The new 8.1 only firing on 4 cylinders.

[gogger]

So I got it in, started on the first crank. Took it to the lake and it started right up, good oil pressure. Didn't sound quite right. Before I could run it much more it stalled and wouldn't restart. Backfired, blew the muffler off the flanges. Pulled it out and took it home. Pulled the plugs and only 4 indicated burning fuel. Then I put new plugs in and it definitely isn't firing on all 8. Starts but running rough. Checked all the connections. Guess I need a MEFI 5 scanner tool to see if it is throwing codes. Any other suggestions while I try to find a scanner.

Bad coil packs? They are brand new I believe.

Just grasping at straws.

[michael hunter]

What fuel and ignition system are you running?

[cadunkle]

Any other suggestions while I try to find a scanner.

I know what I'd do to fix it...

http://img0102.psstatic.com/161288264_marine-holley-carb-850-double-pumper-electric-choke.jpg

http://performanceparts.com/performance_parts_images/msd_8560.jpg

[wotan2525]

I know what I'd do to fix it...

http://img0102.psstatic.com/161288264_marine-holley-carb-850-double-pumper-electric-choke.jpg

http://performanceparts.com/performance_parts_images/msd_8560.jpg

If the only tool you have is a hammer, every problem looks like a nail.

[Moor]

Lots of funny in this thread so far lol

[gogger]

I think it would be hard to find a carb and distributor for the 8.1. It's fuel injected and no distributor. I guess the ecm controls everything. Really a let down after pulling some late nighters and getting it installed. Then a ignition problem. Or so I think.

[gogger]

17586
17587
1758817589

[cadunkle]

I think it would be hard to find a carb and distributor for the 8.1.

If you look on some of the go fast forums it's actually a fairly common conversion. Many people have had issues with the electronics so far as reliability and driveability, and of course past a moderate HP increase it becomes a limiting factor. Intakes are available and the block will accommodate a distributor. Not sure if the cam has a gear or not but that's an easy swap too. I wouldn't convert a perfectly good running stocker in a tow boat for the heck of it, but if I was in as deep as you are I'd definitely be upgrading while it's apart. Also if oil starvation was the cause of the original failure I'd be looking at upgrading to a larger oil pan with baffles if your primary use is surfing.

[michael hunter]

Start with the basics. Run compression on all cylinders. Compare the 4 that fire to the 4 that don't.

[2500HD]

efi is easier to work on than you think. I put a 2004 4.1L in my 74 260z and the efi is awesome to work on, so easy.
Were all the plugs that aren't firing on one side of the Block? If so then your not getting power to coil packs or injectors. The other problem could just be a map sensor or maf sensor. From the look of the plugs i would guess map sensor.

[gogger]

Well I put a sparky tester on it and they all are getting spark. Had it in my mind that it wasn't sparking because of the plugs. Did a compression test and they are all right around 130 psi. I put new plugs in it. NKG Iridium plugs and it started right up and seems to be running better. Some of the plugs that I didn't think were firing appear to have some carbon on them now so maybe it is cleaning up. Could have been some air in the fuel line? I probably didn't run it more than 2 minutes total before it stopped. Ran it another couple minutes tonight.

Backfire yesterday messed up my muffler. Fiberglass muffler blew apart where one of the hoses from the manifold attaches. Kind of like a flange that was attached to the muffler. I epoxied it back in. Not sure if that will hold. But it seems to be holding now, meanwhile I will try to find a new muffler. So I didn't run it long without the muffler attached. Tomorrow that goes back on and I will pull it to the lake and try again.

I want to get an engine scanner so I can run some diagnostics on it. Anyone have or use a Mefi 5 scanner? Any suggestions on what I should get?

[2500HD]

I would almost guarantee that the map sensor is bad or has a bad connection. I had a bad one on my 260z and it ran really rich and backfired. There is a way to check the power supply to it but i forget what it is. If you can find out what vehicle the 8.1 was used in besides boats you can get one for way less than the marine application.

[2500HD]

http://www.rockauto.com/en/moreinfo.php?pk=1111766&cc=1432495&jsn=540

[gogger]

Well I will google it and see what I can come up with.

[Moor]

Lots of funny in this thread so far lol

just want to clarify, i'm not laughing at your problem grogger, i'm laughing at cadunkles solution and wotons response. I can't offer much help here, hope you get it sorted out

[gogger]

just want to clarify, i'm not laughing at your problem grogger, i'm laughing at cadunkles solution and wotons response. I can't offer much help here, hope you get it sorted out

Yep I knew what you meant.

[gogger]

Picked up a new Map sensor and it seems to be all cleared up. Took it to the lake to break it in. Quickly realized I hadn't put the plugs in the exhaust manifold riser plugs in. So ran it a few minutes, then headed back home and put them in. Tomorrow should be the day!

[cadunkle]

Glad you got it figured out. You've had a busy season, but plenty left or at least that's what I keep telling myself as I only have about 2 hours on the Saltare this year. I have a long way to go to get up to my usual 75-100.

[gogger]

Well I did really hustle to get it back up and running. Surprised myself actually. But I am in charge of our Wake the World event here in Ohio this year and it is on the Eighth of August and I really need the boat for it. Wasn't sure if we would have enough room for all the kids. But I can hold a lot on my boat if I need to. So that gave me some inspiration. Plus I really missed it. I know this boat a lot better than I should now. But I feel good about the new engine. I know it doesn't have any salt damage. lol

[Mischief IV]

I wish I had that inspiration...I found one day to work on mine in last two months and it rained as soon as I pulled the tools out and then I screwed up a customer's system remote logging in so off to work I went. Hope WTW goes well and she runs better than ever forever. If anyone deserves a break, it is you. That reunion was tough on the boat but seeing how you take it all in stride, I have to say, you are a better man than me.

[gogger]

Pulled it to work to take it out right after work. Griggs is closer to work and to my buddies that wanted to come out. So I launched it and started it to let it warm up some. While it was idling I was checking out everything and heard water running. Well I am pretty sure I looked at the block, but I missed that I needed to install my engine drain plugs from the old engine on the new one. Amazing how much water comes out those holes. So I loaded it back up, said good bye to my friends. And pulled to my house. Installed the plugs and headed to Deer Creek. It's closer to the house. Launched it again and ran it for about 1.5 hours. I can hear a small exhaust manifold leak, I retorqued the bolts but that didn't help. But otherwise it ran great. So I think I am back in business.