1990 Nissan 240SX not starting after replacing fuel injectors; PLEASE HELP

[Dr.Nurse]

Today a friend and performed the following tasks in order to solve the problem of a leaky fuel injector code on a California Model 1990 Nissan 240SX. The car ran prior to our interventions, but now it has ceased to start for some unknown reason.

1) Replaced the Fuel Injector Connectors via butt connectors and solder because the existing ones had exposed wire and severe corrosion

2) Installed Rebuilt Fuel Injectors with Fresh Seals and O-Rings (Had the injectors rebuilt by Mr.Injector out of Idaho)

3) Replaced the Fuel Filter and Fuel Pump

4) Installed a Fuel Pressure Gauge between the Fuel Filter and Fuel Rail in order to perform future diagnoses.

After performing all of the aforementioned, the car will not start. When I turn the key on to activate the fuel pump, although initially the fuel pressure gauge reads about 43PSI, it quickly goes down while I hear a swooshing sound near the fuel rail. None of the injectors are leaking. It seems to me that the culprit is a faulty Fuel Pressure Regulator but I am hoping that someone with more experience the this matter can shed further light on my dilemma.

Thank you for your kind consideration and any information that you may offer in my plight to smog my car before the Spring Semester begins.

Sincerely,

-Brian

[Ilya]

did you hook up the fuel lines correctly. Fuel pump -> fuel filter -> Fuel Pressure Gauge ->Fuel Rail -> FPR ->Return tank

[Ilya]

Its very easy to get the fuel rail fittings switched

[Rustys14]

I agree with the above, it sounds like you have your fuel lines backwards.

[Dr.Nurse]

Thank you for your speedy replies,

I sure wish it was as simple as mixing up my fuel lines.

I did not undo any of the fuel lines attached to the fuel rail; I left them attached while I managed to install the newly rebuilt injectors.

The only fuel lines I took apart under the hood were the ones going to the fuel filter. I replaced the filter and then installed a T-connector above the filter in order to attach a fuel pressure gauge as shown:

http://www.nicoclub.com/archives/diy-fuel-pressure-tester.html

May I ask if any of you know how to diagnose a faulty fuel pressure regulator without the car being able to start?


When I turn the key on (without starting the car) I see that the fuel pressure goes up to 43PSI but thereafter it declines rapidly as I hear a whooshing sound coming from the firewall side of the fuel rail. Could this be a faulty fuel pressure regulator diaphragm allowing the fuel to pass back to the gas tank?

Another question I have is how does the air trapped in the fuel rail escape once the injectors are installed? Could there be somewhat of a vapor lock issue going on if too much air is left in the fuel system?


Thank you again,

-Brian

[Ilya]

There are fuel lines you have had to removed when you did your fuel pump, check those if they are mixed up in the trunk. If your FPR was good before you did all this work, i dont expect it to go bad. Also make sure your electrical connections are good to the fuel pump.

Air in the fuel system will be pushed out by the pump back to the tank and eventually out of the injectors, no issues there (that wooshing sound you hear at the gas station when you first open the gas thank is air rushing into the tank because the pump creates a vacuum)

How much fuel is in your tank? You need at least half a tank for a new pump to work/prime for the first time.

[RalliartRsX]

A quick note: Whenever you do the pump or injectors, you have to prime the system several times for the system to hold fuel pressure.

If the lines were backward, you would either be seeing a ton of pressure (well over 70psi!) or zero pressure at the fuel pressure gauge. So if you are seeing around 43psi (a stable/consistent 43psi while priming, which lasts around 7 seconds if I remember correctly), there is a good chance the lines are routed correctly. It is pretty evident if the lines are routed backwards as the pump will struggle to make pressure (sounds like a rundown motor or a motor with not enough voltage. Basically a struggling pump is what is sounds like and much different from what you are used to hearing when the system is primed).

I have had to do this 3 times in the past month while going through 3 different sets of injectors! Thought my brand new Aeromotive FP regulator was shot. However, you need to prime the system multiple times in order to remove and bleed all air out of the system.

Go ahead and prime the system (cycle it 4-10 times) and see if it begins to hold pressure.

A faulty fuel pressure regulator will simply not hold pressure.

[Ilya]

You could have an injector massively leaking out fuel into one of your cylinders. I know you said there is no leaks which is very broad so I am assuming your O-RINGS. But a rebuilt injector could be faulty. Smell your engine oil, since all the liquid gasoline that is in the cylinder will drain into the oilpan. Or pull out sparkplugs and shine a flashlight into the hole to see the cylinder tops. I have had that happen to me too.

[Dr.Nurse]

I humbly thank all of you for your well-informed reply.

With regards to your requests:

I checked the dipstick and there was no smell of oil.

I did pull the spark plugs and neither were any wet nor did any smell like fuel; I imagine the injectors are not stuck.

