Electric Pre-Lube Pump

[georigg]

Both Mark 4 Supras I have owned(present one included) appear to suffer from a delay from starting until oil pressure establishes, with the oil light going out.

 

From cold this can be up to about 3 seconds, which means the engine is running with less than minimum oil pressure(manual says 7PSI). This is recognised as the most common cause of eventual engine failure in all cars.

 

In summary, I'm installing a 12volt pre-lube pump, taking the pump inlet from the sump drain plug(replacing this with an elbow-type swagelock fitting, and hard piping round the back of the sump to the pump, (its a gear-type pump used in aero engines & develops approx 30PSI ), from there fitting a Tee at the Oil pressure sensor etc..

 

The pump will be operated by push-switch on the dash, so that at start-up, a push on the switch to establish oil pressure and then turn the engine on the key.........nice and simple, but no more oil-less starts from cold!

 

Pump bought for £82, fittings and 10mm S/S pipe about £20, Relay, push-switch and wiring about £10. I'm intending to fit everything on the engine block, hence hard piping OK but if the pump is installed on a bulkhead, it will need flexible hoses to allow for engine movement......this more expensive!

 

Anyone interested in details, please PM me and I will oblige. I'm currently in contact with the pump manufacturer to establish if he can supply bulk quantities - if a yes I wll post contact details.

 

I know there are kits available to do this but the ones I have seen(so far) are significantly more expensive than above.

 

George

[SUPRASUZUKI]

Interesting.

 

I can't say I've noticed a delay on my car, but I'll pay more attention in future.

[edge]

Yes very interesting

[Mike M]

Very interesting too, Mine sits for roughly two weeks every month and doesn't like it one bit. Usual symtoms are, oil light takes a good few secs to go out, engine tapping and smoke(stem seals probably).

All clears after a minute or two idling but it does worry me for the long term engine life.

[SatSport]

wouldn`t there still be enough oil left in the bearings/bores to last until the pump gets in on the act?

[georigg]

Hi Satsport,

Short answer is no, not really.

 

There will be an oil coating on the shells, but bear in mind that as soon as the engine fires, each piston is exerting a large downward thrust on the con-rod and on to the bearing shell. The main bearings tend to last longer because each pot fires individually not all together, so the downwards force is effectively "shared" by all bearing shells( a lot more complicated than that of course as each pot fires at a different position along the crank so the load on each shell varies in direction and as its distance from the pot).

 

Oil on its own will provide a small lubricant layer but the engine relies on oil pressure to maintain a "wedge" of oil at each shell and no pressure means no oil-wedge.

 

If your oil light does not go out for say 3 seconds between turning the ignition key and oil-light out, then the engine will start at zero revs and rise to about 2000RPM from cold. 2000RPM equates to 33 revs per second, so for at least the first second, and probably more, your engine is turning about 10 to 20 times with almost no oil pressure.

 

This is what kills big end shells over time.

 

This will only happen from cold as the engine will retain enough oil in the passageways etc., to almost instantly develop pressure when hot or for at least 3-4 hours after switching off, its the overnight "off" that's the problem.

 

My first effort was to fit a relay between the ignition coil and the oil pressure sensor such that the ignition would not fire until the oil pressure light went out, but that took about 10-12 seconds turning over on the starter to get to the point that the oil light went out/engine fired.........not good!

 

As an interim just now, from cold, I start the engine as normal, but as soon as the engine fires, I switch off the ignition, so that the oil pump is still "priming" as the revs die off. Usually on the second "start" there is sufficient oil pressure to allow the engine to remain firing. This allows the engine to turn over at higher revs than can be achieved on the starter but without the ignition "pressure" on the big ends.

 

The pre-lube pump removes the necessity to do this.

 

Just as an example, anyone involved in turbine installation or maintenance will know that most of these units are set up with an electric and a machine driven oil pump, for much the same reasons as above, so I'm not being innovative, just copying what's already done elsewhere.

 

Hope above explains.

 

Rgds

George

[Digsy]

Is the tee where the oil rejoins the circuit before the oil filter?

 

The "relay" idea is definately a non starter (no pun intended) because of the amount of raw fuel you'd be dumping down the cylinders before the oil pressure got high enough to fire the engine.

[Chris Wilson]

Or:

 

http://www.racecarsdirect.com/viewlisting.php?view=12300

[georigg]

Hi Digsy,

 

The oil Pressure sensor is normally a tee-off the oil gallery which is fed from the oil filter; one of the fittings I will be using(at the sump connection) will include a small mesh filter so that I'm not flowing unfiltered oil into the pump......(filter will be on the inlet side of the pump). Logic of this is that the electric pump will not be operating for any length of time so in-line mesh filter will not clog & can be cleaned/examined at each oil change.

 

Just had contact with the pump supplier, Dragon Racing can be contacted at [email protected] and reference enquiries to David. Telephone number is 07831 095859

 

Will post photos and pump spec in next post.

George

[georigg]

Pump spec and photos below,

Oil Pump Spec.doc

[SUPRASUZUKI]

Do you need a one-way valve to stop oil pressure bleeding back through the pump and into the sump once the engine's running?

[georigg]

Hi Suprasuzuki,

 

Got it in one! Small NRV at the tee position. Just thinking out loud, this installation could also be good for turbo Supras in that most damage to turbos occur when the ignition is switched off with the turbo still running down..........no oil pressure after you switch off the engine!

 

Although mine is a non-turbo, It should be possible to fit a relay & timing relay in series, to operate the pump for X seconds after switching off the engine............fit a relay off the ignition so that when not energised, the timer relay is powered, running the electric pump for X seconds, enough to allow the turbo to run down to stopped but with oil pressure to its bearings. With the ignition "on", the first relay is powered removing the +ve supply to the timing relay.

