low oil pressure

[traindriver]

I need some guidance on this one.

I took SPF1591 on a five mile drive today. At initial start up I had just over 40 psi at the gauge....this was lower than the 60 psi the motor had on the dyno in Ohio, but I'm running 5W-30 right now as it's only 30 deg outside. I starting driving and the oil pressure did not climb really at all with rpm, I know the Smith's can be a little slow to respond, so I continued gently on. As the oil warmed the pressure predictably dropped and stabilized at 18-20 psi. I limped it back home. The gauge on the Accusump captured the same pressure as the dash gauge, so I don't think it's the gauge.

I have a 7qt Canton pan, with check valve, a remote filter and a 2qt Accumsump. I have a total of 9.5 quarts of oil in the car right now, the dip stick reading matches the level at the initial 7qt fill.

Any help would be greatly apprciated...I'm getting very nervous.

Thanks,

Chuck

[Bob In Ct]

Hey Chuck:
Just for reference, Ive got an SPF with a 351W. I run 5W-30 synthetic year-round and my highway pressure is about 55-60 PSI even on hot days. I never idle below 45-50.

Bob

[Hal Copple]

there are a number of possibilities. But the first thing to do is to immediately call your car's engine builder. They will guide you to the correct answer.

[SCOBRAC]

It is a new engine? There are so many variables from a bad oil pump to a problem with the bearings. Drain the oil and open up the filter(s) look for signs of trouble.. Aluminum / copper might indicate bearings. Steel or iron could be an oil pump or it could be crank material.. It seems unlikely since there were no sounds associated with the drop.

I had a crappy oil pump on a rebuilt 428. It never dropped on me like yours did but I wasn't there for the maiden voyage.. I did have a little higher pressure but my oil pressure maxed out at 38-40.

I pulled the pan, found no damage, replaced the oil pump and I have 75 psi on start up and 45-55 under idle, normal driving conditions. Pull the pan see what there is to see. Inspect the oil, pull a main cap if need be.. Good time to install a windage tray if you didn't have one put in. Try replacing the pump.. It worked for me.. (shameless plug, but I have a new High volume pump listed with a few other things in Parts for Sale)

[KobraKarl]

Faulty high pressure bypass?

[SCOBRAC]

Not on the 351 as such, but the pump has a bypass that could fail.

[traindriver]

Thanks for the leads....this is a brand new rebuilt motor. It has about 3hrs of dyno time and 20 minutes in the car. I'm going to call the builder today.

Chuck

[traindriver]

Hey thanks for all of your input.

My builder had me drain all of the oil, check the pan for metal (none found thankfully), de-plumb the Accusump, refill with 7qts and try it. Instant 60psi. I'm baffled how the Accusump, which essentially dangles as a dead end off of the system could affect oil pressure. My only other thought is too much oil causing foaming and cavitation. With the Accusump nearly empty due to the low pressure problem, the 7qt pan had nearly 9qts. in it. Any thoughts?

Chuck

[Bob In Ct]

Chuck:
I think the 60PSI is proof you're theory is correct.

Bob

[Bob In Ct]

Chuck:
I meant "your".

Bob

[SCOBRAC]

The accusump acts as a collector when charged and should not discharge until you loose oil pressure or you turn the valve. I suspect the valve isn't actually sealing as it should when it is charged. If that is the case the accusump is acting like a sponge, soaking oil up as well as releasing it when it isn't called for.

Many engine builders try to dissuade owners from running Accusumps for this reason. The other side of the coin is the Accusump valve can stick closed negating any potential value.. It's your call. I'm personally on the fence.. Nice product when it works.. Terribly dangerous when it doesn't..

[traindriver]

Michael,

I'll join you on the fence. My engine builder doesn't use them. I may do some bench testing to see if the valve is working properly. I re-read the instructions for it. They state to add 1 qt of oil or add oil to the FULL mark on the dipstick. Suppose you chose the later, and you're using a 2qt model, and precharge it to 7psi as instructed.

You can calculate the volume of oil stored in the tank (assuming a constant temp ideal gas) by using Boyle's Law, which is:

Pressure * Volume = constant

The 2qt tank is 4.0 ID x 12 in long, thus has a volume of 150 in3 at 7 psi. If we compress the air to 60 psi isothermally, the new volume is 17.5 in3. Thus the tank will hold 150 - 17.5 = 132 in3 of oil or 2.29 qts. Yikes, this means that your 7 qt pan now has less than 5 qts in it. Would you drive your baby around down 2+ qts?

Chuck (sorry for the engineer math)

[bnewell]

My engine builder (probably same as yours) told me the same thing when I asked him about them..........does not like to use them. I figured this guy is the expert not me!! My other thought was that if I demanded one and then had a problem.......who's fault is it then???

Brian

[Steve SPF 517]

This is the first negative I have run accross on the Accusump. I am considering putting one in out of concern about starting up an engine that sometimes sits for 2 or 3 weeks. I have good pressure (50-55lbs) all the time and do not want to see that drop. Which is worse for the engine, a cold start after 3 weeks not running or pre-oiling and maybe loosing a few lbs? If properly installed why would you lose the pressure?? HELP??????

[Back in Black]

If you install it and there is ANY change in the normal pattern of oil pressure, hot or cold, shut down immediately and debug. Seems simple to me... And any mechanical or electrical part can fail, so I am none too worried about it. I have a 3 qt electric solenoid controlled unit ready to install, with SS lines. The only problem I have is WHERE to install it Not much room in there, and it's a monster.

Something easy to do to protect against cold starts is synthetic oil. It really does help in this.

[wilf leek]

Now that we have a member's car restored to good oil pressure (Chuck - I had my fingers crossed for you there for a while) I would be VERY interested to understand why an Accusump can affect the running oil pressure on a car.

Someone please come up with an explanation I can live with? I cannot at present understand why a passive reservoir like an Accusump could affect eventual pressure????

Has anyone noticed if there is a substantial difference between the guage pressure on their engine between times when the Accusump solenoid is activated ot not? Think I might do some playing around tonight on mine.

[KobraKarl]

what would happen if you plumbed an accusump on the primary side of the oil pump so that it would draw oil before the block?,and if the valve were open this cycle could repeat ?

ok ok just guessin

[traindriver]

I spoke to the tech support line at Canton today. They were very helpful. It turns out that the 351W pan for Cobras (#15-660C) is a 6 qt pan. This includes the filter. Using a 2qt or 3qt unit with this smaller size pan and a high performance oil pump can cause your oil level in the pan to vary drastically if you use the suggested 7psi precharge. Canton suggested using a higher precharge pressure (~20psi) to effectively reduce the capacity of the Accusump to minimize the oil level variation. I described my low pressure condition and he thought for sure the crank was aierating (sp?) the oil.

For now, I'm just happy to have my oil pressure back and am going to leave well enough alone.

Chuck