Time for more electrical issues...and fuel issues

[ISPKI]

Hey folks, havent posted on her in a while as I havent been able to work on my car much over the winter. Its a 77 280z in case you all didnt know already. So, I havent been able to start it for a while, found that the wires going to the fuel pump were stripped open. Fixed those, got it running again, and it runs pretty shitty like it used to. I also finally got a fuel pressure gauge and got it in the system between the fuel filter and the fuel rail...thingy. The gauge reads about 31-32ish at idle, when I rev the engine up it drops down slightly (around 28ish) then bumps itself up to high 30s right quick. I seem to recall from my research that that is relatively normal behavior. The issue is that as it idles, the rpms slowly drop and get rough/bouncy. This happens very very slowly, usually over a 10-15 minute period of being on. It also gets to the point that I cant drive it. I tried to pull out and drive down the street after letting it idle for a few minutes and it would not even get up a hill. In fact, when I step on the gas a little harder, it makes this bogging noise and wont get over 2000 rpms.

 

In addition to this, the thing is a pain in the ass to start. Now that I have a gauge hooked up to it, it appears as though when the vehicle is off, the fuel system drains out almost completely. There are no leaks from what I can tell (I replaced many of the fuel lines and clamps already) so where the heck is the fuel going? Yesterday it had 31psi in the system when I shut it off. When I tried to start it today, it had 8.

 

The battery, fuel pump, fuel filters, fuel lines, fuses, wires, ignition switch and lock cylinder are all new.

[r0p0doe]

your fuel lines may be clogged, had a similar issues on my old 510. clean out your lines and what not and see whats happens

[ISPKI]

I do not believe it is clogged lines as I replaced most of them with brand new fuel injection hose and new clamps. To my knowledge, there are only two line that I did not replace, the large line coming out of the tank and the return line to the tank. I took the large line off when I removed the tank and cleaned it so I know that the line is not clogged.

 

Also found that the fuel pump does not turn on when the key is turned to "on". I have never had a vehicle that did that, but it seems to make sense to me that it could be one of the reasons that the vehicle is difficult to start.

[ISPKI]

Also - through reading the service manual it says that pressure at idle should be about 30 and the moment the throttle is pressed down, it should jump to 37. Seems like mine is not behaving correctly as it drops before bumping itself up, like the regulator is not responding properly. Could this be an issue with anything else in the system? The AFM perhaps?

 

Also - Where is the fuel return line? is it the line right at the fuel pump or is it the second line coming out of the rail near the filter? I am figuring that if it is the line from the pump, it probably is not the issue since the pump would have to manage the return of the fuel.

[ISPKI]

Not sure if I should have a different thread for each of these but, next issue;

 

The temperature gauge reads right in the middle of the range at all times. As soon as I start the vehicle, the gauge immediately moves to the middle and sits there. Obviously this cant be accurate as it does it no matter how long it sits or how cold it is outside, so, I am going to assume it is probably the temperature sensor. I checked the connections to the sensor and they were badly corroded. I scraped them off mostly, cleaned them out etc etc, but the gauge still reads in the middle at all times. I am going to elevate this issue to the top of my list since, from what the manual says, not getting a temperature reading can make the vehicle difficult to start and run poorly.

[datzenmike]

Gas. The return line comes from the regulator and is piped to the gas tank. The return line is always a larger diameter pipe than the supply.

 

 

 

Temp gauge. Ground the wire to the sender and the gauge should go to full HOT position. If it stays in the middle it might be the gauge is stuck. Does the gas read normally?

[ISPKI]

Gas. The return line comes from the regulator and is piped to the gas tank. The return line is always a larger diameter pipe than the supply.

 

 

 

Temp gauge. Ground the wire to the sender and the gauge should go to full HOT position. If it stays in the middle it might be the gauge is stuck. Does the gas read normally?

 

The fuel gauge reads correctly. At least it seems to be, not sure how accurate it is but it does change when I add gas to the tank heh. The only gauges that do not appear to function correctly are the temp and voltage. Not sure why the voltage gauge suddenly stopped working, that will be the next thing to be fixed once the car is running right.

 

I should have some hours to mess with it tomorrow. I will check the temp sensor with the method you gave me. Thanks.

 

Ya know, I knew saving this thing from going to the junkyard was not going to be easy. I knew fixing up a car that has been neglected this long would not be easy. I did not think it would have so many small issues.

[ISPKI]

Update: I tried grounding the wires from the temp sender and the needle continues to sit in the middle of the gauge. I am assuming that I need to ground one of the wires leading to the gauge itself, not the wire leading into the sender. Regardless, I tried them all and had no change.

Also - I pulled the gauge out and apart, needle is not stuck.

 

I read online about testing the temp sensor with a volt meter. I set the meter to 20k and touched each of the two leads. Got 512ish as a reading.

 

Side question: Is the sender and the sensor the same thing? When I look online they group them together as coolant temperature sender/sensor. Also - What is the little nub thing sticking out of the engine right next to the sensor/sender?

[JonU]

Update: I tried grounding the wires from the temp sender and the needle continues to sit in the middle of the gauge. I am assuming that I need to ground one of the wires leading to the gauge itself, not the wire leading into the sender. Regardless, I tried them all and had no change.

 

Also - I pulled the gauge out and apart, needle is not stuck.

 

I read online about testing the temp sensor with a volt meter. I set the meter to 20k and touched each of the two leads. Got 512ish as a reading.

 

Side question: Is the sender and the sensor the same thing? When I look online they group them together as coolant temperature sender/sensor. Also - What is the little nub thing sticking out of the engine right next to the sensor/sender?

Regarding the side question; I do believe they are usually one piece. I've never seen the separate from each other. Most of my experience is on military stuff (i.e. diesels) so it could be different but i doubt it.

[datzenmike]

There is a temp gauge sender and there is a coolant sensor for the EFI so it knows how warmed up the motor is.