Jump to content

IGNORED

280z cranks, but will not stay running.


77Datz

Recommended Posts

New to this site, I sure hope you guys can help.

I just got a 77 Datsun 280z for my first project car. The car sat for two years with no gas in the tank, and I've been trying to get it started for about a week now. I get plenty of spark, I checked the coil and plugs and they're all fine. I installed a new fuel filter, replaced blown fuses, charged up the battery and put fresh gas in the tank. It turns over fine, starts up for a few seconds then dies. I pulled all the injectors and cleaned them as best I could, new fuel line in the engine compartment as well.

If you push the flap in on the AFM all the injectors spray, so I think it might be the fuel pump, I'll be taking a trip to Harbor Freight to get a fuel pressure testor, but when it starts up it sounds like its starving for fuel. Also, the black fusible link is corroded and the wire is exposed, I know this needs to be replaced, but for the time being I took the link off and jumped the connections with a bit of wire and an alligator clips and it didn't change anything. So as far as I know, its getting spark, and I can only assume at LEAST a little bit of fuel. It'll start with starting fluid but again quickly sputter out.

I also pulled the AFM off the intake and checked it via a ohmmeter and the FSM, which I am lucky enough to have a hardcopy of (guy i bought if from gave me the book with the car) and the AFM checked out fine.

So, I'm thinking it might be the fuel pump, that nasty corroded fusible link, or some other electrical or fuel problem. Thoughts?

Thank you in advance for all your help:)

Link to comment
Share on other sites

You can disconnect the fuel pump, have a friend crank the engine and see what the voltage is at the wires going to the pump. You can also actuate the AFM to see if the contacts are closing (Pins 39 and 36) to keep fuel pump relay energized.

Link to comment
Share on other sites

replaced blown fuses,

It turns over fine, starts up for a few seconds then dies.

If you push the flap in on the AFM all the injectors spray, so I think it might be the fuel pump,

the black fusible link is corroded and the wire is exposed, I know this needs to be replaced, but for the time being I took the link off and jumped the connections with a bit of wire and an alligator clips and it didn't change anything.

It'll start with starting fluid but again quickly sputter out.

he AFM checked out fine.

So, I'm thinking it might be the fuel pump, that nasty corroded fusible link, or some other electrical or fuel problem. Thoughts?)

I would wonder why there were blown fuses in the first place. And recheck the ones you replaced. Maybe they blew again.

Starts for a few seconds then dies is typical of a dirty fuel pump contact switch.

There's no reason for the injectors to click when you push the AFM flap. That's not right and just weird.

I would put the fusible link back, even if it's corroded. If you burn the wiring you'll be even farther up the creek, in a leaky boat.

I would test the fuel pump contact switch like SteveJ said first, moving the AFM flap, while the key is On. That will show you if the fuel pump contact switch is allowing the pump to get power when you let go of the key while Start'ing.

Link to comment
Share on other sites

Well the injectors click and spray when the key is in the "ON" position. From what I've read thats normal. Also, coming out of the harness going to the driver side of the car, (the harness near the battery) coming out of it are two red wires, one goes to the positive, and one goes to the negative terminal of the battery, I can't for the life of me figure out why both of these wires are red. One has a fusible link, the other just has a male/female connection going to the negative terminal of the battery. One red wire is longer than the other, I'll have to take a pic and throw it up here in the morning so you can see what I'm talking about.

Link to comment
Share on other sites

The injectors should only click and spray when engine is turning and the coil is sparking. Or only when the coil is sparking and engine not turning for those who know how to cause that. The ECU fires all of them at every three sparks. Either way, with no spark to send a pulse to the ECU, there shouldn't be any injector firing. Maybe you're leaving out the part about the engine turning over? Or hearing a relay, not the injectors.

The red ground wires have screwed up many people. It's a Datsun thing.

Since the engine will run under the right conditions you probably don't want to mess with too many odd things. Good fuel pressure to the rail should keep the engine running. You probably are losing power to the pump or have a bad one or have a clog somewhere. I would focus on fuel supply.

Link to comment
Share on other sites

That's what I was thinking, like I said I'll be getting a fuel pressure testor tomorrow, how would I go about checking that the fuel pump is getting power when I try to start it? I've already taken the starter wire off and listened for the pump when i turn to the start position. I can hear the fuel pump run, I've taken the hose off the fuel filter, and theres a steady flow of fuel there, but I just don't think its getting enough pressure behind it. I'm just not sure, I've been stumped for a week and its probably just something stupid and simple (i hope, at least)

Link to comment
Share on other sites

  • 4 months later...

I have tested all injectors the a.f.m,. the fuel pump, the connectors to the c.s.i., water temp sensor, and the other water temp sensor thing with the single plug.

The a.f.m. is making the injectors click when you open it. the fuel pump is pumping 38 psi. the c.s.i. is getting no power turning the car over, or with the ignition on run? i have replaced the ignition switch and the water temp sensors are both getting power. would the cold start injector keep it from running. and i am getting great spark i installed an e12-80

Link to comment
Share on other sites

The a.f.m. is making the injectors click when you open it. ...

....the water temp sensors are both getting power.

These two things seem odd. The first is just wrong, the AFM vane opening should not make the injectors click. If the injectors are clicking when you open the AFM vane something weird is going on with your wiring. I don't know where 77Datz ever read that that was normal. It's not.

And the second thing is odd since there is no FSM test for power at the coolant temperature sensor, although it may get power from the ECU when the key is On. I don't know why anyone would do that test, the test is to measure resistance from the ECU connector. What was the voltage reading and how did you measure it?

