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oil pressure gauge progress!

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NutmegCT

NutmegCT

Great Pumpkin
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Oil pressure gauge has been "stuck" at 55psi since arrival a week ago. Engine on, engine off, engine fast, engine idles, gauge always shows 55psi.

So with a *lot* of patient advice from guys here I loosened the line nut and slowly pulled the line away from the gauge.

Voila! The needle dropped to zero. So I know the gauge isn't frozen.

Reconnected the line, started the engine from cold, and the needle slowly moved from zero up to around 45. Engine warmed up, throttle open to around 3000rpm, needle moves up to 55. Back to idle, needle drops to around 45. Are these pressures anywhere near what's to be expected? Way low? Way high?

I cut the ignition, the engine stopped, and ... needle stayed at 45.

I'm thinking the oil line is plugged - make any sense?

If so, I'll open both ends of the line tomorrow and try to blast some air through.

And for the heck of it today, I also did a compression reading on all four cylinders. 120 120 122 120. Throttle not open, engine not fully warm, only one plug out at a time. I don't have a clue what the readings "should" be, but they're almost identical - and that's good.

And the starter button at the firewall sure makes life easier.

Tom
 
Compression test should be with all plugs removed, throttle cracked, and I'd expect readings to increase to something in the 150 range.

Air thru the capillary tube sounds like a good idea. Pressures should be a bit higher at rev, but the reading is being 'skewed' by whatever is causing the block IMO.
 
Tom,

DocE's right oil pressure a little low - blow the line and then see what you get.

The drivers instruction booklet states on page 8, "The gauge should read 70 lb./sq.in. minimum when the car is traveling at normal speeds and the oil is hot. Only a low pressure may be registered when the engine is idling or running at low speeds; this is quite normal."

Then the factory repair manual states, "The correct oil pressure is 40 - 60 lbs. per sq. in. for top gear for road speeds between 30 - 40 mph."

Engine compression pressure with 3 spark plugs fitted and compression gauge in fourth cylinder engine warm, throttle set at tick over, using 20 SAE oil and operating the starter." Average reading = 120 lbs. per sq. in."

Ya gotta love it!
 
Indeed, remove all plugs for compression test but do not be alarmed if you still get 120ish. Most gauges are sufficiently inaccurate that the comparitve number is the most important thing.

BTW, you're removing all the plugs in case there is a leak between cylinders -- that could happen and not be detected if the adjacent cylinder still has the plug in it. Also, the engine will spin much nicer with the plugs out.

Oil pressure sounds fine but you won't really know the low end until your gauge is free to drop below 45 psi.
 
I'd have to say that it's pretty obvious that your oil line is plugged somewhere. There are three pieces to that line. The thin one that is hooked to the gauge. That goes into a braided flex line. The flex line hooks into a steel line with a banjo fitting attached. The plug up can be in anyone of those sections. Also, the banjo fitting is attached to one of the bolts holding the oil filter assembly onto the block. That bolt, or it may be a nut and stud depending on year of car, has a groove in it to allow the oil pressure to run into the banjo fitting and up to the gauge.

The plug up may be in that stud. So you might have to take that stud out and clean it up. Be careful taking off the banjo fitting. There is a copper washer on each side that you don't want to lose.

Keep going, you're almost there. /bcforum/images/%%GRAEMLIN_URL%%/cheers.gif
 
Here's the latest ...

Disconnected the entire line from the engine to the gauge. (Gauge dropped to zero.)

Blew air threw the line - a bit of oil came out but not much. Air came through fine.

Replaced the line. Started the engine, gauge slowly rose to around 50psi.

Cut the engine, and the gauge stayed where it was (at 50).

Then I noticed that if I rap the inst. panel with my knuckles, the needle slowly dropped back to zero. Took a lot of knocking, but the needle did drop back.

Restarted the engine, needle slowly rose to 50-ish. I rapped hard a couple times on the panel and the needle did make it to 55, but no further even tho' the engine was turning 25-3000rpm for a minute. Killed the engine, needle didn't budget from 55 until I again repeatedly rapped my knuckles on the panel.

Would that indicate a faulty gauge?

Thanks.
Tom
 
Tom,
Sounds as if there is something binding the indicator needle.
I am not familiar with the TR3 gauges but if it is similar to the TR6 gauges in construction then it could be that the indicator is rubbing against the steel gauge cover and getting stuck. If the paint is scratched on the needle I would look at that. If that is the case you will need to open the gauge and gently bend the needle so it wont rub against anything.
 
If the gauge face isn't scratched, look closely at the glass. It may be be bent out and just touching the glass with the tip of the needle.
 
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