454 mag problem
 

Its only running on like 4 or 5 cylinders, we've already checked all of the obvious, it happened all the sudden and compresion is fine, any clues?

Re: 454 mag problem
 

fuel or spark?
Check rotor/ cap for arching isolate dropping cylinders.

I had a problem with the shift interupt micro switch causing to shut down cylinders

Re: 454 mag problem
 

EFI/MPI? Not much info to work with. A failure of one of the injector driver circuits will suddenly take out 4 cylinders. Just a WAG.

Dave

Re: 454 mag problem
 

MPI, could both of you guys elaborate, because I did have a broken injector and a nuetrel saftey switch go bad, which is wired around right now

Re: 454 mag problem
 

only 92 hours also, we just had a head rework from a valve seat issue and now this?????? 6 weeks down and counting, there goes the summer

Re: 454 mag problem
 

Need more info!

What year? VST or Cool Fuel?

Did the problem start immediately after reassembly from head work? Or did it run fine for a few hours, then developed a new problem?

Did you check for trouble codes?

What does "checked the obvious stuff" mean?

Have you checked fuel pressure?

Which cylinders are missing?

Dave

Re: 454 mag problem
 

2000
cool fuel
It all happened at the same time, dropped a valve seat
plugs, wires cap, rotor all checked
fuel pressure 42-43
Im not sure which cylinders, but can find out tomorow

Re: 454 mag problem
 

I just got back from the shop and he said the shift micro shuts down 4 cylders to shift into gear and if I wired around the nuetrel saftey switch it is probably stuck in that mode, what do you think, we are trying to fix that now

Re: 454 mag problem
 

is it a Merc or Omc if Merc alpha or bravo?????? if alpha it has a shift interruptor if bravo it does not. only Omc shuts indv. cyclinders Merc grounds the coil for a milisecond.

Re: 454 mag problem
 

It is a Bravo, what does grounding the coil do

Re: 454 mag problem
 

Is this an inboard or sterndrvie? MEFI3 inboards (454/502) have a "Load Anticapation Mode" that adds IAC counts when shifting, but it does not kill four cylinders. Even the shift interrupt switch (Alpha models) momentarily drops IAC counts and retards timing, but does not kill individual cylinders. Not sure what your mechanic is talking about.

Did you check for trouble codes? You can verfiy if you are "stuck" in some improper operation mode with a scan tool.

What do you mean when you say there was a "broken" injector?

Dave

Re: 454 mag problem
 

the injector had a piece broken off the top plastic part, it is a mefi 3, and it just seems to not have any power, I may not be explaining it right since I am not a mechanic but am just trying to get all the ideas I can, can wiring aroungd the n safety affect the way it runs???

Re: 454 mag problem
 

and also no codes, it actually sounds like its out of time but its not

Re: 454 mag problem
 

No.

Did you double check the firing order?
How was the engine timed?
Did you check for trouble codes???

Dave

Re: 454 mag problem
 

timed from #1 on tdc and with a merc comp. and timing light, firing is correct yes we checked for codes, and no codes

Re: 454 mag problem
 

what is an injector driver curcuit? How would i know if this failed, I know its not a ecu prob. because we swapped them and the problem was still there

Re: 454 mag problem
 

The injector driver circuits are in the ECM. Swapping ECMs should eliminate the actual driver as the cause. You could still have an open circuit in the wire harness. You can get an injector test light (noid light) at most auto parts stores.

Have you been through the trouble shooting procedures in the Merc service manual?

Dave

Re: 454 mag problem
 

nO, i HAVE IT AT A LOCAL SHOP AND i DON'T HAVE A MANUAL and they are stumpped along with me , I just wanna use my boat, I have only had it out 3 or 4 times and now its been down for 6 weeks, so all your help is appreciated sorry about the caps, cap lock

Re: 454 mag problem
 

Ok Then Lets Stop Jumping All Over The Place And Go To Basics...
Has Anyone Done A Cylinder Misire Test Ie Kill Cylinder And Look For A Drop In Rpms

Re: 454 mag problem
 

yes at first but I would have to do it again to tell you which ones but I belive it was like 2 on each side

Re: 454 mag problem
 

ok then lets start there see which one arn't firing, then check for spark at those cyls and pull the plugs then we can start to determine y they are not firing :evilb: now we are getting somwhere

Re: 454 mag problem
 

they are all getting spark, I can just tell by they rpm which ones are missing, but it is getting spark

Re: 454 mag problem
 

ttt

Re: 454 mag problem
 

ttt

Re: 454 mag problem
 

ttt

Re: 454 mag problem
 

ok well we have to see whch cyl is dead fire the motor up and one at a time pull each plug wire off the cap and listen for rpm drop then replace it and go on to the next one till you find one with no change and that is the dead cyl use a pair of well insulated pliers this will tell you if you have a dead cyl or if we need to look elsewhere, ps we are not just looking for no spark! this will narrow everything down some

Re: 454 mag problem
 

Ive already done that there are 4 dead, the only thing is I dont remember which ones but it was 4 out of 8 dead

Re: 454 mag problem
 

Which One Does Make A Diferance Are They Next To Each Other Ect

Re: 454 mag problem
 

ttt

Re: 454 mag problem
 

they pretty random and both sides of the block

Re: 454 mag problem
 

ttt :eek: :( :mad:

Re: 454 mag problem
 

Random???????

Re: 454 mag problem
 

like not next to each other, it has compresion and is getting spark, SOMEthing has shut down 4 cylinders and there are no codes, I don't know what else to say

Re: 454 mag problem
 

OK lets look at what we have please correct anything I don't get right .......random cyl not firing but all have spark I take it you checked the firing order, all have compression over 100psi, none are next to each other,
I would have to check the injectors with a noid light and make sure they are getting a signal then check that they are getting the right signal, then id try changing them with known good injectors...pretty much short of a bad computer it has to be injector or spark related please let me know how you make out!!!! and good luck

Re: 454 mag problem
 

liquid,
Any progress on this? Joe seems to agree with me that the signal (power on and off) at each injector should be checked. Each injector driver (there are only two) triggers four injectors, the middle two cylinders on one side of the engine, and the front and back cylinders on the other side. But it would always be the same four cylinders, it would not jump around as you said.

Your problem is a strange one. One thing that I don't think has been mentioned, but that can cause unpredictable problems, is secondary ignition voltage inducted into the knock sensor or ignition control citrcuits. In other words, make sure that the wires that go to the knock sensors and the wires that go to the distributor are not resting against any spark plug wires or coil wire. Its a long shot, but thought I would mention it.

Dave

I got similar problem happening to mine now . Did we ever get his solution

Yeah, redo heads, valves,injectors,fuel pump, water pump,

not all that had to do with the prob, but all that crap broke in the mean time, fixed it all right and sold it