Car: 1989 Firebird Formula
Mods:

stock 305ci >> 355ci; 305 heads (1.84 valves, 58cc); mild cam, 424in lift, 278in duration, 107in lobes.
stock 19# injectors >> SLP LS1 injectors (25#)
stock 305 chip >> chip burnt by LT1 intakes set for 25# injectors
stock exhaust manifolds >> edelbrock street legal headers
old flowmaster cat back >> edelbrock cat back
stock cat >> catco high flow 3" cat
stock leaking FPR >> new stock FPR (not adjustable)
stock coil >> MSD coil

i bought these LS1 SLP injectors a while ago and i've been running them in my 355 TPI. my fuel pressure is exactly where it should be according to the Chilton manual. my plugs ARE white, so i know the car is truely running lean, other than the check engine code i get after closed loop. please let me know what could be making the car run lean! thanks!!!

ps
i changed the pump recently thinking that would help, but it didnt. i got the Venom pump off summit.
my chip is burnt for 25# injectors... so if anything i SHOULD be running rich! right????????

 

come on guys has no one had this problem???

 

Stock fuel pressure isn't enough, buy an adjustible FPR and bump it up to about 46 with vacuum line off, that would probably do the trick. If you know someone with a scanner you can watch the BLM's and adjust FPR to attain the 128 you want.

 

Aren't LS1 injectors rated flow at 58 psi ? (IIRC)
You're running stock TPI fuel pressure than that is your problem.
If that is the case, I wouldn't advise adjusting it to 58 to make it be rated correctly, the bin should be changed to reflect the actual flow you are getting from the 25's at 44 psi or what ever you have.

edit: added formula
"Sqrt (new/old) then * old flow rate"
you only have 21.7# if I was correct on the 58 psi for the LS1 rating and you have 44 psi now.

 

well, If you paid someone to burn this chip for you, they should tell you were the Fuel pressure should be set at. Fine tuning will be necessary of course. There is a formula those guys use to come up with the Fuel injector constant in your program and proper fuel pressure. I burn my own chips so I can tell you from experience. Adjusting from a scanner or a ALDL cable is the true way to dial it it. You can buy one from Moates.net if you want. If you want to get into programming, DIY Prom board is where you want to hang out.

 

http://www.racetronix.com/12561462RFM.html

these are the specs on them

so what are you guys saying i should do exactly??? get a new chip burnt? or get an adjustable FPR? or both??

 

Well, you mentioned that you had a chip burned, right? Who did it? If not you will need it along with an AFPR. Changing injector constant changes everything and the computer doesn't know about it via the stock chip (set at 22lbs if thats what you had stock) I know that guys are running stock chips with 24lb injectors and setting AFPR's to 42 PSI which works but it's still not the proper way of doing it. Welcome to the world of EFI and performance parts...

 

You were right, From the rating of 28 lbs @ 43 psi you should be running rich if the bin is set for 25 lb.
Might want to recheck the base timing to be sure its where it should be.
It should be at the value that was put in the bin so everything matches up.
If fuel pressure is not dropping and your sure there is not a vacuum leak then timing would be the next suspect.

 

well the thing is the car wont even start now so i cant even do anything with timing. i think its not starting b/c the injectors arent firing. when i turn the key on, i hear the fuel pump turn on, but i dont hear the usual sound that comes from the injectors as well..... so i think maybe my computer is bad. any other ideas?

 

Did you adjust the fuel pressure up or something? Get the injectors working properly..

 

You may not find any, but I would check for ECM error codes and re-check the fuel pressure.

When you turn the key to the ON position, have someone read the peak fuel pressure. You do not have to start the engine to check fuel pressure.

Also, the fuel pressure should be about 43psi and stay up there, and not bleed down quickly. The fuel pressure should stay above 20psi for at least 20 minutes.

 

there are no problems with my fuel pressure, i have a fuel pressure guage and the pressure holds for very long. the problem is that the injectors for some reason are NOT getting the command to fire when the car is cranked for SOME reason, i think that reason is the ECM because they get directly connected to it, there are no relays except for 2 10 amp fuses for each set of 4 injectors, but those are perfectly fine in the fuse box.... im gonna change the ECM tomorrow and see what that does, thanks

 

The ECM does NOT fire the injectors during cranking, under 350rpm the injectors are fired by the ignition module. Above 350rpm the ECM takes over and controls the injectors.

