Oil pressure reads Zero

[Aahubb]

Just went for a quick trip on the river this evening and noticed my oil pressure was reading zero. This is a 1985 Merc 260, 350 cid Chevy. I had'nt heard any strange noises from the engine so thought that it might be the sending unit but headed in anyway. As the engine came up to temp the oil pressure started coming up and held steady at 40 psi. Does this sound like a sender or a pump problem? If it's a pump is it very difficult to change with the engine still in the boat? I have about three inches of space under the oil pan but have to stand on my head to get to it. I just replaced the starter motor last week so am not looking forward to climbing back into the hold again!<br />Thanx Guys for any help you can offer.<br />...Aaron<br />1985 Galaxy 24ft cuddy, Merc 260 i/o

 

[John Carpenter]

Re: Oil pressure reads Zero

I had an intermittent problem just like this. The oil pressure would just go to zero like the guage was dead for a few minutes...then back up to normal. No noises that I could hear. My thinking, and my mechanic's...was that the sender or guage was screwy. NOT...blew the engine.<br /><br />Have you by any chance changed to a higher detergent oil? I had...and it did it's job...broke loose a bunch of crud which clogged the pick-up screen on the oil pump. I understand that it's a complete PITA to pull the engine for this, and would never have considered it before I trashed one. However, I would rather pull it to clean it than to replace it.<br /><br />I would have a good mechanic check it out and see if he can confirm or rule out some potential problems. A new sender would be cheap and might help figure out what is wrong. Good luck & don't ignore it.

 

[fireship1]

Re: Oil pressure reads Zero

Hello, There is only one way to be completely sure. Tap an oil pressure gage in where the sender is threaded into the block. Run the engine either in the water or on the trailer and compare the manual handheld gage against the dash mounted gage. If both loose pressure, then you have a problem. The engine will have to be pulled and the oil pan removed to inspect the oil pump pickup and the pump itself. If the handheld gage reads good and the dash drops out, then you know it's an electrical problem (probably the sender). I would guess it the sender might be your problem, as you say you changed the starter recently. Whenever electrical stuff starts acting up after some kind of engine service I would be quick to suspect a wire might have been bumped or loosened during the work. Try inspecting the oil pressure sending unit connection for a loose or corroded wire. I think all of this will point you in the right direction, post back and let us know how it goes. Good luck!

 

[vinney]

Re: Oil pressure reads Zero

You will hear the lifters talking to you and that engine will not run long with no oil pressure. The lifters will clasp. The small block will live on 10 psi per 1000 RPM's. You have a bad oil pressure sender or a bad gauge.

 

[John Carpenter]

Re: Oil pressure reads Zero

Well...no disrespect intended but...you MAY have a bad sender or guage, and you MAY have a bad and/or clogged pump. I...and my mechanic, were sure that I had sensor or guage problems...we were wrong. It did not cost my mechanic a dime.<br /><br />The fact that I am half deaf from years of shooting without ear protection & blowing up stereo speakers didn't help I am sure. My lifters may have been making noise...who knows...can't hear squat. Doesn't matter...YOU are the one that will have to pony up for a new engine. Check it out and determine the cause of the problem...don't assume it is ANYthing. Good luck.

 

[John Carpenter]

Re: Oil pressure reads Zero

Just another comment...as far as won't run long... The engine I blew was in a truck...318 Dodge with 152,000 miles. I drove it with no oil pressure showing for over 100 miles thinking the guage/sender was screwy. Heard no noises (see above...the truck just died. Don't blame it.<br /><br />I doubt that a marine engine would last that long due to the higher rpm's and load. As mentioned by another poster, get another guage in the line and figure out where your problem is.

 

[vinney]

Re: Oil pressure reads Zero

This is a boating forum not an old tired worn out truck forum. Who care about a 318 in a truck with crud. Boats engine don't have crud. You need to find a forum that talks about worn out tired Trucks. The question was about a small block in a boat. I have never seen the oil pump screen ever plugged in a marine engine It doesn't happened. Get a Life.

 

[orion208]

Re: Oil pressure reads Zero

I have the opposite problem my oil pressure reads normal at 2000 rpms as soon as I hit 3000 with 4500 being WOT the gauge shoots up to almost red line always spoils the day out it's a Volvo Penta 4.3 1992 700 hrs.Any Ideas? Thanks

 

[f_inscreenname]

Re: Oil pressure reads Zero

Hay Vinney<br /> You are the one that needs to lighten up. <br />The boat I own now originally came with a 318ci Mopar motor. When I bought it I planed on a total restore including the motor. The original owner said that it ran great with no noise but it could use a freashing up. I planed on using a 360ci in it so I didn't care if he was telling the truth or not. After taking it apart to pull it out off the boat I am glad I never tried to start it. The heads were caked (a inch thick) with flaky dried oil and the oil pan and lifter valley were worse. I did find a feeler gage that was left under the intake (the only thing worth keeping). So I can see what “Relentless” was talking about and yes it can happen with a marine motor. Old Mopar motors are hard core some working with low oil pressure (and other things that would kill most motors) for a long time.So anything is possible. Most on here are not NASCAR mechanics. They just pass on past experiences of there own and if that is what happened to his 318ci I am sure the poster would like to here it even though it may or may not apply to him

 

[vinney]

Re: Oil pressure reads Zero

Sorry Maybe an Old Tired Worn Out boat forum. They haven't used a 318 in 25 years in boats. Maybe You can find an antique boat forum. Marine engines don't cakeup, slug up or clog up oil pump screens. They don't live that long. A marine engine is under load all the time while a old truck engine say a 318 in an old tired pickup. Its under load half the time of a marine engine. I know they taught you that in NASCAR school.

