Annoying/frustrating No Start Condition

[Davidz1911]

Hey everyone, I'm new to these forums but not to Zs or cars in general. I just bought my 1 owner 1978 EFI 280z from a guy in Dallas. Its in amazing shape, paint, interior are both flawless and the mechanical aspects were wonderful too. started up fast as my 2013 car does and ran smooth as can be. I Drove it the whole way back home in Louisiana, about a 200-205 mile trip. Drove like a dream. parked it in my driveway, the next day i took it out and it died on me while driving. Then it started back up fine and i got where i was going, it sat for 10 minutes and cranked but wouldn't start. it was too dark so i went back the next day and tried to get it running. Did my basic checks, while testing for fuel with ether in the intake it fired up while someone was cranking it, and i blipped the throttle and it ran perfectly fine and i drove it around without a problem for 2 days. Now its doing it again and will not fire and stay running. Spark is fine, No vacuum leaks anywhere at all, new fuel pump and filter, new plugs and wires and coil and cap/rotor. its getting pressure to the rail, spraying ether in the intake will make it run but as soon as the gas is pressed it dies. If you don't press the gas it will eventually stall out snd die. I run out of time to work on it due to lack of daylight. I will be checking for power to the ecu and to the injectors tomorrow. Does anyone else have any suggestions of theories on what it might be? Thanks for the help guys!!

[Zed Head]

EGR could be sticking.  That would lean out the mixture (actually not "lean" but "charge-deficient").  

 

Try turning up the idle speed screw to see if you can keep it running while you diagnose things.

 

By the way, you described a "won't stay running" condition, not a "won't start".

[bartsscooterservice]

Spark can still be weak. But it sounds like a fuel problem. If the fuel pressure on the rail is okay, you could check the injectors.

[dutchzcarguy]

I think its a electric problem.. a contact failing in your ignition.. because you say it ran perfect after a fail for some time.. check your wiring.

 

fwiw

Mart

[SteveJ]

If the injectors are firing, you should see about a 2 VDC drop across the injectors when the circuit is complete.

 

 

What is the pressure in the rail? 

 

Have you downloaded the fuel injection bible? http://www.xenons130.com/reference.html

It has some good diagnostics in there.

[rossiz]

i agree that the intermittency and the fact that it runs well when it does run point to electrical.

 

your efi and fuel pump relays are under the fusible links (engine bay, on the passenger side inside a plastic housing) check the wiring/connections to these as well as their condition - along with the fusible links.

 

on your '78 these parts can get a bit of weather due to the fact that they are under the passenger side hood vent. 

 

in general, i'd go over the entire electrical system, one harness at a time - you will undoubtedly find some nasty connections and it's a good way to preemptively fix anything that isn't currently failing. this is not hard to do, and it will really help you get to know your car. just start with the efi system and unplug every connector one at a time, clean with deoxit and a little 400 sand paper and re-connect. hit every ground connection and apply a little dielectric grease after they're re-connected to keep things from corroding afterwards. there are a set of connector plugs in the passenger side footwell that bring power from the engine bay into the cabin and over to the ignition switch - pull 'em apart, clean 'em.

 

you can find a link on this site to the factory service manuals online - fantastic resource. they show the harnesses and their locations and have some decent diagrams calling out wire colors, plug colors etc. which helps to de-mystify the various systems.

 

spending a few hours doing this will pay big dividends and get you a much more reliable ride.

[240260280z]

If it idles all day but won't run under load then it is most likely fuel delivery caused by debris in the fuel tank clogging the lines or pickup.

 

Put a clear fuel filter between the tank and the fuel pump to see what is going on.

 

http://atlanticz.ca/zclub/techtips/fuel/g3filter/index.htm

 

You may also want to clean the small filter on the pump inlet port.

[siteunseen]

I'd go ahead and get the metal filter up front too, cover all your bases.  That drive from Texas could have pulled enough debris to clog it up even though it is new.  A member on here cut one in half and found the cheaper ones had paper filtering element come loose and folded up into itself.  i can't remember if the WIX brand was the good one or the bad one?

 

That fuel pump filter Blue's talking about is inside the "inlet port" of the Bosch OE pump.  Take the hose coming from the tank to the pump off and you'll see it.  It's small and cone shaped.  Post #5, http://www.classiczcars.com/topic/27140-strainer-in-fuel-system-78-280z/

 

Good luck and lets see the car.  

[Davidz1911]

hey guys! thanks for all the awesome replies. If i was using the wrong terminology about the "no start" vs "not staying running" i apologize. I have replaced the fuel filter in the engine bay, I disconnected the fuel line between the filter and the rail and let it run into a clear water bottle, the gas looked as clean as can be. I also replaced all the plugs, plug wires, coil, distributor/cap/rotor. I got to looking at the relays and someone did a hack job of the wiring. WHY i have no idea but they did. They bypassed the fuel pump control relay and so thats why my pump is running 24/7 even when it is just in "ON". one of the other relays, Judging from the wire colors i would say its the fuel pump relay, is super corroded and probably trash. The reason i say assume is bc these are all universal fuses someone put in here, apart from the fuel pump control relay which they jumped. I have new relays and will be swapping them all out, fingers crossed it just the relays.

 

Oh i have the FSM and have been on AtlanticZ and gotten the super clear diagram. Because these no longer have the pigtails, I have to match up each color to the correct pin. however they aren't the same relays as in the diagram. I have them all hooked up correctly with new pigtails i soldered in, now my question. The EFI relay is a 6 prong relay, it has 5 blue wires nd 1 green wire. Can the blue wires be hooked up anywhere ? My logic was that it wouldn't matter as long as power and ground are correct bc when the releay activates it will supply volts to all the wires anyway, or is that completely wrong and I'm just an idiot? i will let y'all know what i figure out. thanks for all the help guys!!

 

Oh one last thing, i had posted this in a few other Z forums and the people who responded told me i was an idiot and didn't know anything about what i was talking about. I come on here and you guys are so polite and awesome. I thought thats what forums were all about was sharing a common interest in our Zs and to help each other out, but i guess only you guys act like that.

 

 

PS heres a pic of my 280z

 

 

 

[Zed Head]

Your symptoms sound like a loss of fuel pressure.  Fuel flow is one thing, correct pressure is another.  You need to measure pressure while the problem happens.  Stick a gauge on and watch.  Fuel pump motors and relays can get hot as current flows and stop working correctly.  I've had a fuel pump that did that as have others here.  The pump created pressure for about 5 minutes then it slowly died away as the motor stopped spinning.

 

I thought your post looked familiar.  You've changed some things but no big deal.  Pretty sure I didn't call you an idiot on the other thread, it took me a while myself to figure out the Z's EFI system.

 

The key is actually measuring things.  Corroded-looking connections can be fine and clean ones can be bad.  You'll waste a lot of time and probably create new problems "fixing" things because they look bad.  Best to measure and confirm first.

[Davidz1911]

I wasn't talking about hybrid, you were actually very helpful and it allowed me to articulate what i was seeing happen better,

i posted on zcarforum and i got lit up by people bashing me. I am in process of running another pressure yes, this time for an extended period, the first time i tested it between the filter and the rail and it was about 36 psi. as for the EFI relay, is there anyway other than opening the harness to match these wire to the correct prongs? i don't see why there are 5 blue wires and 1 green wire, that just makes it difficult to know which goes where.

Thanks guys!

[Davidz1911]

I got it guys!!!!!! thank y'all so much for guiding me through so i didn't loose my sanity!! it was the relays and the hack job of wiring that caused it.