Can't get it to fire!!
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
Can't get it to fire!!
Ok, I am having some problems getting my 1990 to fire.
So far, I have installed a fuel pressure gauge which reads 45lbs at the Aeromotive fuel pressure regulator on the mini-ram.
There is spark at the coil and at a couple of plugs that were pulled. The plugs were BONE DRY though.
We shot a little bit of starter fluid into the intake while cranking and the engine did fire.
I have fuel and spark, so... I am guessing that the injectors are to blame!
I did not build this engine so I know very little about it. The injectors are black and silver and have a 33 on them... I'm guessing 33lb injectors. When disconnected from the computer, they read about 13 ohms.
The stock computer is gone and has been replaced with a FAST XFI system. The system does have power and all 8 injector lights blink while cranking.
Let me know if you need any more info or have any ideas.
Thanks,
-JRW
So far, I have installed a fuel pressure gauge which reads 45lbs at the Aeromotive fuel pressure regulator on the mini-ram.
There is spark at the coil and at a couple of plugs that were pulled. The plugs were BONE DRY though.
We shot a little bit of starter fluid into the intake while cranking and the engine did fire.
I have fuel and spark, so... I am guessing that the injectors are to blame!
I did not build this engine so I know very little about it. The injectors are black and silver and have a 33 on them... I'm guessing 33lb injectors. When disconnected from the computer, they read about 13 ohms.
The stock computer is gone and has been replaced with a FAST XFI system. The system does have power and all 8 injector lights blink while cranking.
Let me know if you need any more info or have any ideas.
Thanks,
-JRW
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
From what you have stated, sounds like your not getting enough fuel into the cylinders to start the engine. If they ohm at 13ohm and are very close to each other then the coils are probably good. That doesn't mean that the injectors are opening when the ECM grounds them though. If spraying starter fluid in the intake and the engine starts, it's a fuel problem.
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
From what you have stated, sounds like your not getting enough fuel into the cylinders to start the engine. If they ohm at 13ohm and are very close to each other then the coils are probably good. That doesn't mean that the injectors are opening when the ECM grounds them though. If spraying starter fluid in the intake and the engine starts, it's a fuel problem.
I want to narrow it down.... injectors or fuel management system.
Thanks,
-JRW
Last edited by XtremeTuning; Jan 21, 2007 at 07:24 PM.
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
Does that sound right?
-JRW
Last edited by XtremeTuning; Jan 21, 2007 at 07:30 PM.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
The from tank fuel lines both connect to the fuel rail on the passenger side. The most left line is the fuel feed line and the most right is the fuel return line. I have never mixed them up as my 86 has two different size fittings. Can only go one one way, but other years are different, but not sure which years.
A mulimeter will not do any good to see if the injectors are actually spraying or not. I'm sure there is a way to tell with out pulling the fuel rail, but I can think of one. You state that the injector connectors are receiving the refrence pulses from the ECM grounding them. I somehow doubt that all 8 injectors are closed shut.
By ohming them you are checking for injector coil reisitance. All injectors brands ohm differently. Usually the stock L98 injectors ohm in the neighborhood of 16 ohm where as the LT1 stock injectors ohm around 12 ohm's. A set of Accel's I had ohmed around 14 ohms. The FSM states as long as all are over 10 ohms and are very close to each other then they are fine. I will read a little more in the FSM to see if it states how to test for stuck injectors, but I don't it does.
A mulimeter will not do any good to see if the injectors are actually spraying or not. I'm sure there is a way to tell with out pulling the fuel rail, but I can think of one. You state that the injector connectors are receiving the refrence pulses from the ECM grounding them. I somehow doubt that all 8 injectors are closed shut.
By ohming them you are checking for injector coil reisitance. All injectors brands ohm differently. Usually the stock L98 injectors ohm in the neighborhood of 16 ohm where as the LT1 stock injectors ohm around 12 ohm's. A set of Accel's I had ohmed around 14 ohms. The FSM states as long as all are over 10 ohms and are very close to each other then they are fine. I will read a little more in the FSM to see if it states how to test for stuck injectors, but I don't it does.
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
The from tank fuel lines both connect to the fuel rail on the passenger side. The most left line is the fuel feed line and the most right is the fuel return line. I have never mixed them up as my 86 has two different size fittings. Can only go one one way, but other years are different, but not sure which years.
A mulimeter will not do any good to see if the injectors are actually spraying or not. I'm sure there is a way to tell with out pulling the fuel rail, but I can think of one. You state that the injector connectors are receiving the refrence pulses from the ECM grounding them. I somehow doubt that all 8 injectors are closed shut.
By ohming them you are checking for injector coil reisitance. All injectors brands ohm differently. Usually the stock L98 injectors ohm in the neighborhood of 16 ohm where as the LT1 stock injectors ohm around 12 ohm's. A set of Accel's I had ohmed around 14 ohms. The FSM states as long as all are over 10 ohms and are very close to each other then they are fine. I will read a little more in the FSM to see if it states how to test for stuck injectors, but I don't it does.
A mulimeter will not do any good to see if the injectors are actually spraying or not. I'm sure there is a way to tell with out pulling the fuel rail, but I can think of one. You state that the injector connectors are receiving the refrence pulses from the ECM grounding them. I somehow doubt that all 8 injectors are closed shut.
