Oil Pressure
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New User
Joined: Jan 2014
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Oil Pressure
First post on the site, hope it works tonight. Anyway, have a 1968 F-100, 390 auto that i have been rescuing since last spring. This past weekend for the first time the oil pressure gauge was pegged below zero while waiting to warm it up for a ride. Shut it off immediately, and decided to join for some help.
Oil level is good, have never had an issue until now. Am I looking at a bad sending unit? Basically, where should I start to diagnose.
Thanks for the help.
Oil level is good, have never had an issue until now. Am I looking at a bad sending unit? Basically, where should I start to diagnose.
Thanks for the help.
Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
I would remove sending unit and install mechanical gauge. Then if you don't see any oil pressure, shut it off and figure out what the problem is.
Was it clattering a lot while running? With no oil pressure you should have heard lifters clattering like no tomorrow.
Was it clattering a lot while running? With no oil pressure you should have heard lifters clattering like no tomorrow.
Laughing Gas
Joined: Jul 2007
Posts: 753
Likes: 133
From: Phoenix
Hello and welcome to the forum. Definately hook up a mechanical gauge, but also pull the distributor and check the pump drive from the dist gear to the oil pump. Then spin up the oil pump drive with a GOOD power drill and check your pressure that way. I have seen a few F.E. engines with worn dist drives rounded out causing low oil pressure numbers. Good Luck!
Lead Driver
Joined: Aug 2003
Posts: 7,592
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From: **** hole San Jose ca.
Hmm no oil PSI, well then I'd remove the oil sender unit plus remover coil wire so motor will not start up. Now this will make a mess so maybe put some rags over the opening and a pan under to catch it.
Now crank the motor over about 10-15 seconds if pump is working you'll see it has come out. If pump is bad no oil will be on the rags or in the pan.
PS
It's always a good idea to install a manual oil psi gauge on these old classic vehicles. I'd Install a Tee where you removed the sending unit from housing so you use both the electric dash gauge & the manual at the same time..
orich
Now crank the motor over about 10-15 seconds if pump is working you'll see it has come out. If pump is bad no oil will be on the rags or in the pan.
PS
It's always a good idea to install a manual oil psi gauge on these old classic vehicles. I'd Install a Tee where you removed the sending unit from housing so you use both the electric dash gauge & the manual at the same time..
orich
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
No clattering? Maybe something happened to the wire feeding the sender. Got critters around ya?
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Oil pressure
Actually, do live around critters, but it stays in the garage at all times. Heading out to work on it now.
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Well, while rooting around to figure access, discovered the sending could spin around, not seated against the jam nut. Also the lead was not very snug, is it supposed to have an angled 90 degree rubber boot?
Anyway, pushed the lead end on sending unit wiggled it around a bit, and started it,
The gauge actually reads farther than it did before, big sigh of relief.
Sorry I panicked so soon without doing the simple, but when I saw no oil pressure......
Glad I joined, I have plenty of things I want to do on this true survivor.
Thanks to all.
Anyway, pushed the lead end on sending unit wiggled it around a bit, and started it,
The gauge actually reads farther than it did before, big sigh of relief.
Sorry I panicked so soon without doing the simple, but when I saw no oil pressure......
Glad I joined, I have plenty of things I want to do on this true survivor.
Thanks to all.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Well now you've learned to poke around before you need to panic, long before you call in the FTE rescue boys. Now is a good time to invest $20 bucks in a repair manual for your old girl that you keep locked away save in your garage at night..
orich
orich
Junior User
Joined: May 2013
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Panic - Been there Done that
Manual gauges can also have problems that cause 0 pressure reading. My dad's '49 GMC 6400 would read Zero at times during the winter. The problem was that moisture would condense in the copper line that went to the gauge and would form a plug of ice that caused the gauge to read zero until engine heat thawed the line.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
And yes seen a few leak. But never break open. Some time in the 60's when vinyl poly tuning started be used. Never saw that break only leak like the copper at the compression joints.
Me, I use 1/4" 1800 psi hyd line T'ed off the oil filter adapter with Idiot.
no leaks in 35yrs.. orich
