Need Major Help 92 V6 3.1
#12
08-22-2009, 07:40 PM
dude...sorry i didn't find this forum sooner, i could have saved you the $130 or so on the new ECM. have been fighting this 'issue' on my 90 3.1 rs since january. i suggest you buy a quality mechanical oil pressure guage [i spent the bucks on autometer] and tee it in at the factory oil pressure sending unit. the factory guages are not very accurate...years ago, i read a comment from a GM engineer that said to consider them 'analog idiot lights'. with the guage hooked up, watch it as you crank the engine. here's how the system works and what you're looking for...
when the key is turned from off to on, the ECM powers the fuel pump [thru the fp relay] for approx 2 seconds then shuts off. this is to prime the lines from the pump to the injectors. when the engine cranks, oil pressure then closes the oil pressure switch [orange wire is battery 12v {unfused...be careful with it}, gray wire runs to the fuel pump] which then provides 12volts to the fuel pump. if theres no oil pressure, theres no power to the fuel pump and hence, no fuel pressure. it's a designed-in system to save the bottom end if you're not mindful of the oil pressure guage while crusing. my problem is intermittent...she can start on command numerous times a day for weeks, then, out of the clear blue, crank with no start. when mine happens, there's no oil pressure. sometimes, allowing it to crank for a few seconds longer than normal will suddenly 'present' oil pressure, and she comes to life [if you try this, be mindful of the duty cycle of the starter motor]. and all of this with NO check engine light. once the engine is lit off, it'll run perfectly.
i'm preparing to install a momentary push button switch parallel with the fuel pump electrical connections at the oil pressure switch [orange & gray] to bring her to life, hopefully with oil pressure quickly following. if that confirms my diagnosis, this winter she'll get a new [factory, NOT aftermarket] oil pump. once back together, i'll systematically dismember the original pump to find out why.
just for your info, the fuel injectors are fed 12v whenever the ign switch is in 'on' and 'start', thru the inj1 & inj2 fuses [inj1 feeds the 3 on the drivers side, inj2 feeds, well, you can figure that out]. the 12v flows out of the injectors to the ECM. if the ECM is recieving reference pulses from the distributor, it then cycles each of the injector 12volts to ground to cycle the injectors.
hope this helps a bit. if you get a chance, let me know what you find / don't find. 220+ thousand miles and i'm still peeking under her skirt to learn a little more about her. also, if you're interested, the $130 or so you spent on the ECM that didn't fix it [i spent it also], would have bought you the factory service manual. LOADS more information than those other manuals will give you [when the other manuals make mention of referring to section 8A or 8C, that's the factory manual. UNBELIEVABLE...you can trace every wire and find every ground]!!! it think it's helms.com or some such thing.
when the key is turned from off to on, the ECM powers the fuel pump [thru the fp relay] for approx 2 seconds then shuts off. this is to prime the lines from the pump to the injectors. when the engine cranks, oil pressure then closes the oil pressure switch [orange wire is battery 12v {unfused...be careful with it}, gray wire runs to the fuel pump] which then provides 12volts to the fuel pump. if theres no oil pressure, theres no power to the fuel pump and hence, no fuel pressure. it's a designed-in system to save the bottom end if you're not mindful of the oil pressure guage while crusing. my problem is intermittent...she can start on command numerous times a day for weeks, then, out of the clear blue, crank with no start. when mine happens, there's no oil pressure. sometimes, allowing it to crank for a few seconds longer than normal will suddenly 'present' oil pressure, and she comes to life [if you try this, be mindful of the duty cycle of the starter motor]. and all of this with NO check engine light. once the engine is lit off, it'll run perfectly.
i'm preparing to install a momentary push button switch parallel with the fuel pump electrical connections at the oil pressure switch [orange & gray] to bring her to life, hopefully with oil pressure quickly following. if that confirms my diagnosis, this winter she'll get a new [factory, NOT aftermarket] oil pump. once back together, i'll systematically dismember the original pump to find out why.
just for your info, the fuel injectors are fed 12v whenever the ign switch is in 'on' and 'start', thru the inj1 & inj2 fuses [inj1 feeds the 3 on the drivers side, inj2 feeds, well, you can figure that out]. the 12v flows out of the injectors to the ECM. if the ECM is recieving reference pulses from the distributor, it then cycles each of the injector 12volts to ground to cycle the injectors.
hope this helps a bit. if you get a chance, let me know what you find / don't find. 220+ thousand miles and i'm still peeking under her skirt to learn a little more about her. also, if you're interested, the $130 or so you spent on the ECM that didn't fix it [i spent it also], would have bought you the factory service manual. LOADS more information than those other manuals will give you [when the other manuals make mention of referring to section 8A or 8C, that's the factory manual. UNBELIEVABLE...you can trace every wire and find every ground]!!! it think it's helms.com or some such thing.
