40 Gas Problem:

40ford

40ford

Well-known member
My 40 has stop running on me twice lately.it runs fine on the road ,but slow driving it stopped running and did not want to crank back.First time it done this I took the fuel line off on the carb side of fuel pump and it was dry.When motor was turned over no gas came out of fuel pump.I shook the car thinking maybe I had something in fuel tank,I finally got gas coming out of pump and put line back on and she cranked right up and drove home with no problem.Second time the car stopped on me and sat for a few minutes and then I pumped the gas pedal and pulled choke until It finally cranked again.I am thinking one of three things.Fuel pump (only a year old),vapor lock (not that hot of a day and never had car to do this before) and possible something in tank blocking off fuel outlet.Any ideas on which way to go? Sorry for long post. Russ
 
My vote would be for number 3.

I had similar symptoms and when I drained the gas tank out came a bug or two.

At one time the gas cap worked loose and fell off. I don't know how long before I noticed it, but apparently it was long enough for the bugs to find their way in.

I got a locking gas cap to prevent that from happening again.

Tom
 
Very high volatility on the fuel we get these days. Fuel pump can't pump vapor. You've identified the problem as a hot fuel pump that cools and begins to pump again. Classic vapor lock.
 
I too would say crap in the FT or a faulty FP.Especially if a China made [new FP].Get a rebuilt USA pump. ken ct.
 
If it won't crank over, it sounds like a loose battery cable or ground connection or loose at the starter, and poking around under the hood makes contact again so it will crank and then it starts.
 
The fuel pump is an Airtex,best on the market now.Made in USA from advance auto and it is only a little over a year old.To bad the warranty just ran out about two months ago.The car turns over good but there is no fuel!I have old fuel pump to start with to see if things change.I noticed the bowl on fuel pump is always full when this happens.Is this normal if pump is bad? Does the gas cap have to be vented or non-vented? Russ
 
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For 40 the gas cap has to be vented, if you have a locking cap it will vent through it. You can remove the inspection cover and the sending unit and look inside the tank and see if there is dirt in the tank that may block the pick up tube. Check fuel line for anywhere there may be an air leak such as an aftermarket fuel filter and any flex fuel lines.
 
I assume the pump is mechanical. If so disconnect the gas line on the tank side of the pump in the engine compartment. Then remove the gas cap and apply shop air to the line in the engine compartment. That will remove anything in the line back to the tank. Don't do this with a full tank of gas. If it happens again consider draining the tank. It may not be the line, but this fix is cheap and easy. Good luck!!
 
Sounds like junk ( rust particles) in the tank. first try driving without the gas cap, maybe it is not vented. does your fuel pump have the glass bowl? if so does it show full when not starting? also check the flex line these go bad often.
 
40ford The airtex pumps work good I have at least 8 of them. The one on my 39 has been over 4 years and still pumps 3 1/2 lbs at start up. When the gas warms up the pressure drops, the hotter the gas the lower the pressure and it also fluctuates due to the vapor when down in the 1 lb or less range. You need to get a laser pointed thermometer for about $40.00 to really pin point the problem. If you don't find the actual problem you will never correct it. Take the temperature of the inlet of the pump, the pump body and the area on the carb where the fuel is stored which is just below the fuel line on the carb. Any old Ford with the crankshaft mounted fan iis going to be more subject to this problem more than generator or 46 type fans. The 39-40 fans throw the air against the front of the block where the other higher fans move some air back over the engine. I say some air because the air pattern of the stock fans I have checked throws most of the air out toward the fenders. The dead air space at the rear and behind the engine gets the pump very hot and at about 122 it starts dropping in fuel pressure, the hotter it gets the lower the pressure. Watch the fuel bowl for bubbles, I'm surprised that you didn't see bubbles and the glass bowl was full. Which means it could be another problem but it sound like the "hot gas symptom". If you don't have a thermometer carry a bottle of water and pore it slowly over the pump and see if it starts right up. I can tell you how to make it less of a problem and also how to fix it if required. G.M.
 
I would rebuild the carburator and replace the fuel pump...those are the easy things to start with...then i would blow out the fuel line to tank and drain it....good luck
 
Just curious Gumpy why would you recommend doing all of this work without performing a few simple tests to possibly to find the problem. A fuel pump can be tested with a pressure gauge and you know exactly if it's good and what pressure it pumps. The fuel line being blown out would be the first thing to do, this should be done with the cap off and not to much pressure. I carry a 3' 1/4" rubber hose to blow out the fuel line on the road. Take the flex line loose from the gas line, the rubber hose will slide nice and tight over the furrule on the gas line to the tank. Remove the cap and blow through the hose with your mouth. I have felt the restriction let loose several time and in most cases will get you home or you may have to do it again. Once the tank has crud in it it won't even dain out through the drain hole even pouring the strained gas back through several times. Tank needs to come off and be cleaned or replaced. G.M.
 
