90 300ZX N/A Car ran rough but ran..replaced fuel pump won't start

[Backinblack05]

I have a 1990 Nissan 300ZX 2+2 N/A that I recently purchased and the car was running rough when I got it. I have replaced the spark plugs, fuel filter, PCV Valves, air filter, etc and the car is still running rough and would die sometimes so I figured it probably needs a new fuel pump. I replaced the fuel pump last week and the car would crank over but it wouldn't start. I figured the new fuel pump was bad so I got a replacement fuel pump today and I installed it and the car still won't start. When I first turn the key it kind of makes two clicks but I don't hear the pump prime anyone have any suggestions? The fuel pump is pretty easy to install so I don't see how I could have really messed anything up...

[everpresentnoob]

You sure you dont want to start a thread about this in the classifieds as well? No need to make multiple posts in all parts of the forum for one issue. Just bad form in general my man...

Now on to the issue... I havent pulled my pump, but basic trouble shooting would be check for power at the pump. make sure connections are clean and tight. If no power there, check your fuses. I believe it is under the hood near the battery. Dont quote me on that location though....

IF you pump is getting power, again knowing that I have NOT pulled a pump in these cars so am unsure how it is set up in the tank, make sure the fuel is able to get through the pump. if you have fuel flow at pump, pull the hose from the finter and ensure you have flow through the filter. IF your last pump died it could have sent crud through the line and clogged the filter. make sure you have good flow there.

With yo saying that your not hearing it prime leads me to thnk its a power issue, so check that first.

[evildky]

On the TT the pump is controlled by a control module that actually regulates ground. not sure if the n/a uses a switch ground or switched hot, either way, I'd start by checking all the fuses, in the kickplate as well as under hood. Next instead of randomly replacing things, check the ecu for codes.

[Backinblack05]

How is the best way to check for power at the pump? I have a multimeter and I have checked the fuses and they seem to be ok. I do not hear the relay in the kickpanel clicking but like I say it was running so I wouldn't think it would be the relay...

[NolimitZ32]

The NA uses the same setup as the TT just with low and high speeds vs low, medium, and high on the TT. Best way to see if you are getting power to the pump is to probe at the connector in the loom that's like 6 inches upstream of the access panel in the trunk.

[Backinblack05]

Ok I finally got it going. I had not replaced the access cover when I replaced the pump because I wanted to check for leaks, etc. I put the access cover back on and it started up. Now my problem is that it is still running exactly the same. It will sometimes have a smooth idle but then I'll rev it up and the idle will become rough and it wants to die. What would be my next step? I have replaced the spark plugs, mass air sensor, pcv valves, fuel filter, air filters...

[NolimitZ32]

Have you ran the codes?

[Backinblack05]

No I am going to do that tonight and see what I get

[NolimitZ32]

Always start with that, it's the easiest thing to do and can usually get you on the right path right away.

[Backinblack05]

First I want to say you all are awesome and I really appreciate the help! I ran the codes last night and I get two:

34 detonation sensor circuit
&
12 air flow meter circuit

[Backinblack05]

Is this the connector for the detonation sensor?



If so mine is not connected and I don't see where it plugs in

[everpresentnoob]

I would search for how to bypass the Det sensor. if its unplugged it probably died on a previous owner. there is a way to do it with a resistor I believe. You rpic wont load for me so I cant see what your talking about.

[Backinblack05]

Yea I actually found the exact same connector in another spot so it looks like the previous owner relocated it. I'm going to have to dig into it tomorrow.

[everpresentnoob]

well, I believe its your O2 sensors that have the same plug... I know one of the plugs is the exact same as the Det sensor. Some people have issues because shops and such unknowingly switch the plugs around.

[NolimitZ32]

There a few connectors that look very close to each other back there a couple 3 pins and a few 2 pins, I don't remember what each is off the top of my head but if the previous owner did a relocate then that's half the headache solved for you, I highly recommend AGAINST bypassing it unless you think you are smarter than that folks that designed this car but that's just my engineering viewpoint on anti-engine-self-destruct-sensor removal. As for the MAF, if its dead then DO NOT buy anything other than the OEM Nissan unit, no other unit works properly with these cars. Let me know if you need one, I may have one laying around that I would be willing to sell. Before you decide to drop money on one do go through the test procedure in the FSM and make sure that it's not your wiring loom or ECU that's causing the problem.