strange knocking noise above 2,000 rpm (5.0 efi 95')

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

The only thing I can logically think is the problem would be a loose or corroded connection. Maybe the main injector harness or computer harness. Should I just clean them and dielectric grease them?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

This is very frusturating. So today I went to start the boat to warm it up before I started to clean connections and check wiring. It ran for about 30 seconds and died. It would not restart. I checked and no injector pulse and no ignition. I tested my signal from the PIP and it varies between 8-12v so it is changing voltage with engine rotation. I took off all grounds and cleaned them. I fixed a bad collant temp sensor I found. I disconnected/reconnected all harnesses and shook all while testing engine. No start. I tested the module, no start. One time it tried to start for a second but quit before it even caught. The only thing I can think of is the ECU.

It is a ford ECU (plastic coated inside against corrosion). I can no longer get an OMC ecu for it so I'd have to get a Ford one and get it flashed to specs, right?

Any other ideas or tests I can do before trying to get a computer?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Well, I took my multimeter and tapped into the voltages coming from the ecu to the injectors. All the positive feeds are solid with good connections. I tested two separate injector feeds and both were giving the same readings under identical load patterns. The ECU is giving good signals to the injectors. I swapped injectors as well as all other components isolating the cylinders. The only thing left is something in the bottom end of the engine. Would a bad ring or similiar bottom end component possibly cause my issues?

 

[Don S]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

The one thing you keep avoiding, and not replying to is a compression test. Do a proper test and post the results for all cylinders. Even if you don't think it's the problem.
Here are some basic procedures for a compression test that actually means something.

View attachment 97-25 Compression Test.pdf

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Don, you're absolutely right. I didn't have the proper tester so my results probably weren't the most accurate. I'm going to get the correct tester and try it again. I might even have to pull the manifolds off but I just replaced the bolts so it will be an easy task. It might be a week until I get to it. I'll let you know. Thanks for talking sense to me and the guide for instructions.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

So today I took off the exhaust manifolds to get to the plugs for an accurate compression test. My bad cylinder read 90,110,120 in sequential order. I tested the others which read about 105-115-125 in sequence. I used some oil in my bad cylinder and it read 130,150,165. Pretty close with the other cylinders as well when I added oil. It is definately bad rings that need replaced. My problem finally arose and now I have to decide if I really feel like pulling the engine and rebuilding the entire bottom end. I'm assuming if the rings are worn that bad; quite a few other parts are probably ready to be replaced as well internally. Bad luck.

 

[Don S]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Sounds like the engines had water in the cylinders, rusted rings in the pistons. Probably pitted cylinder walls from water.
The knocking my be from bent rod or damaged bearing from someone trying to crank the engine when it was hydrolocked.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

I had the heads off and the walls didn't seem bad or pitted at all. Then again, it was only visual. The rods were perfect, so I'm thinking maybe a bearing also. Would you recommend rebuilding the engine or is it more trouble than what it's worth?

 

[Don S]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

The rods were perfect,

How do you know?
I'm referring to the connecting rods, not push rods.

Would you recommend rebuilding the engine or is it more trouble than what it's worth?

If you can rebuild that one, you are going to be a lot better off than buying a long or short block. For one thing, the remanned engines are usually bored out to max oversize. Marine engine manufacturers recommend .030 max over bore, The remanned engines are all .060 over.
If the cylinders measure out ok, and the crank is in good shape, you may need nothing more than new bearings, maybe a piston or two, some new rings and good to go.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Sorry, I thought you were talking about the rush rods. I can rebuild the block about 90% myself. The last one I had the machine shop hone/bore the cylinders along with polishing the crank. I can do all the other mechanical processes myself. I think I might pull the engine and see. No matter what, it'll have to come out and reinstall either a new or rebuilt one. Thanks for all the help!

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Talk about luck, Craig's List comes through for once! I found a guy wanting to sell an OMC setup the same as mine for $600. I can now pick and choose what parts go back into my build as far as assesories are concerned. Plus the parts I can sell will help pay for the build.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Well,, I tested out the used engine and it is about 160-165 on the cylinders. One was a bit low at 155 but within tollerance. I think I'm going to hook up the new engine and test it out. If it runs properly, I'll just stick with it instead with backup parts. Sound like a good idea?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

I put the entire system in and it works! No more knocking noises and what a difference powerwise. My journey is finally over and my thread can finally sink into the achieves. Word to the next person that has this problem; please run all your tests first to prevent a very pissed of wife!