#13
08-22-2009, 08:30 PM
The fuel pump is working as it is suppost to. The pump turns on with the key but if it does not a signal for from oil pressure sending unit within 10 to 12 seconds it cuts off. This is a saftey thing.
If it was starting with spray then ignition is fine. Your Service Engine Soon lite is suppost to be on when ever your motor is not running. It should read code 12 with the engine off. (12= no ref signal from the dis)
If it was starting with spray then ignition is fine. Your Service Engine Soon lite is suppost to be on when ever your motor is not running. It should read code 12 with the engine off. (12= no ref signal from the dis)
Just a FYI. Running the power for the fuel pump thru the oil pressure switch is not to save the motor. Its incase the motor shuts down for some unknown reason, like a wreck, It will keep the fuel pump from becoming a flame thrower. The GM engineers assume if there is oil pressure the motor is consuming the fuel. Back in the early 90's Fords fuel pump safty system was like the Tilt on a pin ball machine. Bump the car to hard and the pump needs reset. I like GMs system much better.
#14
08-24-2009, 10:33 PM
yes, i did read the whole thread. the fact that, at initial key 'on', he has fuel flow when the computer commands the fp relay on is good, but the fact that it will only run if he is spraying raw fuel into the intake says it's a fuel delivery issue. it may possibly be that the fuel injectors are not being cycled by the ecm, but i only wanted him to be 100% sure that pressurized fuel was present at the injectors before he pulled out his wallet and started throwing parts at it.
also, just as a note, he needs to know two other things. 1 - there is a minimum of a 10 second delay between start attempts to allow the vats computer [if equipped] to reset; and 2 - to time the engine, the ref pulse wire from the distributor to the ecm has a connection [just outboard of the ignition coil, close to the ac dryer] that needs to be disconnected to time the engine, but connected back up for the engine to start.
possibly, he could moniter 12v at the gray wire from either the oil pressure sw or the fuel pump relay for 12v while trying to start it, with a volt meter or 12v test light [both wires are connected together to supply the fp with 12v]. when cranking the engine, if the 12v appears for a few seconds then disappears, the fp is only being powered initially when the computer commands the relay and the oil pressure switch isn't picking up after the computer times out the relay.
if the 12v does disappear while cranking the engine, there is a way to confirm that his issue is or is not the fuel pump. in the wiring harness at the fp relay, he should find a red wire coming out of the harness wrapping with a connector on it. it appears to go nowhere to nothing. in fact, applying 12v to it energizes the fp relay, which will power the fp. it was used at the factory to initally fill and pressurize the fuel line to start the car on the assembly line. i recommend tapping off of a 20 amp fuse in the fuse block. however, it's much too tempting to just come off the battery + terminal, since it's under the same hood and only about 30" away. if the temptation is too great, at least install a 20 amp fuse in the wire and DO NOT make it a permenant connection.
i quoted the 2 seconds only because the service manual calls it out, my camaro [with 2 different computers], my 93 suburban and my daughters 99 grand prix all operate at the same 2-3 second cycle. under normal circumstances, the fuel delivery line is full. the check valve just forward of the pump will, over time, allow the pressure in the line to drop when the pump is not running. however, when the line pressure equals the tank pressure [0 psig or atmospheric], no more fuel will physically move out of the line. since gasoline is a liquid and cannot be compressed, the 2 seconds quoted should be ample time for the pump to repressurize the line again.
i do respectfully stand corrected on the reason for supplying the fuel pump through the oil pressure switch. your explanition makes much more sense than mine. it would not be a good thing attempting to open a probably jammed door in a unibody after an accident while a ruptured fuel line is feeding raw 87 octane to flames. however, in my defense, i was going back to the days of the chevy vega with the 'throwaway' aluminum engine. it had the same setup with it's electric fp.
also, just as a note, he needs to know two other things. 1 - there is a minimum of a 10 second delay between start attempts to allow the vats computer [if equipped] to reset; and 2 - to time the engine, the ref pulse wire from the distributor to the ecm has a connection [just outboard of the ignition coil, close to the ac dryer] that needs to be disconnected to time the engine, but connected back up for the engine to start.
possibly, he could moniter 12v at the gray wire from either the oil pressure sw or the fuel pump relay for 12v while trying to start it, with a volt meter or 12v test light [both wires are connected together to supply the fp with 12v]. when cranking the engine, if the 12v appears for a few seconds then disappears, the fp is only being powered initially when the computer commands the relay and the oil pressure switch isn't picking up after the computer times out the relay.
