be no air leaks around the lid on the vacuum tank or any of the gasoline connections to the tank. You should be able to tell by the feel that liquid gas is being pulled (by your sucking on the hose like a drinking straw) from the gas tank to the vacuum tank. If you have air leaks it just won't work.

If you can suck gas from the tank, through the fuel line, through the vacuum tank and, if the manifold vacuum is strong enough to lift liquid gasoline from ground level, it should work - UNLESS - the control needle and levers inside the float tank are mixed up from different makers or models and they won't "trip" when the float goes down, to divert the vacuum to the fuel line, sucking gas into the vacuum tank. As the float in the vacuum tank rises and falls, it will make a faint *tick* and *tock* noise and the vacuum valve opens and closes. When the vacuum tank is full, if you suck on the vacuum line, you should get nothing, not air and not gas, because the internal valve is closed.

:(
The greatest enemy of knowledge is not ignorance; it is the illusion of knowledge.


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Allan
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Re: Start-up problems after lay-off.

Post by Allan » Thu Mar 07, 2019 6:47 am

Thank you Dan, for your comprehensive plan of attack. I will have to install a temporary line from the intake to the vacuum tank so i can incorporate a petcock. A club member made the same suggestion at our meeting last night.

When we first primed the tank on the initial start-up, we did not hear the float click over, and I continued to pour in fuel until it overflowed! The subsequent prime was made because we had taken the fuel line off at the petrol tank to check flow and we had taken the carburetor apart to check it out, so some fuel was lost. This time we heard the click.

When I cleaned out the vacuum tank, I checked all the fittings, cut a new gasket for the top plate and all was assembled with non setting fuel resistant sealant. I will be surprised if there are leaks but pleased if we do find something!
This tank is larger than the one on my tourer which has the fuel tank at the rear of the car. My spare tank is the same as the one on my car, so they are not directly interchangable. Might this larger one be an overkill? It has worked well before this, so perhaps not.

May tomorrow bring better news.

Allan from down under.

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Re: Start-up problems after lay-off.

Post by Duey_C » Mon Mar 11, 2019 7:32 pm

Sorry to bump this.
Allan, did you find the issue yet? I thought I had an idea but I forget what it was.
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Allan
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Re: Start-up problems after lay-off.

Post by Allan » Tue Mar 12, 2019 2:25 am

Duane, tomorrow's the day. I have temporary lines, tap and fuel container to check the vacuum draw. After that, it's top off the tank and a check inside. Next may be an electric pump, but I get a bit stubborn making such alterations to cover my incompetence.

Allan from down under.


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Re: Start-up problems after lay-off.

Post by wayne sheldon » Tue Mar 12, 2019 3:23 am

FIRST! Let me say, I have had several cars over the years that had vacuum tanks, and I like them. Usually, once they are sorted out, they become the mechanical marvel they were in 1915. Usually, just a little cleaning, maybe swap a bad spring out, fix all intake leaks, and make sure that the flap valve between the upper and lower chambers is not warped or allowing "back suction", and they become reliable for thousands of miles of touring with which to amaze your friends that they actually do work.

Then there is that other one.

The short version (yeah, right). Some years ago, I had sold the speedster I had used for several years, and a 200 mile Endurance Run was coming up. I had a project car that I had referred to for years as the "plan B car". It was about half built, really rough, all parts were rejects from other speedster projects, but there it sat. About two weeks before the run, my son said "Why don't we try to make it to the Endurance Run?"
The petrol tank sat low, and way to the back. To make it worse, being half assembled from mis-matched pieces, the rear of the car was lower than the front of the car. However, it had a vacuum tank on the firewall (Yes, model Ts were sometimes equipped with vacuum tanks!). So, we began one of the fastest throw-togethers to ever attempt the Endurance Run! To be fair, I do know of a couple speedsters that were put together in even less time, but with full time jobs and very little time we worked fast! I went through the vacuum tank, all looked nice inside. We fired up the motor for the first time in decades twelve hours before tech inspection a four hour drive away. The whole car was so NOT ready, driven a whole two blocks (from the trailer) before pulling up to the tech inspectors. I said to many people that if it made it to the starting line plus five miles I would be happy with the try.

