*knock knock knock* oh noes

[occupant]

Fuel pump went out in the 454 Suburban. Repeated attempts to start it using old gas, new gas, starter fluid brought fail. Had fuel pump changed. Electric pump, in the tank. Mechanic says it now has a lower end knock from oil diluted with gas. It started ten seconds into his test run after installing the new pump. He shut it off, we pushed it home.

I'm changing the oil before the truck gets driven, have a filter, buying oil at the local c-store, hope they have something not nondetergent. This is (was?) our only running vehicle. Is there anything else I can do to quiet the knock, anything I can add to the oil or fuel to keep my wife from throwing a fit, or the engine from throwing a rod? Oil pressure was 50-60lbs when he looked at the gauge after hearing the noise and right before shutting it down. I've never seen it above 40 really, unless it was ice cold outside.

 

[Zaedock]

How can the oil be diluted with gas, if no gas was being pumped to the TBI?
Even with the cranking attempts, at least some oil is being pumped, so there shouldn't be any bearing damage.

I would run a tank of 93 gas and see if the knock goes away. Sounds like your mechanic is pull'n your leg.

 

[Chris142]

I'd get a 2nd opinion. 454's are usually pretty noisey. Everything from piston slap to a wrist pin to a cracked flexplate will sound like it's coming apart.

 

[occupant]

Well I heard it because I was standing there with him. It's a very faint knock, not a lifter tap. The engine was sewing machine quiet before the fuel pump gave out. I probably poured enough fuel down the TBI in attempts to start it to allow some to seep past the rings. I started out using gas that was 2 months old, but after that failed, I poured some in a styrofoam cup and it was yellow like lemonade. I got fresh clean clear as water gas and tried again but nothing was coming out the injectors at all. Mechanic confirmed the dead pump with his multimeter and changed it out. I think I just spent $242 to find out I used too much gas in my starting attempts.

It's too dark to change the oil but I got 7 quarts of Uni-Lab 10-40 SF oil for 88-back cars (this is an 88 Suburban) (dated 1/07) from the c-store. Better than non-detergent, will change it again if the knock goes away. They only had that oil. My mechanic doesn't stock oil, interestingly enough. I'd rather change it myself, already have a filter. Then if it is still knocking I can start calling junkyards.

 

[addyguy]

If you really DO have a rod knock, in Texas you can probably easily get way with using a 20W-50 oil if you had to.

However, my fist choice would have been a CI or earlier (higher ZDDP) 15w40 diesel oil...don't know if that year of 454 is a roller valvetrain or not...

Like others on here, even if you dumped a bunch of gas into the oil, you 'shouldn't have fried the bearings in the time it took you trying to start the truck. It probably takes a few thousand miles of running with severly fuel diluted oil before bearing wear badly enough to knock.

Keep us updated!

 

[The_Jeff]

I agree with the above, think of adding up the few dry seconds after each oil change over the lifetime of a vehicle and how the bearings do okay with that.

 

[occupant]

*whew*

OK, drained as much oil as I could, only got 4 quarts out of it. Changed filter and added 5 quarts, still off the dipstick, added another and another, knock disappeared after 30 seconds of idling.

One thing you have to remember, this is the only running vehicle we have, the Torino will run with a jump but is not inspected or tagged so I can't just drive to some oil boutique shop to pick up something fancy. The SF 10W-40 will have to do for a few hundred miles until I get time to change it out right with the front end up in the air.

I agree a 15w40 HDEO will do good in this truck. Even with the nearly 8-year old battery and 10W-40 oil it doesn't crank slow at 20 degrees, which is about at cold as it will get here. I just need to keep it running long enough until my wife's Durango gets here.

 

[mechtech2]

Like Zaedok said, less fuel pump pressure will not cause oil dilution.