Oil Pressure Issues

[davekp]

My new to me MK4 w/ 351 Windsor with vintage gauges exhibits fluctuating oil pressure readings at steady cruise. Gauge swings between 25 and 50 psi and places in between sort of randomly. Is this the classic pressure sender issues many have had?

[Jeff Kleiner]

Not to say that it isn’t a possibility but my experience with failed Speedhut senders is either on or off—-no fluctuation. I’d suspect a wiring issue...or real data.

Heff

[Erik W. Treves]

i have had issue like this with bad sending units - best to just hook up a mechanical gauge and check

[Railroad]

I had the same issue with fluctuations. Speedhut sent me a new sending unit and all is good.

[NAZ]

Agree with Erik. Don't throw parts at a problem, a mechanical gauge will eliminate or confirm actual oil pressure issue.

If oil pressure is steady, next is checking the sending unit for fluctuating resistance. If the resistance fluctuates when a mechanical gauge is steady that indicates a bad sending unit. If the ohm reading is steady at the sender, check it at the gauge to eliminate a conductor issue. Systematically troubleshoot the issue and you will find the problem. Hopefully it's simply a loose wire.

[Railroad]

I failed to mention, Speed Hut instructed me on verifying the sending units status, they replaced.
Hope this helps.

[johnnybgoode]

Not to be a smart *** but have you checked to make sure the motor is filled with the correct amount and type of oil? May be worth doing and oil change if the car is new to you. Regards. Scott

[davekp]

Good info here.
I added a tee and a mechanical gauge. It held steady while the electric gauge did it's sweeping thing, occasionally pegging @ 100 and also zero. An ohmeter on the sender read about 130 ohms. I couldn't check the resistance of the sender with the electric gauge hooked up- had to do each separately so the 130 ohm reading could be anywhere on the electric gauge.
Thanks to all!

[Erik W. Treves]

I am guessing the electrical sender is all done... glad your engine has healthy oil pressure

[CFranks]

Good info here.
I added a tee and a mechanical gauge. It held steady while the electric gauge did it's sweeping thing, occasionally pegging @ 100 and also zero. An ohmeter on the sender read about 130 ohms. I couldn't check the resistance of the sender with the electric gauge hooked up- had to do each separately so the 130 ohm reading could be anywhere on the electric gauge.
Thanks to all!

When you were checking the resistance of the sender did it stay constant while the mechanical gauge also stayed constant? If so, then wouldn't that mean the problem is between your sender and the gauge given you're not getting a variable reading from the sender?

[NAZ]

When you were checking the resistance of the sender did it stay constant while the mechanical gauge also stayed constant? If so, then wouldn't that mean the problem is between your sender and the gauge given you're not getting a variable reading from the sender?

That would be a good assumption given the symptoms and means he must next check the resistance of the sender & gauge wire to isolate the problem further.

Now if you knew the ohm scale of the sensor you could also check for accuracy. If the OP has a Speedhut sending unit I believe they are 240-33 ohm 100 PSI (240 ohm = zero) but the OP should verify this. So if he was reading 130 ohms at the sender that would equate to ~37 PSI and the mechanical gauge should also read close to that.

Troubleshooting down to the component level will save $$. Throwing parts at a problem can be a big waste of time and $$.

[Erik W. Treves]

speed hut will normally send you a sender- free of charge - at least for me the last 3 I needed costing me $0.00 :)

[phileas_fogg]

x2 on what Erik said. I had some initial problems with my oil pressure gauge, & Speedhut sent me a new sender for free. As it turned out, my original sender healed itself & has been working properly since.

Dave, if Speedhut turns you down, PM me your address & I'll get that extra sender to you posthaste. It's like the one shown in the picture below.


John

https://live.staticflickr.com/4301/36289767175_3b88e91f3f_4k.jpg (https://flic.kr/p/XhNxsX)IMG_2552 (https://flic.kr/p/XhNxsX) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

[Jeff Kleiner]

Yep, call Speedhut and they'll ship a new sender. They're good about replacing defective and failed parts (they have to be if you catch my drift ;) )

Jeff

[davekp]

Yep, call Speedhut and they'll ship a new sender. They're good about replacing defective and failed parts (they have to be if you catch my drift ;) )

Jeff

Well........................
The sensors are warranted for 5 years only.
New sensor $27
shipping $14

Ouch!

[davekp]

x2 on what Erik said. I had some initial problems with my oil pressure gauge, & Speedhut sent me a new sender for free. As it turned out, my original sender healed itself & has been working properly since.

Dave, if Speedhut turns you down, PM me your address & I'll get that extra sender to you posthaste. It's like the one shown in the picture below.


John

https://live.staticflickr.com/4301/36289767175_3b88e91f3f_4k.jpg (https://flic.kr/p/XhNxsX)IMG_2552 (https://flic.kr/p/XhNxsX) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

Thanks for your generous offer, but I had already ordered one.

[davekp]

Got the new sender installed and all is well. I remoted it from the block ala Jeff Kleiner's suggestion.