Does the Car know if theres no fuel not to spark?
04-30-03, 01:59 AM
#1
Damn Right It's Me
Thread Starter
iTrader: (1)
Join Date: Jan 2003
Location: Chino Hills, Cali
Posts: 1,331
Likes: 0
Received 0 Likes
on
0 Posts
Does the Car know if theres no fuel not to spark?
I cant get my car to start up i just put the motor back in everything is the way it was, CAS is fine injectors get a sirge of voltage when i try to start fuses and everything look fine something im missing?
04-30-03, 02:01 AM
#2
Super Raterhater
iTrader: (6)
Join Date: Dec 2001
Location: NY, MA, MI, OR, TX, and now LA or AZ!
Posts: 10,628
Likes: 0
Received 2 Likes
on
2 Posts
Injectors always see voltage, it's when they're pulsed with 'negative' that they fire. Check your EGI fuses (under the hood on the drivers strut tower) and then the 'Motor' fuse inside the car's fusebox, Also, try priming the fuel system by jumpering the fuel pump connector (located near the passanger strut tower, yellow plug, two pin) Double check your AFM/plug wires/CAS/etc, if still no go, try to get someone to hold the AFM flapper open slightly and try again, perhaps there's a bad vac leak somewhere.
04-30-03, 02:06 AM
#5
Super Raterhater
iTrader: (6)
Join Date: Dec 2001
Location: NY, MA, MI, OR, TX, and now LA or AZ!
Posts: 10,628
Likes: 0
Received 2 Likes
on
2 Posts
It pressurizes the fuel system (usually after you've had the engine apart/out of the car, the system is obviously depressurized/fuel isn't in the lines, you jumper that connector and it runs the fuel pump so that it's pressurized, basically priming the fuel system so no air is left) Be *SURE* to remove that jumper (just a 2" peice of wire with 2 crimp male ends on it) before going anywhere, if you were to get in an accident the fuel pump wouldn't shut off!
04-30-03, 02:10 AM
#7
Senior Member
Join Date: Sep 2002
Location: Louisiana
Posts: 613
Likes: 0
Received 0 Likes
on
0 Posts
nope, it doesn't....it should still spark even if you aren't getting fuel. do you think youre not getting fuel or do you know it? What have you checked/tested so far?
Four main things to check--fuel, air, spark, compression
Pull the plugs and see if they are wet. While the plugs are out check compression. see if you can smell fuel in the engine. If not, then check the whole fuel system before you go anywhere else. Make sure the fuel pump is coming on when you go to start it. Once you know you have fuel getting to the engine, go on to the next--make sure your afm is plugged in properly. That is the big thing with air--the afm. a stock rx7 will not run without the afm unless you have a standalone running the engine. Also--tell us NA or tII, year, and what mods?
Once the afm is ok, check for spark. once spark is cool, if it still doesnt start, you might look at your ECU.
Oh, before all of this, double check all your wiring and connections. Just thought about what you said about putting the engine back in, and more times than not, we miss something simple.
Four main things to check--fuel, air, spark, compression
Pull the plugs and see if they are wet. While the plugs are out check compression. see if you can smell fuel in the engine. If not, then check the whole fuel system before you go anywhere else. Make sure the fuel pump is coming on when you go to start it. Once you know you have fuel getting to the engine, go on to the next--make sure your afm is plugged in properly. That is the big thing with air--the afm. a stock rx7 will not run without the afm unless you have a standalone running the engine. Also--tell us NA or tII, year, and what mods?
Once the afm is ok, check for spark. once spark is cool, if it still doesnt start, you might look at your ECU.
Oh, before all of this, double check all your wiring and connections. Just thought about what you said about putting the engine back in, and more times than not, we miss something simple.
Trending Topics
04-30-03, 02:11 AM
#8
Super Raterhater
iTrader: (6)
Join Date: Dec 2001
Location: NY, MA, MI, OR, TX, and now LA or AZ!
Posts: 10,628
Likes: 0
Received 2 Likes
on
2 Posts
The CAS controls fuel and spark, and is the only thing that will trigger them, it doesn't really look for conditions such as if they injectors have fuel (as it assumes the fuel pump is running already)
04-30-03, 02:24 AM
#9
Damn Right It's Me
Thread Starter
iTrader: (1)
Join Date: Jan 2003
Location: Chino Hills, Cali
Posts: 1,331
Likes: 0
Received 0 Likes
on
0 Posts
Yeah ran the fuel pump the sec injector rail isnt getting fuel so probably that might be my issue still no spark though very weird. I was thinkin I fried my ECU there was some smoke by the battery a few weeks ago when i had to roll my window up. I have a 87 GXL only mod is exaust which i got a week before the engine mishap alwasy happens that way =/. Thanks for the help appreciate it no one has been able to help much.
04-30-03, 03:15 AM
#10
Damn Right It's Me
Thread Starter
iTrader: (1)
Join Date: Jan 2003
Location: Chino Hills, Cali
Posts: 1,331
Likes: 0
Received 0 Likes
on
0 Posts
after some investigation here i found that the fuel is making it to the rail but the valve with the vac line on it is not opening to let the fuel in, should that be open all the time free flowing the fuel? Would this mean vaccum leak?
