4.0 missfire

[abes]

It's a 90' zero mile 4.0 rebuilt motor. I finally got it started but its got a miss that i havnt been able to figure out. It has a new fuel pump, cap, rotor, wires, spark plugs. Dist. rotor is @ 5 o'clock when @ tdc, so i think the timing is ok. Firing order ok. I checked every cable to cyl. for spark and they all have spark, but i noticed that when i removed the #1 cyl cable there was no change. I removed the spark plug and saw no sign of fuel burn. I reinstalled everything started the truck and disconnected the injector still nothing. I changed the injector still nothing. Dont know what else to do PLEASE HELP........ Thanks.

[rickoregon]

Are you getting signal to that injector? You should be able to hear it clicking, if it's injecting.

[abes]

Thing is, i dont know how to check if injector is getting signal. I have a multimeter, but dont know what reading to look for....The clip to the injector looks fine, no oxidation, intact.. Can timing be an issue?

[VegasAnthony]

timing??

[abes]

what would it run like if it was one tooth off??? It starts and idles, but sounds like its running on 4 cyl..Its pretty much on the 5 o'clock mark @ the dist.

[muduck18]

I removed the spark plug and saw no sign of fuel burn.
fuel burn? by that you mean that the plug was wet? or dry, brown, white?

sounds to me like timing, same type of thing happened to my dad when he put the wrong plug wire on the wrong spot on the distributor with his 4.0. triple check that. then go for your timing chaing and check that if you still can't figure it out.
who rebuilt it? and do you know if they lined the chain up right?

i am not much help because i ask to many questions...




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= my $0.02 + inflation = 5.00/gal

[abes]

the resrt of the plugs are dry brown. #1 no color..

[abes]

A far as corrct wire to cap. checked it @ least 5 times

[muduck18]

ok, its an injector swap the injector with another one and see if you can brown that plug.that will tell you if its injector or wire or what-not. (as long as that plug has spark that is...) I am assumeing you tested that too... ok i just went up and read that you did that. so yeah fuel delivery next step...

[langer1]

Thing is, i dont know how to check if injector is getting signal. I have a multimeter, but dont know what reading to look for....The clip to the injector looks fine, no oxidation, intact.. Can timing be an issue?
Buy a set of noid lights there made for that, testing injectors.

[Matthew Currie]

First of all, since this is a fresh rebuild, perhaps you should get a vacuum gauge, or test the compression, to ensure that you're getting compression. But assuming you have compression on all 6, here's a quick way to test the injectors.

Each injector plug can be swapped with its nearest neighbor. When the injectors are working right, if you pull one while the engine is idling, it will bog slightly, then regain original rpms. If you pull either a dead connector, or pull it from a dead injector, there will be no change at all. So pull connectors until you find one that causes no change. Now swap the connectors between neighboring cylinders, and test again. If pulling the same cylinder still causes no change, it's the injector. If pulling the same connector causes no change, it's the wiring.

Depending on what kind of injector connectors you have (there seem to be several variants), if you have the kind that have a square metal retaining spring in them, do yourself a favor, and remove the springs from the ones you're testing, before you do this, so you won't be struggling with the plugs while leaning into the hood of a running car.

[abes]

I pulled off the entire fuel rail w/ the injectors still connected and turned the engine over. Finally noticed that the injector on cyl. 1 was not spraying.(i just changed it yesterday with a junk yard donate). I removed it opened it up w/a
12 volt wire rig and sprayed some carb cleaner through it a few times & tapped it a few times on the concrete... VIOLA starded to spray again. Put that bad boy back in & the missfire mystery has been solved. THANKS TO ALL YOU GUYS.YOUR HELP HAS BEEN GREAT............

[rickoregon]

Way to go, Abes! Good job. It's amazing what difference a little more fuel can make! 8-) Good post.