Here are a couple of pictures of the ’56 Merc oil sending unit that Gary forwarded to me to post.  He mentions again that the oil pressure gauge on the ’56 Merc does not work without the condenser being hooked up to this particular sending unit.

 

 

Lorena, Texas (South of Waco)

Thanks Ted and Gary,

Do you guys know where I could find one for my 56 Merc. Do you know the Motorcraft Part. No.?

thanks again, Tom

roviwancanobe

The B6A-9278-A is the correct part number for a 56 Merc.

If it looks like the picture above it is correct.

The Ford sender units are much smaller and are part number B6A-9278-B.



I think you have a grounding problem with your sender unit. Take a cheater cord with alligator clips on each end or a single booster cable and hook one clip to the base or the rim of your sender unit and hook the other clip to a good ground on the engine block or your negative battery post. Your car should be negative ground. If your oil pressure improves a poor grounding is the problem. Do you have the ground wire hooked from the engine to the firewall?



I prefer not to use Teflon tape on sender units due to the problems like you are having. I use a pipe sealant and only place the sealant above the first two threads.



marv

Still need HELP!!

I tried what Marv. suggested and it didn't change at all. I gounded the sender to the battery neg. I bought a condenser and connected and gounded it with no change!!!

I tested wire going into and out of gage and have 12volts at both ends also have 12 volts at connection to sender. The gage does move about 1/8". When I take the wire off and put it to ground the needle goes all the way across some this makes me think the gage is all right.

Don't know where to go from hear.

thanks, Tom

roviwancanobe

Can you look on your sender unit on the hex part above the threads. There should be a number there. That is the pressure trip point of the sender unit. If I remember it should be 7 for 7 psig. .......oops got mixed up with idiot light sender. For a guage sender unit there should also be a number same place if I remember either 50 or 70, that will be 50 psi or 70 psi for full deflection of the guage



Could you post a picture of the sending units you have. It may help us with knowing what you have got.



When you hooked the mechanical guage up did you use the same port on the engine block?



When the key is turned "off" what position does the guage indicate ... full pressure or nil pressure. Turn key on and observe same. Give us a report.



Can you do a continuity test on the sending unit. Test from the terminal to the senders base. It should show an open circuit.



Start the engine and do a resistance test on the sender unit. You will have to pull the sender wire off or you will feed 12V through your meter and might damage it when testing continuity.

Some meters have fuses to protect them, some have reset buttons, others have smoke.

marv

I think that you have the wrong sender you need one that is grd. senstive the higher the oil pressure the more it connects to grd. so the higher the higher the gage will read a condenser on the gage will absorb voltage just like a condenser in a dizzy load it up and give to your friend  OOCH ! so find a sender that is grd sensitive weather it,s grd in or grd out just my thought  look at uap napa  SHAKEY PETE

Hi guys, Marv pics of sender. When I hooked up Mechanical gage I DID use the same port. When the key off the gage shows below zero and when I turn the key on it doesn't move until I start the engine and it move about 1/8" up to the zero on the gage. I did do a continuity test on the sender  and when I touch the terminal and the base of the sender it doesn't move. I touch the terminal and put a small nail into the base of sender where the oil goes and lightly pushed on the nail with the other continuity wire attached and to show continuity. I haven't done a resistance test yet. I will tomorrow. I'll also take the sender off and see what it says on top can't read it when its on engine.

thanks, Tom

roviwancanobe

I touch the terminal and put a small nail into the base of sender where the oil goes and lightly pushed on the nail with the other continuity wire attached and to show continuity.(quote)





Be careful pushing a nail into the chamber as you could rupture the diaphragm some are very thin metal others are rubberized.



Do you have another mechanical guage to compare with the one you are using. (I am just trying to eliminate possible areas of errors)



If you get the resistance reading that will give some indications. Set your meter to the lowest range usually 200 ohms for start. Leave the condenser removed when doing the testing.



Did you see the number on the hex I asked about. If you have a sending unit which is rated for 100+ psi or even worse a higher design operating pressure and a guage which is designed for a 50 psi operating pressure the amount of needle deflection will be proportional because guage deflection is dependent upon resistance differential to ground or earth as the Aussies say. A higher pressure designed sending unit will take a higher oil pressure to post a full guage deflection.



marv

Tom, the number on the condenser which is strapped and grounded to the sending unit is  FDC18826-A  hope this helps because in the wayyyyyyyyyyyyyyy past when I drove these cars on a regular basis they really wanted this exact type of condenser. If you could just find a good used one it would be worth getting. You would think if all the stars would line up something close would be compatible enough to work ???

-Gary Burnette-

Thanks guys for your help! This is what I found out--

1) I did a resistance test to the sender and it shows 60 ohms with engine running. Marv. what does this show me?

2) I looked on top of sender, all it says is USA and up with a arrow pointing up and I have it installed that way. (pics attached)

3)I bought the condenser at Advance Auto it is a BWD V10028-------G141Z

4)I ck'd with meter from sender unit post to grd. no reading.

5) I installed another sender no. 75I50 (pic attached) and it shows 80 psi when I start the engine.

6) I ch'd wire from gage again 12 volts.

Do you think theirs a resistor in the gage and 12 volts is to much? I have 12v going in & 12 v coming out to sender.

thanks Tom

roviwancanobe