When tooling around town ive noticed that the oil pressure gauge takes forever to build up. How long should it take? What am I looking for/at to rectify this?
Thx
Thx
Oil Pressure Slow to Build
- Thread starter PJ40
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Oil pressure should come up almost immediately(couple of seconds) upon start. This is a hydraulic system so pressure is transmitted almost immediately.
Has this problem just recently surfaced?(like one day it was ok and the next, not?) Several things may be at work here-The oil sending unit may be failing(but I think if so it would fail totally-you wouldn't see pressure at all);
The sending unit, or pressure lines may be partially restricted, causing the pressure to build slower.
The gauge is going south(see Rudi's posts on cluster gauges to get a better handle on this).
Would be great if you had a parallel mechanical pressure gauge to confirm the readings.
Has this problem just recently surfaced?(like one day it was ok and the next, not?) Several things may be at work here-The oil sending unit may be failing(but I think if so it would fail totally-you wouldn't see pressure at all);
The sending unit, or pressure lines may be partially restricted, causing the pressure to build slower.
The gauge is going south(see Rudi's posts on cluster gauges to get a better handle on this).
Would be great if you had a parallel mechanical pressure gauge to confirm the readings.
Stock oil pressure gauges are notorious for for moving slowly. Maybe clean the connection at the sender, maybe clean the ground to the gauge...also seems to be affected by available voltage, low battery=slower gauge. If in doubt, install a mechanical gauge.
bj40green
Tssss, tssss
Yes, the stock sender is slow but maximum 2 seconds behind.
The stock sender is a complicated sender because there is also a Voltage Regulator inside that "Bell".
That VR is first activated by oil pressure and after that starts sending signal to the gauge.
Note that the OIL gauge needle doesn't move when you turn the key.
The FUEL gauge will always respond to the key and the TEMP gauge will only respond if the engine is still warm.
Check contacts and use an external/parallel mechanical gauge to check the readings and behavior or your cluster gauge.
Rudi
The stock sender is a complicated sender because there is also a Voltage Regulator inside that "Bell".
That VR is first activated by oil pressure and after that starts sending signal to the gauge.
Note that the OIL gauge needle doesn't move when you turn the key.
The FUEL gauge will always respond to the key and the TEMP gauge will only respond if the engine is still warm.
Check contacts and use an external/parallel mechanical gauge to check the readings and behavior or your cluster gauge.
Rudi
ok, so I'm tooling along down to the hardware store. The oil pressure cluster gauge is riding it's normal one click just below the first mark. The mechanical gauge I have is showing normal(55 PSI) Suddenly, the cluster gauge goes to the 'H' level. The mech gauge is still showing normal 55 #. I'm thinking "the cluster gauge or the sender just died" The cluster gauge continues to move around at the high end-never goes back down.- mech gauge always shows the norm 55 psi.
I figure the sender is prob the first thing to replace-so I do(Intermotor sender) After new install, the cluster gauge now is buried deep left, and only comes up to the low mark--mech gauge still shows 55 psi.(oil level is normal, temp is normal)
Seem to remember a post by Rudi on the cluster gauges, but can't find the one specific to my problem. Any help would be greatly appreciated.
Gary
I figure the sender is prob the first thing to replace-so I do(Intermotor sender) After new install, the cluster gauge now is buried deep left, and only comes up to the low mark--mech gauge still shows 55 psi.(oil level is normal, temp is normal)
Seem to remember a post by Rudi on the cluster gauges, but can't find the one specific to my problem. Any help would be greatly appreciated.
Gary
bj40green
Tssss, tssss
Your replacement OIL sender should look like one of these.
(pic's from CCOT)
As said before.... that OIL sender is a bit complicated because it has a Voltage Regulator build in.
So.... if your replacement doesn't looks like one of these it will not work.
The fact that, with the new sender, the needle stays at the left means that the new sender has a too high resistance.
You can check the cluster OIL gauge with a 3 Watt test light. The FSM says 3.4W but a 3W will work. That is the one that is also used for the cluster lights.
and check the OIL sender
Rudi
As said before.... that OIL sender is a bit complicated because it has a Voltage Regulator build in.
So.... if your replacement doesn't looks like one of these it will not work.
The fact that, with the new sender, the needle stays at the left means that the new sender has a too high resistance.
You can check the cluster OIL gauge with a 3 Watt test light. The FSM says 3.4W but a 3W will work. That is the one that is also used for the cluster lights.
and check the OIL sender
Rudi
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This reply is late for sure, but it did get done---Tested the gauge as per your and FSM instructions---gauge and light responded as good. When testing the sender- the bulb initially was bright, then immediately went out, then VERY dim and fluctuating(engine RPM was ~ 750)
I checked the resistance on the old sender(the one I thought failed) and it read 50.6 Ohms. Checked the new sender and the resistance was infinity(engine off). Sounds like you have it pegged--the new sender has too much resistance---So how do I get a sender with the correct resistance? Do you, or anyone else, know what the correct sender resistance should be?
