5.7 EFI shift interupt

[monterey98]

hey all.

please i need your help, i see you understand a lot about shift interrupt switch, i have a 5.7efi with current problem missing, backfiring and tachometer jumping (fake reading), i cannot locate the switch, i wonder if this would cause my problems, how can i unplug and go for a test.
i appreciate your time.


i saw this post at http://forums.iboats.com/showthread.php?p=1930449#post1930449
but cannot find it. and this one http://forums.iboats.com/showthread.php?t=206841
and thought they might be related to my issue

 

[Don S]

Re: 5.7 EFI shift interupt

There are more than one type of EFI system, and several different setups over the years. You give no information as to year, model or anything else on your engine. Do you have a serial number handy? Boat year and engiine year aren't always the same either.
There are hundreds of things that can cause a miss and backfiring, and a bunch will cause the tach to jump, but I would say it's a 99% chance that it's NOT the shift interrupt switch.

 

[monterey98]

Re: 5.7 EFI shift interupt

wow 99%, ok so i dont want to even try to change that interrupter switch, i dont have my serial number handy but i can go get it if thats important, i have a 1998 monterey montura 24ft, 5.7 v8 efi (says digital ignition).

i changed cap, rotor, wires, plugs, check the fuel pressure and shows 36psi all the time, but in top speed backfires, before that misses and tach goes crazy all the time, i unhooked the tach and nothing happened.

i found a CodeMate MEFI Code Reader at http://www.rinda.com/marine/marine.htm for $40, do you think can help me for good?

give me some directions please.

 

[monterey98]

Re: 5.7 EFI shift interupt

Hello.

im back and still not figure out whats going on with my boat. its a 1998 monterey montura 24ft with a 5.7 efi tbi, alpha one outdrive S/N is 0L02412. i hear a lot about the shift interrupter switch but you already said 99% its not that.
Last year i spent $1k changing the whole fuel pump and regulator, didnt change my problem, i dont know what else to do, i have a home made code reader that blinks 12 times if im not wrong, that means no code.

when i take the boat out i run fine for an hour or so, then sits for 2 or 3 hours, when i take it back home close to the dock tach start jumping and i hear, louder now, backfires, popping and missing, speed wont go over 30mph.

do you have any idea what could be?

thanks for ur time.

 

[ssb33r]

Re: 5.7 EFI shift interupt

Coil

 

[achris]

Re: 5.7 EFI shift interupt

That serial number is incomplete... Needs another digit.

Silly question, but what brand of spark plug are you running?

 

[monterey98]

Re: 5.7 EFI shift interupt

yeah, im sorry guys, my serial number is 0L025412. outdrive alpha one. spark plug is a champion i think, dont recall, i install them days ago, cleaned the rotor and cap.

took out last night for a test, while on forward gear low speed, i unplug the shift interrupter switch but the engine almost died on me, lost his composure i would say, so i plugged back. I dont know if it would do that, i just need to try going? is this the right thing to happen when we unplug?

Last night was just me, pretty light weight, but starting to miss and popping around 4200rpm, i think thats normal right? its the limit for these engines?

but the question is: why sometimes pops ad misses around 25mph, and the tachometer starts to dance, jumping up and down. i got a new fuel pump and regulator installed last yr.

what else im missing? the other day a guy said its 99% that is not the shift switch.

what else could be? can i test the coil? tach jumping gotta be the coil?

thanks

 

[Don S]

Re: 5.7 EFI shift interupt

spark plug is a champion i think,

For sure check, if they are Champion, it's a good chance that is your running problem. I have cured many running problems due to Champions being installed by just installing the correct plugs. Why I always tell people not to use them.

Use the correct AC plug. MR43LTS or the NGK BPR6EFS

 

[monterey98]

Re: 5.7 EFI shift interupt

for the last 3 years ive been using ngk and the problem still there. you are saying if i go install ngks back will fix my problem?

btw the old one i changed was in good condition.

 

[Don S]

Re: 5.7 EFI shift interupt

for the last 3 years ive been using ngk and the problem still there. you are saying if i go install ngks back will fix my problem?

btw the old one i changed was in good condition.

What do you mean the old one? One what? There are 8 spark plugs.
You also never said you had NGK and had the problem

We can only go by what you say, and if you don't tell us what's going on, we sure can't help you find the problem.
Have you done a compression test? Is the cap and rotor new? Plug wires crossed?

Did the problem just suddenly happen while you were out on the water, or did it happen after you had been working on it? or after taking it out of storage ????????

 

[monterey98]

Re: 5.7 EFI shift interupt

im sorry.
what i meant is since i own this boat i was using before ngks and i always got this problem with tach jumping and missing wot.

i change all 8 plugs days ago, removing the ngks and installing champions (i remember white and red boxes)....


and i unplugged the shift switch yesterday with no success. you said it its not the shift switch right?

did a compression test last summer and read ok, dont recall what numbers i had, engine runs fine steady on idle, rotor and cap changed less the 1 year old, plugs wire not corroded (i checked continuity last year with a ohmmeter).

the problem started to happen couple years ago, few months after i bought, dont know what caused it, i change the tachometer as well and still there.

when i put in the water and drive for a good hour, then sits after 3 hours, after that i head home, driving for 20 min tach starts jumps and popping occurs not allowing me to go over 30mph, and i cant read the tach bounces all over.

do you understand my explanation? lol

im lost man.

