Need New Oil Pump - Recommendations?

[Captain Obvious]

First off, let me acknowledge that I'm sure this question has been asked a hundred times, and yes, I've searched. But unless I'm missing something, the search capabilities of the forum leave a lot to be desired.**

So, I want to replace the oil pump in my 77 because I've got low oil pressure. I've checked the pressure with a mechanical gauge, so I know it's a real problem and not simply a sender or gauge issue. I've truly got low oil pressure. I don't know yet if it's the sole source of my problems, but I've pulled the oil pump out and it doesn't look too healthy inside.

Any recommendations as to which oil pump to use? Direct year replacement? Higher volume ZX pump? Cheap ebay no-name? Datsun genuine? Melling? NAPA? Doesn't matter, they're all the same?

I understand the differences between higher volume and higher pressure, and I understand that pressure and volume will be related if you're not bouncing off the high pressure relief inside the pump itself, so what's the deal? Why would I want either of them?

**[RANT]Searching for oil pump turns up every post with either the word "oil" or "pump" in it, which is just about every post this forum has, including every fuel pump post.

Searching for "oil pump" (putting quotes around the two words intending to force an exact string) does nothing different than without quotes, so I can't seem to force the word "oil" to be followed by the word "pump".

Negative keywords like -fuel don't seem to have any effect.

And there's no hints, helps, or anything like that which I could find, even on the advanced search page.

So, am I missing something? [/RANT]

[SteveJ]

I can't help you on oil pump selection.

For searching, let Google do the walking. Use this text in the dialog box for the search on Google: "oil pump" site:classiczcars.com

Here is what I got from that search.

[steve91tt]

If it were me I'd go for the higher volume turbo pump. They are readily available from auto parts stores and are a direct bolt on for your engine.

[Jeff G 78]

What do you mean by "it doesn't look too healthy inside"? Is there any debris, or is it just showing signs of wear from age? Did you measure the internals per the FSM?

I always replace the pump when I rebuild an engine, but low pressure is likely due to bearings than the pump itself. The only times I've seen a pump look bad inside where when shavings were forced through, causing damage in the form of dents and abrasions in the rotor and body. It might just be time for an engine rebuild.

[siteunseen]

E-mailed Melling tech and he suggested their 152. I bought one from Advance online with promo code for $55. They're a little heavier than aluminum but I don't mind a pound or so up front.

[Captain Obvious]

The only times I've seen a pump look bad inside where when shavings were forced through, causing damage in the form of dents and abrasions in the rotor and body. It might just be time for an engine rebuild.

Funny you mention that... Mine looks like shavings were forced through causing damage in the form of dents and abrasions in the rotor and body. :laugh: I didn't even bother to measure anything.

I'm assuming that something grenaded inside the engine at some point in the past before I owned the car. Under magnification I was able to pick out some small chips that were still embedded in the rotor assy. I don't know what they were from, but I can tell you that they were non-magnetic. Probably aluminum, so best case is that they were material torn off from inside the pump body itself. It's pretty gruesome.

So, I understand that the oil pump might not be the only problem, but after seeing inside the pump, it's clearly at least part of the problem. At this point, I'm hoping that any debris that made it through the pump got caught up in the oil filter and my "plan" is that a new pump will take car of it without having to rip the whole engine apart. I've not yet even had a season of enjoyment out of this one yet!

The PO did a rebuild on the engine shortly before I bought the car, and although I'm always skeptical of anyone's work other than my own, I'm inclined to believe he knew what he was doing. Curious though with all the money he spent on the motot that he did not replace the oil pump.

Anyway, used cars are always a crapshoot. I'm hoping that a pump will fix it, but I'm aware it might not.

If it were me I'd go for the higher volume turbo pump. They are readily available from auto parts stores and are a direct bolt on for your engine.

Brand independant? No-name ebay is just as good as genuine Nissan? Anything from RockAuto is good too?

And SteveJ, those search results are light-years better than what I could turn up. Thanks for the tip.

[Jeff G 78]

I can't remember for sure, but I think I got my last turbo pump from RockAuto. It works great in my race car. If not there, it was MSA. I'll go dig out the receipt and edit my post.

Good luck with the motor.

[Captain Obvious]

Good luck with the motor.

Thanks Jeff, I appreciate it! I'm hoping for the best.

On that subject... Do you know off-hand what is lubed pre-filter? Just the distributor shaft and oil pump itself? Everything else is post-filter?

[Jeff G 78]

Good question. I don't have the answer. I wonder if the FSM has an oil flow diagram?

[Captain Obvious]

I wonder if the FSM has an oil flow diagram?

Yes, the FSM has some pics, but they're lacking in detail and it's hard to figure out what's what. Here's one from the 72 manual, and another from 77. Only reason I know that the distributor shaft and drive gear are unfiltered is from looking at the pump design iteslf.

[Jeff G 78]

OK, that makes sense. If there is any debris in the oil pan, the pump eats anything that will fit through the pickup screen. From there, the filter removes the particles before they get to the bearings or head. You might luck out and repair it with just a new pump.

I haven't found the oil pump receipt yet. I know I bought engine rebuild parts from RockAuto and MSA. I'll look again tonight.

[steve91tt]

Given the shavings that you found in the pump, it might be worth the effort to drop the pan and clean the oil pickup screen to make sure there is nothing there that would harm your new pump or starve it for oil.