Fuel Cut

[Indiana]

There's no pressure limit for OEM injectors that anyone has measured but it would be a pressure so high that the injector just plain couldn't physically be opened.

 

So now you back to misfires at 18psi, which is nothing at least to me, and you have those generic injectors, a new fuel pump, some new wires and which spark plugs I don't remember and a MAF that has the honeycomb in the end right? You got rid of those metal things that separate the plug wires didn't use? Are the wires separated from each other with the plastic holders?

 

Let it run up to higher boost where that happens and immediately when you hear it misfire SHUT IT OFF. Pull over, and take the spark plugs out and look at them. You say you don't have money for a wideband then that's fine you don't need one anyway. Rich is rich wide or narrow its just how much rich you don't know and imo, who cares you can't do crap about it with a stock ECU anyway. Spend your money someplace else like the grocery store. When the plugs couldn't fire that's when you need to look at them, not a mile later and not 100 feet later but right when its happening. If you can't see what the air fuel is at all, then that's all you can do. The condition of the plug can change quickly.

 

How do you know that its not the knock sensor going off and cutting timing back and that seems like a misfire? Those new injectors can get dirty just the same if not quicker and rotten fuel lines and tank can ruin a new injectors just as quick as it can an old one.

[Blue]

Indiana, I meant that I do not think the stock sized injectors will provide enough fuel for the boost levels, especially on a bigger turbo.

[Caliber308]

Indiana, I meant that I do not think the stock sized injectors will provide enough fuel for the boost levels, especially on a bigger turbo.

 

I'm not Indy, but what are you saying?

 

Bill

[Caliber308]

Personally, I wouldn't try for more than 16psi on stock injectors. You start running out of fuel quick. That's what I've been told.

 

?? I have ran Stock Injectors to 20 psi boost. Granted, it was with a 1989 ECU and a TD05H17C. Who ever is telling you these things needs to show proof that you will run out of fuel at 16 psi boost with the stock injectors. Otherwise, it is only B.S.The Stock Injectors will handle the boost. The question is this, will the Stock 1987 ECU handle it. I have heard some say 14.7 psi boost on the 87 ECU. I have boosted to 15 psi on the 87 ECU. Which isn't saying much. So, as far as the ECU goes??? Now, on the Stock Injectors....I don't believe that the max. boost on them is 16 psi.

 

Blue, My Stock Fuel Injectors were tested by Witchhunter at 43.5 psi. The max. Fuel pressure output on a Stock Fuel Pump is appox. 70 psi. The max. Fuel Pressure output on the Stock Fuel Pressure Regulator is 38 psi. So, how can you run out of fuel? Maybe with a 1987 ECU? Even with a MBC set at 20 psi, and Fuel pressure set at 40 psi( via a MSD-2222.).I never ran lean.

 

Bill

Edited September 28, 2011 by Caliber308

[Killtodie]

My fuel pressure gauge went to 100psi when I bent the fuel return hose.

 

And I have an 88 ECU

[trini2dbone]

put an 89 ecu in it nd that shud fix ur problem

[Lance_S]

i am running 15 lbs on an evo3 DSM S16G and have to cut my fuel back off my maft or I get pig rich. The reason I am interested in this thread is because I am having the same symptoms as todie. I am misfiring at WOT since I turned the boost up from 10 lbs. Guess I better start swapping wires....

[Caliber308]

i am running 15 lbs on an evo3 DSM S16G and have to cut my fuel back off my maft or I get pig rich. The reason I am interested in this thread is because I am having the same symptoms as todie. I am misfiring at WOT since I turned the boost up from 10 lbs. Guess I better start swapping wires....

 

Check out your Spark Plug wires and the Spark Plug gap your running. Toadie doesn't know what he is running.....He still hasn't installed a Wideband.

 

Bill

Edited October 1, 2011 by Caliber308

[Lance_S]

I am at .037 on all of the plugs. The wires are the blue ngk's. I will run a resistance test on them tomorrow. I am gonna lean it out a click on the maft and recheck it right now.

[Caliber308]

I am at .037 on all of the plugs. The wires are the blue ngk's. I will run a resistance test on them tomorrow. I am gonna lean it out a click on the maft and recheck it right now.