 

[cobra 3.0]

Re: Oil pressure reads Zero

Let's be nice folks! Our experiences and knowledge may vary about different things. If you know more than the next guy, great! There's no need to tear the other guy down.

 

[llerrad]

Re: Oil pressure reads Zero

This must be a site for Chief Petty Officer bashing, very petty.

 

[f_inscreenname]

Re: Oil pressure reads Zero

Vinney <br /> “Maybe an Old Tired Worn Out boat forum” dude maybe you can kiss my .... There is a lot of people here with old boats and yes they ask questions about them all the time. Have you ever herd of the “Project Boats and Backyard Boat Building” forum here. Lots of tired old boats there. I am sure they would love your comment. You are in the services business “owner/operator marine service business” I can not believe you would ever talk to a customer that way so why do it here? If you are just that smart and have to talk down to us to show your superiority as far as I am concerned you can keep it. <br />As for “ Marine engines don't cake up, slug up or clog up oil pump screens. They don't live that long.” The motor in question is almost 20 years old. Is that long enough?<br /> “A marine engine is under load all the time while a old truck engine say a 318 in an old tired pickup. Its under load half the time of a marine engine.” So you are saying that it can happen just twice as fast?<br />“Maybe You can find an antique boat form.” Yes my boat is a antique (1972 John Allmand / Super Nova-360ci Mopar/320HP) and I am pretty proud of it. The first forum I joined after I bought it was this one (most here know what they are talking about). If you would have answered my first post I don't think I would have come back. I am just happy you did not.<br />Aahubb<br /> I hate to agree with Vinney but I also doubt the screen is clogged and I will not hi jack your post anymore for pointless bickering Sorry<br /> <br /> P.S. As for going to another forum, I aint goin anywhere.

 

[rogerwa]

Re: Oil pressure reads Zero

I don't need to be in the business understand what to do.. Either buy a new sender and install it and find out if the pressure issue is gone or hook up a manual guage and test it that way. Pretty clear to me. Take the lowest cost path to achieve the same end. Whether Vinnie is right or not is not relevant..

 

[TwoBallScrewBall]

Re: Oil pressure reads Zero

I think your oil sender is near the starter, I would start out by checking that wire. If you bumped it, it could ahve loosened the nut and that could be the problem.

 

[Aahubb]

Re: Oil pressure reads Zero

UPDATE: I now have oil pressure! I was so sure that the sending unit was bad I went ahead and replaced it. Seemed to work ok at first but after a few minutes the dash gauge dropped to zero again... ohhh s$$$$t please not the oil pump! Got to thinking about some of the comments here so started checking out my earlier work and found the wiring harness connector not fully seated. Since this is on top of the engine I must have pushed against it while reaching for the starter. So thanks guys, you were great help<br />Or as the saying goes.. Oils well that ends well

 

[John Carpenter]

Re: Oil pressure reads Zero

Vinney...thank you so much for your constructive remarks. You are a piece of work pal...not the first time I have seen you lose it when someone had the nerve to have another point of view. What a fountain of wisdom you are. Respond or not, but you and I are done.<br /><br />For everyone else...the truck was 6 yrs old, I put a lot of miles on them. Any Chrysler mechanic will tell you that the 318 is known for this problem...doesn't make any difference what the application is. When we tore mine down, it also had a half inch layer of crud throughout the engine & the pickup screen on the oil pump was clogged except for an opening about the size of a pencil. I was simply trying to make the point that no one should assume that they know what is wrong with any engine...and a little effort to pinpoint the problem could save an expensive re-power. Just trying to be helpful like most of the people on here...don't claim to be an expert, but do have a little experience.

 

[vinney]

Re: Oil pressure reads Zero

The one thing about this forum is you are entitled to nothing. Its funny how people think they are owed something. One thing about life is no one owes you anything. As for marine engines they don't clog pick up screens. As for your old engine the question was about a 1996 small block chevy not an old tired chrysler. If you want to talk about tired chrysler you can do it in antique forum. There used to be a bunch of guys here that knew the boat business but left. They got tired of the misinformation and people giving poor information. Like 318 sludge stories. So I hope your story help someone out there BUT the person asking about oil pressure in a chevy small block YOU didn't do a thing for. Great job PAL. The only thing the same about YOUR TRUCK 318 and a boat is the steering wheel. Marine engine don't sludge up. Anything different is misinformation Get it. You make someone chase a problem that isn't there. What are you going to tell him to pull the engine and oil pan off and find nothing wrong but a bad sender or bad oil pressure gauge. Thats why alot of good guys left this forum. Misinformation. Good job.