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Car Forum / Chevrolet / Chevrolet Trucks / October 200693 chevy 350 no fuel pump power coming out of ecm to relay
working on a 93 chevy pu 350 i dont get the power out of the ecm when key is turned on ot turned to start i went to the back of the ecm and when i put power to the wire the relay kicks in and so does the fuel pump, but do not get any thing out of ecm so i put in a reman ecm same thing no power to the relay i also have checked the out puts of the ign switch and powers and grounds to ecm <going nuts> >working on a 93 chevy pu 350 i dont get the power out of the ecm when key >is turned on ot turned to start i went to the back of the ecm and when i >put power to the wire the relay kicks in and so does the fuel pump, but do >not get any thing out of ecm so i put in a reman ecm same thing no power to >the relay i also have checked the out puts of the ign switch and powers and >grounds to ecm <going nuts> I need to look it up in a wiring diagram to be sure on how it is routed but there is a oil pressure cutout switch that is bypassed during engine start by a relay to provide power to pump and as I recall the ECM will not provide fuel pump power itself until oil pressure switch is closed hence the need for a startup bypass. ----------------- TheSnoMan.com > I need to look it up in a wiring diagram to be sure on how it is > routed but there is a oil pressure cutout switch that is bypassed > during engine start by a relay to provide power to pump and as I > recall the ECM will not provide fuel pump power itself until oil > pressure switch is closed hence the need for a startup bypass. Sno, how many times do people have to tell you guys on here that "that" is not how the oil pressure switch works regarding the fuel pump?! It's the other way around, the oil pressure switch is designed to "keep" the fuel pump working in case the fuel pump relay goes belly up while the engine is running. If you lose the relay, "then" and only then will you have to rely on the oil pressure switch closing in order for the fuel pump to work. I don't know about early decades, but I know that in the 90's, GM never "cutout" the fuel pump with the oil pressure switch. Please! Get your facts straight so that the poor saps asking for advice here on the newsgroup won't be led down some f.cking garden path! If in fact you can read a wiring diagram properly, you will see exactly what I mean. Ian >Sno, how many times do people have to tell you guys on here >that "that" is not how the oil pressure switch works regarding [quoted text clipped - 6 lines] >know that in the 90's, GM never "cutout" the fuel pump >with the oil pressure switch. Not so sure about that, I need to pull wiring. The oil pressure swith is supposed to be a fail safe to shut engine down if oil pressure is lost completely. You are not looking for solutions only conflict. ----------------- TheSnoMan.com >>Sno, how many times do people have to tell you guys on here >>that "that" is not how the oil pressure switch works regarding [quoted text clipped - 12 lines] > ----------------- > TheSnoMan.com Check your crank fuse it should be a 5 amp fuse in lower right hand corner of fuse box. It's the fuse in between your ecm and the relay. Shiiden Kai is right the Oil Pressure switch is a back up it bypasses the relay and will send 12v from the junction block thru a fusible link right to the in-line fuse for the pump. I know for a fact that all of our trucks will start and run with the O.P. switch wires disconnected. I think they use an ignition reference pulse to make sure the engine is running ??? or maybe they monitor both and as long as it has one it runs ? > >Sno, how many times do people have to tell you guys on here > >that "that" is not how the oil pressure switch works regarding [quoted text clipped - 8 lines] > > Not so sure about that, I need to pull wiring. Yes, pull a wiring diagram. You'll see that the oil pressure switch is connected in parallel with the fuel pump relay. > The oil pressure swith > is supposed to be a fail safe to shut engine down if oil pressure is > lost completely. No, that is the vehicle operators job. The oil pressure switch is a fail safe in case the fuel pump relay fails, and when both fail, those of us with brains know how to jumper the fuel pump test lead. > You are not looking for solutions only conflict. We're talking things have have been standard GM design for over 25 years. The world isn't going to conform to you no matter how