My 77 F250 400 won't turn over.

It was running two days ago when the transport delivered it. The heater core had blown though and was leaking all over the place inside the cab. (The former owner just replaced the radiator, but not the heater core. Also the truck was bending push rods. the valves were stuck/gummed shut. He replaced 2 valves, all the lifters, all the push rods, hand lapped all the valves and reassembled. Truck was running even with leaking heater pump)

Today I replaced the heater core and cleaned up the mess, but it only cranks now. The truck had been sitting for years, so the gas is old and the exhaust smelt like it. Even though the tank is full, the gas gauge reads empty. I suspect either bad gas, trash in the fuel line and/or fuel tank.

Any suggestions on where and how I begin my search would be greatly appreciated.

 

try disconnecting the line from the gas tank to the fuel pump and run a line from a gas can to the fuel pump with fresh gas but check and make sure the carb or the line from the carb to the pump isnt plugged.

 

To the OP...The first line your first post is confused... do you mean it won't crank or it won't start????

 

Poor choice of words on my part. It will not start, cranks and cranks....

Appreciate your assistance FD55. Checking those lines will be a first for me, but I'll give your suggestion a try after church tomorrow.

 

Update: It doesn't appear to be the fuel or trash in the lines. It's spraying fuel just fine. (Though I've not check the pressure yet)

It's cranking, but no spark. Got out a meter and been testing various voltage readings. There is power going into the Ignition coil and going out of the coil. But there is no spark on the other end of the distributor line. When we were reattaching the lines onto the new heater core, my brother basically got on/into the engine compartment. We looked for any damaged/dangling wires caused by his weight and nothing appears hurt.

So I'm starting to think the Ignition Module is the issue. The meter shows there is power getting to the module, but after reading another thread about a similar issue, we didn't test all the wires or with the ignition in both positions. Maybe after I read the DSII guide and try out those tests I'll have better news to report back.

I only wish I was more knowledgeable about electrical issues.

 

check the resestor on your dist. or if you have points check them.

 

Excellent advice Nuckles

After metering various parts of the DSII system, it appears the ballast resistor is over resisting. At least that's what the meter is telling me. The parts store didn't have any in stock, but a shiny new one is order and should be here Tuesday.

I'll report back if that finally solves my spark issue.

 

If you have a DSII Ignition it uses a resistor wire that's wrapped up in your harness, what did you order? What reading did you get?

 

If its a keeper spend a little money and buy a mallory unilite system about 2or 3 wires and no more spark problems

 

Well.... the way you phrased your questions, you have me questioning a few things. My F250 is a stock ignition system or at least appears to be. From reading another thread with a similar issues, it sounded like the stock system was the DSII. If that's not the case, then I have a major assumption incorrect (yeah, I shouldn't assume anything. ).

My brother and I ran through the various tests. Part 2 Test 4 is the Ballast Resistor test. We measured the ohms between the BATT terminal of the ignition coil connector and the red wire of the going into the ignition module. It should have read between .8 to 1.6 ohms. We got a reading of 70 ohms.

The fix reads, replace ballast resistor. If that's suppose to be simply a resistor wire with the appropriate length, then my brother and I mistook what is probably a condenser that runs just off of the TACH for the ballast resister. (this is simple to replace... running a new resistor wire to exact length sounds more challenging).

If this helps clarify things and I've made poor assumptions, please steer me back onto the path. The part I described as the ballast resistor is a simple metal cylinder about 3 cm in length and 1/2 an inch in diameter with a short black wire running out of it to a small grey plug just off the ignition coil.

 

It's a noise suppressor helps prevent radio interference caused by ignition

 

Ouch. Thanks for letting me know stinky7. I'm chasing the wrong rabbit (part). The ohm reading we got I'm confident was properly done, so with such a high reading... the resistor (wire) is what needs fixed. This makes more sense to me because while replacing the heater core, there was stress placed upon the wiring harness under the dash. It was after replacing that the truck stopped sparking.

From what I've gathered, the resister wire is pink or pink striped with the words do not cut or splice along its length. Hopefully I can discover the issue following its path.

 

I think you should just check voltage at your ignition coil with your ignition switch in the run position, if i remember it should be between 5-8 volts, if so then your resistor wire is ok, maybe others will chime in to cofirm or correct what i have said, good luck

 

You should have 12 vdc to the coil while it is cranking supplied by the green(?) wire on the starter solenoid. When you drop to the run position, power drops to ~6 vdc.

 

The good news is my mechanic buddy was able to assist me in diagnosing the spark issue. It looks like the ignition module is bad as it is reading 0 voltage, but the wires test fine running into and out of it. So yay, issue identified.

Instead of replacing the ignition module, I've decided to simplify the truck's ignition system to a standard distributor and three wire system. No more computer controlled firing. Going back to manual timing which eliminates one more circuit board. (which is to my liking.)

I've not picked out a specific brand/parts yet, but will report back how my solution works out.