Engine rough running - at wits end

[Zed Head]

What pump is it?  Brand and model.

[the_tool_man]

8 hours ago, Zed Head said:

What pump is it?  Brand and model.

Bosch OEM replacement, purchased 6 years ago. The price has tripled since then.

https://zcardepot.com/products/electric-fuel-pump-fuel-injection-oem-280z-280zx-75-83?_pos=21&_sid=289a78e44&_ss=r

Edited October 19, 2023 by the_tool_man

[the_tool_man]

Anyone have thoughts on the tank coating options?  Looking at how complex the inside is, I doubt very seriously that I can slosh something around and get it all coated.  As evidence, my previous effort failed miserably.  I'm thinking with the tank cut open, I could coat the internal baffles, leaving a band of uncoated metal near the heat-affected zone of the weld, and then slosh coating in the welded tank to get those areas.  Some parts would get double-coated, but maybe that's okay.

My employer sends components to a few vendors in our area for hard chrome plating and anodizing.  I may reach out to them to see if they could galvanize the tank, either as halves or whole.  I think OEMs have tanks stamped and welded from galvanized sheets.  I would imagine the galvanize is affected locally by welding, but it still protected anodically by the remainder of the zinc.  If that's the case, having the halves galvanized might work great.  I'll report back what I find.

[Yarb]

Check out S30.world. They reproduce new tanks that are really nice.

[the_tool_man]

1 hour ago, Yarb said:

Check out S30.world. They reproduce new tanks that are really nice.

Oh, I have. At ~$800 shipped to the US, I'm looking at repair options first.

[Yarb]

The problem I ran into was after being red coated twice, pin holes began to appear just above the seam and decided to pull the trigger instead of throwing more money away. 45 year old thin metal just wont last forever. Worth a shot if you can get it done cheaply.

[Patcon]

On 10/18/2023 at 9:20 PM, the_tool_man said:

We switched back to the jug, just to confirm it would run again...BUT IT DIDN'T. It behaved exactly the same. After some head scratching we unhooked the pump discharge and dumped it into a bucket to test the pump. It flowed strong. We hooked it back to the car and it built proper fuel pressure. The car started right up.

Clearly the pump needed help priming. But why? We were sucking out of tanks that were higher than the pump. In the case of the jug, it was lifting a foot or so to the neck of the jug, and then downhill to the pump. If the pump builds 35psi it should push air or fuel past the FPR. I can only speculate that the pump has too much clearance allowing air to backflow (at around 11psi). Does that mean the pump is bad? FWIW it is almost new, with maybe an hour on it. I'm curious to hear what you think.

Does anyone have thoughts on this? Should the factory pump setup self prime without cracking lines?

[Captain Obvious]

I've had problems with the stock pump priming sometimes. Usually will prime, but sometimes won't.

And if you think about the way it works, it's not surprising. I'm thinking that the insides of the pump and the impeller bits are not a gas tight fit. It pumps the fuel because of the relative incompressability of the liquid and the fact that even though there would be some losses between the parts, the majority of the fuel will be moved from one spot to another. Not necessarily the same thing will happen with a gas.

[Zed Head]

Somewhere out there, either in the FSM or the Owners Manual there is direction by Nissan that the pump might need to be primed if you run out of fuel.  I took a look at what I have but couldn't find it, but I'm sure that I've seen it.

I remember worrying about it when I ran out of gas on my 78 parts car.  But it had an aftermarket pump and fired right up after I put a couple of gallons in.  I assumed at the time that that the OEM pumps must be different.