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oil light on

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tab a Thon Basom
central, KS, USA   USA
After sitting for 6+ months (not that unusual), I started my carbed '80 TR8. Oil light comes on when key turned to on, goes off while cranking, then turns back on once engine starts. Runs, and sounds, ok, for a few seconds, until it dies--which I presume is because the fuel pump has been stopped.

I haven't heard of this before, but I guess it's possible for the (three-prong) switch to 'stick' in a position (WO to WN) so oil light won't go out, and fuel pump will quit?

To test, rather than checking oil pressure itself, can I substitute a single prong oil pressure switch? Jumpering W to WN would run the fuel pump but disable oil light? Not sure if/how to get light to work for testing?

Thanks.

Thon

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darrellwalker Darrell Walker
Vancouver, Washington, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
If you suspect the switch is gummed up, you could remove it, and spray something like WD40 inside a few times, and see what comes out. You could try a more aggressive solvent, but I don't know what materials are inside the switch, so WD40 would be a safe place to start.



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

Mr. Nuts Peter N
Tucumcari, NM, USA   USA
Yes, you could do that. But, it's not what I would do first. Sounds to me like you lost prime on the oil system. You have a few options......I'd pull the distributer and spin the oil pump over with a dummy oil shaft I have for doing that with the key on. The light will go out in a few minutes when the system self primes. This way you are not running the engine with no oil pressure while the system primes.

If you don't have a dummy oil shaft tool, you could simply turn the oil pump shaft with a screw driver. If it turns super easy, you have no oil in the pump and you know you lost prime.

Now, you get to make a dummy oil shaft to turn the pump and prime the system. Or, simply jump the fuel pump wires at the oil pressure switch plug and start the engine. Run it for few minutes and then plug the harness back into the oil pressure sender. It should have primed, and now the light will be out. But you will be running the engine without any oil pressure.

I'm sure you'll find the oil pressure switch is fine.



Edited 1 time(s). Last edit at 2017-11-21 11:01 AM by Mr. Nuts.

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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1499172 by tab a After sitting for 6+ months (not that unusual), I started my carbed '80 TR8. Oil light comes on when key turned to on, goes off while cranking, then turns back on once engine starts. Runs, and sounds, ok, for a few seconds, until it dies--which I presume is because the fuel pump has been stopped.

I haven't heard of this before, but I guess it's possible for the (three-prong) switch to 'stick' in a position (WO to WN) so oil light won't go out, and fuel pump will quit?

To test, rather than checking oil pressure itself, can I substitute a single prong oil pressure switch? Jumpering W to WN would run the fuel pump but disable oil light? Not sure if/how to get light to work for testing?

Thanks.

Thon

The oil pressure sensor carries the full current of the fuel pump, and so can fail. I would NOT disable the oil light, nor would I jumper the sender to force the fuel pump to run.

Question: Does your oil filter have an anti-drain back valve? If not, you should replace it to prevent the loss of the prime in your oil pump. Admittedly, this is not terribly likely, but it is a very good idea to make sure the filter has one. Many filters do not, but those are for engines that have a valve built into the oil system.

I would bet the OP sensor has failed. Pull it, and take it to your FLAPS. They will have a replacement, if not for a TR8 then for a Land Rover Discovery. If that fails, ask them to go through their parts looking for a physical match, or crack open a catalog. I replaced mine with one from a Rover SD1. Not identical, but three terminals and electrically equivalent.

The circuitry is intended to disable the fuel pump in the event of a rollover or loss of oil pressure. Thus it protects the engine and you.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

Bergie Bob Berg
Powell, Ohio, USA   USA
See attached...should be at most auto parts stores for TR8 -3 prong oil pressure switch...replace...pull plugs and turn over with starter...should bring up pressure...


Attachments:
image.jpeg    36.5 KB
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tab a Thon Basom
central, KS, USA   USA
Hmmmm..... not to say pump couldn't have lost prime, but it's never happened before, and it's sat unused for significantly longer periods of time. Have others had problems with this?

Don't know if filter has anti-drainback. I typically use Wix. Anyone know?

I don't want to disable the oil light permanently. Just looking for ways to test, with what I have.

Thanks for the ideas. Will let you know what I find.

Thon

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