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OK, so it cranks over OK but won't start. The comment that it wouldn't "crank" or "finally cranked.." made me think the starter wasn't working. Remove the glass bowl on the fuel pump and check the fine screen at the top for rust particles. My '40 is making rust like crazy right now. I think the ethanol in the gas is loosening years worth of rust in the tank. I put one of those clear glass cleanable filters in line near the tank. After a few miles of running the scsreen clogs with rust. When it quits the rust flakes settle down off trhe screen and it restarts. The filter is real easy to remove and clean but it's happening too often now so off with the tank.
 
guess you could plumb a new line into the FP, and run that into a can of gas....if you get good gas spurting from FP, then perhaps the problem is back toward the tank.....flex line??....or junk in the tank....good luck....Mike
 
I'm voting with George on this, Since your engine runs ok running down the road but burps when running at slower speed it most likely some type of vapor lock problem especially if you are forced to use this hippy 10% ethanol fuel.

There are a couple places to check, First check the flex hose line from the firewall to pump, these are notorious for deteriorating and cracking. If they crack even slightly the fuel pump sucks air and there is an issue, if you have not replaced that line recently it might be time for a new line or at least a check.

Second review the entire fuel line system from the carb to the tank for any area that comes near an exhaust manifold or muffler. Radiant heat from these is sufficient enough to cause the fuel to boil within the fuel line and shutting off the fuel flow. While the stock exhaust is on the passenger side and out of the way you still should check how close the feed line is to the driver side exhaust manifold , if you have added dual exhaust this might be the area that needs a look.

The ability to start your car after a short period of cool down time points to some type of fuel vaporization issue. A quick check on your fuel supply is to splice a small clear fuel filter in the flex line from the line to the carb. These are available at the hardware store for lawn movers. This will indicate if you have fuel to the carb or show bubbles building up if you have a fuel vaporization problem, they will also prevent any fine rust from filtering thru the system as a bonus. Any way before you replace a lot of parts and do needless work check for a hot spot in the fuel input line.

If both of these suggestions can be ruled out then the next step is to determine if the carb is percolating or the fuel pump. To do this you will have to take it for a ride and duplicate the frame work where it stops running correctly. At that time a temp check should be done at both the carb, the fuel line to the carb or the pump itself and this answer is similar to a previous post, determine the hotter spot either using a laser style temp gun or carefully with you hand. If you find the source of the problem you are going to have to heat shield it some how.
 
Dick even a heat sheild won't work when it gets 87 degrees like it was here today. On a 39 or 40 the heat gets so hot at the rear even the air cleaner is 125 + degrees. I made an expensive 4 ply insulater under the pump front and rear which helped some but the pump still gets over 125, loses fuel pressure and boils in the carb. Today it was 87 about 3:00 PM and I took the 39 out for about an hour. !/2"spacer under the carb, fuel line 2"s away from the 130 degree firewall insulated with foam tube from below the firewall where the line is cool up over the flex fitting on the pump. 1" spacer under the pump stand and short glass fuel bowl. Shorter bowl keeps the thumb screw under the bowl up a little higher from the heat. All of these helped when it was 83 out but could still get "hot gas" at idle and heat build up after shut off if the hood was down. I installed a 12 volt 5" 120 cfm computer fan above the pump and that keeps the pump cool. I run the fan off the 6 to 12 radio converter. The engine only got to 178 but when I came back opened the hood the pump was 123 which is right on the border line, the fuel pressure was down to 1 1/2 PSI and jumping around some. The air cleaner, bottom of the hood and the fan body was 125 so the fan was blowing 125 air down on the pump. This will keep it right on the border line but I would like a little margin. Tomorrow I want to get it hot in slow traffic so the fuel is 123 and drive for a few miles and see if the pump temp comes down. I'm also set up to try a return line and may see if that makes any differance. If it is a hot summer this will be a big problem. G.M.
 
Yes George, based upon the temps this spring, driving and old car this summer is going to be a challenge. I am of the belief that a retro fit return line is going to be necessary to circulate the fuel and keep it cool. I have been fooling around with a Kinsler fuel injection pill holder spliced in the output side of the fuel pump. I am trying to determine what diameter orifice pill I can install that will flow fuel to the carb and direct excess to the tank so the line fuel remains cool. I have been trying this with the idea that the retrun is controlled by a low pressure spring. The return is opened when the line pressure reaches a little over 2 lbs like the float closing and then shuts down as the float opens up requiring more fuel. The pump would always be in a constant cycle either pumping fuel to the carb or returning it to the tank. Keeping the fuel cool will help reduce the pump temp.
 
Is there a screen or something in the fuel tank for outlet or is it just a hole for outlet line? Russ
 
Dick when the fuel gets hot the pressure gets down to 1 lb or even a little lower. I have a needle valve right after the fuel pump to try a small return line. I wil try it this week while it's still hot and see what it does.G.M.
 
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