HarleyTechTalk

alright folks... My oil pressure light has been on since a I picked it up from the dealer last Friday after getting a new drive belt and had them do a fluid change while there.

I removed the wire from the sensor and the light went out, touched it to the sensor and comes back on. So I don't think it's grounding out somewhere in between. In the process of removing the wire, I noticed the top portion of the sensor was cracked. So I replaced it with a new sensor... Light is still on and at all RPMs

There is no rattle or knocking at all from the engine top or bottom.

I pulled the sensor off and started the engine and oil does flow from the sensor hole. It's not spraying out, but at an idle it's a steady stream.


As a reminder, I did lose the oil pump back in April this year and replaced with a stock replacement. Have ridden 2000+ miles since the change with no issues. Perhaps a piece of debris got dislodged during the oil change and caught in a passage?

I hope your not riding it.  Put a gauge in the sensor hole for a brief test.  Idle and around 2,00O but brief. What happened to the previous pump? 

Maybe the dealer removed the screen for cleaning and caused a problem at that point.

Quote from: kd on December 08, 2023, 07:58:27 PMI hope your not riding it.  Put a gauge in the sensor hole for a brief test.  Idle and around 2,00 but brief. What happened to the previous pump?

Maybe the dealer removed the screen for cleaning and caused a problem at that point.

I'm not exactly sure what happened first. But the pump drive gear exploded.

I rode it off the trailer and out to the office and back. About 8 miles total to see if it would go out when warm, no luck. Oil is definitely flowing, and tappet screen is clear.

I'll throw a gauge on it and see what it says.

Lifters would clatter with no oil pressure . Unless solids

In your first post, first sentence, the Dealer effed it up

These days, the parts guy at the dealer chuckles and says the Evo is older then the service technicians that work there. 

Quote from: 98s1lightning on December 11, 2023, 10:07:06 AMIn your first post, first sentence, the Dealer effed it up

These days, the parts guy at the dealer chuckles and says the Evo is older then the service technicians that work there.

Perhaps... My bet is the fluid change dislodged some debris that is now partially blocking an oil passage... Just my feelings.


When I did the oil pump repair, I was on a very tight time constraint. So I didn't drop the oil pan or open the crankcase. I flushed it and inspected with a light and borescope, but it wouldn't surprise me a bit if a piece of metal, gasket, or just junk from the hoses got into the oil system and is now in one of those little oil passages.

A pressure gauge would help tell the story.

Idk how to post pics but VULCAN makes a nice stainless gauge adapter for where the lifter screen is accessed

Six, put a gauge on it.  Your an engineer.  You know all about facts and how important they are.  Flow doesn't need pressure when you have roller bearings dumping the oil.

My point with the screen is checking the flow through there too. With that plug installed again, wrap the tip of an air nozzle and blow backwards through the oil pressure gauge port.  (The screen chamber feeds the oil pressure gauge gallery directly.)  Reinstall the gauge and check for a change in pressure.  If anything is holding a valve open there will be a huge pressure drop. 

The other thing not mentioned yet is the "new" oil filter.  If the bypass is open it can cause similar issues.  It is also one of the last things changed before the oil pressure drop.  If the oil pressure drop was immediately after the service it's a top candidate.  BTW, were any oil lines removed for any reason?

I want to repeat, if you can't confirm oil flowing in a decent amount through the screen port or the gauge port on the crankcase, don't get too carried away with running it.

You mention that the Dealer did a Fluid Change on Your EVO.
Do You happen to know if they put a Twin Cam Oil Filter on there instead of an EVO Filter?
I have heard numerous times over the years that the Twin Cam Filter is more restrictive of Oil flow than an EVO Filter.
I don't have any hands-on personal experience with that, I have always used the Evo Filter on an EVO, and a T/C Filter on a T/C.
So, how true that statement may be, I really don't know.
Someone may have a better explanation about the Filter usage than Me.

Quote from: kd on December 11, 2023, 07:22:45 PMSix, put a gauge on it.  Your an engineer.  You know all about facts and how important they are.  Flow doesn't need pressure when you have roller bearings dumping the oil.

My point with the screen is checking the flow through there too. With that plug installed again, wrap the tip of an air nozzle and blow backwards through the oil pressure gauge port.  (The screen chamber feeds the oil pressure gauge gallery directly.)  Reinstall the gauge and check for a change in pressure.  If anything is holding a valve open there will be a huge pressure drop. 

The other thing not mentioned yet is the "new" oil filter.  If the bypass is open it can cause similar issues.  It is also one of the last things changed before the oil pressure drop.  If the oil pressure drop was immediately after the service it's a top candidate.  BTW, were any oil lines removed for any reason?