 

I beg to differ on that one. The ECU does NOT control TIMING below 400 RPM. Injectors are under full ECU control, even when cranking.

 

This may not be your problem, butttt, when I installed my 395 stroker motor and hooked everything up including the distributor, the engine would not fire up. The injectors were not getting a pulse width signal. This signal comes from the electronic modual in the distributor. My electronic modual went bad just sitting on the shelf for 5 months, go figure. I bought a new distributor, installed it, and the engine fired up with the first turn of the key.

 

Injectors are not under control of the ECU during cranking, the ignition module is. Since you are unaware of this and have not evened opened a book before opening your mouth I am posting the exact troubleshooting pages that confirm this.

 

I'm not going to get hostile,

Here is how it really works:
The ECU recieves a signal from the Ignition Module - called the REF pulse. The ECU fires the injectors.

The ignition module is always needed to fire the injectors (because ECU needs the signal), BUT, the ECU is in control.

I'm a fuel injection engineer. Really. I have all the books. I passed Euro 3 by more than 50% yesterday. I'm in China calibrating for an OEM here.

Edit: I'll let you retract your statement without an apology. But next time, don't accuse me of being uneducated in EFI. I do it every day. I.... argh. I could go on and on.

 

well, guys it ended up being the F**** computer...... out of all the things..... i just bought a brand new computer in december, i guess it was faulty or something b/c now i get no codes, and the car fires right up, every time. thanks everyone for the help!

 

I get that you're a really sharp guy, but you've misinterpreted the diag procedure.

The ignition module has no route in the schematic that would allow it to close ground on the injectors...it's physically not possible for the ign mod to cycle the injectors independently of the ECM.

RednGold spelled it out and I've troubleshot a few GM injector systems also. The ign mod provides reference pulses to the ECM, after which the ECM closes the fuel pump relay and begins cycling the injectors.

 

I'm running the constant of 28 in the chip and I'm running pig rich. When I had it set at 25 the plugs were black as could be.

 

I never said the ignition module was connected directly to the injectors. Let me put it another way, under 350rpm the ignition module generates the signal needed to drive the injectors. It cannot do this directly due to the low current so it needs a "relay" to handle the larger current just like when you wire up fog light, etc.... This relay is the injector driver inside the ECM. Under 350rpm the ECM isn't commanding the injector driver, the ignition module is. After 350rpm the ECM takes over and switches the injector driver relay.

As far as the "I'm a fuel injection engineer" big deal. A fuel injection system is a handful of wires and components. I engineer full aircraft systems including flight control systems on corporate jets. We have thousands or wires and hundreds of major components. Don't challenge me with a job description RedandGold.

 

This could just be a misunderstanding...

We're saying the microcontroller sees the ref pulses from the ign mod and fires the injectors...same as it does at all other states of engine operation.

You're saying that below 350rpm the ign mod has direct connectivity with the injector drivers and bypasses the microcontroller? And then above 350rpm that connectivity is dropped so the microcontroller manages the injector drivers?

 

I'm not trying to keep any hostility going here, so just bear with me. I really don't care who does what at the moment, Just want to get the facts out there for debate if needed.

Since I've been following this and feel the need to find clarity, There's a few things about the description of operation that I'd like to discuss.

There are calibration parameters within the bin that dictate the PW during cranking. They define which ref pulse to fire on and have values/multipliers to compensate for barometric pressure and also temperature. If they are all used effectivly or not is debatable but not the topic here.

This is evident both in the code and in the troubleshooting chart above. Notice that if the TPS is above a certain value that the injectors will not fire (clear flood mode, so to speak). There is no direct hardware link for this function to be implemented (that I can find in schematics anyway) Calibration table is shown below.
I have modified it and indeed, the fuel will stop if I enter "0" at lower values in the table.
This is just one of the functions I see that is controlled by the software during cranking.
I'm looking at the $8D mask in particular and I don't assume that it would be the same for all types of injection systems. I do not know.
If there is a hardware "relay" that is directly using the DRP, how would the calibration be able to make the corrections to the PW?

I want to state VERY clearly, This post is not meant to provoke hostility. Just get all the facts out.

I welcome any more information that anyone can provide so that this post stays true to the facts. I'm interested in finding out how it all works too!

 

J Millican, you can still save some face by retracting some of your statements. I never meant to insult you or provoke you in my first post. The second post was just to correct you about my book reading. I don't just deal with hardware. I design algorithms, debug software, calibrate, select components, modify components, troubleshoot hardware, etc... We're almost finished with our latest designed from scratch ECU - it's for an OEM. It's not backyard mechanic stuff here. I wasn't challenging you to a job description contest, but I know a little about EFI. I know you know your LT1 intakes, but you're mistaken on this one part of the control.

