Hi,

I got a 1980 280ZX NA that has seen better days. The car runs but I suspect it is running a little rich. It smells like gas and not running great, it has also fouled a few spark plugs.

Fuel pressure is about ~8 PSI higher than it should, the fuel pressure regulator is working. If I remove the hose to the manifold the presure shoots up with 10psi.

This is what I have done so far:

1. Replaced fuel damper
2. Replaced fuel filter
3. Fixed vacuum leaks
4. Adjusted timing

What is my next thing? To remove the fuel lines and inspect them?

Or should I just let it be?Maybe it is ok if it is running a little rich?

plan is to build a Chump/Lemons car.

thanks

 

If it's 8psi higher than is should be, sounds like it's "not" working properly. So... what's the fuel pressure at?

Have you checked the CHTS and AFM? Those are the two sensors that commonly cause the engine to run rich.

 

Hmm..I guess your are right in that it is not working.

The fuel pressure regulator makes sure that the fuel pressure is a difference from manifold pressure.

So if manifold vaccum is wrong, fuel pressure is wrong.

Maybe I have another vacuum leak. I should get one of those cool gauges!

 

Hi,

I want to install a permanent vacuum gauge, where is the best place to fit it?

One site (http://www.atlanticz.ca/zclub/techtips/vacuum/) recommended the brake booster but this will not work for me since I want it to permanent.

Thanks

 

Merged threads.

The easiest way to hard install a vacuum gauge is to use a vacuum line T... take your pick of about 5 different lines that connect straight to manifold vacuum.

And you still haven't said what the fuel pressure reading actually was...

 

Hi.

During idle i measure about 39 psi. When flooring it I get almost 50.
It goes down to low 30 when releasing the pedal after flooring it.

When zero manifold vacuum the pressure should be 36.2 so I don't understand how I can have more than that. The fuel pressure regulator is new.

What can cause a high fuel pressure?

 

Where'd you get the fuel pressure regulator?
Stock style or aftermarket?
Have you tried just leaving it disconnected from vacuum?

There have been quite a few people who have posted about dead or improperly functioning non-oem "stock" fuel pressure regs they bought from the parts store / online. Ironically I've been using a $20 ebay adjustable FPR for 10 years now with no problems.

 

I would belive that the fuel pressure regulator is aftermarket. But fuel pressure goes up when a lot I remove the hose.

But the thing is that the fuel pressure should be close to 40 without the hose, it is much more without the house.

Not sure how I can get so much, would clogged lines do it?

And why would it run rich when the pressure is to high? Most pump deliver a lower volume when the pressure goes up.

 

Maybe I wasn't clear in my previous posts... it sounds like the FPR is not working properly.

More pressure = injectors spray more fuel. Might want to do some research to understand this concept.
Think about a water / garden hose... if you turn it on to trickle, not much pressure, not much spray. You turn it on full blast... lots of water sprays out.

So... we can dance around other possibilities, or you could just obtain a tested and working FPR.

 

Mine was also $20 from Ebay

Will do some more research around the FPR, hurts a bit to buy a new FPR for $80!

I guess a clogged return line could be an option?

Someone suggested that the gauge might just be off...

 

Is it adjustable? Post a pic of the FPR.

 

Some new findings.

1. Vacuum seems to be great, about 18-20 hg at idle. Goes to 0 att full throttle and bangs up to almost 30 for a breif period when throtle is released.

2. I removed the fuel return after the FPR and dumped that into a can instead. Guess what? NO DIFFERANCE!
So either the FPR or gauge is bad.

FPR is not adjustable.

 

I recently replaced my FPR for not regulating properly: when I aspirated the vacuum line on the FPR by mouth (as it shows in the manual, go suck on a hose) you could taste fuel, which meant it was leaking.

I also got an Ebay cheap FPR, and it works great, adjustable with a gauge on it.