many things you and Al Gore invented. > Not so sure about that, I need to pull wiring. The oil pressure swith > is supposed to be a fail safe to shut engine down if oil pressure is > lost completely. You are not looking for solutions only conflict. No, I'm trying to make sure that people aren't led down the garden path by incorrect fact spouting guys like you. I mean, look at your above statement! You don't know how something as simple as the oil pressure switch works in conjunction with the fuel pump relay! Which is ok, we all can't know everything about everything, but wouldn't it make more sense to do some research before you offer that kind of incorrect advice? The solution is for you to shape up and start stating what "you know", not what "you think". And if what "you know" is incorrect, admit it, learn from it...and go research stuff. Ian >> Not so sure about that, I need to pull wiring. The oil pressure swith >> is supposed to be a fail safe to shut engine down if oil pressure is [quoted text clipped - 13 lines] > > Ian Ian, we had attempted to a more gentle approach with him to no avail. It failed miserably. He does not give a damn what he says or what consequences come from his wrong and incorrect answer's. It is my belief that if it continues he is liable to get a unsuspecting person hurt. But he cares not. So over at our ng we treated him with as much abuse as possible. It does work after a bit. Roy ok thats not the problem i am not getting the when you turn on the key i am not gettting the fuel pump relay on nothing out of the back of the ecm if i put voltage there it all works but i have put in a new ecm not it i am a ASE master tech and i dint get lost much but i have gone down the flow charts from alldata 3 times and it says replace ecm ???????? > ok thats not the problem i am not getting the when you turn on the > key i am not gettting the fuel pump relay on nothing out of the back > of the ecm if i put voltage there it all works but i have put in a > new ecm not it i am a ASE master tech and i dint get lost much but i > have gone down the flow charts from alldata 3 times and it says > replace ecm ???????? Unfortunately, I can't understand a word you are saying. Ian In article <62393520e688831f4a55c653270b98dd@localhost.talkaboutautos.com>, > ok thats not the problem i am not getting the when you turn on the key i am > not gettting the fuel pump relay on nothing out of the back of the ecm if i > put voltage there it all works but i have put in a new ecm not it i am a > ASE master tech and i dint get lost much but i have gone down the flow > charts from alldata 3 times and it says replace ecm ???????? Which ECM terminal are you putting 12 volts to? Terminal B12 with a dark green-white wire or Terminal F6 with a grey wire? Also, what does the pump do if you jumper the orange wire to grey wire at the oil pressure switch? green and white wire, jumpering it works, the ecm should be putting 12 volts out to the relay at key on and it is not.i have at the relay connector a ground,12 volts battery,and the fuel pump out,all i need is the 12 volts from the computer and there should be a primer run when key is turned on In article <7b3463ed5cd6e1ff3c337b3d6e5ca412@localhost.talkaboutautos.com>, > green and white wire, jumpering it works, the ecm should be putting 12 > volts out to the relay at key on and it is not.i have at the relay > connector a ground,12 volts battery,and the fuel pump out,all i need is > the 12 volts from the computer and there should be a primer run when key > is turned on Is there 12 volts at terminal E16 orange wire (ECM battery feed) Is there 12 volts at terminals E15 and F15 when the ignition is switched on? (ECM ignition feed) I'd extract the B12, E15, E16 and E16 terminals from the connectors and check them for proper contact tension. It's also possible that your new ECM is DOA. > In article > <7b3463ed5cd6e1ff3c337b3d6e5ca412@localhost.talkaboutautos.com>, [quoted text clipped - 14 lines] > > It's also possible that your new ECM is DOA. Have to hand it to you and Ian. You guy's are on top of this stuff:) Been around long enough to appreciate real help. Thanks from all of us. This is of topic but I'd like to tell you about something that kicked my butt for a week. 2002 Cavalier. It sat for a few weeks and when I tried to start it the battery was dead. Hooked up a trickle charger and tried again a few hours later. Started right up, but no dash. No tach, speedometer, temp or gas gauge. No indicator lamps except "theft." Looked