Thanks to the others who stated the facts.

The ignition module is always needed on those ECUs, because that's how the ECU detects RPM, and it bases it's injections to occur in relation to those REF pulses. A bad ignition module can cause no injections (and is quite often the case), but the module doesn't control the injections.

 

I think that since Millican bought a car w/ a warranty, he's already forgetting how to work on them...

 

i actually saw on another poast that these injectors that i have make TPI cars run LEAN! i dont know where the guy got this information from, but i just wanted to know, who else has heard this, and is there anything i can do about it?????

by the way, my plugs ARE WHITE, and have been white ever since i've been using these injectors, just a slight bit of brown on them, but mostly white. this has been scaring me, but most people have just been telling me not to worry about it. please, anyone with information let me know IMMEDIATELY

here is the post, towards the bottom:
https://www.thirdgen.org/techbb2/sho...=slp+injectors

 

Raising the fuel pressure may do the trick or you will need to adjust your chip. The injectors are not the problem, tuning is the problem. What is your fuel pressure set at?

 

Sounds cool.. Yeah always swap those ecu's when you have certain troubles.. I don't know about those slp's inj.. Seems to me there problems as I have heard.. Get a good matched injector in there that is put into the ecu the correct rating.. And tune from there..

 

i guess i just need someone to tune my darn chip, or show me what to do........ i got a code 36 today, gonna find out what it means in a minute

 

on the contrary, i checked my pressure at idle today with another guage and it read 33 psi, same with my every day guage, it shows about 35 psi....... ugh it used to show 40-45 psi ATLEAST, a couple months ago it just dropped one day aboout 10 psi. im gonna try to get to the bottom of this, any ideas??

 

Replace the in-line fuel filter, or maybe the fuel pump is failing.

 

Want to point out something which I think wasn't too clear in the posts above, and I hear this all the time from customers as well. The SLP injectors that they used to sell as take off units for $99 or so were originally used on LS1s, which had stock fuel pressure at 58 psi I believe. The injectors will flow 28 lbs at this fuel pressure, but they flow 25 psi at stock tpi fuel pressure which is 3 bars (43.5 psi). By setting the injector size to 25 inside the prom, theres no need to worry about moving fuel pressure anywhere other than stock, that would actually be detrimental.

bigchief, if the plugs look white, you might want to check into some other things, as the engine is probably running lean. Try to get a scantool or laptop hooked up to the car.

Once you do so, take a look and check that your oxygen sensor is working properly (fluctuates alot with the engine warm, above and below .450 volts), and check your TPS and CTS while you are at it as well.

More importantly, take a look at what your BLMs are at. If they are below 128, the ECM is trying to take out fuel based on oxygen sensor voltage. If they are above 128, it is trying to add fuel based on oxygen sensor voltage.

 

i've got a laptop hooked up to it using TunerProRT. my oxygen sensor reads all over the place like it should. my BLM's at WOT are at 128 exactly, and at idle they are low like 108 at the lowest

i think something else is wrong now, if you can help me. whenever i turn OFF my car, i hear the fuel pump still running for about 5-10 seconds, then turn off. is this normal? because im thinking about it being related to my Mass air flow sensor burn off relay, and the fuel pump turning on after the car is turned off, instead of the burn off relay turning on and doing ITS job.

i'm only saying this because i've been getting a code 36 lately, which is supposed to be a problem related to the MAF burn off relay. any ideas?

i'm pretty sure the MAF burnoff relay has 2 orange wires going to it, and its the relay that is the closest to the firewall. and the fuel pump relay is the one that looks different from the other two, it is more squared, also the connector is completely different. is this correct???

oxygen sensor voltage is in the 900's while at WOT

 

I have been working on Turbine Engines now for almost 11 years and it still appears to me that it is easier to work on turbine system than a Fuel Injection System. But, it is almost the same principle.

Adjust the EMFS Electro-mechanical Fuel System
Adjust the IGV Inlet Guide Vanes
Adjust the PTS Power Turbine Stator's

ECU Controls all for maximum output

No TPS, IAC or Injector Contants.

 

well, you were right about one thing, and that was the computer. my computer was actually bad, throwing ridiuclous codes. replaced it, problems all solved