ETHANRA64

okaaaaay....

swapped a 1jz vvti jzs171 into my 83 celica.


The engine fires right up and runs. I have a walbro fuel pump ran off of the stock celica harness. The circuit is designed in such a way that as soon as the ignition switch is no longer in the crank position, a circuit opening relay shuts the fuel pump off. Since the original 22re engine and computer are no longer there, there is nothing to tell the fuel pump to stay on so this is normal.

The engine idles (very smooth, sounds great) for about ten seconds then dies when it looses fuel


Ive jumped the circuit opening relay for the fuel pump so now the fuel pump runs as long as the key is in the on position. So now the engine doesn't die...BUT now it runs WAY rich, really choppy idle, smoke everywhere, smells like the 76 monte carlo i used to drive in high school that had a carburetor way to big for the engine set up.

Shouldnt the fuel pressure regulator prevent excess fuel to go to the engine?? Does this mean i have a bad regulator? Or is there something more common that you guys have seen with this engine that could cause something like this. Im using the stock celica fuel return line down the chassis which is quite a bit smaller than what came on the 1jz so perhaps unused fuel is trying to go back to the tank but cant...i figured my stock fuel lines should be fine for the stock 1jz. what do you guys think?

FYI the engine is bone stock with a 3" open downpipe, stock computer.

ETHANRA64

So i disconnected the fuel return line at the chassis where the restriction would be and just let it dump into a gas can. Engine still idles very choppy. It will rev but revs choppy as well (no change from before) and still smells really rich so that wasnt the problem.

Any suggestions on where else to look that might cause an extreme rich condition?

Vrank

iTrader: (4)

It could be a number of things, I'd start by checking codes to see if there's something that can help you narrow it down. Going by your other thread, there were mistakes in the wiring, so I wouldn't rule that out.

INTIMAZY

iTrader: (5)

Fuel systems 101:

We have return fuel systems. The fuel ECU throttles down the pump to reduce heat and improve pump life. They depend on a fuel pressure regulator to control fuel supply to the injectors. The PSI behind the injector doesn't matter as much as you would think. It won't make the car go from smooth to diesel unless the pressure goes from the factory ~38psi to 100+psi.

If this was a modern return-less system run exclusively off a fuel ECU this could be a different issue.

My bet? You have a spark issue or an injector thats stuck open. As long as theres 10-70psi behind the injector your fuel system should be fine. Test the regulator by taking it off and seeing if it runs better. Walbros have an internal bypass (don't remember how many PSI) and it will simply dump excess fuel back on itself if over-pressured. The motor will run without the regulator in a closed return-less setup temporarily if needed.

ETHANRA64

okay so i think i found my problem. I believe I have one or more injectors stuck open or partially stuck open. They all pulse just fine. Ive confirmed the fuel return is adequate.

I did somewhat of a power balance test to see how much the idle changed when disabling fuel on each different cylinder.

I unplugged 4 out of the 6 injectors on the fuel rail and it still idled almost exactly the same....

This would explain why it idles better when the fuel pump is off until it runs out of gas since there is no pressure forcing fuel through a -should be closed- injector.


I removed all 6 injectors and im sending them out for a rebuild. i'll make an update when i get them installed but im pretty confident thats the issue. ive tripple checked everything else. This also made me see how dirty the t/b is and gave me a good opportunity to clean it haha.


Thanks for the info!!!

estomax

iTrader: (2)

did your car idle choppy the whole time? when the engine is warm or cold?

ETHANRA64

Yeah it was bad the whole time until I turned off the fuel pump then it smoothed out until it ran out of fuel.


Might be a week or so till I see the injectors but this'll give me an opportunity to build a front bumper.

ETHANRA64

Okay just figured i'd update this thread now that I've got it fixed in case somebody else runs into the same issue.


It was the maf...

The engine i ordered didnt come with a maf so i did some research and found what i though was the correct part number. The maf i had installed was for the older twin turbo non-vvti model. Not sure why the fuel pump being on or off made it idle different...

I found the correct part number maf for my engine and found it was only available in japan or russia. Cross referenced the number and found that an 02-07 wrx sti uses the same maf. Ordered one up, installed it, and the car rips!!

The symptoms were so weird i ended up replacing everything in my fuel & ignition system before i figured it out but oh well! now ive got a new Tomei AFPR (which actually changed the symtpoms...made it idle rough all the time), rebuilt injectors, new coils, plugs, and wires


Thanks for the help