89 2.9 Ranger backfires through intake

[Hans89ranger]

I had a dead battery so I jumped the truck and it started but was charging at 12v so I replaced the alt with an old one I had from a parts truck and still the same result. I put a trickle charge on overnight and the next morning it started and was charging at 14v. I let it run about 15 minutes, I put the headlights on along with a/c on high and all was fine. I shut it off and about a half hour later it started no problem but it has a back fire through the intake,it ran perfect perfect before. I checked all electrical connections and vacuum hoses and all seems okay. If anybody has any ideas I would appreciate any advice,thanks

 

[RonD]

Welcome to TRS

I doubt the charging system and backfire are related so disregard "it didn't do it before..xxxxx.........?" and look at the problem as "it does this now"

Backfire in intake can be lean fuel mix or spark timing, and maybe even a burnt or sticking valve

If engine was warm already then lean fuel mix can self ignite when intake valve opens and lean mix is sucked in, it ignites while intake valve is still open, so backfire
Vacuum leak can cause the Lean mix
This can't happen with cold engine

A spark usually can't ignite air/fuel mix, lean or rich, because it isn't a vapor yet, it needs to be heated with compression, AFTER its sucked in, so intake valve would be closed
But if its warm outside and fuel is also warm then there may be enough vapor in the mix for a mistimed spark to ignite it
And this "might" be related to charging system, longshot............

A Vehicles spark system runs at vehicle voltage, which is 13.5-14.5volts from alternator
If system was running at 12volts for awhile the spark may not have been "hot" enough to ignite the mix, but now it is
So you may want to check timing and make sure spark plug wires are in the right order and NOT touching each other

 

[Hans89ranger]

Welcome to TRS

I doubt the charging system and backfire are related so disregard "it didn't do it before..xxxxx.........?" and look at the problem as "it does this now"

Backfire in intake can be lean fuel mix or spark timing, and maybe even a burnt or sticking valve

If engine was warm already then lean fuel mix can self ignite when intake valve opens and lean mix is sucked in, it ignites while intake valve is still open, so backfire
Vacuum leak can cause the Lean mix
This can't happen with cold engine

A spark usually can't ignite air/fuel mix, lean or rich, because it isn't a vapor yet, it needs to be heated with compression, AFTER its sucked in, so intake valve would be closed
But if its warm outside and fuel is also warm then there may be enough vapor in the mix for a mistimed spark to ignite it
And this "might" be related to charging system, longshot............

A Vehicles spark system runs at vehicle voltage, which is 13.5-14.5volts from alternator
If system was running at 12volts for awhile the spark may not have been "hot" enough to ignite the mix, but now it is
So you may want to check timing and make sure spark plug wires are in the right order and NOT touching each other

Thanks Ron for your reply, I found the # 2 cylinder was not firing, it had spark but when I pulled the wire off it stopped backfiring. I then removed the left hand valve cover and to my surprise the pushrod was just laying there. I marked and loosened the adjuster nut and reinstalled the pushrod and tightened back plus a half turn extra. It runs great now but I may try to slip a new lifter in it happens again. It still make noise intermittently. I’m thinking the lifter pumped it self dry and threw the pushrod. Again thanks for your input,

 

[PetroleumJunkie412]

In order to do lifters, heads have to come off, sadly...

Any FE (390) block lifters fit, same size, so your options are out there beyond what the book states.

If one dried out, almost guaranteed your rocker shafts are full of sludge. They have to be kept CLEAN, along with the oil passage coming up through the heads.

2.9s HATE dirt. Full stop.

 

[RonD]

Hey Good stuff

Thanks for the update and the FIX
I have to say exhaust valve not open would cause that but never crossed my mind