 

Try opening up the gap to .039, or close it to .035. Sometimes you have to play with the gap for your set up. My set up runs best at .039 Spark Plug gap. Remember, You want the widest Spark Plug gap possible prior to flame out. Also, Have you checked your Fuel Pressure reading on WOT boost? If your still running the Stock FPR (36 to 38) psi. Then at 15 psi Turbo boost your Fuel Pressure should read 51 to 53 psi at WOT. I run Magnecor 8.5mm Spark Plug wires. Never misfired.

 

Bill

Edited October 1, 2011 by Caliber308

[Lance_S]

OK, Todie, start pulling fuel out. Your prolly pig rich like I was. I was having the exact same symptoms as you. I was afraid to pull out fuel under load at wot because I didn't want to go lean. I was in the 10's on my afr. It was too rich. I backed my maft off 3 clicks off at wot and finally it stopped kicking on me. Runs smooth as silk now and I am around 12.4 to 12.7 on the wideband.

 

Hope that helps.

 

Lance

[Caliber308]

OK, Todie, start pulling fuel out. Your prolly pig rich like I was. I was having the exact same symptoms as you. I was afraid to pull out fuel under load at wot because I didn't want to go lean. I was in the 10's on my afr. It was too rich. I backed my maft off 3 clicks off at wot and finally it stopped kicking on me. Runs smooth as silk now and I am around 12.4 to 12.7 on the wideband.

 

Hope that helps.

 

Lance

 

 

10.0 AFR at WOT would have caused you to miss out BIGTIME!!!! I have heard guys that run 14.0 AFR at WOT...A little too lean for me. P.S. You still need to get a reading at WOT on what your FP is

 

Bill

Edited October 1, 2011 by Caliber308

[Lance_S]

BTW, I have pulled a TON of fuel out of my system to get my afr numbers to be correct. I am running 14 lbs of boost at 550 cfm with a stock pump. I could easily go to 18 to 20. The idea that a stock pump can't keep up with a 550 cfm turbo at any boost level under 20 is rubbish. With that being said. I have a new tank, new lines, new filters and new pump so it's running ideally. These are assumptions that are in place. If your pump is having to push through clogged filters then it may not be able to support the mod.

 

L

[Lance_S]

 

 

10.0 AFR at WOT would have caused you to miss out BIGTIME!!!! I have heard guys that run 14.0 AFR at WOT...A little too lean for me. P.S. You still need to get a reading at WOT on your FP Gauge

 

Bill

 

 

Your right Bill,

 

I think that the word was most guys wanted to be at 12 or under at wot so that was my goal. I didn't intend to be in the 10's but I ended up there. I pulled a ton of fuel out. I was at a base of 2, idle at 3, mid range at -1 and wot at 1. I first pulled base back 1 to 1, still bucked on me. Then pulled base back again to 0, still bucked. Pulled wot back to 0, still bucked. Finally pulled wot back to -1 and it cleaned up.

 

With every reduction of one on the base it's like pulling one off the entire map so in the end I pulled 2 off idle, 2 off mid range and FOUR off wot. But that is what it took. Again, afr is around 14 at idle, 15 at cruise and 12.2 to 12.6 at wot. That's with a .037 gap on NGK 7's. I could go one colder now that I have a bigger turbo. One thing at a time. I guess I was just gun shy on the afr wanting to be safe. Obviously, when the boost goes up, the fuel balance from fat to lean is more critical.

 

Fat at 10 lbs won't make the motor fall on it's face but at 15 it will, and that's with the same fuel settings. You would think that it would run leaner with more air and more boost, and it might, but it's not bucking at 10 lbs like it did at 14. Interesting to think about anyway. Either way, good lesson learned.

 

BTW, there is a BIG difference in output from 10 to 14 lbs :-). My clutch is slipping in 4th now, lol. There is always something that is next when the power goes up.

 

Todie, sorry for hijacking your thread. Hopefully, if you are not already lean, you can pull some fuel out and it will clean up your bucking problem. It did for me, that's why I jumped in here. Didn't mean to take over.

 

Thanks bro,

 

Lance

[Caliber308]

BTW, I have pulled a TON of fuel out of my system to get my afr numbers to be correct. I am running 14 lbs of boost at 550 cfm with a stock pump. I could easily go to 18 to 20. The idea that a stock pump can't keep up with a 550 cfm turbo at any boost level under 20 is rubbish. With that being said. I have a new tank, new lines, new filters and new pump so it's running ideally. These are assumptions that are in place. If your pump is having to push through clogged filters then it may not be able to support the mod.