I checked the resistance on the old sender(the one I thought failed) and it read 50.6 Ohms. Checked the new sender and the resistance was infinity(engine off). Sounds like you have it pegged--the new sender has too much resistance---So how do I get a sender with the correct resistance? Do you, or anyone else, know what the correct sender resistance should be?
bj40green
Tssss, tssss
Good. One down, one to go.
If you used the right wattage bulb the light should be dim (but not very dim) and the frequency of the flashing should vary with the rpm's.
I don't know the "cold" resistance but I can check tomorrow at daylight. I've never checked it but looking at the FSM it shows that at no pressure (engine off) the circuit is open, which means no resistance at all and that is also what the FSM says. "the bulb should not light when the engine is stopped"
If your sender reads 50 ohms, it means that the VR contacts are stuck together.
Does the needle move when you turn the key to the "on' position? It should not.
How about buy an OEM one or an aftermarket from a reliable vendor?
Rudi
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Did a little testing on this before I took it back to the store--
Old sender showed 58.xx Ohms on the bench. The new one showed infinity(no continuity). I hooked up an air pressure regulator off my compressor to supply varying pressure to the sender. The new sender showed no continuity until the supplied pressure exceeded 78 psi, then it dropped to 58 Ohms. My educated guess is the sender was designed for a system that ran oil pressure greater than 80 psi--which of course, an FJ40 will never reach{oil pump bypass is supposed to be regulated at ~53 psi(I think)}
I put the old one(sender) back in, and for some reason, now it seems to be reading normal(at the first low mark)
The sender I bought was an Intermotor sender--I thought it would be matched to the gauge in a 40, but I guess not.
Old sender showed 58.xx Ohms on the bench. The new one showed infinity(no continuity). I hooked up an air pressure regulator off my compressor to supply varying pressure to the sender. The new sender showed no continuity until the supplied pressure exceeded 78 psi, then it dropped to 58 Ohms. My educated guess is the sender was designed for a system that ran oil pressure greater than 80 psi--which of course, an FJ40 will never reach{oil pump bypass is supposed to be regulated at ~53 psi(I think)}
I put the old one(sender) back in, and for some reason, now it seems to be reading normal(at the first low mark)
The sender I bought was an Intermotor sender--I thought it would be matched to the gauge in a 40, but I guess not.
bj40green
Tssss, tssss
The 4 marks on the OIL gauge represents 0, 28.4, 56.8 and 85.2 psi, or for the metric people... 0, 2, 4 and 6 kg/cm²
The OEM sender is not a variable resistor that sends a signal to the OIL gauge.
The resistance is the heating element of the Voltage Regulator. This VR makes a "wobbly" 6 to 12V (effective 0-6V) for the OIL gauge. This "wobbly" 6V is what the test light shows. A dim flashing which flashes faster when the RPM's go up.
I'm glad that your gauge is working again. Did you do the same pressure test with your compressor to the old sender?
Rudi
The OEM sender is not a variable resistor that sends a signal to the OIL gauge.
The resistance is the heating element of the Voltage Regulator. This VR makes a "wobbly" 6 to 12V (effective 0-6V) for the OIL gauge. This "wobbly" 6V is what the test light shows. A dim flashing which flashes faster when the RPM's go up.
I'm glad that your gauge is working again. Did you do the same pressure test with your compressor to the old sender?
Rudi
Yes--did the same test--it started at ~58 Ohms and stayed there up to the 100 psi I tested at.- since it seems to be working now--maybe I blew out some gunk??
Come to think of it, this might even be a novel way to troubleshoot a non-responding oil pressure gauge---Do the 3.4 bulb check, and if that doesn't work, pop the sender with 125 psi air a couple of times to see if the sender is just gummed up.
Come to think of it, this might even be a novel way to troubleshoot a non-responding oil pressure gauge---Do the 3.4 bulb check, and if that doesn't work, pop the sender with 125 psi air a couple of times to see if the sender is just gummed up.
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bj40green
Tssss, tssss
My guess..... the contacts were stuck and you blew them open.
When there is no pressure (engine is off) the contacts should be open.
As soon as the engine is running at idle the VR starts working, sending a little voltage to the gauge.
When the engine revs up, the working point of the VR moves up and thus sending a higher voltage to the gauge.
The resistance doesn't change during this process.
Rudi