if the 12v does disappear while cranking the engine, there is a way to confirm that his issue is or is not the fuel pump. in the wiring harness at the fp relay, he should find a red wire coming out of the harness wrapping with a connector on it. it appears to go nowhere to nothing. in fact, applying 12v to it energizes the fp relay, which will power the fp. it was used at the factory to initally fill and pressurize the fuel line to start the car on the assembly line. i recommend tapping off of a 20 amp fuse in the fuse block. however, it's much too tempting to just come off the battery + terminal, since it's under the same hood and only about 30" away. if the temptation is too great, at least install a 20 amp fuse in the wire and DO NOT make it a permenant connection.
i quoted the 2 seconds only because the service manual calls it out, my camaro [with 2 different computers], my 93 suburban and my daughters 99 grand prix all operate at the same 2-3 second cycle. under normal circumstances, the fuel delivery line is full. the check valve just forward of the pump will, over time, allow the pressure in the line to drop when the pump is not running. however, when the line pressure equals the tank pressure [0 psig or atmospheric], no more fuel will physically move out of the line. since gasoline is a liquid and cannot be compressed, the 2 seconds quoted should be ample time for the pump to repressurize the line again.
i do respectfully stand corrected on the reason for supplying the fuel pump through the oil pressure switch. your explanition makes much more sense than mine. it would not be a good thing attempting to open a probably jammed door in a unibody after an accident while a ruptured fuel line is feeding raw 87 octane to flames. however, in my defense, i was going back to the days of the chevy vega with the 'throwaway' aluminum engine. it had the same setup with it's electric fp.
#15
04-29-2014, 02:25 PM
I'm not sure if this post should go here or not, but I'm in need of major help with my 1992 Camaro RS V6 3.1. Fuel pressure is good at the pressure check valve. Fuel pump is working good. The problem is.. When I try to start it, it turns over but will not fire. So, I took the intake off and had someone spray gas into the intake, and I tried to start it.. It will start and continue to run as long as someone is spraying gas into the intake. I wondered if it was the Injectors, however I'm not sure how all of the injectors could have stopped working at the same time. I also do not know what all controls the injectors, could it be a relay or fuse, if so where are the fuses and what relay works the injectors. Anything else you suggest I try, please go ahead and suggest it. I am at the end of my ropes with the crimson bird..lol Been trying to fix it but to no avail. ~ 92 Crimson.
#16
08-09-2015, 10:34 PM
Same problem!
I have the same car, 1992 camaro rs 3.1L V6 and when I spray starting fluid in the throttle body air intake it wants to start right up with no problem. but when i don't have any spray in it just cranks over and doesn't start. i have pulled the distributor and reset it on the number one spark plug because previous people messed it up but it transmits a good spark so that's all good, i also have tested the fuel pressure before the fuel filter after the fuel filter and at the shrader valve and they all have good fuel pressure around 44 psi. i also just put all new spark plugs in because the old one were fouled out. i tested the fuel injector wires to see if the wires were hot and they are with the key off and on, i was told by a well trusted mechanic i know that when you crank your engine over the ground wire to the fuel injectors should blink, i tested it and as soon as you crank the engine you loose power. i thought maybe the ECM could have gone bad but i wouldn't think it would only make the fuel injectors to not work. so right now I'm trying to find the fuel injector relay and replace it since its only $15. if someone could help me resolve this it would be great and i am going to test the oil pressure counteracting the fuel pressure idea.
#17
08-09-2015, 10:38 PM
dude...sorry i didn't find this forum sooner, i could have saved you the $130 or so on the new ECM. have been fighting this 'issue' on my 90 3.1 rs since january. i suggest you buy a quality mechanical oil pressure guage [i spent the bucks on autometer] and tee it in at the factory oil pressure sending unit. the factory guages are not very accurate...years ago, i read a comment from a GM engineer that said to consider them 'analog idiot lights'. with the guage hooked up, watch it as you crank the engine. here's how the system works and what you're looking for...
when the key is turned from off to on, the ECM powers the fuel pump [thru the fp relay] for approx 2 seconds then shuts off. this is to prime the lines from the pump to the injectors. when the engine cranks, oil pressure then closes the oil pressure switch [orange wire is battery 12v {unfused...be careful with it}, gray wire runs to the fuel pump] which then provides 12volts to the fuel pump. if theres no oil pressure, theres no power to the fuel pump and hence, no fuel pressure. it's a designed-in system to save the bottom end if you're not mindful of the oil pressure guage while crusing. my problem is intermittent...she can start on command numerous times a day for weeks, then, out of the clear blue, crank with no start. when mine happens, there's no oil pressure. sometimes, allowing it to crank for a few seconds longer than normal will suddenly 'present' oil pressure, and she comes to life [if you try this, be mindful of the duty cycle of the starter motor]. and all of this with NO check engine light. once the engine is lit off, it'll run perfectly.
