. So if I haven’t damaged my pushrods can I spray seafoam in there and it will clean out the intake ? 
Running rough
Thread Starter
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Mountain Pass
Joined: Sep 2017
Posts: 218
Likes: 7
From: Kalispell Montana
Running rough
Hey guys ,
About a week ago . I poured some seafoam in some old gas thinking it would somehow revive the fuel and dumped about 5gallons of it my truck . I drove it for a few days and then it started running really bad . It bogged down when I touched the throttle and would buck down the highway like some of the cylinders weren’t firing . After hoping I could just use the fuel and fill it with some high octane afterwards and then realizing that wasn’t happening I drained the fuel , or at least all I could without removing the tank . There was probably 1/2 gallon left in there . And filled it with 5 gallons of premium and let it run for 10min and the drove it . I live on a hill and the whole way down it it was backfiring . I took it on some backroads and left it in 2nd and drove at 2500rpm for about 1min and it was still bucking and backfiring worse than before till it backfired so big it stalled . It started up again pretty easy and seemed to run a little better . Is this still fuel related or is something else wrong now ?
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
?? Don't do that. Was the old fuel in the tank already or? Guess it doesn't matter much now. Stale varnished fuel coats intake parts with a kind of glue, it can cause stuck valves and bent pushrods.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Hm, tough to say for sure what the problem is, but popping and backfiring through carb and general ****tiness would result.
I'd maybe pull the valve covers and turn the engine over with a breaker bar on the crank. Observe the valve train carefully. How old was the fuel??
What can happen, the stuff will burn OK, or seems to. Then after the engine cools down and sits overnight say - the next time ya go to start it, the push rods all fold over like spaghetti because the valves are stuck in the guides or whatever. Guess I'd be inclined to use MMO, only because I'm more familiar with that.
Maybe that's all a coincidence and something else is going on here, but it is a known problem that running old, stale or varnished fuel can cause trouble, just as you describe. Sorry to be the bearer of bad news. Hope I'm wrong. Let us know what you find though...
I'd maybe pull the valve covers and turn the engine over with a breaker bar on the crank. Observe the valve train carefully. How old was the fuel??
What can happen, the stuff will burn OK, or seems to. Then after the engine cools down and sits overnight say - the next time ya go to start it, the push rods all fold over like spaghetti because the valves are stuck in the guides or whatever. Guess I'd be inclined to use MMO, only because I'm more familiar with that.
Maybe that's all a coincidence and something else is going on here, but it is a known problem that running old, stale or varnished fuel can cause trouble, just as you describe. Sorry to be the bearer of bad news. Hope I'm wrong. Let us know what you find though...
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Mountain Pass
Joined: Mar 2008
Posts: 184
Likes: 0
From: S.C.
I don't know about bent pushrods, but backfiring will sure blow the power valve in the Carb. then it will run exactly the way you explain.
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Thread Starter
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Mountain Pass
Joined: Sep 2017
Posts: 218
Likes: 7
From: Kalispell Montana
Dang ,don’t tell me to take my valve covers off lol it’ll be 5° out tomorrow and snowing and I have no place to work indoors . I had them off earlier this summer and took me three tries to get them to seal 
what if I just turn my engine over by hand to make sure everything is freed up then get some seafoam that I can dump in my fuel and some seafoam spray and follow their directions on cleaning it out ? I don’t want to be cutting corners so let me know if it’s
Important that I check other stuff out first .
What is the power valve ? And how would I check it ? The backfires seemed like they were through the exhaust (not pasative ) if that makes a difference
what if I just turn my engine over by hand to make sure everything is freed up then get some seafoam that I can dump in my fuel and some seafoam spray and follow their directions on cleaning it out ? I don’t want to be cutting corners so let me know if it’sImportant that I check other stuff out first .
What is the power valve ? And how would I check it ? The backfires seemed like they were through the exhaust (not pasative ) if that makes a difference
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Keep in mind none of us have seen the truck or know the deal. All we can go by is your description, the info you provide. It could be that your only problem with the truck is a bum ignition points condenser. "Could be."
It's just that you specifically mentioned pouring 5 gallons of old gas into the tank and then ... that's when the trouble began.
It's just that you specifically mentioned pouring 5 gallons of old gas into the tank and then ... that's when the trouble began.
Cargo Master
Joined: May 2015
Posts: 2,350
Likes: 7
From: Garland, Tx
2X ^^^^^
I was thinking if it’s out the back, it’s could be power to the coil. But the possibilities are off the chart. Therefore, we are going to shake you down like a $2 alley **** and get all the info from you before we start throwing parts at it and hope one sticks.
I was thinking if it’s out the back, it’s could be power to the coil. But the possibilities are off the chart. Therefore, we are going to shake you down like a $2 alley **** and get all the info from you before we start throwing parts at it and hope one sticks.
Thread Starter
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Mountain Pass
Joined: Sep 2017
Posts: 218
Likes: 7
From: Kalispell Montana
By backfire I mean it’s coming out the back of my truck . I understand that you guys can only throw ideas out from what I’ve told you And I appreciate all the ideas you guys give me . So ask away...
Thread Starter
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Mountain Pass
Joined: Sep 2017
Posts: 218
Likes: 7
From: Kalispell Montana
Haha ... 68 f250 hiboy . I think its actualy a 68 body and engine on a 72 frame. At least that’s what the guy told me when I bought it . It’s got a 390 with a 4bbl carb . I believe it has points and it has manifolds . Hopefully headers soon