Mystified -- No Oil Pressure Issue

[JeffYoung]

Guys, I'm stumped. I have an ITS Triumph TR8. Build a new motor for it after killing a ring and rocker arm in March, got it installed. Bottom in was done by a machine shop, new bearings obviously, new .020 pistons. We did everything elese. Had a bitch of a time priming the pump, but eventualy got it primed and ran it in over about 2 hours of contnuous fast idling to heat cycle it -- no oil pressure issues.

Went to the track. Ran 3 easy laps, with the pressure fine. Lap 4, going uphill in a twist bit at VIR, look down and no pressure. I shut it down before pieces went everywhere, but it will need new bearings...

In any event, started to dismantle the oil pump at the track -- dry. Plenty of oil in the sump. Have an accusump and remote oil filter and cooler, but we had run the motor for 2 hours to "fill up" the system and the sump level was fine on initial shutdown.

We took the motor apart this weekend expecting to see either an oil galley plug popped off or a pickup tube issue. Saw neither.

So, we're putting it back together but very afraid that we having solved the problem, whatever it may be.

Any ideas guys? We are stumped.

Thanks.

Jeff

[BMW RACER]

Jeff. Don't know anything about TR8s but I am English. Have you checked the oil pressure relief valve? Have you tried spinning the pump by itself? I think just putting the motor back together is going to end in tears. Can you check through the oil system one item at a time to make sure it's all working as it should?
Good luck.
John

[seckerich]

Sounds like you still have a problem with the pump pickup. If it was that hard to prime it must be sucking air somewhere. Check the clearance in the impeller and see that there is not a leak besides the tube. It might have starved for oil on track and cavitated at VIR. How is the accusump routed? I always pick up on the outlet side of the remote filter assembly and use the filter as a check valve. Gives the shortest route to the bearings for oil flow. Also check your clearance from the pickup to the bottom of the pan to be sure it is not sucking down. Good Luck!
Steve

[JeffYoung]

Guys,thanks for the response.

Oil pump gears looked fine Steve, but you are right we should check clearance and since they are cheap I'll buy new ones. Relief valve appeared to be working.

There was a small dent in the pick up tube screen. Steve, not sure what you mean when you say it (the tube) should not be sucking down? Which way should the tube be oriented.

I'll have to check the car (it is in Burlington at a buddy's shop) but I think the accusump is routed on the outlet side, and then the oil flows around to the cooler, the filter and then back in the motor....this sounds a bit odd to me now thinking about it.....I'ln confirm this week.

Thanks again guys.

[joeg]

...and remeber the normal assembly rules--pack the oil pump with vaseline so you have less of a start up issue.

Your accusump routing seems strange; how are the check valves in that system?

[seckerich]

With the motor upside down on the stand put some clay on the pickup tube at its highest point and test fit the pan. If the tube is hitting or too close to the bottom it is like putting your hand over a drain--no flow. I try for min 3/8 to 1/2 clearance. I run the oil out of the motor to the cooler, then back to the external filter. finally run the line to the motor,and the acusump line from the outlet side of the external filter. This gives the shortest distance and volume for the accusump to pressure and uses the filter check valve instead of running an external check. Some say it is better your way as it stops trash from entering the cooler with the filter in line. I have better luck not killing motors my way!!
Steve

[Bill Miller]

Jeff,

I agree w/ the others, the Accusump plumbing seems a bit backwards. As someone else eluded to, I have my accusump between the last 'piece' (remote filter) and the return to the block. There's a check valve between the filter and the "T" that goes to the Accusump and the block. Did you guys check the oil pump w/ a feeler gauge before you put the car back together? Was the clearence w/in spec?



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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

[Bill Miller]

Actually, I mis-spoke. I use a screw-on Canton filter, rather than an external filter, so my plumbing runs as follows:

Engine -> Filter -> Cooler -> Check Valve -> T-fitting -< Accusump/Engine return.

If you use a remote filter that has a good check valve, that's probably fine. I put an extra one in because I wanted it controlled at the "T". I also agree w/ putting the cooler down-stream of the filter, as it may save the cooler in the event of an engine failure.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

[John Herman]

Were the oil pump, pickup and/or pan, new? (If new, I'm assuming auto parts store instead of NOS.) Were they reused from a known running engine? Or are they parts from another application which are supposed to work? Next, is the pump drive system good and intact? Check the pickup screen for stuff, like gobs of silicone, old gasket material. Check for any cracks which allowed the pump to suck air. Make sure flat surfaces are flat to promote good seals. Even with new stuff, I try to give it a decent look-over. With costs being what they are today, everyone is looking to save a buck, and some new stuff is junk. Is it at all possible that something plugged or restricted the oil drainback holes, which caused the pump to pump the pan dry? Finally, though you said the pump was dry, was it possible the bearing clearances were off, causing the bearing problem, and then plugging up the pump with stuff (or at least giving that indication). Even if the relief stuck open, the pump shouldn't be "dry." Another far fetched theory, is it possible that as your oil heated up, the pressure dropped, allowing the Accusump to discharge, thus overfilling the pan, causing the oil to become severly airated by the crank, which caused the pump to lose prime...I think for now, I'd remove all the fancy stuff until the problem is solved. You mention that it was hard to prime the pump. Could it have been too hard to get the oil to where the oil sending unit is located? Could the cooler be plugged or undersized for the application? Did the machine shop (or you) get fancy and try something on the edge? I've had shops offer to do lots of racey stuff, so now I am addement about what I want and don't want. I know these problems suck from both a time and $ standpoint. Good luck.

[Mark LaBarre]

If your oil pump was dry...
Is there a pick up tube that goes into the pump that could not be sealing right (sucking air)?
Otherwise, I'd check what drives the pump.
Good luck.

[JeffYoung]

Guys, lots of valuable information above -- many thanks. I'll get back to it later this week and I'll let you know what I find out.

Thanks again -- sometimes this board is an amazing resource.

Jeff

[JohnRW]

I have seen brand new remote filter elements get plugged up in less than an hour's running time.

A few years ago I was sharing paddock space with a buddy and his EP Mazda RX3 at Summit Point. Car ran fine on a new motor for the Friday test day, Saturday am first qualifying session...he starts the car to get to the grid and zero oil pressure. Hmmm.

He pulled the oil system apart, checked all the lines, used my nitrogen tank to check the gauge, diddled with the pressure bypass valve, you name it. Didn't find it until after qualifying session #2 in the afternoon - the filter (can't remember if it was a Mecca or a flat screen...just wasn't a screw-on canister type) was clogged. Don't remember what he found (time marches on...) but it was surprising as hell. Race filters don't have 'bypass valves' like street filters (but Fram will still charge you more for an HP1/HP4), but I'd never seen a race filter clog up like that. Maybe it was too effective.

Changed the filter element and everything was happy and healthy.

[JeffYoung]

Well, motor is rebuilt, in car and ready for Road Atlanta (mostly) in two weeks.

Primed right up and has good oil pressure. A total mystery as to why pressure was lost in the first place.

[trd77]

Jeff, good luck at RA. I hope everything goes well. I will be at Mid-Ohio the first weekend in August, I will let you know how that goes. Keep us up to date on the new motor at RA