By ohming them you are checking for injector coil reisitance. All injectors brands ohm differently. Usually the stock L98 injectors ohm in the neighborhood of 16 ohm where as the LT1 stock injectors ohm around 12 ohm's. A set of Accel's I had ohmed around 14 ohms. The FSM states as long as all are over 10 ohms and are very close to each other then they are fine. I will read a little more in the FSM to see if it states how to test for stuck injectors, but I don't it does.
I wish I could tell you more about the injectors... but again I know nothing about them.
Anyone else?
-JRW
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Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
There is a way to test just the injectors. You will need a injector tester (J-34730-3), not sure where one can be had. By doing this you disconnect the injector connector and connect the tester to the injector terminals. a fuel pressure guage will be needed to see pressure drop. With 12v and a ground to the tester you can press a button to see if the pressure drops which means the injectors is opening. This is to test each injector seperately.
Not sure if you want to go through with this, but as I said..hard to believe all 8 would be stuck closed. More like a injector wiring problem, but you said it checks out.
Maybe someone has a simplier solution. Good luck.
Not sure if you want to go through with this, but as I said..hard to believe all 8 would be stuck closed. More like a injector wiring problem, but you said it checks out.
Maybe someone has a simplier solution. Good luck.
Racer
Joined: Oct 2006
Posts: 283
Likes: 0
How long has the car been sitting. Bad gas (gums up) could clog all of the injectors shut. If the car has been sitting for a few years, might be worth it to take em out and have them inspected. Also, any recent cam or ignition work done on the engine?
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
The car came with a dead battery so I changed that. I was able to run it a couple of times then it sat for a month or two. Now it just wont fire.
I have to figure out how I know that the injectors are receiving the propper signal from the XFI system. Nothing really changed from the last time it was run... as far as I know.
Thanks,
-JRW
Team Owner
Joined: Jan 2003
Posts: 20,324
Likes: 250
From: Summerland B.C. Canada
Everyone tells me the mini ram is a breeze to work on. If thats the case, it should be easy to pull the fuel rail with injectors and see if there is fuel being injected at a GOOD rate.
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
Well, I just got off the phone with the FAST tech support and I have a few things to try.
It seems that one wire on the injector should be +12v at all times and the other will be either floating or ground.... ground will open the injector.
For some reason, I don't think I had a full 12 volts at the injector... more like 3 volts so there might be a bad relay inline.
Ill check it out tonight and post back.
BTW- When you call FAST's number now... you get Comp Cams... guess it was taken over!
Thanks,
-JRW
It seems that one wire on the injector should be +12v at all times and the other will be either floating or ground.... ground will open the injector.
For some reason, I don't think I had a full 12 volts at the injector... more like 3 volts so there might be a bad relay inline.
Ill check it out tonight and post back.
BTW- When you call FAST's number now... you get Comp Cams... guess it was taken over!
Thanks,
-JRW
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
That sounds like a more likely cause of the injectors not opening.
Right bank injectors have a pink w/black stripe wire that is 12v (ignition switch "on" and crank controlled..fuse feed. The other wire is light blue is ECM controlled.
Left bank injectors have a pink w/black stripe wire same as above. The other wire is light green and ECM controlled.
Both the light blue and green wires are controlled by the ECM when refrence pulses are received from the distrubitor. The faster the RPM's the faster the ECM grounds those two circuits.
This is what my 86 has and not sure if the wiring insulation color changed as the years went on. If so, it shouldn't be hard to figure out which is which. Whether the wiring harness is stock or aftermarket.
Time to test the wiring at the injectors and at the ECM.
Right bank injectors have a pink w/black stripe wire that is 12v (ignition switch "on" and crank controlled..fuse feed. The other wire is light blue is ECM controlled.
Left bank injectors have a pink w/black stripe wire same as above. The other wire is light green and ECM controlled.
Both the light blue and green wires are controlled by the ECM when refrence pulses are received from the distrubitor. The faster the RPM's the faster the ECM grounds those two circuits.
This is what my 86 has and not sure if the wiring insulation color changed as the years went on. If so, it shouldn't be hard to figure out which is which. Whether the wiring harness is stock or aftermarket.
Time to test the wiring at the injectors and at the ECM.
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
ITS ALIVE!!!
After all the trouble shooting and crazyness.... it was a part costing less then a dollar.
Ill expain it here in case anyone else is having the same problem and finds this thread in a search.
Not sure if this is how it works with all systems, but with the FAST XFI system you get +12v off of the better which runs through a 30a fuse. After that it goes into a relay and on to each injector.
Well, I must have shorted out the relay when I changed batteries... popped in a new one... and it was alive!!!
Thanks for the help,
-JRW
After all the trouble shooting and crazyness.... it was a part costing less then a dollar.
Ill expain it here in case anyone else is having the same problem and finds this thread in a search.
Not sure if this is how it works with all systems, but with the FAST XFI system you get +12v off of the better which runs through a 30a fuse. After that it goes into a relay and on to each injector.
Well, I must have shorted out the relay when I changed batteries... popped in a new one... and it was alive!!!
Thanks for the help,
-JRW
