sup guys

driving my 69 stang around with a 390fe/427 cam/HV oil pump w/6000 miles on a rebuilt engine and my rocker arms start rattling. look at my oil pressure and it is fixed at 20psi. pull over check my oil about a qt low and grab some oil right quick on the way to the garage-no difference. park the car and scratch my head and start tearing things apart...

oil pan taken off - no gunk and clear of crap in the screen
oil pump - appear fine, can't tell if the bypass spring is gone or not
oil sender unit - clean
passages to oil sender unit - clear
oil pump tests fine, got a drill out and some oil and was throwing stuff all over the place (can the bypass spring still be bad?)
hi-perf oil shaft - fine, no wear on dist or oil pump
oil filter - no collapsing, oil had some minute shavings sparkling in the sun but i am not surpsied for a new engine, i have always seen some (bearings bad?)

so i figure maybe something is stuck in the engine someplace, now this happens...

i put in new oil, new filter, same oil pump, and batten the oil pan down. i take the gauge off the oil sending unit and to my surprise no oil shoots out of it when i start the car, zero.

i think this is a oil pump problem (bad bypass spring dumping oil back in the pan?)

i don't think this is a rocker arms assembly problem for oiling because no oil shot out of the sender unit with the gauge line off and i know the pump throws oil (bypass spring status unknown)

it could'nt be bearings because again no oil shot out of the sender unit

how does an oil pump bypass spring get stuck? just as this happended i had mashed the acclerator hard, could i have got the spring stuck open?

any opinions/comments much appreciated

PS this 390 has the oil gallery mods/plugs done to it, oil pressure ranges 20-90 when it worked.

 

Why didn't you test the pump and check the bypass spring when you had it out?

 

I might try pulling the distributor and spinning the oil pump with a drill to verify the pump is/is not working. With the valve cover off, you should see some oil flow if the pump works.

If you don't see any oil, I would be tempted to check the bearings for damage, and at least replace the oil pump. What kind of oil pressure guage do you have?

And welcome to FTE!

 

First, WELCOME to FTE

Something is seriously wrong if there isn't even a dribble out the disconnected oil-gauge line.

Using a drill, spin the oil pump through the distributor hole. I used a 5/16" socket, and ground the outside diameter of the socket down so it would fit in the hole You could use an old distributor shaft too. Spin it counterclockwise.

It's possible the pump isn't primed with oil, and that's why it didn't pump anything when you started it this time.

This is dangerous. Make sure you don't run it very long if AT ALL without oil pressure.

The bypass valve in the oil pump can be "cocked" in the bore, and get stuck wide open.

Many here on this site would never think of putting an oil pump in a motor without disassembling it and de-burring everything, checking clearances, etc. Chances are, there was a burr on the valve piston, or a nick in the bore. Or some other piece of dirt got in there and stuck it wide open. And YES - it would happen at high RPMs.

Report back how it works out!

 

thks for the info guys

yes i did take the pump off and try it out and it worked fine, throwing a whole lot of volume at a battery-powered drill speed.

oil gauge was a vdo, put another on to chk pressue and it was the same. connected to the sender unit nothing came out (oil). clear passages and all - amazing.

i did run it with the valve covers off and no oil out the bolts.

here is what i did notice - with the pan off the aft 2 main caps and journals were soaked in oil, but the other fwd 2 caps were not. it looked like the pump was just throwing oil back in the pan and oil was kicking up in the back part by the baffle

will be checking the caps/bearings this weekend - any suggestions on which one to check rather than all of them. not farmiliar with 390 lower oiling flow - thks

ps how bad does a bearing have to go out before it gums up an oil passage to the top end? can a large enough single piece get up there? never had it happen before

pps how can you tell your bypass valve is bad - its springy and not coked from what i can tell

i am a chevy guy so ford's throw me for a loop! (uh....go ford)