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Discussion Starter · #1 ·
Ok since my last post I have tried various new things. Let me bring you up to speed. I have a 78 z. It is getting too much fuel. Or not enough air? I can run it for about 10 minutes, sometimes longer sometimes not at all. It will rev up and down and spit out black smoke. Here is a list of things that have been changed.

Cap, rotor, plugs, wires, mass airflow meter, thermotime, temp sensor(water), air regulator, fuel injectors, cold start valve.

a list of things I have not changed,

Fuel pressure regulator, throttle positions sensor, (I have another tps but form a 75 will try this later today)

As you can see i have all but replaced most componenets. Any ideas on this would be greatly appreciated. One last thing, when i disconnect the TPS harness it seems to run a little better. Drivable? I am at my wits end. If I can't get it fixed in the next couple of days I am going to dump it.

Thank you
Tim
 

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Discussion Starter · #2 ·
Tim, I'm wondering if you cleaned the contacts to the connectors of all of the items you replaced? Maybe even do some diagnostics with an ohm meter?

Have you checked timing? Timing chain slack? Valves adjusted, not too tight?
Please don't dump it just yet! I brought mine back from complete dead, you can do this!

Steve G
 

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> Ok since my last post I have tried various
> new things. Let me bring you up to speed. I
> have a 78 z. It is getting too much fuel. Or
> not enough air? I can run it for about 10
> minutes, sometimes longer sometimes not at
> all. It will rev up and down and spit out
> black smoke. Here is a list of things that
> have been changed.

> Cap, rotor, plugs, wires, mass airflow
> meter, thermotime, temp sensor(water), air
> regulator, fuel injectors, cold start valve.

> a list of things I have not changed,

I once had a persistent problem with my 1981ZX NA running very rich. The connections on the injectors had corroded with this green patina that you see with copper corrosion. This stuff has a very high resistence to electricity. I cleaned them all good and then it ran fine. Check all the various electrical connections on the fuel injection system for any type of corrosion.

> Fuel pressure regulator, throttle positions
> sensor, (I have another tps but form a 75
> will try this later today)

> As you can see i have all but replaced most
> componenets. Any ideas on this would be
> greatly appreciated. One last thing, when i
> disconnect the TPS harness it seems to run a
> little better. Drivable? I am at my wits
> end. If I can't get it fixed in the next
> couple of days I am going to dump it.

> Thank you
> Tim
 

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Discussion Starter · #4 ·
> Ok since my last post I have tried various
> new things. Let me bring you up to speed. I
> have a 78 z. It is getting too much fuel. Or
> not enough air? I can run it for about 10
> minutes, sometimes longer sometimes not at
> all. It will rev up and down and spit out
> black smoke. Here is a list of things that
> have been changed.

> Cap, rotor, plugs, wires, mass airflow
> meter, thermotime, temp sensor(water), air
> regulator, fuel injectors, cold start valve.

> a list of things I have not changed,

> Fuel pressure regulator, throttle positions
> sensor, (I have another tps but form a 75
> will try this later today)

> As you can see i have all but replaced most
> componenets. Any ideas on this would be
> greatly appreciated. One last thing, when i
> disconnect the TPS harness it seems to run a
> little better. Drivable? I am at my wits
> end. If I can't get it fixed in the next
> couple of days I am going to dump it.

> Thank you
> Tim
Good day. I've experienced also some of your same issues. You may wish to check your firing order, vacuum lines, and if you can keep it running long enough, the timing or move the distributor a little in one direction or the other as when I got mine, it was firing way to early. Last but not least, the ignition control module. Good luck and let us know how you progress. Don't give up.
 

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Discussion Starter · #5 ·
Black smoke? Check compression. Then also disconnect 7th injector (cold start) and run again.. Wish I could tell you more.
 

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Discussion Starter · #6 ·
Here is an update.

I switched out my TPS for the other one I had. It did run better. after it got warm it died. the temp needle was in the middle. It still however smoked a little bit. and the exhaust note was a lot louder more rumble. Got me on this one. Anyway another thing I looked at was after it died I left the key in the on position, so the fuel pump was pumping. I then squeezed the return line for the fuel back to the tank. This is the line from the fuel pressure regulator to the tank. There was nothing running through it. Is this suppose to be like this? I would have to think NO. But i am not sure. Can someone please try this and let me know ASAP. I think my regulator may be bad.