under the hood and saw evidence of pack rats. So I looked at every wire, pulled the air box and battery looked everywhere. Could not find any damage. Checked both instrument panel feed fuses, both good. At about this time I realized the battery was about gone, and that was why it went dead in the first place, so I removed it and went to get a new one. Replaced the battery, car started and drove perfect, still no dash. At about this point I figured the dash and body computer had somehow got out of sync or reset improperly. So I disconnected the battery for a few days. Realizing I had the battery disconnected for a few hours just before this I was really beyond logic and just practicing poor troubleshooting. Hooked up the battery and everything worked. Been driving it about a six months since then and it's fine. Even went on a 7,000 mile plus trip. The pack rats did get the back up light circuit and it's one of my "round to it's." When I was checking the serial feed to the dash, I discovered All Data had two serial wires (class 2 serial data) shown, both 0.35 PPL, both circuit number 1807. Makes it interesting:) Al > In article > <7b3463ed5cd6e1ff3c337b3d6e5ca412@localhost.talkaboutautos.com>, [quoted text clipped - 14 lines] > > It's also possible that your new ECM is DOA. Have to hand it to you and Ian. You guy's are on top of this stuff:) Been around long enough to appreciate real help. Thanks from all of us. This is of topic but I'd like to tell you about something that kicked my butt for a week. 2002 Cavalier. It sat for a few weeks and when I tried to start it the battery was dead. Hooked up a trickle charger and tried again a few hours later. Started right up, but no dash. No tach, speedometer, temp or gas gauge. No indicator lamps except "theft." Looked under the hood and saw evidence of pack rats. So I looked at every wire, pulled the air box and battery looked everywhere. Could not find any damage. Checked both instrument panel feed fuses, both good. At about this time I realized the battery was about gone, and that was why it went dead in the first place, so I removed it and went to get a new one. Replaced the battery, car started and drove perfect, still no dash. At about this point I figured the dash and body computer had somehow got out of sync or reset improperly. So I disconnected the battery for a few days. Realizing I had the battery disconnected for a few hours just before this I was really beyond logic and just practicing poor troubleshooting. Hooked up the battery and everything worked. Been driving it about a six months since then and it's fine. Even went on a 7,000 mile plus trip. The pack rats did get the back up light circuit and it's one of my "round to it's." When I was checking the serial feed to the dash, I discovered All Data had two serial wires (class 2 serial data) shown, both 0.35 PPL, both circuit number 1807. Makes it interesting:) Al > In article > <7b3463ed5cd6e1ff3c337b3d6e5ca412@localhost.talkaboutautos.com>, [quoted text clipped - 14 lines] > > It's also possible that your new ECM is DOA. Good stuff cuda. Not like that snojob info. Brian...Chart A-5 in my Helm/GM book says F6 should have power for only 2 seconds after the key is turned on without starting. Then you have to have the key off for 10 seconds to reset. Be sure you are watching your meter as the key goes on...you get only two seconds. There should also be "12V when cranking or any time reference pulses are received". That chart also indicates that if you have 12V at 440 orange / E16 and you don't get 12V out at F6 it is a bad F6 connection or control module. Please TRIPLE CHECK the fusible link and the power at E16. Then try these tests and check the connections suggested by cuda and report back to us. Another trick that I did checking the pump and logic on my 93 4.3 was to jump fused 12V in on the downstream side of the inline fuse. This will run the pump directly as long as the pump works and the 450 ground is good at the frame. Your pump will run all day like this. Then you should be able to start your engine and check F6 again for 12V. If you have 12V at E16 and not at F6, while the engine is running, I'm 99% the PCM is bad. Also, if you can get 4 psi oil pressure while cranking, your fuel pump should start anyway. (Don't believe what snojob writes.) Now you haven't told us you can't get the engine to run so please don't be offended if I'm telling you something you already know. Sniffer |
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