Engine cranks but will not fire.

[dsb6291]

1979 F-150 5.8L DBBL

A little over a year ago my truck would not start. I had let it sit for too long and the battery died. I replaced the battery and the truck finally started up. I drove it all day after that and it ran great. Started up every time, until the next morning. Since then I have not been able to get it to start. I replaced the battery, the coil, the distributor cap, the rotor, the spark plugs and cables, the starter solenoid, the starter was checked and is good (which is apparent since the engine cranks), and I even checked to see if the timing was off by twisting the distributor and trying to start the truck, but to no avail. It was proposed that since the truck sat for a year that the fuel may have “gone bad”. I took a fuel sample and the gas looks like apple juice. So, since then every time I’ve tried to start the engine throughout this troubleshooting process I’ve hooked a fuel line from the fuel pump to a gas can with fresh gas in it.
So, I’ve got spark, good gas, and air as far as I know. The engine cranks and cranks but never fires. Does anyone have any ideas of what might be going on?
Thank you.

 

[DNFXDLI]

I was gonna suggest ignition module or magnetic pickup...but you say you've got spark...did you check the spark at just one of the plugs or at the coil?
Did you mark the distributor and put it back where it was?

 

[5.0Flareside]

are you sure the gas is getting to the carb? maybe the fuel pump is no good. try by squirting some gas down the carb and then cranking it. if it starts its something to do with the pump. maybe a blown fuse. or its a bad pump.

 

[DNFXDLI]

Should be a mechanical pump if stock...and checking it can't hurt, but they normally puke gas everywhere when toast.

 

[UNRULEE]

I had a very rusty rear tank on my '79 F250 that caused the inlet line on the fuel pump to be completely clogged on several occations. Pull the outlet line of the fuel pump off (and aim in a safe direction!!!) and crank the motor over.

Don't stop there though, like stated before, make sure the carb is putting fuel down the engine. I had to take the carb apart a few times and clean all of the rust debris out to get it to properly deliver fuel. The rust was so fine that it'd get past the 2 (yeah 2) fuel filters that I had on it. The tank has since been replaced with a plastic one.

 

[LEB Ben]

As these guys said...check to make sure the carb is getting fuel. If it's not work back to the outlet side of fuel pump pump...then to the inlet side. Also besure to check and find all filters. Stock and some aftermarket carbs have screw in filter in the carb, check the inline filter from the pump to the carb (if you have one) and also check to see if any PO's put a filter from the tank to the pump along the framerail.

 

[Fellro]

Always try priming with gas before messing with anything, especially on one that has say for extended periods of time. It isn't exactly unusual for a vehicle to sit for a long time and then varnish up the carb passages.

 

[78freewheeler]

i say ignition module or ignition switch i had the same problem. it would fire then when you throttle it it would slowly die. sometimes it would run then a sudden loss of power. if you try to start it and it fires try to returnb the key to the run position then back it off just a little bit and throttle it at the same time and you should be able to find out where it runs if it does this then it is either the module or switch. i replaced both so not real sure which one it was but its def fixed now. just my 2 cents

 

[Jotun]

I had a very rusty rear tank on my '79 F250 that caused the inlet line on the fuel pump to be completely clogged on several occations. Pull the outlet line of the fuel pump off (and aim in a safe direction!!!) and crank the motor over.

Don't stop there though, like stated before, make sure the carb is putting fuel down the engine. I had to take the carb apart a few times and clean all of the rust debris out to get it to properly deliver fuel. The rust was so fine that it'd get past the 2 (yeah 2) fuel filters that I had on it. The tank has since been replaced with a plastic one.

What he said rebuild the carb replace all inline fuel filters and I would suggest replacing all fuel lines as well. The diaphram in the Fuel pump is probably shot if it is old letting it sit for a year will dry it out and put holes in it or tear it after a day of driving. So my guess is that if you complete those tasks you should be back to picking up chicks in no time!

 

[TexasRho83]

The rust was so fine that it'd get past the 2 (yeah 2) fuel filters that I had on it.

Were you using the see through glass filters with the 5 micron filter insert? Those babies catch it all. I have 2 in-line filters as well with the finer one right before the carb and the cheapo plastic one closer to the pump.