AMC oil pressure problem

Hi all. I'm new to the forum. Since amcforum.net closed, there is nowhere to talk AMC on the net. I'm glad I found this site. I do have a problem, however. I have a 69 AMX 390 4 speed. (This IS NOT the problem!) I have noticed in the past couple days that when taking off hard or when running down the road at about 50 and punching the gas, the oil pressure drops hard. The gauge says it drops pretty well completely off to nothing, then after about 10 or 15 seconds, it slowly builds back up and runs at the normal pressure. I haven't noticed the car running any differently, and there aren't any knocks or noises. When idling, the car has about 40 pounds of pressure. As I said, I haven't noticed a thing different about the way the car runs, but this problem kind of has me stumped and worried. I saw an earlier post about what sounded like the same problem. I think it might have been a newer Jeep with a different motor, so I wanted some insight as to what this might be. Any help would be greatly appreciated, I'm tired of worrying about the car!

It sounds like the oil pickup is uncovering. It may be too high in the pan, or not enough oil. You might try running 1/2 quart or so over full and see if it helps. I have seen a couple of pickups develop stress cracks where the head is welded to the tube, and they suck air there.

BTW - The AMC forum is back up with a new owner as www.amcforums.com .


Bob
tufcj

Thanks. I have a problem with getting an accurate oil level reading too, I think. It seems that when you pull the dipstick out, the curve of the dipstick tube is too sharp and causes the oil to be wiped off the dipstick and you can't really tell where the oil level is. If you remove the dipstick really carefully, you can center it in the tube so that it doesn't rub either side as you're pulling it out and the oil level reading is completely different. Is this something you're familiar with? This isn't anything major, but it is kind of a pain when you're checking oil.

So you say fill about 1/2 quart above full and that could help?

Also, thanks for the link to the new amc website, I've been having withdrawls.

Dont know if this is you problem or not, but I have read on here about a couple motors sucking up the bottom of the pan or pulling the pickup to the bottom of the pan. I guess it might could be sucking the pickup to the bottom of the pan and blocking off the oil flow. I guess when you hit the gas the engine rpm suddenly increases, and so does your oil pump, so the oil pump suddently suck more oil than normal with enough pressure to suck the pickup to the bottom of the pan. Its a wild thought but could be somthing to keep in mind. I think the pickups are supposed to have a plastic "button" on the bottom to keep it from being sucked to the pan. Some people braze a 1/4in nut to the bottom when the plastic one is missing. I did that for my new engine.

Don't forget the AMC mailing list a amxfiles.com :mrgreen: :mrgreen:

BTW - The AMC forum is back up with a new owner as www.amcforums.com .


Bob
tufcj[/quote]

My 71 401 Javelin started doing the exact same thing. Have you found out what is causing the problem gopak12??? I would love to know before I start tearing into my car. It runs great other than this scary problem. Thanks, Scott

I put a couple of gasketed roofing screws into the bottom of my pickup to keep it from sucking up the pan.

http://www.amclives.com/ has replacement white plastic or nylon sump spacers to replace the original one that goes in the small hole on the bottom of the sump. It's purpose is, of course, to keep the bottom of the pan from getting sucked up to the sump. After thirty some years, a lot of the originals have fallen either on their own or by someone scraping valve seals or timing gear teeth out of the sump pickup.

I have had at least 2, that I remember, that did not have the spacer in them anymore.

Ah...YES....

#7541 Each $7.50 Oil Pick Up Spacer Plastic All New Stock

Oil pressure going down when rpm is going up is a classic symptom of worn out cam bearings, as well. Didn't just have a timing chain installed?

One of my AMXs broke down a couple of decades ago, on the road about 1,000 miles from home & I had to pay a Chevy dealership to replace the timing chain & a bunch of pushrods. Evidently they let the coolant pour into the oilpan because the oil pressure went south shortly after that & I couldn't find where they charged me for oil or filter!!!