 

L

 

Lance,

 

A Super 16 G doesn't even start making power until 15 psi boost. Also, Any boost over 15 psi should have a Upgraded Fuel Pressure Regulator. If I were you, I would not push the Stock Fuel Pump too far into high boost. The members on this site who have been doing this for many years know this. But, it is your car, your Stock Fuel Pump and your money to spend. We can only advise you. What you do or don't do is totally up to you.

 

Bill

[Lance_S]

No worries. I am at 14 lbs now. I did a compression test on the system today to track down any air leaks. I then compared the autometer procomp boost gauge that I just installed against a secondary gauge to make sure it was accurate and it is. I take it slow. I will continue to bring up the boost a little at a time. Hell, I was waaaaayy fat as you know so I tend to live on the safe side of fuel. If I start to get lean I will not hesitate to change the pump out for a bosch or walbro. Either way, I am just glad the bucking issue is resolved.

 

Thanks again,

 

L

[Blue]

Well I for one, am question the source of a lot of my information. He's been readin this thread, as I've seen, and he knows who he is.

[Indiana]

I looked back to the beginning of this and from what I see, it appears that

 

 

you had fried plug wires and finally replaced them or at least the bad one

you have a busted ignitor -to me this makes it junk they can do many things and there's no test for them and its random and is effected by vibrations if its internally cracked

you have spark plugs you've replaced I can't tell how many times and with what exactly

you swapped injectors or you have those generic replacements I can't tell now

you have base fuel pressure that's too high and I have no idea how you got it there

you say it misfires and blows out black smoke that means there is plenty of gas, it won't "misfire" lean, it will just detonate and blow up or melt

you know it has some strange noise at higher boost and it wasn't the manifolds or is that now gone

 

If your base fuel pressure is 41 how did you get it there? If it is that high then at 15 psi you have 56psi and if you push the gas pedal in a higher gear you end up pig rich because of that additional base pressure and the ECU can't do anything with it and when you have the fuel spray flowing down past the throttle plate before its 100% mixed and if its too rich even those 7031 plugs won't help you it will just misfire no matter what the gap is. If you have the larger non OEM injector in the wrong place then the primary fires against the throttle plate and makes a dripping mess that you try and burn until there is boost then you blow raw puddled fuel into the cylinders.

I can't remember when there was SIX pages and seems like every time a question is asked something new comes up.

 

How many psi fuel can stock injectors take? More than anyone has ran through them I'd say. I know I ran those at base 40ish with 30psi boost one entire season on a stock pump. It was a NEW stock pump and upgraded lines but there was plenty of fuel. The pump also supplied fuel for a cold start valve that came on around 20 psi and just litterally sprays continuously the fuel while under boost and all from the "whimpy" stock pump. I could show you the 282/344 dyno run sheet I guess and the funny part was that was on the 3rd pull of 6 where the head lifted and spewed oil out the back of the head on the very first pull so I guess if I could make that on a blown headgasket who knows what it really made but that's the engine that tore the dowel pin out of the aluminum flywheel because it was too short.

 

There's something missing from this picture its either from not asking the right questions or not getting all the information or its not be followed. You can't just make a list of 75 things for a person to check and expect them to do it. You have to start with something then wait and see what the response is and all you can do is try your best. If you could just speak all this would have been over in a couple minutes and just took one or two days. Its been what now seems like weeks.

 

Get rid of that junk BUSTED ignitor box. Those things have internal circuits that can CHANGE the ignition timing. The ignitor is what the ECU tells to cut timing back for knock or high altitude the ECU no zero control over ignition and if its cracked inside or failed or just WET do not use it.

 

Get a good ignitor and those OEM injectors you said someone had you could try those ones you are using now even if new can be messed up by dirt in the fuel lines and the hose from the filter to the throttle body. The entire system must be clean and the injectors are the last thing cleaned. If you have base pressure that is 41 and are using a stock fuel pressure regulator and that is correct its likely your return line is mashed and that is what is causing the additional pressure. When you raise pressure under boost that also likely increases that as well. There is to be no restrictions in the return line.

 

You said it has a 1G MAF didn't you? That plug on there and doesn't wiggle

 

This is all assuming there's nothing mechanical wrong with your engine.