Driving with a dead Oil Pressure Sender Unit

I guess you can, but I wouldn't unless you have to.

I have a little lifter tic on my car. Not driving it unless I have to, even though everyone says it's fine.

 

I always thought that was the most important gauge to have in a car. It’s a stop NOW gauge, right?

 

Dayan,

You've diagnosed the reason for for the pegged needle on your oil pressure gauge. A replacement sender is necessary and easily installed. Consider purchasing this oil pressure sender boot to help protect your new sender and extend its life...


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It's available at Ricambi America: 135940-B OIL PRESSURE SENDER COVER

Is your car safe to drive? It most likely is. A true complete loss of oil pressure makes itself known very quickly.

Barry

 

Surely it won't take long to source and fit a new sender?

Are you more worried about the gauge electrics than the engine?

The terminal post marked G is for the gauge. WK is for the warning light. Don't let the WK wire lug touch earth (ground) or it will put the light on. By off-scale, do you mean fully clockwise? I'm sure the gauge is quite capable of handling an open circuit sender.

Here's a typical gauge circuit... but I haven't confirmed the resistances.

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If you're only going to drive the car a couple of times until you get a new sender, you could probably even superglue the lugs onto the sender (as long as there is some good metal to metal contact). Zip tie the wires so that if they do come loose, they don't fall down. and clean up the lugs before installing the new one.

You'll need a 24mm open ended spanner and, in some cases a heat gun (or warm up the engine and be careful not to burn yourself). The amount of force required to remove the old sender can be a little scary. The thing it screws into is really expensive. The sender can let go with a loud crack which scares the hell out of you.
Torque specs are 25Nm (18lbs/ft) for the sender, but unless you have a crowsfoot or something similar, you won't be able to use a torque wrench. Don't apply too much torque to the nuts on the electrical contacts. As you can see, these posts are very fragile.

One of the first jobs I did on my car was change the oil pressure sender. The previous owner had drilled into the top of a broken post and put a self-tapping screw into the hole

 

I just swapped the the oil pressure sender with a new one as a preventive measure and I got the boot too, but working under the intake runners there is just no room and could not finagle the dang boot on. It also does nto fit amazing on the 348 sender btw. The sender is under the intake plenum and is protected somewhat, definitely from rain water, so I pulled it back out, removed the boot and reinstalled it as it was originally.

 

It should fit perfectly. The same sender is used on both the 348 and F355 - Part No. 135940

 

I'm sure that's what he means, Ian. The needle pegs all the way to the right - clockwise with a failed sender.

 

It sounds like the 348's sender is harder to get to than the 355's. One of the biggest problem I found in removing the 355's was finding a place to position a long spanner on the sender without it hitting wiring harnesses and other engine bay components.

Before the application of heat, I had a ring spanner hooked up to the end of my open ender for extra leverage and it still didn't move.

 

The sender boot is a good idea on my F355 Challenge but is essential on my 550. Its position makes it very vulnerable to standing water and road crud. There are a set of louvers on the undertray which afford it some protection...


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Several louvers on my undertray broke over the years so I had this hardware cloth screen assembly fabricated to replace the louvers. The boot was installed on the sender about five years ago. The sender is the same Part No. 135940 used on my F355. Since its installation, my oil pressure gauge has behaved normally. Prior to that, I would get the needle pegged high scenario about every two or three years.

 

Don't worry, the oil pressure and temperature have no inputs into the engine management system. Coolant (water) temperature does matter.

 

Dayan, to help reassure you further, I once did a two-day HPDE track event with my 550's oil pressure gauge giving these same erroneously high readings. This was several years ago before the boot became available. Nothing happened to the car that day or anytime it happened previous to that.

 

Ain't that the truth! You'll know when it happens, because your wallet will simultaneously fly out the window.

@DaisyCutter we have the boot + sender in stock, and ship worldwide everyday via FedEx.

 

Right, Dayan.

Both the 550 and F355 give high readings when the sender fails or the contacts need cleaning. It never happened with my F355 but I cleaned the contacts and installed the boot prophylactically.

With dirty contacts on the 550, oil pressure read normally at idle but pegged the needle high when driving. After cleaning the contacts and installing the boot, this hasn't happened again in ~5 years.

We have to be confident that the oil pumps are functioning normally when this occurs and that the problem is either with the sender or the gauge. Historically, it's just about always the sender. And as Ian mentioned, the sender-gauge circuit is isolated from the engine management system.

Order the sender and boot from Daniel at Ricambi America so you can fix the matter quickly.

Barry