Fuel Cut: What is it? How do I fix it? [merged]

[Slanted J]

All fuel cut threads are combined here.

I've tried doing a search but to no avail.

I was just wondering what Fuel Cut is. I've heard it tossed around alot, but do not actually know the details behind it. And, naturally, I can gather that its when the fuel is cut off, but when and why.


Thanx,
Jon

 

[oldman]

Mike, what's the problem with the logger? Are you having problems hooking it up? The sooner you get that log the better.

 

[Boost95]

Nothing is wrong with it. I need to replace the o-ring in my turbo or I need to upgrade to a 16g. Thanks for your help

 

[moparmadd]

so today i got back in town, went into work and found my buddy's 1g Mass Air, so i took it home, slapped it on, took it out, hist fuel cut hard once, tried to again, then i kept beating her like a red headed stepped child and couldnt get it to do it again. so in other words, solution = mass airflow sensor was baaaaaaaaaaaaaaad

 

[oldman]

Always reset the computer after fixing fuel cut, good work.

 

[moparmadd]

not familiar with resetting the computer (1st dsm)... not sure if i want to though since it involves disconnecting the battery and last time i did that i couldnt get my keyless entry the owner before me put on to work for a weeks. but if its for a good cause ill reset the bird

 

[oldman]

The more fuel cut you hit, the lower the pre set limit for fuel cut as part of the safety features in the ECU, resetting the ECU will return the value back to default. If you are afraid to disconnect the battery, you can disconnect the ecu for 30 seconds. With that said, it will also return to default by itself after some driving, without hitting fuel cut again of course. If you hit fuel cut again, reset the ECU.

 

[huafist]

(I'm uping my post count too )
Fuel filter is located on the pump and also on the passenger side firewall. Inside of a black canister.

ummm... the fuel filter isn't in anything - it sits on the firewall above the charcoal canister. There's a line that runs from the top of it to the fuel rail.

 

[Defiant]

And I always have to mention plugs and wires.

 

[laserspeeddemon]

Nothing is wrong with it. I need to replace the o-ring in my turbo or I need to upgrade to a 16g. Thanks for your help

you are assuming, I've yet to blow the O-ring on the compressor side, and I'm not nice to turbos. I have been through 4, 14b's. Now I am beating the piss out my 16g.

It's unlikely that its your cause, and if was, your turbo would hiss. If the turbo seal inside the core on the compressor side was out then that would account for the hissing inside the crankcase.

Either way replacing the turbo may be a good step regardless, seeing how most 14b's are old and worn out.

But in the end, you should not assume.

 

[Boost95]

What am I assuming? What else would leak externally in that area? I dont think it would eb the fact of blowing the o-ring out from beating it, but in my case it woudl be from age with 174k on it! My turbo does hiss under decel and I cant hear it spool up at all. 16g is on the way from Extreme PSI

 

[laserspeeddemon]

What am I assuming? What else would leak externally in that area? I dont think it would eb the fact of blowing the o-ring out from beating it, but in my case it woudl be from age with 174k on it! My turbo does hiss under decel and I cant hear it spool up at all. 16g is on the way from Extreme PSI

just as well.

I know I hate it when I pay big money to fix a part that I thought was the problem only to find out that its not (EI: paid for new injectors when the fuel filter was bad). I just wanted to let you know what I have gone through in personal exp.

 

[Boost95]

I ran into another problem. I figured Id post in here instead of starting another thread. After putting the new turbo in I had a leak at the oil feed line for the turbo. I removed the feed line and got all new crush washers. Now the line where it comes from the head is probably stripped and it still leaks at the turbo. I am real sick of this car

 

[laserspeeddemon]

I ran into another problem. I figured Id post in here instead of starting another thread. After putting the new turbo in I had a leak at the oil feed line for the turbo. I removed the feed line and got all new crush washers. Now the line where it comes from the head is probably stripped and it still leaks at the turbo. I am real sick of this car

Yes, that line is one of the HARDEST line to get in without striping it. You will need a helicoil kit to repair it. After you get the helicoil in (I suggest you get a professional shop to do it), put the banjo bolt into the HEAD first, then fangle with the bolt/line alignment at the turbo. A better option is to use a Stainless-steel oil line, that way you can get some flex in the line. How far are you from DC?

 

[ddavisaf]

Ignore everything else he said. This is your best option
If you don't want to dish out the 30 bucks to get a SS oil feed line then the helicoil is the way to go. But that'll cost you at least 30 bucks shop time.... sooo.....

A better option is to use a Stainless-steel oil line, that way you can get some flex in the line.

 

[laserspeeddemon]

Ignore everything else he said. This is your best option
If you don't want to dish out the 30 bucks to get a SS oil feed line then the helicoil is the way to go. But that'll cost you at least 30 bucks shop time.... sooo.....

ok smarty pants, how is he going to screw the new banjo bolt for the SS line in, if the threads for the oil feed line from the head are stripped. AND if he relocates the SS line (say "from the oil pump") then how is he going to block of the orginal oil feed line hole with a bolt (say "from a 1g N/T") if the threads from the oil feed line from the head are stripped.

