78 280z Severe Driving Problems

[kinser86]

9 hours ago, Captain Obvious said:

So what's the bottom line? It sounds much better. Are you calling this a success now?

The thread was about severe driving problems. Are you claiming victory? That would be sweet!

I still need to check if the fuel pressure is high or not. The gauge seemed to do fine with the compressed air sweep but still seems to read high on the car even with 20inHg at idle. If it truly is high, then I am not done yet ?. I have blown through the fuel rail and hard lines on the chassis with compressed air at about 120PSI with a clean towel covering the outlets and did not observe any particulates. I need to try a different gauge and see if I get the same results.

[Captain Obvious]

I bought a differential pressure gauge. Hook one side to the fuel rail. Hook the other side to the intake manifold.

My fuel pressure "seemed" like it was all over the place, but when measured differentially (as you really should), it was rock steady at 36psi even when you goosed the throttle. It's really deceptive when just measuring one side.

So why doesn't everyone do that? Because they're expensive and delicate. I got lucky and found one on ebay for cheap. I'll post a pic when I get a chance.

[wheee!]

Interesting. My setup will have a pressure gauge on the entrance to the fuel rail, and another at the FPR return. That should give me the same setup basically. Pressure before and after the rail.

[Captain Obvious]

Here's the theory for the differential pressure gauge I have. It's essentially just a piston (which also happens to be a magnet) sliding back and forth in a tube. That magnetic piston is coupled to the gauge needle so there is no process fluids (whatever you are measuring) in the meter movement area.

Operates like this:

And this is hooked up to the car. Too big to leave in there all the time, but it's fantastic for diagnostic purposes. One side pushes while the other side pulls. The pressure reading would go down if you disconnect the vacuum side because that side isn't pulling:

 

[kinser86]

11 hours ago, Captain Obvious said:

Here's the theory for the differential pressure gauge I have. It's essentially just a piston (which also happens to be a magnet) sliding back and forth in a tube. That magnetic piston is coupled to the gauge needle so there is no process fluids (whatever you are measuring) in the meter movement area.

Very interesting. There are some Ashcroft differential pressure gauges on eBay currently for a decent price. 0-60 PSI with a max pressure of 3,000PSI and 1/4"NPT(F). Something like this should work in this application correct? If so then it would be worth a purchase to have in the toolbox.

[Zed Head]

11 hours ago, wheee! said:

Interesting. My setup will have a pressure gauge on the entrance to the fuel rail, and another at the FPR return. That should give me the same setup basically. Pressure before and after the rail.

Actually this is not quite the same.  You need to compare pressure inside the rail to "pressure" inside the manifold.  The big confuser for the fuel pressure regulator operation is that they/we use vacuum for the measurement on one side and pressure for the other side.  Convert vacuum to pressure and do some math and you can see what's happening.  That's what I did in post #103.  But I have to go search around for proper values every time this topic comes up.

CO's cool tool is a direct reading of what's happening.  But a calculator and two gauges will get you there too.

Kinser you almost seem more interested in the measurement and diagnosis than actually driving the car.  You will do well here...

[Captain Obvious]

I didn't dig into the specs of that Ashcroft differential gauge, but the biggest thing you would have to watch for is something compatible with gasoline. The Orange Research gauge I have is all metal body and piston and has Teflon seals. It also magnetically couples the internal piston to the meter movement so the gas never gets to the needle. It's completely segregated.

I don't know anything about the Ashcroft, but if it can handle the gasoline, then it should work fine.

I don't remember what I spent on mine, but its very convenient having it at my disposal. No math. No units conversions. Direct reading.

[kinser86]

40 minutes ago, Zed Head said:

Kinser you almost seem more interested in the measurement and diagnosis than actually driving the car.  You will do well here...

I think so too Zed. I plan my methods during the week and attack during the weekend. My hope is that any unfortunate individual who has to go through what I am/did with this car can reference this at some point and use the numbers to make the right decision rather than throwing money/time where it shouldn't go.

4 minutes ago, Captain Obvious said:

I didn't dig into the specs of that Ashcroft differential gauge, but the biggest thing you would have to watch for is something compatible with gasoline. The Orange Research gauge I have is all metal body and piston and has Teflon seals. It also magnetically couples the internal piston to the meter movement so the gas never gets to the needle. It's completely segregated.

I don't know anything about the Ashcroft, but if it can handle the gasoline, then it should work fine.

I don't remember what I spent on mine, but its very convenient having it at my disposal. No math. No units conversions. Direct reading.

Fortunately Ashcroft has very good documentation on their website. The item currently on eBay is:

Model: 25-1130FL-25S-XV2-60#

25: Size (2.5")

1130: Series

F: Body Material (Aluminum) (The stainless bodies have a higher max pressure rating of 6,000-PSI)

L: Case Fill (Glycerin Fill)

25: Process Connection Size (1/4" NPT Female)

S: Process Connection Location (In line)

XV2: Options (1-SPST switch with terminal strip)

60#: Range (60 PSI)

More importantly, the o-rings are Buna-N so gasoline should not be a problem. For the cost it is worth a shot.

[Captain Obvious]

Well for twenty-five bucks, it's certainly worth a shot. If it works as well as mine, it'll answer any questions about the real pressure that the injectors actually see. I took a quick look at Ashcroft's website and I couldn't find a diagram that explained the basic theory of operation for the internals. I did see some mention of magnet(s), so I assume it's the same magnetically coupled meter movement concept as the one I have, but I couldn't 100% determine.

11 hours ago, kinser86 said:

My hope is that any unfortunate individual who has to go through what I am/did with this car can reference this at some point and use the numbers to make the right decision rather than throwing money/time where it shouldn't go.

This whole thing sounds like a typical 280Z story to me.      Most of us have been through it. So far, you made a simple mistake and screwed up your ignition timing and vacuum hose routing, Your PO put in a fuel pump that was incompatible with the stock pressure regulator. And you paid for an injector cleaning that had to be done twice because the first time didn't work out as intended. Nothing unusual so far.

Admiral goal to keep that sort of stuff from happening to anyone else, but I wonder if you're trying to prevent the un-preventable. 

[kinser86]

Here is a snapshot of the mechanics of the gauge:

Gauge Mechanics

Gauge Datasheet

I ordered the one from eBay and it is on it's way. I will post videos of course of it in action. For the time being, we are going to clean up some of the car and drive it some more and I will keep an eye on the plugs.

[Zed Head]

On 10/4/2018 at 7:16 AM, Captain Obvious said:

Your PO put in a fuel pump that was incompatible with the stock pressure regulator.

Actually, the pressure readings are the same before and after the pump change.  42 psi.  Hence the thought that there's a bad gauge somewhere.  It's been the same gauge reading fuel pressure from the beginning.

The parts stores will loan a fuel pressure gauge, among other things.  I don't know why I don't take more advantage, they have quite a selection.

https://www.oreillyauto.com/rental-tools

[Captain Obvious]

 

53 minutes ago, Zed Head said:

Actually, the pressure readings are the same before and after the pump change.  42 psi.  Hence the thought that there's a bad gauge somewhere.  It's been the same gauge reading fuel pressure from the beginning.

Oh.  I was going from the text above when the OP said "At this point I felt the fuel pump was too much for the car and we pulled it and replaced it with a Delphi stock replacement." and "With the stock pump replacement, the fuel pressure still seems a little high but not as high as with the previous pump."

I didn't have time to sit and wait for all the videos to load and run calculations on multiple gauges and stuff. I was just going off the text and assumed there was a reduction in fuel pressure with the stock style pump.

Edited October 6, 2018 by Captain Obvious