 

PS..........Mine is a Blackbird along with the Supra.........great bike!

 

Rgds

George

[Digsy]

Just to play devil's advocate for a second:

 

The idea of a pre-lube pump sounds great - too much oil pressure can only ever be a problem in engine's with hydraulic tappets or when you are trying to downsize the oil pump to make the engine more efficient.

 

However… If there is a problem with oil pressures then surely the root cause will either be a leak inside the engine (too much bearing clearance due to wear, for example) allowing the pressure to bleed away or a problem inside the pump (again, probably leakage within the rotorset due to wear) which means that the pump can't deliver enough oil to maintain the proper pressure. What I'm getting at is that adding a pre-lube pump might just be hiding a bigger problem.

 

I've got a 120,000 mile NA which I've owned since 26,000 miles and it too seems to take forever to extinguish the oil pressure lamp. On some days there is even a slight tap that goes with it, so I guess one of my big ends is a bit worn. It has, however, done this for years without seeming getting any worse. I went through a phase of being massively paranoid about it but these days I just live with it. What I have started doing is using a decent quality 15W50 oil at service time. Of course, it might pick up and spin a big end bearing tomorrow.

 

I can totally see why you might opt for adding a prelube pump, though - the only other possible fixes (new pump or new bearings) are both engine-out jobs.

 

CW: Aren't those Accusump things meant as a cheap solution to oil starvation during cornering in race cars - kind of like a budget dry sump.

[SUPRASUZUKI]

 

CW: Aren't those Accusump things meant as a cheap solution to oil starvation during cornering in race cars - kind of like a budget dry sump.

 

I believe they fit these to the new Lotus track car. Not sure whether it's a standard fit or option though.

[markjodrell]

How about turning the engine over a couple of times on the ignition but not long enough for it to start up , if you know what I mean.

[SUPRASUZUKI]

I like the idea, particularly running the pump after 'ignition off' to feed the turbo bearings after the engine has stopped.

[Digsy]

I believe they fit these to the new Lotus track car. Not sure whether it's a standard fit or option though.

 

I believe they do

[georigg]

Hi all,,

 

Ref Mark, thats what I do at present, but your still turning the engine over with no/little oil present.

 

Ref Digsy, I did look at an alternative unit which used a steel pressure bottle which is fed with oil as the engine runs....a solenoid valve shuts off when the engine stops and oil is fed from the bottle back into the engine on next start. Costs about £300+ depending on bottle size etc, so I still prefer the pre-lube pump.

 

On my last Supra, I sold it with over 140K miles on it, but that was after an expensive overhaul, following the engine basically crapping out on me. The oil light came on at tick-over, it never developed more than 40PSI.........bearing shot, oil pump gone etc.. even in hot weather, the oil light came on at low revs! Engine running on synthetic etc.

 

It seems to me at least, that spending about £100 now will save me a lot more money later.

 

I will post pictures etc of the installation when completed.

Rgds

George

[SUPRASUZUKI]

 

Ref Digsy, I did look at an alternative unit which used a steel pressure bottle which is fed with oil as the engine runs....a solenoid valve shuts off when the engine stops and oil is fed from the bottle back into the engine on next start. Costs about £300+ depending on bottle size etc, so I still prefer the pre-lube pump.

 

 

I will post pictures etc of the installation when completed.

Rgds

George

 

Accusump is sort of what you describe here, maintaining oil pressure under severe oil surge conditions (hard cornering, braking, accelerating, rolling:blink:).

I look forward to the pic's.

[Digsy]

I think there may be some mileage in something that cuts fuelling until oil pressure rises above a set point - not ignition for the reasons I've already stated.

 

Turning the engine over with low oil pressure shouldn't do too much damage as there will be no gas firing loads to speak of and because the engine speed is low the inertia loads will also be low. What you don't want is the engine actually firing with low/no oil pressure.

 

What a pre-lube pump on a static engine will do is fill the galleries. What it won't do it fill the bearing clearances - not as effectively as when the engine is turning running, anyway. Also, oil feed to the big end is actually helped by the crank rotation, which centrifuges the oil up the drillings in the crank.

[paul mac]

i do like inovation but this seems like overkill to me, i am sure there are 200,000 + mile supras out there that are just plain well maintained without the need for this, there is NO substitute for good basic maintenance

[Chris Wilson]

I thought the same, but didn't want to be a killjoy

[georigg]

Totally agree with all posters, particularly the points concerning good maintenance. Again a personal view, but I never fit cheap, after-market oil filters as these tend not to be constructed just as good as OE.

 

A good oil filter will have a positive seal non return arrangement internally(usually a rubber flap-valve arrangement) which prevents oil draining out the filter, the cheap ones usually have the flap but the compounding of the rubber is pretty poor, which allows the oil to drain back to the sump. Same comments for oil; I use semi synth in both car and bike(12,000RPM red line on the bike, developing about 160BHP from 1100cc). Both car & bike get oil/air filters and semi synth change-outs at 6K intervals etc..

 

Just a quick "last post" on one of the points raised above; the pressure a pump develops is a function of the relationship between its volumetric output and the sum of all leakage paths through the lubricated system. One large output area will starve smaller ones, but since the "output areas" on an engine are the bearing clearances, oil will circulate to all bearings(unless of course one is completely shot and all/most oil will leak through this path, resulting in a lower developed pressure being attained). Small leakage area, large® developed output will result in the pump operating "up its curve" & developing a higher pressure. There are other factors as well, viscosity, temperature etc.

 

I like the idea of this mod; its up to others to agree or disagree but for me, I will be fitting it, if only to see if practice lives up to theory......etc......etc!

 

Best regards

George