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1996 7.4L LX Intermittent clattering?

R

redhook98

New member
I have an intermittent clattering noise towards the front of my 1996 7.4L LX (with Bravo 3) engine. It is a fuel injected unit. The clattering is intermittent and does not seem to correspond to anything in particular. Just comes and goes . Only notice at idle. Hoping it is just a water pump going bad.

Put about 20 hours on it last year when it was doing this. No issues. Oil pressure good, no water in oil, 300 hours on motor, always maintained.

Have video but can not upload.
 
Appears to be coming from the raw water pump/fuel pump assembly. What would make an intermittent clattering there, and only at idle/low RPMS? Is there a small pushrod or is the fuel pump working off a cam on the raw water pump shaft?
 
Docksidemarineservices said:
Take the fuel pump driver off and pull the fuel pump off of it. It is supposed to be serviced regularly. Gear oil inside.
Click to expand...

I had never heard of that. Never had a Merc with the fuel pump mounted like this either. So are you saying to remove the fuel pump from the raw water assembly and add (or change) the gear oil? Is it just 80/90w? That could be what the clattering is?
 
Take the whole pump driver (Water Pump and fuel) disassemble it, clean it, inspect it and reassemble it and fill it with HI Perf Gear oil that is in the out drive.
 
I pulled the fuel pump off and it was almost all gas in the reservoir. Black gas. I thought there would be a solid cam, but instead I see a loose ring that spins around the shaft. Is there supposed to be bearings in that ring, or is it loose? My water pump was not leaking and the bearings feel tight.
 
You need to replace the fuel pump. Wash out the Driver and fill it with The outdrive oil. The ring is supposed to be loose. I usually remove the driver complete and pull it apart tiy check the bearings......Big $$$$$ part.
 
Docksidemarineservices said:
You need to replace the fuel pump. Wash out the Driver and fill it with The outdrive oil. The ring is supposed to be loose. I usually remove the driver complete and pull it apart tiy check the bearings......Big $$$$$ part.
Click to expand...


Yep, got one on the way. Washed the reservoir out. Didn't find any metal bits. Fresh oil is in. Makes a big difference with that cam ring. Bearings and seals still good.
 
OK, got the new fuel pump on and it seems to take care of 99% of the clattering. Can still hear an occasional clatter, but not much. My big question though before I go out and buy a new raw water pump is "how much noise does the raw water pump make when it is good"? Am I supposed to hear the pump, or am I just to sensitized to anything making noise in that area now? It's hard to describe, but it is almost like a deep but subtle bearing noise. A hollow tube to that area does not tell me much. No grinding or anything out of the ordinary, I htink. Bearings and seals are tight though. New lube oil is in the pump. Am I worrying about nothing now?
 
Are you sure it's not the transmission coupler? Common problem if the motor is idling a bit too slow and not smooth enough>


Jeff
 
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