Volvo 8.1 OSI-DF Random misfire

The Main Exchange

Need some help on this one. Start from cold runs on all 8. Pull out of marina approx. 1000 rpm runs on all 8. Get on plane approx 3800rpm cruise after 10 seconds drops a cylinder. Come off plane and idle on 7, switch off, restart and most of the time it will restart on all 8. 1000rpm back to marina and it will randomly keep dropping a cylinder.

I have so far done the following trying to fix this problem; All 8 injectors rebuilt, 8 new Volvo plugs, all plug wires (Volvo) replaced last year. Could it be a coil pack?

Any suggestions? I am going to the boat tonight to recheck all connections and grounds.

Thanks everyone and hope you are all having a good holiday!!

Handymans342

Yes, it could be a coil pack. Anyway to hook up a computer?

The Main Exchange

Had a Volvo dealer in Seattle hook to the engine and no codes, ran all the cylinder efficiency checks all good. If I don't find anything tonight I was going to replace one coil pack and run the engine and move it to each cylinder until the misfire stops??

Michael T

@RW2006. I assume when you say "randomly dropping a cylinder" you mean that it is NOT the same cylinder each time. Could your spark distribution cap be cracked, even a hairline one? Is there carbon arcing inside the cap? The swapping out of a coil pack seems relevant. I also assume your coil wires are properly separated to avoid cross firing? As well, your alternator is producing 13-14 volts at 3800rpm, - not tanking? I think that's what a Volvo should be doing. Was the alternator ever replaced? I think I heard once that Volvo's alternator diodes are particular to the Volvo ignition system and must be O.E.M. Final question, was any repair done just prior to this? If so, what?

The Main Exchange

MT, no distributor it has 8 coils packs 4 on each valve cover. I have no way of telling if it is the same cylinder but it can run great for a while then repeatedly keep dropping a cylinder. Voltage is good. I rebuilt the engine last year and have run for approx. 140 hrs on the rebuild. This problem started a couple of months ago hence the rebuilt injectors etc.. I replaced the plug wires when I rebuilt the engine and plugs 2 weeks ago. 

F1100

check the coil packs do a resistance check, then check spark plug gaps, and then if it has a obd2 sensor see if its throwing a code. It could also be the ecu. Check the wiring to the coil packs.

The Main Exchange

Thank you for the advice still checking all the connections

F1100

I assume you swapped the coil packs before you went and started rebuilding injectors and changing plugs no? Swap the coil packs and see if the miss swaps cylinders with the packs. If its a miss at high rpm its most likely the coil pack since low rpm it will still light off, however higher rpm will cause it to miss.

In all cases identify whats the root cause before you start replacing things for no reason.. Thats what mechanics like to do

Worst case it could be the ECU as well, however the pack swap will show that.

Michael T

@RW2006. If you can get the engine to run when it is on the "7 cylinder mode" you can isolate a suspect cylinder by removing a wire at a time. If nothing happens that cylinder/wire/plug/coil pack is the culprit. If the revs drop when the wire is removed then that cylinder/wire/plug/coil pack is okay. keep going around the engine until you find the culprit. If the cylinder fail is rotating that will lead you to the suspect also.

The Main Exchange

@MT, I was going to try that this weekend problem is it runs on all 8 when cold and the wires are hard to get off the plugs.
@F1100, I don't know which cylinder is the culprit. I was thinking of replacing 1 pack and keep moving it until it stopped missing. I had the injectors rebuilt as the engine seemed down on power and that fixed the top end speed issue.

F1100

Yep you can do that too, just buy 1 new coil pack, and swap until the miss goes away. Will take a bit of time, however you have 1:8 chance

Best way however is to do a resistance check..it will 100% show if that coil pack is bad.

The Main Exchange

@1100 good idea I will do that this weekend might save some time!!

Michael T

@RW2006. Very interested in eventual solution. Please advise us via post if you have the time. Would be great for future reference!

The Main Exchange

@MT, Looks like its the coils, too hard to figure out which one so I am replacing all 8. I was told that they can start to act up with a lot of hours on them due to duty cycle etc.. I have 450hrs on mine so that should be it. Will update the post once installed and tested.

F1100

Its 100% easy to find the bad one... check the resistance of them...and 100% you will find the faulty one.. you dont even have to unscrew them all.

find out what the good coil resistance value is..and voila you will easily find the bad one.

Dont just throw money away for no reason, coils can last years and years... it was most likely a faulty winding.

your mechanic sounds like he wants to sell you 8 coil packs instead of one. They can literally last YEARS on low HP applications like these boat engines.

Michael T

....or remove one ignition lead at a time until you find the cylinder that doesn't alter the rpm - that's the one with the bad coil or whatever - you have choices to find the culprit: meter or old school.... LOL

The Main Exchange

Just a quick update, I installed new spark plug wires tonight but it was a little too windy to go out so I fixed the HVAC instead. Planning on taking it out tomorrow after work, will post update then!

Michael T

Fingers crossed Richard! You know it could have been something as simple as a wire that wasn't totally bad but was starting to leak (spark-out) and was partially grounding out on the block or beginning to cross fire on another wire! If so, you probably got it!