I want to repeat, if you can't confirm oil flowing in a decent amount through the screen port or the gauge port on the crankcase, don't get too carried away with running it.

yeah, I'm working on getting a gauge.

I pulled the tappet screen, it was clean, and there was oil there, but I didn't run to see how much was coming through. I've read about dealers using TC filters, the service ticket calls out the correct -80A filter, but who knows.

Quote from: SixShooter14 on December 11, 2023, 07:52:17 PMI've read about dealers using TC filters, the service ticket calls out the correct -80A filter, but who knows.

That's an old wives tail. They don't interchange.

Quote from: Ohio HD on December 11, 2023, 08:02:46 PM

Quote from: SixShooter14 on December 11, 2023, 07:52:17 PMI've read about dealers using TC filters, the service ticket calls out the correct -80A filter, but who knows.

That's an old wives tail. They don't interchange.

filter.... oil filter... 

Quote from: SixShooter14 on December 11, 2023, 08:04:02 PM

Quote from: Ohio HD on December 11, 2023, 08:02:46 PM

Quote from: SixShooter14 on December 11, 2023, 07:52:17 PMI've read about dealers using TC filters, the service ticket calls out the correct -80A filter, but who knows.

That's an old wives tail. They don't interchange.

filter.... oil filter... 

    man, I need to clean these reading glasses....   

Quote from: Ohio HD on December 11, 2023, 08:09:20 PM    man, I need to clean these reading glasses....   

hey, I got a laugh out of it... I had to reread my post twice to make sure I spelled it right.

Quote from: SixShooter14 on December 11, 2023, 07:52:17 PM

Quote from: kd on December 11, 2023, 07:22:45 PMSix, put a gauge on it.  Your an engineer.  You know all about facts and how important they are.  Flow doesn't need pressure when you have roller bearings dumping the oil.

My point with the screen is checking the flow through there too. With that plug installed again, wrap the tip of an air nozzle and blow backwards through the oil pressure gauge port.  (The screen chamber feeds the oil pressure gauge gallery directly.)  Reinstall the gauge and check for a change in pressure.  If anything is holding a valve open there will be a huge pressure drop. 

The other thing not mentioned yet is the "new" oil filter.  If the bypass is open it can cause similar issues.  It is also one of the last things changed before the oil pressure drop.  If the oil pressure drop was immediately after the service it's a top candidate.  BTW, were any oil lines removed for any reason?

I want to repeat, if you can't confirm oil flowing in a decent amount through the screen port or the gauge port on the crankcase, don't get too carried away with running it.

yeah, I'm working on getting a gauge.

I pulled the tappet screen, it was clean, and there was oil there, but I didn't run to see how much was coming through. I've read about dealers using TC filters, the service ticket calls out the correct -80A filter, but who knows.

Yes, I realize you checked the screen.  My point is blowing back may confirm there is air passing through the system and not plugged.  Restarting it and getting better oil flow will indicate a change. 

As far as the filter goes, if oil isn't getting to the pump (or the lack of sump oil due to low flow causes the sump return system to pick up, carry and introduce air) the pressure can be defeated.  The aerated oil can cause cavitation in the pump and consequently no pressure. 

Quote from: kd on December 11, 2023, 08:48:47 PMYes, I realize you checked the screen.  My point is blowing back may confirm there is air passing through the system and not plugged.  Restarting it and getting better oil flow will indicate a change. 

As far as the filter goes, if oil isn't getting to the pump (or the lack of sump oil due to low flow causes the sump return system to pick up, carry and introduce air) the pressure can be defeated.  The aerated oil can cause cavitation in the pump and consequently no pressure. 

no luck there. blew air in the pressure sensor hole and it sprayed out the tappet screen hole, a small bit of oil. Started and didn't see any oil in the screen hole and still no pressure.

Quote from: SixShooter14 on December 11, 2023, 08:58:35 PM

Quote from: kd on December 11, 2023, 08:48:47 PMYes, I realize you checked the screen.  My point is blowing back may confirm there is air passing through the system and not plugged.  Restarting it and getting better oil flow will indicate a change. 

As far as the filter goes, if oil isn't getting to the pump (or the lack of sump oil due to low flow causes the sump return system to pick up, carry and introduce air) the pressure can be defeated.  The aerated oil can cause cavitation in the pump and consequently no pressure. 

no luck there. blew air in the pressure sensor hole and it sprayed out the tappet screen hole, a small bit of oil. Started and didn't see any oil in the screen hole and still no pressure.

The oil passes through the screen chamber on the way to the gallery to the pressure switch.  All you did was blow out that link.  With the pressure switch in, blow into the screen chamber with a rag sealing the air nozzle.  That will push back on that part of the gallery and clear it.  Not important but it will also feed past the pressure switch to the lifters and pushrods. 