One more thing. Every single connector that is electrical is either new or clean. Very clean. No problem with corrosion on any connector. Also timing is fine and timing chain is good. Valves are fine as well.

thanks for the input. This is really helping me out a lot.
Tim Yardley
 

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Tim,
Your fuel pump is capable of delivering over 65 psi and will do so if your pressure regulator is not working and bypassing some of the fuel. YOu can confirm just by disconnecting the return line - aim it into a jar. If it is not passing fuel then it needs to be replaced.
You can also install a pressure gauge on the fuel line between the fuel filter and the fuel rail. It would ideally read 36.3 psi. If it is over 40 you definitely have a faulty regulator.
Also, did you clean the connectors that are hidden in your wiring harness about 16 up the wire from the temperature sensor and thermotine switch? There is a lump in your wiring where shrink tubing is concealing some bullet connectors that love to corrode and cause immense frustration.
Phantom
 

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Discussion Starter · #8 ·
I cleaned all the hidden bullet connectors too. Trust me I got them ALL. I will test the pressure tomorrow morning. when I disconnect the return line and put it in a jar, will it flow fast or slow. and can i do this without the car running.

i.e Disconnect the return line after fuel rail. then trun ignition key to on. fuel pump comes on and then fuel should come out of the return line. Will this be a sudden burst of fuel or will it be a drizzle?

I can tell just by squeezing the return line that there is not pressure there with the ignition in the on position. I will try the same thing when the car is running to see how much pressure I can feel throught the hose. Basically I can pinch the hose closed with little force from my fingers.

Thanks again.
Tim Yardley
 

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My FPR went but my car would not start at all...

My car ran Great and then one day it was dead nothing it had gas spark and would kinda fire but it would not start it ended up being the FPR
now I don't know about your car but mine when the FPR went the car would not start at all
and also the return line from the fuel rail would shoot gas out no problem its not that powerful its about the same as the gas coming out of the fuel filter if you did that
well the FPR was $68 and the labor to install it was $180 them bastards! oh well it runs great now
but 5 days ago I put it back in the shop for a new timing chain and Im getting it back tomorrow YAY!

Good Luck!

Jeff 280ZXT
 

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Discussion Starter · #10 ·
If I were diagnosing this the first thing I'd ask you is if the car just started doing this, if it's something that's been gradually getting worse, or if it just started happening after you worked on it at some point in the recent past.

Assuming it's recent and you didn't inadvertenly bring it on by something you did, and you have already followed the excellent advice so far posted, here are a couple of things that come to mind:
1) check one or more of the plugs to make sure it/they are getting big fat sparks.
2) You never mentioned changing the air cleaner. Sounds pretty obvious, but if it's plugged the engine could be starving for air.
3) Have you recently washed the car with one of those pressure sprayers under the hood? The throttle position sensor is easy to get wet this way and slow to dry out. It can make the car run like you describe.
4) You don't mention where you live, the normal daytime temperature or if it's been raining/snowing a lot on the car. Any way you could be getting water in the fuel? Zs are really sensitive to water in fuel. If the car's been sitting, you can get condensation in the tank. Never experienced this problem myself, but have been told the car will run pretty much like you describe.
5) Here's a weird one: if you've done any recent stick or wire welding on the car and didn't unhook the battery, I've been told that it can play **** with the electonics.
6) Another strange one: The rubber connector that connects your air flow box to the engine can rot and get splits in the accordion-like folds. If it gets those, it will screw up the air mixture.

Good luck!
 

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> Ok since my last post I have tried various
> new things. Let me bring you up to speed. I
> have a 78 z. It is getting too much fuel. Or
> not enough air? I can run it for about 10
> minutes, sometimes longer sometimes not at
> all. It will rev up and down and spit out
> black smoke. Here is a list of things that
> have been changed.

> Cap, rotor, plugs, wires, mass airflow
> meter, thermotime, temp sensor(water), air
> regulator, fuel injectors, cold start valve.

> a list of things I have not changed,

> Fuel pressure regulator, throttle positions
> sensor, (I have another tps but form a 75
> will try this later today)

> As you can see i have all but replaced most
> componenets. Any ideas on this would be
> greatly appreciated. One last thing, when i
> disconnect the TPS harness it seems to run a
> little better. Drivable? I am at my wits
> end. If I can't get it fixed in the next
> couple of days I am going to dump it.

> Thank you
> Tim

Tim' where did you get your new AFM? I had a lot of trouble with my 83 untill I replaced my shody aftermarket AFM. with a good one.
 
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