Backfire
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Cargo Master
Joined: Feb 2007
Posts: 2,477
Likes: 21
From: Taylorsville, NC
Backfire
The truck in my signature has been sitting on the carport since Oct. when the trans failed while pulling the TT.
I've been starting and letting it run every month on fast idle, up to around 150*.
Today I did the same but revved it up several times before I shut it down. Every time I revved it, it backfired out the exhaust on deceleration.
I was already thinking about doing a compression test before I spent the money on the trans because the pump is close to 100,000 mi and injectors have gray paint on them so they are probably close to 200,000 mi. So now I'm looking at 4,000+/-
Now I wonder if a compression test is a "must do" before spending on the trans and probably pump and injectors. If I have to spend more money for a valve job, I'll have way more money in it than it's worth.
Any guidance appreciated.
I've been starting and letting it run every month on fast idle, up to around 150*.
Today I did the same but revved it up several times before I shut it down. Every time I revved it, it backfired out the exhaust on deceleration.
I was already thinking about doing a compression test before I spent the money on the trans because the pump is close to 100,000 mi and injectors have gray paint on them so they are probably close to 200,000 mi. So now I'm looking at 4,000+/-
Now I wonder if a compression test is a "must do" before spending on the trans and probably pump and injectors. If I have to spend more money for a valve job, I'll have way more money in it than it's worth.
Any guidance appreciated.
Postmaster
Joined: Dec 2011
Posts: 3,860
Likes: 7
I'll bet one of your lifters just plain pumped down(and possibly stuck).
Let it warm up and it might well go away.
The lifters on these trucks are generally pretty decent, but remember that they are designed to take up the slack in the rockers, and not 'pump up'. So when you have a valve open(and effectively pushing against the lifter) over quite a while, it'll probably slowly lose pressure. It'll take a bit to regain that pressure with the engine running.
Also remember that at any given crankshaft angle, you should have at least one or two valves being partway open.
Let it warm up and it might well go away.
The lifters on these trucks are generally pretty decent, but remember that they are designed to take up the slack in the rockers, and not 'pump up'. So when you have a valve open(and effectively pushing against the lifter) over quite a while, it'll probably slowly lose pressure. It'll take a bit to regain that pressure with the engine running.
Also remember that at any given crankshaft angle, you should have at least one or two valves being partway open.
i ain't rite
Joined: Mar 2005
Posts: 65,564
Likes: 5,601
From: Marlboro Mental Hospital.
agreed. let it get to full operating temp, and vary the idle too.
if i let my IDI sit at idle for more than 15 minutes or so i loose an injector and it will not start working again until i run it at speed for a minute or so.
i need injectors, but am not going to put them in until i pull the cab and reseal the engine.
if i let my IDI sit at idle for more than 15 minutes or so i loose an injector and it will not start working again until i run it at speed for a minute or so.
i need injectors, but am not going to put them in until i pull the cab and reseal the engine.
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