04-30-03, 12:54 PM
#14
Senior Member
Join Date: Sep 2002
Location: Louisiana
Posts: 613
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by MrFuzzy
Yeah ran the fuel pump the sec injector rail isnt getting fuel so probably that might be my issue still no spark though very weird. I was thinkin I fried my ECU there was some smoke by the battery a few weeks ago when i had to roll my window up. I have a 87 GXL only mod is exaust which i got a week before the engine mishap alwasy happens that way =/. Thanks for the help appreciate it no one has been able to help much.
Yeah ran the fuel pump the sec injector rail isnt getting fuel so probably that might be my issue still no spark though very weird. I was thinkin I fried my ECU there was some smoke by the battery a few weeks ago when i had to roll my window up. I have a 87 GXL only mod is exaust which i got a week before the engine mishap alwasy happens that way =/. Thanks for the help appreciate it no one has been able to help much.
04-30-03, 01:09 PM
#15
Damn Right It's Me
Thread Starter
iTrader: (1)
Join Date: Jan 2003
Location: Chino Hills, Cali
Posts: 1,331
Likes: 0
Received 0 Likes
on
0 Posts
Yeah fuel was on backwards still not spark im gonna check the coil when i get home. Should i hear the fuel pump when starting the car?
04-30-03, 01:20 PM
#16
Originally posted by SonicRaT
Injectors always see voltage, it's when they're pulsed with 'negative' that they fire.
Injectors always see voltage, it's when they're pulsed with 'negative' that they fire.
I hate to do this, but when voltage is applied, THEN the injectors open.
SO its the positive pulses that cause the injector to fire, not the negative.
Jarrett
04-30-03, 01:27 PM
#17
Despise Enmity
Join Date: May 2001
Location: Richmond, VA
Posts: 2,420
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by J-Rat
Hey Sonic,
I hate to do this, but when voltage is applied, THEN the injectors open.
SO its the positive pulses that cause the injector to fire, not the negative.
Jarrett
Hey Sonic,
I hate to do this, but when voltage is applied, THEN the injectors open.
SO its the positive pulses that cause the injector to fire, not the negative.
Jarrett
04-30-03, 01:36 PM
#19
Despise Enmity
Join Date: May 2001
Location: Richmond, VA
Posts: 2,420
Likes: 0
Received 0 Likes
on
0 Posts
The injectors are fed +12V from the main relay (on the driver's side fender just behind the trailing coils) when the key is in the ON position. When the car is running the injectors pulse as the ECU gives the injectors a pulsed ground. From idle to 3700 rpm, the primary injectors' pulse width is gradually increasing, with zero pulses on the secondaries. When the transfer occurs, the primary injectors drop from 80% duty cycle to 40%, and the secondaries come in at 40%. With bad grounding, I believe the ECU has a hard time sending out the ground pulses when all four injectors come on suddenly (the car usually doesn't stumble if you accelerate slowly through this rpm zone).
04-30-03, 01:46 PM
#20
Okay, I understand what he was saying...
There is 12V on one side of the injector. But there is no ground applied to the other pole. So there is no complete circut for the 12V to make. That means that even though 12V is being applied to the injector, if you put a multimeter on both poles of the injector, you wont see voltage.
Once the ground is applied (or pulsed) that completes the circut and actuall APPLIES the 12V across the injector and completes the circut.
So in essence, he is right, the ground completes the circut. But the injectors are opened by 12V.
Jarrett
There is 12V on one side of the injector. But there is no ground applied to the other pole. So there is no complete circut for the 12V to make. That means that even though 12V is being applied to the injector, if you put a multimeter on both poles of the injector, you wont see voltage.
Once the ground is applied (or pulsed) that completes the circut and actuall APPLIES the 12V across the injector and completes the circut.
So in essence, he is right, the ground completes the circut. But the injectors are opened by 12V.
Jarrett
04-30-03, 01:50 PM
#21
Despise Enmity
Join Date: May 2001
Location: Richmond, VA
Posts: 2,420
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by J-Rat
Okay, I understand what he was saying...
There is 12V on one side of the injector. But there is no ground applied to the other pole. So there is no complete circut for the 12V to make. That means that even though 12V is being applied to the injector, if you put a multimeter on both poles of the injector, you wont see voltage.
Once the ground is applied (or pulsed) that completes the circut and actuall APPLIES the 12V across the injector and completes the circut.
So in essence, he is right, the ground completes the circut. But the injectors are opened by 12V.
Jarrett
Okay, I understand what he was saying...
There is 12V on one side of the injector. But there is no ground applied to the other pole. So there is no complete circut for the 12V to make. That means that even though 12V is being applied to the injector, if you put a multimeter on both poles of the injector, you wont see voltage.
Once the ground is applied (or pulsed) that completes the circut and actuall APPLIES the 12V across the injector and completes the circut.
So in essence, he is right, the ground completes the circut. But the injectors are opened by 12V.
Jarrett
04-30-03, 07:16 PM
#23
Senior Member
Join Date: Sep 2002
Location: Louisiana
Posts: 613
Likes: 0
Received 0 Likes
on
0 Posts
thats right fuzzy--you have a leading and trailing plug in each chamber. They are both used equally at the same time, unlike the injectors at lower rpms. It will still try to start of one coil is bad. But I don't know if it would actually start. I have heard of someone driving with only one rotor giving power, but for different reasons.
Thread
Thread Starter
Forum
Replies
Last Post
trickster
2nd Generation Specific (1986-1992)
25
07-01-23 04:40 PM