fuel injector problems
09-21-11, 07:37 PM
#1
Full Member
Thread Starter
Join Date: Dec 2002
Location: Aurora, CO
Posts: 225
Likes: 0
Received 0 Likes
on
0 Posts
fuel injector problems
I'm having some trouble with my '87 GXL, and could use some guidance.
First, a little background. I bought the car a little over a year ago as a project, did some basic things to it and got it running half-decent. The previous owner put turbo injectors in the car, and has a SAFC to tune then down to NA levels. The car started running like crap one day. It had no power until about 3800 RPM where it had full power all of the sudden. I was able to get the car running the best at this point by cranking the fuel to +50% from 1000-4000 rpms on the SAFC, and then had it at -15% or so in the high RPMs. Like this it still ran like crap though.
So I decided to take off the intake manifold and check out the injectors. The previous owner modded the resistor pack to run the high-impedance turbo injectors he put in. But it turns out, the primary injectors are actually low-impedance! I believe the secondaries are indeed high-impedance though.
So, how could the car run so long like this? I was reading that running low-imp injectors without a resistor pack could "burn out the drivers in the ecu", or something like that. Is that true?
If its true, do my car's symptoms sound consistent with an ECU with "burned out injector drivers"? It would start okay, and would idle with gas, but revving it, especially with load would bog it down. Maybe only one of the injectors was working??
I bought some low impedance NA injectors, so I want to return the car to the stock injector config. I cut the 2 wires that the previous owner had spliced onto the resistor pack. I can't really tell how it's supposed to look stock, but at the end opposite of where the wires are coming in, is it supposed to be connected there? Hard to describe, but I can take pics if needed. I check the resistance according to the manual, so I think what I did is fine.
Lastly, when I pulled out the old injectors, one of the plastic clips broke, and ended up falling into the injector hole. How big of a deal is this? Should I try my best to get it out, or will it not do much since its plastic (and not a screw or something).
First, a little background. I bought the car a little over a year ago as a project, did some basic things to it and got it running half-decent. The previous owner put turbo injectors in the car, and has a SAFC to tune then down to NA levels. The car started running like crap one day. It had no power until about 3800 RPM where it had full power all of the sudden. I was able to get the car running the best at this point by cranking the fuel to +50% from 1000-4000 rpms on the SAFC, and then had it at -15% or so in the high RPMs. Like this it still ran like crap though.
So I decided to take off the intake manifold and check out the injectors. The previous owner modded the resistor pack to run the high-impedance turbo injectors he put in. But it turns out, the primary injectors are actually low-impedance! I believe the secondaries are indeed high-impedance though.
So, how could the car run so long like this? I was reading that running low-imp injectors without a resistor pack could "burn out the drivers in the ecu", or something like that. Is that true?
If its true, do my car's symptoms sound consistent with an ECU with "burned out injector drivers"? It would start okay, and would idle with gas, but revving it, especially with load would bog it down. Maybe only one of the injectors was working??
I bought some low impedance NA injectors, so I want to return the car to the stock injector config. I cut the 2 wires that the previous owner had spliced onto the resistor pack. I can't really tell how it's supposed to look stock, but at the end opposite of where the wires are coming in, is it supposed to be connected there? Hard to describe, but I can take pics if needed. I check the resistance according to the manual, so I think what I did is fine.
Lastly, when I pulled out the old injectors, one of the plastic clips broke, and ended up falling into the injector hole. How big of a deal is this? Should I try my best to get it out, or will it not do much since its plastic (and not a screw or something).
09-23-11, 02:46 PM
#2
I guess it's possible, but if you had to have the %corr maxed out to +50 at low rpm, then remove fuel above 4000 rpm, that really doesn't make logical sense that it could be an injector issue. If the previous owner wired in resistors for the low impedance injectors, but left them off for the high impedance ones, then I really wouldn't see any issue with that. At any rate, there's really no reason to install turbo injectors in the NA engine. It just serves no purpose. The NA injectors won't get maxed out so long as it's still NA.
Anyways, the way the SAFC works is that it modifies the AFM signal going to the ecu. In other words, when it gets installed, the signal wire going to the ECU from the AFM gets cut. The signal the AFM makes goes to the SAFC for modification, then tricks the ECU into thinking there is more or less air entering the engine, based on the %corr at that specific RPM and throttle position. It's possibly an AFM issue, if you haven't caught on by now. If you have to add %corr to it at low rpm, then the AFM could be getting stuck until enough airflow "un-sticks" it.
Or one of the primary injectors is just NOT coming on at all. Easy way to tell that is with a digital logic probe (an LED test light). Hook it up to +12v and check for injector operation at the ECU. Check for pulsed ground at the injector wires. If no pulsed ground, bad ECU. If there is, check the resistance of the injector itself.
Try fishing the plastic piece out of that hole. Any foreign material inside the engine is not good.
Anyways, the way the SAFC works is that it modifies the AFM signal going to the ecu. In other words, when it gets installed, the signal wire going to the ECU from the AFM gets cut. The signal the AFM makes goes to the SAFC for modification, then tricks the ECU into thinking there is more or less air entering the engine, based on the %corr at that specific RPM and throttle position. It's possibly an AFM issue, if you haven't caught on by now. If you have to add %corr to it at low rpm, then the AFM could be getting stuck until enough airflow "un-sticks" it.
Or one of the primary injectors is just NOT coming on at all. Easy way to tell that is with a digital logic probe (an LED test light). Hook it up to +12v and check for injector operation at the ECU. Check for pulsed ground at the injector wires. If no pulsed ground, bad ECU. If there is, check the resistance of the injector itself.
Try fishing the plastic piece out of that hole. Any foreign material inside the engine is not good.
09-23-11, 09:12 PM
#3
Rotary Freak
https://www.rx7club.com/showthread.p...SISTOR+PACKAGE
In that thread just above these words, I pasted a jpg of what the original wiring to the resistor pack should look like. I posted this jpg several times in the past. I found this one by doing a Search and using HAILERS as the name and the item being searched for as SOLENOID RESISTOR PACKAGE. There a a number of threads found using those two search terms.
There is a potential of harming the injector drivers when the resistor package is not used on low impedence injectors, not a guarantee that the drivers will be destroyed.
In that thread just above these words, I pasted a jpg of what the original wiring to the resistor pack should look like. I posted this jpg several times in the past. I found this one by doing a Search and using HAILERS as the name and the item being searched for as SOLENOID RESISTOR PACKAGE. There a a number of threads found using those two search terms.
There is a potential of harming the injector drivers when the resistor package is not used on low impedence injectors, not a guarantee that the drivers will be destroyed.
Thread
Thread Starter
Forum
Replies
Last Post
82streetracer
1st Generation Specific (1979-1985)
7
08-23-15 09:28 AM
86rxNa
2nd Generation Specific (1986-1992)
2
08-11-15 11:51 AM