So, the AFM causing the injectors to click is odd. But, the main reason for the engine to start the die immediately, is because the fuel pump contact switch is not being made in the AFM. You can test that also with an ohm-meter by measuring resistance at those two pins at the ECU connector and moving the AFM vane.

post-20342-14150825803644_thumb.jpg

post-20342-14150825803827_thumb.jpg

Edited by Zed Head
Link to comment
Share on other sites

i used a test light so +12 volts, and i pulled the plastic side cover off the a.f.m. for the test. I am running a w48 intake off of a maxima with the 280z wiring harness i have already swapped the throttle body because of the electronically controlled idle control on the maxima it will run for a minute very occaisionally but when it does it just dies my initial thought is vacuum leak but the starting fluid test did othing so all vaccum ports are capped and there are no leaks.

Link to comment
Share on other sites

i used a test light so +12 volts, and i pulled the plastic side cover off the a.f.m. for the test. I am running a w48 intake off of a maxima with the 280z wiring harness i have already swapped the throttle body because of the electronically controlled idle control on the maxima it will run for a minute very occaisionally but when it does it just dies my initial thought is vacuum leak but the starting fluid test did othing so all vaccum ports are capped and there are no leaks.

Pretty sure that some test lights don't need 12 volts to light. So you might be in the range of the ECU voltage, whatever it is, probably in the 5 volt vicinity. You should still measure resistance from the ECU connector. The pin numbers are in the drawing I attached.

The method for moving the AFM vane is okay, but the injectors still shouldn't click. Maybe what you heard was the fuel pump relay clicking, under the dash by the hood release handle. If the injectors are clicking when you move the AFM vane you should figure out why. They shouldn't be doing that.

I don't know what you mean by "electronically controlled idle control". Good luck with that. And in your first post you said the engine dies immediately, now you say it runs for a minute, so not too clear on what's really happening. Since you're running a different intake manifold and throttle body, make sure the BCDD (if the W48 has one) and the EGR system aren't leaking.

Link to comment
Share on other sites

so it runs intermittently sometimes it just fires enough to turn the motor faster than the starter. and sometimes it runs when running it will not rev or it will die it also idles at around 2500 there is no tach so its hard to pinpoint exactly. but it runs.... kinda. the bcdd system has a wire that has no mate on my harness. it is the factory bcdd system, and factory harness. im tempted to just save 700 and get su's from ztherapy. unless there's something that makes sense thanks for the help.

Link to comment
Share on other sites

  • 2 weeks later...

fuel pressure regulator is out or giant vacuum leak but i did the starting fluid test for leaks (the one where you spray all around the intake while turning it over) and there are none, i also re- checked and re-tightened all of my bolts to my intake and we should be good

Link to comment
Share on other sites

Have you tested the FPR? Its a simple check, it sounds like you are running out of fuel, so I still think its the fuel pump switch, where ever that might be in your setup, you get enough fuel to start and run for few seconds then the fuel pump kicks off. I agree with Zed, the injectors should click when you push the AFM vane. A carb system is goign to run you about $900 with carbs, intake manifold, fuel pump etc.

Link to comment
Share on other sites

  • 1 year later...

Was this ever resolved? I have the VERY same problem (77 as well). The only difference is that I've got an initial 9-10 volts showing at the fuel pump wiring under the passenger seat during cranking, but as soon as it starts, voltage goes back to zero and it dies. I've checked the AFM, Relay under the drivers side dash, FPR, ECU pins, thermotime switch, temp sensor, oil pressure sensor etc ... I'm at my wits end

Link to comment
Share on other sites

It is usually the switch under the ignition key that develops carbon on the contacts.

 

Replace it or remove and flush with solvent while turning.

 

It screws to the back of the ignition key mechanical assembly so the only thing you have to remove is the steering column plastic housing.

 

If I recall correctly there are two small philips screws behind the switch so you may have to stand beside the car and looks through the front wind shield as you turn the screws.

Link to comment
Share on other sites

Kind of sounds more like the AFM contacts, if he's only losing power to the pump.  If it was the ignition switch he'd lose all power.

 

Details on the "checks" and whether or not this is a new problem on a car that was running or a problem that came with the car would help.  The easy way to check the AFM contacts is to turn the key on and move the AFM vane.  The pump should get power.  If it's quiet, you'll hear it running.  I've had my AFM contracts get dirty and kill power to the pump.  The engine would only start, run for a few seconds, then die.

Link to comment
Share on other sites

I bought the car about 2.5 years ago and went through it from front to rear .. it seemed that I had everything ironed out. Running/driving etc. I got in it one day, drove it around for a bit and then stored it for a year .. when I pulled it out of storage, it seemed to be running fine in the driveway and then one time I cranked it up and it started all this .. AFM is new/rebuilt from MSA and have done all the continuity checks on all the components and sensors. This is why it's so aggravating. I was thinking AFM as well, pulled the plastic cover and checked everything as in the tech tips page .. and still .. a spike of 10v during cranking, then an immediate decline to 0 .. ugh

Link to comment
Share on other sites

I don't think that the test I described is written up in the usual places.  And what you're writing doesn't tell much, but does fit a dirty AFM switch.  

 

The 10 volts is normal.  The starter drops the voltage as it uses amps.

 

You can test the AFM contact switch at the AFM, or at the EFI relay with an ohm-meter, but the easiest most direct test is to take the black cover off of the side of the AFM, or take the inlet hose off, turn the key to On/Run, then move the AFM vane.  If you have the cover off and there is power to the AFM contacts you might actually see a tiny spark.  The contacts look like a tiny set of distributor points and are actuated by a bent rod when the AFM vane moves.  It's very simple.  All it takes is a piece of hair or dust to hold the contacts open.  Probably why Nissan changed the system.

 

I would do that test. You'll know more than you do now.

 

Forgot to say - I have cleaned the contacts in an AFM with the striking pad from a book of matches.  Never did figure out what exactly was blocking it.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.