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steady88

280zx revs up in park, but has no power in drive.

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Gidday

 

You have probably already tried this but,

 

Assuming all the injectors are getting fuel, I would be doing two things

1. Compression test

2. Swapping one of the injectors from No. 1,2 or 3 with one from 4,5 or 6

 

Just my 2 cents

 

Cheers

 

PB

 

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Have you checked the resistors for the injectors? I think they are mounted near the manifolds on the side of the engine bay....

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Having now recieved the PDF's of the workshop manual, and the use of a multi meter, you have begun checking and testing all components in sequence?

If not , why?

The injectors are on "group fire" in the Bosch L Jetronic system, and your unplugging them to "discover" the above is not correct procedure, as they fire when you think they are not supposed to.

This helps to relieve their max duty, and the Dropping Resistors in inner guard are to "clip" volt/amp spikes.

 

The TPS sounds like it may be faulty, it is a four stage variable potentiometer, the correct operation of the AFM and its flapper valve can cause issues if not right.

 

As before, get a multi meter, the manual, and start from the beginning of the test procedures.

Not difficult, but to have a proffessional workshop go through this, if they can be bothered will take a couple of hours labour, you will save yourself that.!

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disconnect both vaccuum hoses to the disributor and plug them and try it then if this makes a big change the distributor needs overhauling, the most common fault i find with 280zx is air flow meter sticky flap or electrical component malfunction internally very common.

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Thanks for the advice everyone! I cleaned out the fuel sender unit from the tank, as the fuel line to the pump was full of red gunk. I also replaced the fuel pump as it was also full of gunk. Now the car runs very well and has lots of up and go!

 

My problem now is, the runs great for about 5 - 10 minutes, then slowly starts to run worse and loose power. Now here's the interesting thing which I can't work out. I wanted to rule out if this was a fuel pressure issue, or something else, so I disconnected the fuel pump to relieve the pressure. When I do this, and plug the pump back in, the car runs great for another 5 - 10 minutes. I thought, ah, this has to be fuel pressure. I swapped my fuel pressure regulator for another one and put a fuel pressure gauge between the filter and the rail, and the pressure is right on spec. I don't understand??? Why does reducing the fuel pressure (unplug the fuel pump for a minute) make it run good for another 5 - 10 minutes - because, as soon as I plug the pump back in, the pressure builds up straight away anyway.

 

I should also note, that the car is warmed up and appears to make no difference if the car is warm or cold.

 

Cheers!

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Having now recieved the PDF's of the workshop manual, and the use of a multi meter, you have begun checking and testing all components in sequence?

If not , why?

 

As before, get a multi meter, the manual, and start from the beginning of the test procedures.

Not difficult, but to have a proffessional workshop go through this, if they can be bothered will take a couple of hours labour, you will save yourself that.!

 

I have checked the sensors with a multimeter and they are all good. I have tried to test the harness connector at the ECU, as per the FSM only to discover that the pins do not match the FSM, in fact, many are missing.

 

One thing I will note, if I disconnect the TPS, there is no difference to the way the car runs. Not sure how big of a difference it is suppose to make...

 

I'm new to this world and want to learn and have the enjoyment of fixing the car myself.

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Thanks for the advice everyone! I cleaned out the fuel sender unit from the tank, as the fuel line to the pump was full of red gunk. I also replaced the fuel pump as it was also full of gunk. Now the car runs very well and has lots of up and go!

 

My problem now is, the runs great for about 5 - 10 minutes, then slowly starts to run worse and loose power. Now here's the interesting thing which I can't work out. I wanted to rule out if this was a fuel pressure issue, or something else, so I disconnected the fuel pump to relieve the pressure. When I do this, and plug the pump back in, the car runs great for another 5 - 10 minutes.

 

Disconnected how?  Electrically disconnected, or removing a hose?

 

I'm going to guess you are disconnecting a hose, and I'm also going to guess you didn't clean the fuel tank itself out when you cleaned the pickup.  If that's the case, pull the pickup out again, and you'll more than likely find a new buildup of crud on it.  Over that 5 or 10 mins of running, the pump sucks all the loose crud off the bottom of the tank, and even when the car is switched off, holds it there by suction, as the fuel lines are sealed up to the reg.  Over time, the crud will slowly drop off the pickup by itself, but when you disconnect the hose at the pump, it allows air into the hose to the pickup, and most of the crud is washed off by the fuel in the pickup tube suddenly returning to the tank.

 

This was a common fault with the early Land Rover Freelanders, the plastic lining on the inside of the tank would come off in thin sheets, and clog the pickup screen over a period of driving, until the car stopped.  Half an hour later, you'd be able to drive again for a little while.  The only solution was to completely drain the tank, remove the intank fuel pump, and stick your arm in with a rag and wipe all the loose crap out.  I suspect a Zed tank doesn't have a big enough hole in it for this approach, so you may have to remove the tank, and either wash it out properly yourself, or take it to someone to be cleaned.  Some radiator places will wash out fuel tanks for you.  The bigger issue though, is when you say 'red gunk', I'm immediately thinking rust.  The tank may not be worth saving, depending how bad it is....

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Disconnected how?  Electrically disconnected, or removing a hose?

 

I electronically disconnected the fuel pump. Besides wiping it out with metho, I didn't clean the tank as it was clean and there was no crud in the tank at all. The only crud was actually in the sender pipe going to the pump. Even the strainer in the tank was clean.

 

I have since checked the strainer and pipes and all were still clean. Even the fuel filter was clean. But what you are staying is interesting. There could be a build up somewhere which goes down when reducing that pressure. But, the fuel pressure gauge shows about 31psi and doesn't change at all when the car has a lack of power. You would think there would be a change in pressure.

 

When I originally saw the red gunk, I thought exactly the same. Rust. But, I now think it was the old fuel in the pipe. It seems to have only been in the metal pipe, not in the rubber hoses. Perhaps some sort of reaction to metal. Inside the tank is amazingly clean. There was some discolouration on the bottom, but thats about it. I did my best and wiped it out with metho while I had it open. But, I'm confident it is clean.

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What happened with this?

 

 

I've come along way, but I still have a problem and I'm pretty sure it's fuel pressure related. I have a fuel pressure gauge hooked up between the fuel filter and the rail and discovered after a short amount of driving, or even just idling, the fuel pressure sometimes drops from around 30-34psi to as low as 15psi. I found that removing the fuel cap would solve the problem and so I though it was an issue with vacuum or the tank breathing. But, this no longer makes any difference.

 

I have changed the fuel lines from the tank to the pump and also and have changed the fuel filter a couple of times and have even cut the filters open to discover they weren't clogged, just a couple of black specs. The pressure doesn't always consistently drop down low, just have noticed it a few times. I have also changed the pressure regulator, but perhaps the replacement could be stuffed. I know that if I revv the engine, the fuel pressure drops about 6 - 8 PSI.

 

At the moment, the car is drivable, but it does run very rough and struggles to get over 60kmph. Up until about 2 weeks ago, It was running much better, not perfect, but I was able to comfortably cruiser on the highway at 110.

 

On a side note, might be unrelated - the other night when I stopped the car, I checked the pressure and it was 15PSI, then next morning, without starting the car, the pressure was sitting at 30PSI.

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I would just put in a new electric pump. There are some good after-market efi pumps available at fair prices. I would also replace the wiring to the pump. Lastly, check the exhaust around the fuel tank is in good condition. I have seen dodgy exhaust systems blowing hot air all over the fuel tank, which causes it to heat up and vapour lock etc.

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