1979 ignition trouble....i think
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1979 ignition trouble....i think
picked up a 79 F250 2 wheel drive recently. Smoked bad so I changed valve stem seals and it all but stopped it. ran smoothly around the yard but on the road under load it developed and odd skip. More like a pop or sputter. My assumption was i didnt get the valves adjusted right but went back and rechecked. Everything seems right but i'm no expert.the problem just being occasional makes me think fuel or ignition. Did a full tune up. Plugs, wires, cap, rotor and ignition module. Seemed a good bit better but still there. Cleaned and greased all the connections from ignition module to distributor. Still has the sputter. Im drawing blanks here. Maybe the rockers are a little off? Who knows. By the way the engine is a 351M/4 speed. A wire with bad insulation bouncing around around shorting maybe? Wire check is my next step. I dont know
Any help would be appreciated
Any help would be appreciated
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it was running nicely before. Of course I assumed it was a mistake on my part. Funny thing is that when I took the first valve cover off I noticed a pushrod off a rocker. It was bent pretty badly so i replaced it. No trouble with the sputter even with bent pushrod. I wont be suprised at anything being the problem. Truck sat a while before i got it. Fuel pump and starter went bad as soon as I got it. The carb could be needing a rebuild. Timing hasnt been touched since I got it. In fact, the distributor is stuck so i need to get that worked loose.The sputter sounds like its spitting back out of the carb. Hard to tell honestly. that would be timing correct? Maybe the timing chain jumped
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From: Stanley, VA
Did this truck sit for a long time before you got it? The reason I asked is if it sat it's possible the valve that had a bent pushrod is stuck in the open position.
I would run a compression check, paying particular attention to the cylinder that had the bad pushrod.
If you do run the test, Ford doesn't publish specific figures for cranking compression. All they say is the low cylinder needs to be within 25% of the high cylinder, I would rather see no more than 20%. As for actual figures, a good engine with a strong battery and stock cam should be at least 110 PSI.
The test is run with all eight plugs out, the throttle blocked wide open and a good, fully charged battery. Anything else will give unreliable figures.
I would run a compression check, paying particular attention to the cylinder that had the bad pushrod.
If you do run the test, Ford doesn't publish specific figures for cranking compression. All they say is the low cylinder needs to be within 25% of the high cylinder, I would rather see no more than 20%. As for actual figures, a good engine with a strong battery and stock cam should be at least 110 PSI.
The test is run with all eight plugs out, the throttle blocked wide open and a good, fully charged battery. Anything else will give unreliable figures.
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the truck had sat for quite a while apparently before i got it. i will do a compression check later today. I do know that all the valves do seem to moving freely but that says nothing about the compression. i will let you know the results as soon as i get a chance to check compression
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The compression check looked good. All cylinders between 120 and 140. Most in the 120-130 range. before I got started on the compression check I was running the enging and working the throttle. The engine spit back pretty hard out of the carb. I assume thats the sputting ive been hearing. Wouldnt that be the timing causing it to pop OUT of the carb?
Hotshot
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From: Stanley, VA
The compression is definitely good. My next instinct (guess) is that it's crossfire, either between plug wires or inside the distributor cap, but seeing as you've replaced those,it kinda rules that out.
Have you double and triple checked the firing order?
Have you double and triple checked the firing order?
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not yet. i assumed it was good since it was running good in the beginning. But anything is possible. I'll check it out the next chance i get. Thanks for the help
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I'd set the timing, and do basic adjustment to carb, run it, then come back with questions. It's not even worth guessing what the problem could be when you haven't even checked & set the basics.
1. check plugs, clean/regap/replace
2. check plug wires, or better, just replace them
3. check dist cap & rotor, or just replace them
4. check ALL vacuum hoses. Any truck thats been sitting a while likely has dried out lines. Better, just buy 4 feet at your local auto place and replace them. All of them
5. change your fuel filter
6. put NEW gas in the tank
7. go to youtube and watch a video on how to adjust your timing and carb
8. set the timing and carb. then come back when you have a starting point we can work with - Otherwise, every half wit that just replaces parts till their truck works will have you going in circles for years.
6.
1. start it
2. set idle to factory spec
3. . set timing to factory spec (look at the decal on the valve cover) - i.e. "break loose" the distributor, plug the vacuum advance line go
1. check plugs, clean/regap/replace
2. check plug wires, or better, just replace them
3. check dist cap & rotor, or just replace them
4. check ALL vacuum hoses. Any truck thats been sitting a while likely has dried out lines. Better, just buy 4 feet at your local auto place and replace them. All of them
5. change your fuel filter
6. put NEW gas in the tank
7. go to youtube and watch a video on how to adjust your timing and carb
8. set the timing and carb. then come back when you have a starting point we can work with - Otherwise, every half wit that just replaces parts till their truck works will have you going in circles for years.
6.
1. start it
2. set idle to factory spec
3. . set timing to factory spec (look at the decal on the valve cover) - i.e. "break loose" the distributor, plug the vacuum advance line go
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