I have a '78 F250 with a 351M. For a few months now, we've had problems starting the truck after it has been sitting for a week or so. It would crank and crank, but never turn over. We poured gasoline down it's throat, and it would fire right up, at least for a bit. After a couple of these cough-sputters, it would roar to life then idle like a king. But now, it seems to be a new problem.

We had run the car completely out of gasoline. We poured some gasoline into the tank and got her to a gas station. We drove the car for a few minutes, just enough to get everything warm. A couple of hours later, it wouldn't start at all. We tried pouring gas down it's throat, but still no go. Now I'm very confused. I was of the mentality that an engine needs gas, spark, and compression to function. I didn't check the compression, but I doubt that would've changed from a 5 minute drive. I poured gas down the open carb (a little at first, we waited for 20 minutes, then tried again, to avoid a flooded engine effect). I pulled a spark plug wire, and made sure that it could spark to the block. It had a healthy blue spark.

What else should I check? I'm quite frustrated by this engine, as we are planning on driving it for 600 miles in three weeks. This vehicle used to be very reliable. And now it's starting to scare me.

Any help is appreciated.

 

I would be too.


You have done everything I would have so far.

Pull a couple of spark plugs and see if they are wet

How much gas (in Ounces) were you pouring down the carb ?

 

Is the air cleaner normally in place? I'm thinking evaporation through the float bowl vents when it sits for a while. May be due for a new fuel pump.

Also, as Dennis says, you may have fouled the plugs by pouring gas down it's gullet.

 

We're going to let it sit overnight, and tomorrow, we'll try to start 'er up again. If it doesn't start then, we'll pull the plugs and see if they are wet. Thanks for the tips, I hope that we can solve this problem before we drive it across a few states.

 

Well, after a night left in the parking lot, my truck thought about what it had done wrong and was ready to behave again. In the morning she fired up on the second crank. I was careful not to mash on the peddle until I let her try "dry" first. In retrospect, it is possible that I gave her too much gas last night before she could get going. I worsened the effect by pouring gas down her gullet, as had been the solution previously. Perhaps a tune-up of the carb is in order. But, if it happens again I'll pull the plugs to see if they are wet.

Bdox, yes the air cleaner stays on while it sits. I'm not sure how to cure the evaporation problem, and you're right the fuel pump may be past its prime. But, since I'm low on time and funds, we're just going to have to ignore that problem for now. Besides, I don't plan on letting her sit for more than a few days anymore. I want to keep her moving so we can see if any problems develop before our big trip.

 

And the problem still continues. I parked the truck for a few hours while the welder worked his magic (for the art car, see my Project Truck thread for details). Afterwards, the truck just wouldn't fire up. Same symptoms. You can smell the gas spraying into the carb, the spark is fine, the starter seems to be working fine, but maybe just a little slow from the drained battery.

Any help or suggestions? Is it the ignition coil? The starter? The wires? Am I flooding the engine?

I'm getting quite frustrated.

 

Where are you checking for spark ?

You need to check from the coil to the dist cap to the spark plugs.

are you pumping the pedal before key to start and during crank ?

are you just turning the key to start without touching the gas pedal ?


Please post exactly what transpires when you do what you do

 

I'll take careful notes of what I do tonight, when we try to bring the truck back to it's garage.

 

So, the truck started yesterday.

I turned the key for 3-4 seconds, without pressing on the gas at all. No start. Then I repeated with just a slight tap of the gas. It fired right up. It roared to life and we drove it around for 20-30 minutes. I will use this method every time now. Of course, the real test is to try when the engine is hot after driving around.

I think it's a heat problem. If it isn't starting, all we have to do is wait for about 5-6 hours and it will start up fine. I'm thinking about changing the starter out, and perhaps some cables. The cables look as old as the truck.

Today I'll try to tune up the carb a bit, and properly adjust the idle. For some reason, I think that it's getting too much gasoline when it's warm. That's the only thing I can think of, as it sure isn't a lack of gas that is causing the problem.

I haven't checked for spark in a thorough way. The truck always dies across town, away from my tools. So I relied on simple solutions to check the spark. I put a bolt in the boot from a spark plug and made sure that it would spark to the block.

Please lend some ideas.

 

Sounds like the carb is either boiling the fuel out of the bowl into the engine, the power valve is blown in the carb, or the carb has a hairline crack that lets fuel leak into the intake when it gets hot.
Next tiime you try to start it hot, hold it to the floor while cranking. If it's flooded, it will start easier this way.

 

As long as the starter cranks the engine over.... the starter is fine,

Usually a hot start problem if the starter cranks okay the cause is fuel evaporation or the timing is out.


For checking spark plugs they have a device that installs between the rubber boot and the plug. You might pickup one for future use.

 

GAH. I don't know but I like an old saying that my dad pounded into my head. "check the cheapest things first. In this case, how's your fuel filter? My truck was having problems with running smooth and replacing the plugs and fuel filter made a world of difference.

Just a nice trick that I just heard at work, get someone to turn the engine over in the dark. This way you might see if any of your spark plug cables need replacing. That will only show where it might be arcing though.

 

Thanks, Ranger Gord, I do need to change the fuel filter. I had been putting that off, but it's probably a good time. The spark plug wires are new, but one of the spark plugs is faulty I think. I can hear/see #4 sparking after it gets good and warmed up. The engine never really seems to stutter from this though.

 

I changed the fuel filter, battery cables, and starter today. Definitely a large improvement in starting. We'll see if we experience the same starting problem in the next few days. As our trip approaches (less than 3 weeks!) we'll be driving this truck more and more to work out any kinks that pop up.

I also plugged some tiny leaks in the freeze plugs with some stop-leak stuff. It seems to work well, but we will see in the upcoming weeks.

I'm off to change that spark plug and buy some coolant (we had been using just water till we plugged those leaks).

Thanks for the help.

 

This sounds like the same problem I had with my 78 F-150 with a 302 M5OD. It would start great when it was cold, never had any problems last winter at any time. This summer after a 20 minute drive if you shut it off for 10 - 15 minutes you would have to wait until morning before it would start again.
Changed the distributor cap and rotor it still had the problem, new plugs and wires still had the problem, put a new ignition control module on it still had the problem, changed the coil, still had the problem.

The fuel filter was ok as was the fuel pump there was fuel in the carb, it cranked over just fine but just did not want to start. I tried to adjust the timing and found out that I could not turn the distributor, sooooo after half a can of penetrating spray and a little help from a small bar the distributor was loose and the timing was adjusted, it still had the problem and would not start if it was warm.

It that point I pulled the distributor and found that the shaft was binding, turned realy hard. Replaced the distributor, reset the timing and have not had the problem since. Probably could have just swapped out the pickup in the distributor but I figured I would be better off in the long run to just replace the entire thing.

Hope this helps