We did better than that, even though we did not get even half way to the lunch stop.
Problems began a few miles after the starting line. The car had sat outside for a few years, part of the time with no cap on the petrol tank. It wasn't the vacuum tank that gave us trouble (in the beginning). I had vacuumed out the gasoline tank, and thought I got most of the junk and dirt from inside. But some stuff managed to plug the fuel line. And again. And again. And again. Every time, I pulled the top off the vacuum tank, checked for dirt inside, confirmed the blockage area (fuel line from petrol tank to vacuum tank), after close inspection, reassemble and drive until it quits again.
Then the next thing. It had only gone a couple miles since I had looked very closely at the internals of the vacuum tank. They had looked really fine. But the car started to falter again, only this time, differently. I had a bad feeling. We pulled the top off the vacuum tank, and found a sinker instead of a float. It had been less than fifteen minutes since I looked at and shook a nearly pristine float. Now it had SIX cracks, age fatigue splits from the lower seam to the upper seam!
I suspect that some remnant of the oak leaves that had fallen inside the petrol tank resulted in formation of a mild acid. Otherwise, I can't figure out how the float could have failed so quickly SO badly!

We rigged a manually operated control for the vacuum tank to be worked from the mechanician's seat and continued the Run. Until a tire blew out about twenty miles later.
At some point, maybe I will tell the rest of the story.

All that Allan to point out that sometimes, even if you KNOW you put it together and it WAS good? Sometimes something else can make a failure you don't expect in what was fine.


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Re: Start-up problems after lay-off.

Post by wayne sheldon » Tue Mar 12, 2019 3:32 am

And, carefully check that flapper valve between the upper and lower chambers! Some of them are metal, and corrosion or other issues can make them not seal well enough. Others were made of an early form of plastic. They can warp with age. Either type, if they do not seal VERY well, will allow the vacuum in the upper chamber to suck the fuel from the lower chamber instead of the petrol tank. It results in carburetor fuel starvation followed by a quick refill after the engine quits. Eventually requiring priming the vacuum tank again. Sort of sounds like the problem you are having.


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Re: Start-up problems after lay-off.

Post by Allan » Wed Mar 13, 2019 7:40 am

Problem solved!!!!!!!!
The cause of the difficulty was a couple of klutzes. The first was the fellow who cleaned/rebuilt the vacuum tank 5 years ago. He fitted the right angled fittings in the top of the tank just finger tight, because their orientation was as yet to be set.

Second klutz hooked up the pipes to the fittings as aligned and snugged them up.

The first klutz didn't check this work and went chasing tails as described earlier. When chasing one of these tails, the vacuum line was disconnected to check suction. When refitting it, it was noticed that the tank top for that fitting was marked 'Fuel'.

No wonder it didn't work!

I swapped the pipes over, primed the vacuum tank, and got a free start first up. She ran like a beaut for a minute or so, before dying. That was an easy fix. Just turn the tap on at the base of the tank. 10 minutes of continuous running, and three more free starts. All is well.

Which leaves the question, what are the chances that TWO unions on the tank could both be aligned with the pipes so that all a second klutz had to do was screw the pipes on?

Allan from down under.


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Re: Start-up problems after lay-off.

Post by Dallas Landers » Wed Mar 13, 2019 9:24 am

Allan, glad it was an easy fix. Once in a while I have to stop and start at square one. Then I get that "ah ha" moment. Thats a great feeling when you figure out a head scratcher.
And free starts to boot!
Cheers!

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Re: Start-up problems after lay-off.

Post by Duey_C » Thu Mar 14, 2019 9:51 pm

Ditto on Dallas's post. :)
Good to hear ya got it sorted.
:lol: That machine let you know you had it right! :lol:
Since I lost my mind mind, I feel more liberated

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