1976 280z engine runs rough then dies, will not idle.

[Dave WM]

cant help as my internet connection will not support videos right now, ZH is on it, do exactly what he ask. and no you have to disconnect the vacuum line AT the FPR.

[Zed Head]

1 minute ago, mbz said:

Also, is there another place I could disconnect the vacuum hose from that is easier to access that would give the same results you are looking for...? (ie; the vacuum line going to the carbon filter canister).

If the vacuum line to the FPR is connected to the carbon canister that might be part of your problem.  It should be connected directly to the intake manifold.

So, yes disconnect the other end.  But make sure that it is actually the hose that connects to the FPR.  Then if you want to have some fun, blow and suck on the end of the hsoe and watch the gauge.  You should see a response.  But get that baseline no vacuum number first.

[Dave WM]

if you had one, I would go so far as to hookup a vacuum line only to the FPR, like a mini vac used for bleeding breaks. You should be able to drop the pressure (flow more return fuel to the tank) by increasing the vacuum.

 

[mbz]

Just now, Zed Head said:

If the vacuum line to the FPR is connected to the carbon canister that might be part of your problem.  It should be connected directly to the intake manifold.

It is connected directly to the intake manifold.

[Zed Head]

Some explanation - the FPR reacts to either vacuum or air pressure on that hose.  Vacuum will cause the fuel pressure to decrease, pressure will cause it to increase.  So if you find the end of the hose that connects to the FPR and blow on it the pressure will increase slightly,  If you suck on it the fuel pressure will decrease slightly.

[mbz]

OK so when I disconnect the vacuum line from the FPR while the engine is running, what should I expect to see...?

The fuel pressure rise or drop?

[mbz]

Just now, Zed Head said:

If you suck on it the fuel pressure will decrease slightly.

Should I expect a mouthful of fuel....? Or would that be only if there was fuel leaking into the FPR?

Pardon my ignorance, but I'm just trying to be prepared if I'm going to get a mouthful of fuel.

[Dave WM]

3 minutes ago, mbz said:

OK so when I disconnect the vacuum line from the FPR while the engine is running, what should I expect to see...?

The fuel pressure rise or drop?

assuming an intake manifold vacuum (typical of a NA engine at idle) it should rise without vacuum. so disconnect and it goes up.

[Zed Head]

3 minutes ago, mbz said:

Should I expect a mouthful of fuel....? Or would that be only if there was fuel leaking into the FPR?

Pardon my ignorance, but I'm just trying to be prepared if I'm going to get a mouthful of fuel.

Not if the FPR is intact.  I would start the engine and get a fuel pressure reading.  The disconnect the hose and you should see a rise in fuel pressure, because you have removed engine vacuum from the FPR.

That's really all you need to do.  Those two numbers will tell a lot.

[Zed Head]

Sometimes I yell at my television set...

[mbz]

OK So let's see if I understand this next test:

Checking the vacuum on the fuel pressure regulator as it affects the fuel pressure while the engine is running.

1). Disconnect the vacuum line from the FPR while engine is running.

2). Check fuel pressure gauge. If pressure goes up that means _______________________. If pressure goes down that means ______________________.

3). Suck on the vacuum hose from the FPR. Check fuel pressure gauge. Fuel pressure should go down.

4). Blow on the vacuum line from the FPR. Check fuel pressure gauge. Fuel pressure should go up.

Am I understanding this correctly?

If I am, what do these results tell me?

 

[mbz]

2 minutes ago, Zed Head said:

Sometimes I yell at my television set...

I appreciate your patience.....