MerCruiser 5.0 MPI pinging/detonation at higher RPMs

[QBhoy]

I’d be checking the retaining bolt is secure. Awkward thing to tighten down.

 

[Lou C]

Crow foot wrench

 

[QBhoy]

Crow foot wrench

Be the tool for the job I’d say. Possible with a normal, but a fiddle

 

[Lou C]

I still have the one I bought in 1973 or so. One end is for the Chevrolet, the other end is for the Ford. Had one of both in the old days, a 5.7 liter Chevrolet and a 5.0 liter Ford.
just like this, the 9/16ths was Chevrolet, the 1/2" was Ford....

https://www.amazon.com/DURATECH-Distributor-Clamp-Wrench-2-Piece/dp/B0B24ZHMTN/ref=asc_df_B0B24ZHMTN?tag=bingshoppinga-20&linkCode=df0&hvadid=80195759881317&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583795280096398&psc=1

 

[QBhoy]

I still have the one I bought in 1973 or so. One end is for the Chevrolet, the other end is for the Ford. Had one of both in the old days, a 5.7 liter Chevrolet and a 5.0 liter Ford.
just like this, the 9/16ths was Chevrolet, the 1/2" was Ford....

https://www.amazon.com/DURATECH-Distributor-Clamp-Wrench-2-Piece/dp/B0B24ZHMTN/ref=asc_df_B0B24ZHMTN?tag=bingshoppinga-20&linkCode=df0&hvadid=80195759881317&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583795280096398&psc=1

View attachment 376483

Great to hear stuff like that. I’ll need to get me one.
On another note…are you trying to make me jealous here ? I’d love to have been brought up with that kind of v8 car culture as an option. Almost sure I was meant to be born over there ! Outwith a very narrow selection of cars available here…owning a v8 here would usually have to be a result of having a boat with one. Even the few cars that so have one…aren’t a realistic everyday option at all. Just couldn’t swallow the cost of putting fuel in them.

 

[Lou C]

I’m looking for a newer Grand Cherokee I already have 2, a 1998 6 cyl and a 2007 Hemi V8. Next one V8 or nothing.

 

[nola mike]

Video posted by OP clearly shows the hei/flat cap style distributor commonly found on merc mpi engines

Based on the decent amount of corrosion on external areas of the engine seen in the video one would guess the distributor cap itself is suspect. As far as the movment seen on the distributor I'd verify the clamp bolt is secure and if continues to have movement removal and inspection of the complete distributor assy would be next

How would a loose clamp down bolt lead to that upper wobble with the shaft not having play?

 

[badfish29]

^ Yea what he said. The clamp down bolt is definitely tight and secure. The shaft doesn't move at all. It's only the head where the rotor and cap screw on to. I think I probably need a whole new distributor I'm just wondering if this is a normal amount of play. I don't have access to anything else with this same distributor to use as a reference so I was wondering if someone can check on their motor.

 

[04fxdwgi25]

That dist wobble is surely not right. You can see the sensor gap change as it moves. That will effect the timing big time. Does that dist a 2 part assy / have separate parts that bolt together? I suspect the screws / bolts are loose or MIA.

Definitely needs yo come out and be corrected / replaced if need be.

 

[dubs283]

How would a loose clamp down bolt lead to that upper wobble with the shaft not having play?

I don't know. I was suggesting items to inspect thinking pragmatically. Sounds like OP is sure the clamp bolt is secure therefore further troubleshooting is required.

I've removed and installed this type of distributor many times. Can't recall any time I've worked on one that wobbles like OPs. I would say it's time to remove the distributor assy and inspect (like in my previous post)

OP can continue to ask questions waiting for someone to post the true reason for the issue or can inspect the issue on their own. I don't know the exact reason for the issue therefore I can only offer suggestions for troubleshooting.

 

[badfish29]

I haven't had time to pull the distributor yet but I will today. Judging by the responses I've received it probably needs to be replaced so I'll most likely just go ahead and do that. I'll post how it goes and if it fixes my issue. Thank you

 

[nola mike]

I don't know. I was suggesting items to inspect thinking pragmatically. Sounds like OP is sure the clamp bolt is secure therefore further troubleshooting is required.

I've removed and installed this type of distributor many times. Can't recall any time I've worked on one that wobbles like OPs. I would say it's time to remove the distributor assy and inspect (like in my previous post)

OP can continue to ask questions waiting for someone to post the true reason for the issue or can inspect the issue on their own. I don't know the exact reason for the issue therefore I can only offer suggestions for troubleshooting.

Wasn't meant to be snarky...a few people posted the same thing, and I didn't see how that could be the issue.

 

[nola mike]

Great to hear stuff like that. I’ll need to get me one.
On another note…are you trying to make me jealous here ? I’d love to have been brought up with that kind of v8 car culture as an option. Almost sure I was meant to be born over there ! Outwith a very narrow selection of cars available here…owning a v8 here would usually have to be a result of having a boat with one. Even the few cars that so have one…aren’t a realistic everyday option at all. Just couldn’t swallow the cost of putting fuel in them.

At least you can buy a car with a stick shift...

 

[badfish29]

So I pulled the old distributor and the plastic was definitely cracked at the head area allowing it to rock back and forth like it did. I got a new one and installed it but the problem still doesn't seem to have gone away. I did a fuel pressure test and at full throttle I was getting right around 43 PSI so I think the pump is fine. I'm still pretty sure it's gotta be fuel related so I'm going to get a new set of injectors and see how that goes. If that doesn't fix it I'll suck it up and call in a professional.

 

[nola mike]

So I pulled the old distributor and the plastic was definitely cracked at the head area allowing it to rock back and forth like it did. I got a new one and installed it but the problem still doesn't seem to have gone away. I did a fuel pressure test and at full throttle I was getting right around 43 PSI so I think the pump is fine. I'm still pretty sure it's gotta be fuel related so I'm going to get a new set of injectors and see how that goes. If that doesn't fix it I'll suck it up and call in a professional.

Is there no knock sensor? Have you tried swapping injectors and/or plugs to a different cylinder? Have you eye balled the flow from the injectors or put a noid light on them?

 

[QBhoy]

At least you can buy a car with a stick shift...

Haha. That’s true

 

[Scott Danforth]

I wouldnt waste money on new injectors. I would send out what you have for flow testing and cleaning.

 

[badfish29]

Well actually I finally had a look at the 2 injectors that I suspected had been changed and after doing some research I found that they are the wrong ones. They are too small and don't flow enough which I'm guessing is causing a lean condition. I also suspect that this boat sat for an extended period of time which probably has caused the rest of the injectors to be at least partially clogged. So I figured after buying 2 of the correct injectors and getting the rest cleaned I can buy a new set of OEM refurbished ones for the same price so I did. I'll post up if that fixes it after I get a chance to install them.

 

[todhunter]

I know you've already bought new injectors but for future reference, the place I use for injector servicing charges $10 per injector for cleaning and flow testing, plus $10 for shipping, so $90 for a full set of 8.