Is my 7.4 MPI seizing up?

[BigDog98]

Need help please. I have a 1999 7.4 MPI S/N - 0L085399 , I believe it is a MEFI2 . Anyways i have an issue where i would turn the key to start and the starter or engine would make a loud thump noise like metal on metal getting stuck. Almost sounds like the gear in the starter is getting stuck with the flywheel or even like a seized up motor. However if i play around with the starter and bump it in and out with the key it would free up and start right up and run fine the whole day. I have already replaced the starter with a aftermarket and same issue happened again but once again i was able to free it up and start it up. The weird thing is that when it starts up after the engine makes a loud noise like it sucking in a lot of air and then it calms down. Is it possible that the engine is seizing up? But it runs good and strong when you get it going. Any input would be greatly appreciated. Thank You

 

[Scott Danforth]

Stop running your motor.

Most likely you have a manifold to riser gasket leak and you are hydrolocking.

Next time pull your plugs, i bet water comes out of a cylinder or two

 

[QBhoy]

As scott says. Probably hydraulic locking. Check the plugs for signs of moisture, as well as the dipstick and oil filler cap.

 

[tpenfield]

+1 to the manifold gasket and related hydrolock. If you find water in the cylinders . . . it's time to drain down the exhaust manifolds and take the elbows off for an inspection.

 

[HT32BSX115]

it's time to drain down the exhaust manifolds and take the elbows off for an inspection.

Yes. You may have leaking riser gaskets that allow a little water to run back into open exhaust valves immediately after shutdown.

fresh water or salt? Closed cooled? either way, it doesn't take much water in a cyl to briefly hydrolock the engine. Cranking or waiting for a while may allow water to leak past the rings and start normally.

Pull all 8 spark plugs and have someone roll the engine with the starter while you look. It will be pretty obvious when water shoots out of one side or the other!

 

[BigDog98]

OK so a little update. I went down to the boat today and decided to run a compression test. I usually do one at the beginning of every season. I pulled the plugs and turned the engine over to see if anything would shoot out of the cylinders and it was dry. Engine turned over freely with the plugs out. The compression results. The lowest compression i had was in #3 and it was 140 , the highest compression was 160 and most of the other cylinders has 150psi. I ran a compression test in April and all my cylinders were 160 on the dot. However i ran the compression test with a cold engine today and usually i do it after a nice run. However the plugs were different colors and some of the had some crud build up on the electrode. I replaced the plugs in April along with the wires , Cap N Roater and a few other things.

 

[QBhoy]

Did you do this right after it didn't turnover properly ? Or otherwise ? All being well and no water ingress it would point towards a lack of cranking amps or a poor connection/starter/bendix/solinoid etc. Either that or your flywheel is worn and or damaged.

 

[BigDog98]

Did you do this right after it didn't turnover properly ? Or otherwise ? All being well and no water ingress it would point towards a lack of cranking amps or a poor connection/starter/bendix/solinoid etc. Either that or your flywheel is worn and or damaged.

Im not sure. The first thing I did was do the compression test when I got to the boat. I did not try starting it before. But it sat all day.

 

[CurrentObsession]

I would start with the easiest and least expensive thing to do.......replace the slave solenoid. $25 and 1/2 hour of time.

 

[Scott Danforth]

I would start with the easiest and least expensive thing to do.......replace the slave solenoid. $25 and 1/2 hour of time.

NO...NO...NO

nothing indicates a failed slave solenoid