Clarification:

When I cranked over the engine, it would not sputter/fire at all; completely dead. It seemed as though there was no functional ignition at all.

Here is what is strange though:

The following day, I went back to the 240SX to rule out a malfunctioning fuel pressure regulator. However, upon cranking the car, it started flawlessly.

Is it possible because we disconnected the battery overnight, that perhaps clearing the ROM on the ECU got rid of the problem??

Even stranger is that now when I turn the key, (without starting the engine) the fuel pressure now holds constant at 43psi and there is no longer a whooshing sound coming from the fuel pressure regulator. I don't understand how clearing the ECU ROM could have caused this, since all the ECU does, is tell the fuel pressure regulator solenoid to either allow vacuum from the motor or not. Since the engine was not running at the time, then the regulator should have remained closed (in the absence of vacuum) to allow for more fuel pressure to aid in starting the vehicle right?

I am going to assume that RalliartRsX was right in that I did not prime the system enough times and perhaps the whooshing sound was simply air being squeezed out of the fuel rail and back to the tank via the fuel pressure regulator. Somehow it lets air through but does not let fuel through?

Anyway, the check engine light turned off and I was as happy as could be; earlier today I took the car down and got it smogged and to my surprise, the smog tech was adamant to comment on just how well it passed for the millage (>250,000miles).

However, ironically enough, once the car passed smog and the smog tech turned off the motor, the car would no longer start. :ROFL

I was able to get a jump start and took the car back to my friend's house to diagnose the problem.

With a voltmeter on the battery, we tried to turn over the engine. The volts dropped from approximately 12.8 to 0.1; the battery was toast.

We then proceeded to install a functional battery. Afterwards we started the car and checked to see that the alternator was charging the battery; it was. While the car was running, it read 14.6 volts and would rise a bit upon acceleration. From this we inferred that the alternator was functioning as it should.


However, while the car is at rest, with the positive battery terminal connected, and the negative battery terminal disconnected, there is an approximate .067milliamp drain going from the negative battery terminal to the ground strap. Because of this, we resorted to leaving the battery disconnected until we could identify and remedy the drain.

Q: Do you have any suggestions for how to diagnose such a battery drain? We were thinking about going through the fuse box and systematically pulling fuses until we could see that the battery drain cease; using this strategy as a guide to pinpoint which section of the electrical system to target.

Again, thank you so much for your help.

-Brian

[RalliartRsX]

I don't understand how clearing the ECU ROM could have caused this, since all the ECU does, is tell the fuel pressure regulator solenoid to either allow vacuum from the motor or not. Since the engine was not running at the time, then the regulator should have remained closed (in the absence of vacuum) to allow for more fuel pressure to aid in starting the vehicle right?

This entire statement is False. The ECU has NOTHING to do with controlling fuel pressure at all! Vacuum and (if adjustable) orifice size affects (what the adjustable fuel actually adjusts) fuel pressure and nothing else. The fuel pressure on the SR and KA are simply mechanically driven (vacuum, boost, orifice size, etc)

What the ECU controls is cranking injection (the amount of fuel during starting that is injected per cylinder) to increase the amount of fuel to aid in getting the engine started.


As I said, you needed to prime the system a few times (or even 1 or 2 times.....every system is slightly different) and I am sure that is EXACTLY what the problem was!

I am not sure why people would suggest crossed lines when the fuel pressure being 43psi (and holding during prime) would suggest the lines are ran correctly........

Lower and Upper O-rings, although can easily be destroyed during install, are fairly robust seals as they are made of a special fuel compatible material (Nitrile for instance). You will normally tear them if you force them in.

Glad you got it sorted!

[Ilya]

.067 milliamperes or .067 amperes? Very big difference. 0.067 milliamperes is the amount my microcontroller pulls while in sleep mode.

[Def]

0.067 mA is nothing. Your battery probably has on the order of 30-50 amp hours. So 0.067 mA of draw at 30 Ah is 447,761 hours of storage. The internal discharge rate of the battery is at least a few mA if not higher.

BTW - you had air in your fuel system, and finally primed it up. It takes a long time at 2 sec a go (normal priming length).

[jrmto]

My car is doing the same. It like doesn't fire up but I have spark

[Ilya]

Try to replicate the symptoms as much as possible so we all know what the commonalities are. You can try to start measuring voltage at the starter as you try to start the car. Bad battery terminals. Bad starter. Anything is possible.

I had a bad battery and the starter was going out, had no ide what it was. Tried to jump the car a few times and no cranking. So I knew it wasn't the battery. Installed a new starter and jump started it and it worked. Then connected my bad battery and it wouldn't start. So I knew I had to get a new battery.

Try to change one variable at a time, no matter how much of a hassle it is.

When the car didnt start, what was the fuel pressure?