Do you have another filter to try?

Quote from: kd on December 11, 2023, 09:19:28 PM

Quote from: SixShooter14 on December 11, 2023, 08:58:35 PM

Quote from: kd on December 11, 2023, 08:48:47 PMYes, I realize you checked the screen.  My point is blowing back may confirm there is air passing through the system and not plugged.  Restarting it and getting better oil flow will indicate a change. 

As far as the filter goes, if oil isn't getting to the pump (or the lack of sump oil due to low flow causes the sump return system to pick up, carry and introduce air) the pressure can be defeated.  The aerated oil can cause cavitation in the pump and consequently no pressure. 

no luck there. blew air in the pressure sensor hole and it sprayed out the tappet screen hole, a small bit of oil. Started and didn't see any oil in the screen hole and still no pressure.

The oil passes through the screen chamber on the way to the gallery to the pressure switch.  All you did was blow out that link.  With the pressure switch in, blow into the screen chamber with a rag sealing the air nozzle.  That will push back on that part of the gallery and clear it.  Not important but it will also feed past the pressure switch to the lifters and pushrods. 

Do you have another filter to try?

I sure do. I have several known good filters.

Quote from: SixShooter14 on December 11, 2023, 09:20:39 PM

Quote from: kd on December 11, 2023, 09:19:28 PM

Quote from: SixShooter14 on December 11, 2023, 08:58:35 PM

Quote from: kd on December 11, 2023, 08:48:47 PMYes, I realize you checked the screen.  My point is blowing back may confirm there is air passing through the system and not plugged.  Restarting it and getting better oil flow will indicate a change. 

As far as the filter goes, if oil isn't getting to the pump (or the lack of sump oil due to low flow causes the sump return system to pick up, carry and introduce air) the pressure can be defeated.  The aerated oil can cause cavitation in the pump and consequently no pressure. 

no luck there. blew air in the pressure sensor hole and it sprayed out the tappet screen hole, a small bit of oil. Started and didn't see any oil in the screen hole and still no pressure.

The oil passes through the screen chamber on the way to the gallery to the pressure switch.  All you did was blow out that link.  With the pressure switch in, blow into the screen chamber with a rag sealing the air nozzle.  That will push back on that part of the gallery and clear it.  Not important but it will also feed past the pressure switch to the lifters and pushrods. 

Do you have another filter to try?

I sure do. I have several known good filters.

If you know it to be correct for your Evo you can always try one.  If it's not visually identical it may be wrong. (The twin cam filter should work but with reduced flow due to filter element difference.). If it works then you found the problem.  If not wrap the filter and save it for you next service. 

Quote from: kd on December 11, 2023, 09:34:32 PMIf you know it to be correct for your Evo you can always try one.  If it's not visually identical it may be wrong. (The twin cam filter should work but with reduced flow due to filter element difference.). If it works then you found the problem.  If not wrap the filter and save it for you next service. 

thanks, I'll swap them tomorrow and see what happens. Also gonna double check hoses and fittings. Never know if something is pinching a line or something.

I did blow air into the screen hole with the pressure sensor in. No luck, ran it for a few seconds but no oil in the screen hole, so I shut her down.

Quote from: kd on December 11, 2023, 07:22:45 PMThe other thing not mentioned yet is the "new" oil filter.  If the bypass is open it can cause similar issues. 

The oil filter is on the scavenge side of the oil circuit, it will have no effect on oil pressure.

Quote from: Dan89flstc on December 12, 2023, 05:09:38 AM

Quote from: kd on December 11, 2023, 07:22:45 PMThe other thing not mentioned yet is the "new" oil filter.  If the bypass is open it can cause similar issues. 

The oil filter is on the scavenge side of the oil circuit, it will have no effect on oil pressure.

correct^^^^^^^^^^^^

I had a 1998 Evo Ultra come in about two years ago with "low oil pressure". It checked good with a mechanical gauge. It took two or three new sending units to get one that turned off the light. If I recall correctly, the one that worked came from Cycle Pro.

Quote from: kd on December 11, 2023, 09:34:32 PMIf you know it to be correct for your Evo you can always try one.  If it's not visually identical it may be wrong. (The twin cam filter should work but with reduced flow due to filter element difference.). If it works then you found the problem.  If not wrap the filter and save it for you next service. 

tried swapping the filter but no luck. still not getting oil through the tappet screen hole. gauge is installed in the sensor hole and is of course showing 0.

I thought maybe the pump had lost prime or gotten air in it during the fluid change. So I pulled the check ball out the top of the pump and poured in a good bit of oil and turned it over with the plugs removed. No luck, the oil in the check valve hole isn't even moving.

At this point, I'm thinking the pump gears aren't turning, maybe a sheared key?