212rowboat

got some bad news for you, but some good news, too:

You can't always find a bad coil pack by checking resistance... but the issue you're encountering is most likely a coil pack.  

coil packs can be tricky... yours sounds classical... the things are internally isolated with a ceramic like two part epoxy, and when it is cold they are pretty dang sturdy- not demonstrating any issues at all- but when you get them warm? The epoxy separates and allows cracks to form that doesn't isolate the current too well at all, allowing an internal ground to happen.  It will only manifest and can only be checked when at operating temperature, and rarely shows anything externally.  A resistance check with ye 'ol multimeter will show this, as stated, but not always- to hedge your bets do it when the coil packs are at operating temps and the isolation material is still separated, because when the packs cool and the casing contracts, you'll look right past it.

if you wanna figure out which cylinder, just pull the plugs and observe the tips... your off firing cylinder will most likely have build up the others don't have. If you don't wanna mess with that, as it can be a PITA, simply pull the boots off and hold near intake manifold and see which ones bridge the gap.  If you have a competent pilot, you can do this idling back to the marina.  

The Main Exchange

@212, I was also told that with 450hrs the coils could be going bad, so I replaced all 8 coils with GM ones still the same. So far new VP plugs, GM coils, VP plug wires, sea trial tonight, fingers crossed!!! I also had an good conversation with a fuel injector guy in NY. He was saying about a possible bad injector coil when warm/hot and he can bench test the injectors hot. The company who rebuilt mine could not test hot. If the problem is still there tonight I am going to disconnect the injectors one by one until I find the cylinder, easier said then done when out on the water.

On a light note this reminds me of a Blondie song: One way or another I'm gonna find ya
I'm gonna getcha getcha getcha getcha.

Needed some humor this morning!

212rowboat

check out five-o motorsports for injectors...  the guy's name is bruce... you can likely buy a set new in box that have been bench flow rated and grouped cheaper than you can have a set rebuilt.  

but another couple things... 

injector O-rings are tricky.. if you crushed one while you were installing them, which is silly easy to do, you could have a bad seat and that cold lend to your issue... 

or another, and it took me a LONG time to figure this one out- 

whether EV6 or EV1 connectors on the injector harness, the blades and spades are easy to bend, and since they are driven off of impedance/resistance, it is incredibly important for the blades to have full seating across the spade- no twist on those blades whatsoever... they are easy to bend while pushing them on to seat, and the bend is easy to miss while inspecting them... make sure the blades are in FULL contact with the female spade... you can pull the spark plug on a cylinder encountering this and there will be zero evidence of over fueling/no burn- because there is no fuel going to it.  and the computer thinks it's firing the injector just fine... so.. it's really hard to spot... give it a look see..  

The Main Exchange

@212 I had my injectors rebuilt for $25 each and new are approx. $85 each.

212rowboat

I hope that wasn't just baskets and ultrasonic jewelry cleaners.... that seems to be the normal price when that is the procedure... they often flow as much as 20cc's apart when that happens... or, the spray pattern is altered on one where something bounced off of it under the noise and took a piece of the tip with it... 

in all honesty, and I'm not trying to be a jerk when I say this: Injectors are hearty pieces of equipment with gas engines... they rarely go bad, and they rarely need cleaning... they will last the life of an engine in almost all cases will outlive the engine... however, a lot of subtle things can go wrong when they are messed with.  It's really easy to do.  

The Main Exchange

@212 I agree with you and I am hoping that I had a plug wire gone bad even though they only had 150hrs on them. I replaced them July 2014 when I rebuilt the engine. 

The Main Exchange

OK here’s the update: Started the engine ran ok from cold. Pulled out of the marina and started to load the engine approx. 1500 rpm had a couple of stumbles onto to 7 cylinders. I messed with the injector harness and connectors problem went away on its own. Ran the boat for about 30 mins at approx. 4k rpm and WOT no issues. The misfire didn’t come back so was it a slightly fouled plug from the possible bad plug wires that cleared itself? I don’t know but will sea trial again this weekend. Thanks you guys for all of your suggestions I really appreciate the support.

Michael T

Nice work Richard. You may be right about a fouled plug burning off some cr*p or it might have been a loose connection. Anyway, looks like you nailed it! Most of us start with the easiest (and cheapest) fix by checking grounds, wiring and connections before we go for the big $$$$ fixes. It is often something simple.

raybo3

Sounds like a corroded pin on one of the connectors..........

The Main Exchange

Update: Ran second sea trial last night for approx. 30 mins, no misfire and engine felt great running on the numbers that I always see, 3800 rpm 28.5 knots. So far so good will run another sea trial this week, weather dependent and hopefully go away overnight on Saturday!

Thank you everyone for your support and advice.

Dream_Inn

That is good, but I'm with Raybo.  I'm betting it is a connector issue.  I've seen the main harness connector going to the engine give many different problems.  A buddy had one where you could jiggle it a bit and the fuel pump would shut off.  Lots of things go thru it.

Michael T

Great diagnosis  Richard. Cheapest repair is to check all grounds and connections first. 

The Main Exchange

Update: Sea trial # 2 on Sat. Started from cold left the marina got on plane boat ran fine. Same numbers as before, so we ran for approx. 15-20 minutes at 3800rpm. Headed back to the marina dropped to 1500rpm, then 1000rpm then as normal idle as I maneuver into the marina. Went to turn into our row and low and behold the engine dropped a cylinder for approx. <10 seconds. I went into neutral then reverse to stop the boat back into neutral then the engine came back onto all 8 and never missed again. Tied up in the slip sounded great.

I am going to call a Volvo dealer and have the scan tool diacom hooked up and run the boat. I am at a loss but the whole injector solenoid getting hot theory is sounding that it could be the culprit. Will keep you guys posted.