i'm preparing to install a momentary push button switch parallel with the fuel pump electrical connections at the oil pressure switch [orange & gray] to bring her to life, hopefully with oil pressure quickly following. if that confirms my diagnosis, this winter she'll get a new [factory, NOT aftermarket] oil pump. once back together, i'll systematically dismember the original pump to find out why.
just for your info, the fuel injectors are fed 12v whenever the ign switch is in 'on' and 'start', thru the inj1 & inj2 fuses [inj1 feeds the 3 on the drivers side, inj2 feeds, well, you can figure that out]. the 12v flows out of the injectors to the ECM. if the ECM is recieving reference pulses from the distributor, it then cycles each of the injector 12volts to ground to cycle the injectors.
hope this helps a bit. if you get a chance, let me know what you find / don't find. 220+ thousand miles and i'm still peeking under her skirt to learn a little more about her. also, if you're interested, the $130 or so you spent on the ECM that didn't fix it [i spent it also], would have bought you the factory service manual. LOADS more information than those other manuals will give you [when the other manuals make mention of referring to section 8A or 8C, that's the factory manual. UNBELIEVABLE...you can trace every wire and find every ground]!!! it think it's helms.com or some such thing.
when the key is turned from off to on, the ECM powers the fuel pump [thru the fp relay] for approx 2 seconds then shuts off. this is to prime the lines from the pump to the injectors. when the engine cranks, oil pressure then closes the oil pressure switch [orange wire is battery 12v {unfused...be careful with it}, gray wire runs to the fuel pump] which then provides 12volts to the fuel pump. if theres no oil pressure, theres no power to the fuel pump and hence, no fuel pressure. it's a designed-in system to save the bottom end if you're not mindful of the oil pressure guage while crusing. my problem is intermittent...she can start on command numerous times a day for weeks, then, out of the clear blue, crank with no start. when mine happens, there's no oil pressure. sometimes, allowing it to crank for a few seconds longer than normal will suddenly 'present' oil pressure, and she comes to life [if you try this, be mindful of the duty cycle of the starter motor]. and all of this with NO check engine light. once the engine is lit off, it'll run perfectly.
i'm preparing to install a momentary push button switch parallel with the fuel pump electrical connections at the oil pressure switch [orange & gray] to bring her to life, hopefully with oil pressure quickly following. if that confirms my diagnosis, this winter she'll get a new [factory, NOT aftermarket] oil pump. once back together, i'll systematically dismember the original pump to find out why.
just for your info, the fuel injectors are fed 12v whenever the ign switch is in 'on' and 'start', thru the inj1 & inj2 fuses [inj1 feeds the 3 on the drivers side, inj2 feeds, well, you can figure that out]. the 12v flows out of the injectors to the ECM. if the ECM is recieving reference pulses from the distributor, it then cycles each of the injector 12volts to ground to cycle the injectors.
hope this helps a bit. if you get a chance, let me know what you find / don't find. 220+ thousand miles and i'm still peeking under her skirt to learn a little more about her. also, if you're interested, the $130 or so you spent on the ECM that didn't fix it [i spent it also], would have bought you the factory service manual. LOADS more information than those other manuals will give you [when the other manuals make mention of referring to section 8A or 8C, that's the factory manual. UNBELIEVABLE...you can trace every wire and find every ground]!!! it think it's helms.com or some such thing.
#18
08-10-2015, 10:25 AM
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
... when the engine cranks, oil pressure then closes the oil pressure switch [orange wire is battery 12v {unfused...be careful with it}, gray wire runs to the fuel pump] which then provides 12volts to the fuel pump. if theres no oil pressure, theres no power to the fuel pump and hence, no fuel pressure. it's a designed-in system to save the bottom end if you're not mindful of the oil pressure guage while crusing.
#19
08-10-2015, 05:37 PM
Where is the Fuel Pump Relay???
(QUOTE) The main power source is the fuel pump relay, which switches on once there is an ignition signal (engine running). (QUOTE) where is the fpr at on my 1992 3.1L V6??? Its the 25th anniversary edition if that helps.
Last edited by 1992CamaroRs; 08-10-2015 at 05:41 PM.
#20
07-19-2021, 10:54 AM
3.1 L 92 camaro, injectors not firing
My 92 camaro with the 3.1 liter engine, the injectors are not firing. I've replaced the fuse that was bad for bank 1. The other one was still good. I've also replaced the ecm and the distributor. My question is what else could be causing the injectors on both banks not to fire