Help with Throttle Position Sensor 78 280 Z

[zeenubee]

in reply to Zed Head. et al...it doesn't cough or backfire...it bogs down, no smell of gas that I can tell...I do think he messed with the distributor because he replaced the cap...small crack. I will re-check the fuel pressure. I did notice in the efi bible that the picture of the FPR shows two inlets....one side of mine is blocked off...don't know who did.. this may be PO, but the car ran fine when I bought it in 2002. I have most hand tools, but don't have a timing light, think I have a cheap multimeter. I will start with the efi bible and check the values if I can figure out how to do it...seems pretty simple...then I will check the plugs as suggested...thought maybe the mice had partially plugged the exhaust with soybeans as I find them everywhere in my garage...they used the air filter for their main bathroom....no evidence of chewed wire yet, but I haven't been up under the dash yet. Thanks guys! will let you know more over the weekend hopefully.

[EuroDat]

Can you take some photo's of the fuel rail and that kind of stuff.

You mention one side of the FPR is blocked off. Maybe there are other things wrong as well and a photo can say a thousand words.

[FastWoman]

If you have anything blocked off on your FPR, then you have a problem. I'm guessing your return line is blocked off, and the fuel rail is running at the full output pressure of the fuel pump, which would be in the neighborhood of 45 psi. Instead, it should be running in the neighborhood of 30 psi. Higher pressure means too much fuel injected. That's likely why your engine is choking -- or at least one of the reasons.

Take a look at where your steel fuel lines enter the engine compartment from under the car on the passenger side. One of them will go to the fuel filter and is your supply line. There should be another one right next to it. I bet it's blocked off. There should be a fuel line between the fuel pressure regulator and that steel line to carry return flow back to the tank. Before hooking it up, blow some air through it to make certain it's not blocked with rust and debris. If it's blocked, you'll still have the same fuel pressure problem.

I agree with Euro: A picture would tell us a lot.

Edited December 13, 2013 by FastWoman

[siteunseen]

if your FPR has 2 inlets on the side and the return on the bottom, vacuum up top, it's for a '77 and older. They changed in '78 to 1 inlet. Motorsport! Fuel Pressure Regulator, 75-77 280Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts

[TomoHawk]

There is one inlet from the fuel rail, and one outlet to the return hard line, and one vacuum line connection.

[zeenubee]

OK...will check the pic in efi bible, take a pic of my set up, and check the return line also...wont be able to do this til sun or mon....thanks!!!!.....one ,more thing to learn...how to post a pic here ()

[EuroDat]

Might be a good idea to put the model and build date in your signature.

The 78 has the FPR with one inlet (N47). If one is blocked??? That must be the return line or the vacuum line. Either way its getting to much fuel pressure and that will make it run rich.

The fuel injector is in simple words an on/off valve. The size (in the process industry we call it the Cv value) of the injector is based on the pressure drop across the tip. Google "Cv pressure drop" or "Cv values" in metric its called Kvs and wikki will give you a good read on the relationship between flow and pressure.

The FPR maintains the pressure drop across the fuel injector at 36psi. The ECU does all its calculations based on this and if its out of spec, it will effect everything the ECU does.

BTW: The two inlet version (N42) was used upto juli 77. In August 77 they they changed over to the fuel rail in your model.

Chas

[EuroDat]

Might be a good idea to put the model and build date in your signature. I just noticed your first post again "getting the 78 running".

The 78 has the FPR with one inlet (N47). If one is blocked??? That must be the return line or the vacuum line. Either way its getting to much fuel pressure and that will make it run rich.

The fuel injector is in simple words an on/off valve. The size (in the process industry we call it the Cv value) of the injector is based on the pressure drop across the tip. Google "Cv pressure drop" or "Cv values" in metric its called Kvs and wikki will give you a good read on the relationship between flow and pressure.

The FPR maintains the pressure drop across the fuel injector at 36psi. The ECU does all its calculations based on this and if its out of spec, it will effect everything the ECU does.

BTW: The two inlet version (N42) was used upto juli 77. In August 77 they they changed over to the fuel rail in your model.

Chas

[siteunseen]

OK...will check the pic in efi bible, take a pic of my set up, and check the return line also...wont be able to do this til sun or mon....thanks!!!!.....one ,more thing to learn...how to post a pic here ()

Click Go Advanced. Scroll down to Additional Options. Click Manage Attachments, a small window will open. Click Add Files, then click Select Files. Find your picture from your camera or your hard drive, then in that box click Open then it'll close and go back to the 1st small box. Click Upload Files. They should appear on the bottom left of the light blue bar at the bottom. Click Done. That's how mine works.

Edited December 15, 2013 by siteunseen

[zeenubee]

Ok, here goes...don't know how this will turn out...thanks Alabama for your help...did not have time to do any testing but I welcome any and all comments on what you see! I have more pics if needed

[Zed Head]

Pictures look great. Well-sized.

Looks like someone installed a 75-77 FPR on your 78 fuel rail. It should work fine, but that's why it's not attached properly and has the blocked off port. Not the safest set-up either since the only thing holding the FPR on is the hose clamps on the inlet and outlet ports (unless there's a bolt that I can't see in the picture). If the clamps loosen it could pop right off and the engine would get dowsed with gasoline. Check those clamps and see if you can get a bolt in to the bracket.

The part of your situation that seems most important is that the engine died and you had to have the car towed. If it was a simple tuning problem, you should be able to drive around with low power all day. Does the engine start now? If so, it could be a heat-related problem, if not, maybe something broke unrelated to the low power problem.

[TomoHawk]

FWIW I dug up a couple diagrams that ought to help. the first is the fuel pressure regulator, and shows you where the different connection go, and the second is entire fuel injection rail, to show where the hoses and metal tubes go.

These are both for the 1978 L28E engine.