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Engine cutting out problem

Guest rbl2

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What would cause my engine to cut out at around 35 mph?

It starts fine, idles fine, revs up fine, and goes through first and second gears fine, even if I wind them out. Get up to 35 mph in high gear and it starts to cut out. No back firing at all.

Everything is new except the wiring. The carb was professionally rebuilt about 2 years ago. I just recently replaced the low speed jet tube in it as the one in it had a fracture running almost its entire length.

What brought that on was a problem with rust in the gas tank. The gas tank has recently been professionally cooked and sealed. I placed a clear plastic filter about 18" from the gas tank. It's not readily visible unless you crawl under the car but it does allow me to look for rust. I see nothing in it.

I also placed a sediment bowl just before the vacuum tank. This would allow me to see any water that might be in the fuel. There is none.

The gas tank work, fuel filter and sediment bowl, and carb work have all been done in the last few weeks. It ran ok for about 40 miles and started this problem again. I say again because it was doing it before.

I'm tempted to say it's an electrical problem and it may well be. A week or so back when all this started "again" it also at one point wouldn't turn over and blew the fuse to the headlights.

Long story short I concluded the problem was in the ignition switch, which needed to be wiggled to work anyhow. I made that conclusion because if I bypassed the ignition switch the starter would turn over. I took it apart, cleaned the contacts and reassembled it. It works better now then ever and even the headlights are brighter. But the engine still cuts out.

It's as if its running out of fuel as it does sputter but does not backfire.

I'm at a loss here. Any suggestions would be greatly appreciated. If I had some C4 I'd consider using it. I'm tired of chasing this gremlin. I want to drive my car, not stare at it and see a bottomless money pit.

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have you changed the rubber hoses in the fuel line system?sometimes they will suck shut and cut back on fuel supply which possibly not cause a backfire.There is hoses at the tank and at the pump.Also if the vent hole in your gas cap is plugged it could cause a situation where the pump can't pull enough fuel out of the tank(loosen cap and try it)If it's a gremlin it's usually a small problem that is not obvious.GOOD LUCK----just guessing as you didn't say what make & model-----another thought maybe plugged exhaust?

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Guest simplyconnected

Sorry you're still having problems. If you suspect it's running out of gas, it probably is. One of the biggest clues is the LACK of gas-smell in the air. Normally, when the electrical goes out, the engine still processes gas, and you can smell it everywhere.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrgoodwrench2001</div><div class="ubbcode-body">Also if the vent hole in your gas cap is plugged it could cause a situation where the pump can't pull enough fuel out of the tank(loosen cap and try it)</div></div> I agree, and I assume you actually HAVE a vent hose. You might have either a non-vented cap (when it should be), or a vent hole plugged with sealer. They're usually on the top of the tank, and about 1/4". Pull the hose off and stick a wire in there; see if it's clear.

Next time your engine quits, uncap the gas tank and see if it sucks air back in. There won't be much. Then see if your car starts. You might have to prime, just to get the vacuum going again.

One clue to your trouble is, speed doesn't matter much, but sustained time/distance does. How long do you drive before it quits? 40 miles?

How fast does the engine recover after it shuts down? Is there a heat issue, or does it fire right up? By the way, did your tank have a pick-up with a screen inside?

We will address electrical after the fuel supply is ruled out. Headlights (intact) do not cause fuses to blow unless the voltage regulator is stuck on, causing an over-voltage situation. Usually, wires shorting to the body cause fuses to blow.

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  • 2 weeks later...

Here's what I've done so far.

I checked all the electrical connections and cleaned them. That didn't help.

I removed the bowl from the carb and found very small amounts of a very fine dirt that appeared to be metal as it was shiney. I removed the carb and sparyed everything down with B12.

I then disconnected the fuel line from the modern filter by the gas tank. I allowed the fuel to flow through the filter. It flowed quite freely.

I then disconnected the fuel line from the vacuum tank on the gas tank side. I wrapped a clean, white, cotton rag around the other end of the fuel line and using a compressor blew it out. I did not find any dirt on the rag. I then moved the rag to the other end and blew the line out again. Still, I did not fing any dirt on the rag.

Then I removed the inner tank from the vacuum tank to look for rust or dirt. I saw none but did take note that there was very little fuel in the lower chamber and none in the upper chamber.

This is the 4 screw vac tank. The shut off valve on the bottom of the inner tank looks to be no more than a fiber board. It moved freely but only a little. I have no idea how much it is supposed to move.

I went to clean it out, using B12, and noticed that the B12 would flow very slowly out and sometimes not at all. I tried to clean it and free it up some but could not.

Fortunately, I had another. The second one allowed fuel to flow freely passed the fiber board valve.

I sprayed liberal amounts of B12 on the mechanisms that attach to the float in the vacuum tank and gently wiggled them hoping to remove any dirt that may be there. I then reassembled it and reattached the fuel lines to it.

The gasket appeared to be very old and thin so I made a new one from paper gasket material about 3/32" thick.

Then I removed the lines from the vac tank to the carb amd also blew them out.

Meanwhile, an older mechanic suggested the coil was overheating, even though it is a new one. The coil sits on top of the oil filter. He told me that the next time it quit to put hands on and see how hot it was.

The car started and ran fine, until I took it down the road. Again it sputtered out. The coil was very hot to the touch. Hotter than the oil filter. So I raised it about 1/4-3/8". This would allow air to flow between the coil and filter.

Then I removed the bowl from the carb and found more, but not as much, of the same shiney "dirt" I had found there before. I cleaned it out, replaced the bowl, and drove away.

No problems this time. After 30 miles I removed the bowl from the carb again and again found more, but even less of the dirt. I drove about 40 miles with no problems and again removed the bowl from the carb. This time I found only a very tiny am't of the dirt in the bowl. I have now put 90 miles on it without it sputtering out.

What was the problem? I'm not sure. It may have been a combination of things.

Where did the dirt in the carb come from? Damifiknow. I have trouble imaging it getting past a brand new modern filter as well as the sediment bowl, which shows no dirt at all.

Could it have been the gasket in the vac tank? Maybe. It was rather thin and old.

Have I fixed it? Let me drive it another hundred miles or so before passing final judgement. Meanwhile, it seems to be doing just fine.

Having said that, I'll wake up tomorrow only to find all the fenders have fallen off, the tires will be flat, the seat fallen through the floor, the steearing wheel in pieces, and gremlin poo all over everything. mad.gif

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