The oil pressure sender on my '88 IROC (VIN-F, 305) failed recently so, having replaced it before, I knew it would be relatively easy. (Note, I had replaced it in the late 90s and then in 2017 when I pulled the engine to rework it.) I realized that after "loosening it" with a deep-well socket for far too long that the body of the sender is spinning. I then thought to remove the dist cap to have access to the 14mm nut on the underside of the sender. Well, there is too little room to get an open box wrench in there and then even turn it. The 14mm crowfoot wrench won't work because the body of the sender blocks an extension from being inserted. A side rant: why could't the upper body be dimpled with the base or have some other means to ensure that the body will not slip?

What tool could I used to remove the sender via the 14mm nut on the bottom?

 

If it's the large body sending unit they actually made a special tool that clipped on and had a wrench part on the lower part and a 3/8" square for an extension on the upper part. Snap-On Tools USA S6156 SAE 9/16" Oil Sending Unit Removal Tool - 3/8" Drive | eBay I used to own one of these many moons ago.
Aside from this tool patience and perseverance are your best tools.

 

Thanks for the response. I am making an offer for one on eBay.
--greg

 

Harbor Freight has stubby style wrenches. Saved my life in the few times I needed them.

 

thanks. yes, I was thinking of running up to HF to see what could possibly work. There is so little room between it and the firewall. Heck, I even thought of removing the ignition module from the distributor to have a bit more clearance.

UPDATE: Got a 14mm stubby wrench from HF but no go. Flipped in one direction it will slide on nut but no room to turn, flip it the other way and it will not slide on. I hope the special service tool, when it arrives, will work. Again, why can they not make the housing such that it is guaranteed to not spin freely of the nipple under torque?

 

Just use a torch and bend a cheap 9/16 wrench.

 

thought of that fleetingly but really have to be set up for that with the right torch I would guess.

 

Try a basin wrench. Something like https://www.homedepot.com/p/Husky-1-...-111/206830601

 

interesting thought, though there may not be enough clearance . I have one and will try it in the a.m.

 

So, I picked up a special service tool as recommended, but still cannot get the danged thing out. First, the wrench is 9/16 but the "nut" on the bottom of the sender is 14mm. The wrench is about to slip and round the nut so I then tried to shim the wrench opening with metalic tape. No luck: the entire elbow into which the sender is screwed turns toward the firewall without the stem of the sender breaking loose.

I see there is a Nissan 14mm oil pressure sender wrench, which I may give a shot or I may try to bend a 14mm flare nut. Also, I will have to figure out how to get a second wrench in there to hold the elbow while trying to break the pressure sender loose.

Oh, I did try my smaller plumber (basin) wrench, but there is so little room back there that I cannot get it snugged on.

what was supposed to be a five minute job has lead to the car just sitting.....

 

Look at Snap-On FRHLM14. Potential downsides: the center to center is 2" and it's 0.45" thick.

 

I took a couple of days away from the car and, instead, worked around the yard. This morning I went out with a clear head and a renewed sense of purposeful calm. I took the ignition module off to have a bit more clearance and got it off. I did use the 9/16" SPT which fits like a charm. (Note, I thought the nut on the bottom of the sender was 14mm, but that's probably because it wasn't seating properly and slipped down as I pushed the ratchet into the 3/8" opening on the tool and because the new sender does have a 14mm nut!) I did get it installed and fired the engine up. The oil pressure gauge is bouncing and showing low even though there is a fresh 5qts of oil. Reading low doesn't bother me since I have to just remove and reset the needle. However, the bouncing is troublesome--and, yes, the connector is fully seated on the sender--but that may be due to a loose connection or a dirty connection on the backside of the instrument panel which I removed last year.

thanks to all.

 

14mm = .5512" approx
9/16" = .5625"

Only about .011" (just over .25mm) different; the thickness of acoupla sheets of copy paper

There are several metric sizes that are extremely close to Imperial ones, close enough to interchange. 5/16" & 8mm, ¾" & 19mm, 9/32" & 7mm, 7/8" & 22mm for example. 9/16" & 14mm are well and widely known to be one of those close matches as well.

The sending unit square is mos def 9/16" in actuality. Been that size since before there was anything metric at all on American cars.