 

[Don S]

Re: 5.7 EFI shift interupt

I would be checking the coil wire and coil and see if you are getting arching to the connectors. Look for cracks or corrosion on the coil. Also check the plug wires with an ohmmeter to make sure they are have continuity. Also make sure the ends aren't corroded.
If you are getting an arching on the coil, it is shorting the spark to ground or to your tach which is why it's jumping.

 

[monterey98]

Re: 5.7 EFI shift interupt

good. how do i check my coil? what arching means? lol

i really think could be the coil, i already called many dealers today nobody has one and its $100, only to get it next wednesday.

can i buy a coil for vehicles? do you know the part number? or its not recommended.

thanks

 

[monterey98]

Re: 5.7 EFI shift interupt



looks like a car coil wont work for me, i can find the same on but no bracket to bolt on the engine.

but this looks like a bad coil guys? is this the source of my problems?

thanks

 

[Don S]

Re: 5.7 EFI shift interupt

Here is a link to the OEM service manual http://www.4shared.com/office/JOT2vS2W/24__GM_V8_50-57_98-01.html?

You need to spend some time in sections 5-C through G before you go broke throwing parts at it.

I nor anyone here can look at those two pictures and tell you if the coil is good or bad. Where the high tenstion lead hooks on looks suspect. It should be straight across, not curved like pieces are missing, but I can't see all the way around nor can I see if there is cracks on the top of the coil. There is also rust where the boot goes on. What do the wires look like? Did you check them?

Throwing parts at it like you have with the fuel system is going to cost you a fortune, and not find the answer. You need to follow step by step in the proper order to find the problem. You will need a scan tool, since many problems will show up on the scan, but are not something that will set a code, but shows something is not right. You also need a fuel pressure gauge.

Have you done a compression test ???? A couple of burned or warped valves will cause your problem.

 

[achris]

Re: 5.7 EFI shift interupt

good. how do i check my coil? what arching means? lol

i really think could be the coil, i already called many dealers today nobody has one and its $100, only to get it next wednesday.

can i buy a coil for vehicles? do you know the part number? or its not recommended.

thanks

I'm guessing, by the use of some of your phrases and a few words you don't understand, that you are not a native English speaker.... Where are you located?

Arching is when the spark made by the coil jumps across the outside of the coil, where it should not jump... It might be worth running the engine at night and looking for sparks around the distributor and coil and all the spark plug leads....

Also take the Champion spark plugs out and put NGKs or AC-Delco spark plugs back in... Champion spark plugs cause many problems... You really don't need new problems right now....

Chris........

 

[monterey98]

Re: 5.7 EFI shift interupt

Im from Destin-FL.
i will do a night test tomorrow night before replacing the coil.

I dont see no cracks, compression looks ok to me, wires looks ok, continuity reads fine.
I dont have a scan tool, a guy here charges $200 to diagnostic and he said he cannot guarantee to tell me what it is.

I can install the ngk's back tomorrow and test the coil at night, should i do it at idle speed?
my fuel pressure reads 30 psi, last time i checked.

I heard that my valves could have a problem but i don't know. this time of the yr to have someone do this type of work i wont have my boat ready in months, they are super busy.

 

[Don S]

Re: 5.7 EFI shift interupt

I heard that my valves could have a problem but i don't know. this time of the yr to have someone do this type of work i wont have my boat ready in months, they are super busy.

This is what I'm talking about, you bounce from one thing to another, do some basic troubleshooting and read the manual not a bunch of old unrelated threads.
So the shops are busy this time of year, you started this thread in Sept. 2010.

 

[monterey98]

Re: 5.7 EFI shift interupt

Yup..so you see my friend since 2010 I've been dealing with this.

I had a problem with the boat stalling on me but now is blower running 24/7 lol. I learned how to manage vapor locking.

We live on the beautiful emerald coast of florida $120/hour shop time and the only honest/reliable guy I know retire and he didn't have a scan tool...lol

We need honests and cheaper shops.

But I don't trust these dealers/mechanics here, the other day I had a faulty buzzer they charged me $600 to fix imagine this right now...lol

I just got back from the water no popping today but the tach was jumping like a boucing ball can never see the rpm's, I forgot to check the coil in the dark...

I AM LOST MAN...

 

[monterey98]

Re: 5.7 EFI shift interupt

update guys.

hi Don, i just got back from a test. i drove for an hour and experienced the popping and tach jumping but on my way back I install a jumper wire on the shift interrupter switch and guess what, it's a different boat, more smooth running, more responsive, more powerfull, i could reach 4700 rpm's and almost 47mph.

Tomorrow i will use the boat all day with the jumper wire to make sure my problem goes away changing this switch.

any recommendations?

kinda happy WE found the problem....lol

thanks