Either way he HAS To get a helicoil. Wether or not he wants a SS line is up to him, but again the SS line is a MUCH better option and not much more costly.

BOOOOYAH!!! Whos bad?

 

[ddavisaf]

The banjo bolts aren't needed
You can buy an adapter that screws into the turbo. More than one actually. I have a straight adapter, others get a 90* adapter.
It's neat too because it's blue and matches my car.
However wrong this may be to do, you can still thread a bolt into the hole. Find a bolt that doesn't have the same thread pitch and put some loctite on it if you're in a crunch. It's not the best way to do it, but it will work and won't leak.
Just don't go crazy with it so you don't get metal shavings in your head.
Or get yourself some bubble gum, a paper clip, and a potato and McGavire something in.

 

[laserspeeddemon]

The banjo bolts aren't needed
You can buy an adapter that screws into the turbo. More than one actually. I have a straight adapter, others get a 90* adapter.
It's neat too because it's blue and matches my car.
However wrong this may be to do, you can still thread a bolt into the hole. Find a bolt that doesn't have the same thread pitch and put some loctite on it if you're in a crunch. It's not the best way to do it, but it will work and won't leak.
Just don't go crazy with it so you don't get metal shavings in your head.
Or get yourself some bubble gum, a paper clip, and a potato and McGavire something in.

There good reason to half-a*s a job. Get a helicoil and use the bolt from a 1g head to block it, then call Forced Performance, they sell an oil feed line relocating the line to the oil filter housing for maximum oil pressure for $65.

http://linux.forcedperformance.net/...reen=PROD&Store_Code=FP&Product_Code=FPMLSS1G

 

[shallowshowcase]

installed the fmic and ran 15-16lb on evo III... before it wouldnt hit fuel cut,,, but once the front mount went on BAM like a wall, so i had to take even more fuel out to get it not to backfire like that.....


i figured with a front mount and more air flow id be adding fuel? why did i have to take fuel back out?

 

[ICE_T]

hmmm,. what kind of intercooler and piping you put??,. you don't change anything after the turbo??

you don't suppose to have fuel cut after swap with a e16g at 15-16psi.. you run the 450cc again??

 

[shallowshowcase]

i had 15psi with 450s, i put on a johnny racecar fmic with DIY piping, i leaned it out and it runs fine and i have it at 16psi, but i just figured id be adding fuel once i upped it to 16 and added the short route piping... i mean the car is running fine, only thing diff is i had to take off the valve cover breather hose and the charcoal canister hose and run them to the bottom of the bay facing the ground.... and i have GM maf so that cant be the problem since the maf is the last thing in my piping....

 

[oldman]

Have you done a boost leak test after the fmic install?

 

[shallowshowcase]

no just a jerk-yank test

if i had a boost leak how would that cause fuel cut if im still only running 16psi????

 

[steve]

Why would you think you need to add or subtract fuel for raising boost pressure or putting a front mount on. The MAF is going to measure the air being used and cause the ECU to inject the correct amount of fuel as long as your not leaking boost or exceeding the MAF's ability to measure.

I understand retuning the car once you put a FMIC on since the charge temps should go down and you can lean the car out a bit more than you can on a SMIC but unless the increase in boost starts causing knock you wouldn't need to add fuel just for an increase in boost pressure.

If your hitting fuel cut it's time to pressure test the system. That should have been part of the FMIC install.

Keep in mind that if your leaking air under boost then the turbo will just work harder to make the same pressure until the turbo can't keep up with the leaks. But all that lost air is counted and can trigger the fuel cut test in the ECU.

Steve

 

[oldman]

no just a jerk-yank test

if i had a boost leak how would that cause fuel cut if im still only running 16psi????

First let's make it clear that fuel cut is triggered by high air flow, not by lack of fuel.

Two thing happen with boost leaks that concerns the subject at hand.

1. ECU injects fuel for the missing air which was already metered at the maf resulting in rich conditions.

2. MAF reading sky rockets triggering the ECU to stop the firings of the injectors aka FUEL CUT.

Boost leak test is a must following any work done to the intake tract, you will most likely have to re-tune again once you fix the leaks, if in fact you have leaks.

edit: steve beat me to it.

 

[shallowshowcase]

well the GM MAF is the last component in my intake tract, i assumed whatever went through there would be measured and be the exact air going through the engine even if some leaked out in my fmic piping


i guess steve said it when he said installing an fmic could cause me to have to lean it out... so i guess at my SMIC tune was too much fuel for the FMIC at the same PSI and just needed some fuel taken out... i still dont see how a boost leak will effect it if i know there isnt a leak after the GM MAF, air leaking out before it shouldnt matter i didnt think


but you guys have been here before and id be stupid not to listen so i guess i gotta do some leak testing thanks