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Dave Nova
Dave Nova, Chevrolet Technician
Category: Chevy
Satisfied Customers: 19452
Experience:  ASE Master Certification. GM World Class Certification
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Chevrolet Silverado 1500 Hi. I have a hand full of questions

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Hi. I have a hand full of questions about the ignition switch, coil. control module, fuel pump relay, ecm and such for my 1995 chevy truck c1500 5.7 first. which wire do i check coming out of the harness to see if i have 12v going to the coil when i switch the ignition switch to on? white? Or the other one? pink orange color. And if i dont have power there. Is that a bad ignition switch? thanks
Hello and thank you for using JustAnswer. My name is XXXXX XXXXX I will do my best to help you with your Chevy problem. The pink wire at the coil should have power with the key on. If you do not have power there be sure to check all fuses. If all fuses are good then replace the ignition switch.
Customer: replied 6 years ago.
Hi there. Thank you for replying. I have no problem paying the amount i was told. Im just not sure when i should ok the payment. After im dont with more of my questions? or before. So i will ask another and see what happens. Heres another question. Say everything was working properly on my truck. while its running. If i pulled out the fuel pump relay. Should it stay running or die? Mine dies when i pull it out. I was told it should still run because of the oil pressure switch back up curcuit. I have a couple other quetion to help me pinpoint my problem. But i just want to ask 1 or 2 at a time so i dont get cunfused. Thanks for all the help. ron

You can accept whenever you would like to. I will continue to follow up with you until you are satisfied. The engine should continue to run when the fuel pump relay is removed. The power should be supplied through the oil pressure switch. The oil pressure switch is at the back of the engine behind the distributor.



Customer: replied 6 years ago.
Hi thank you. THis is great. Its helping me a lot. So since it dies. could there be any other problems or is it ususly the oil speasure switch? and would unpluging it and jumping the wirers going to it be the way to test it to see if its bad? Also. Does the ecm get its power from the ignition switch when its turned on? Or does it get its power from somewere else reguardless if the ignition switch is turned on or working? This will lead into my next question. and i will explain what was happening in detail so you can get a good idea of what was going on from the begining. thanks ron
You can place a jumper wire across the connector for the oil pressure switch. Disconnect the connector and place a jumper wire across the orange and gray wires. The engine should then continue to run with the fuel pump relay removed. Make sure to remove the jumper wire after completing this test, as the fuel pump will continue to run with this jumper in place even with the key turned off.
Dave Nova and other Chevy Specialists are ready to help you
Customer: replied 6 years ago.

hi. ok great. As soon as i get it back running i will do that test. Im going to go ahead and try to pay now. So you know im happy with your help. Then i'll ask a couple more questions. thanks ron


p.s. How about this question? what do you think?

Does the ecm get its power from the ignition switch when its turned on? Or does it get its power from somewere else reguardless if the ignition switch is turned on or working?


Customer: replied 6 years ago.
Hi david. While im waiting to hear back from you on that last question. Im writing up the complete story from the begining like i mentioned. So you have a complete and full understanding of whats going on. and in what order things happen. so you can probably totaly guess what the problem is. When im done writing it up. Do you just want me to send it? Or wait till you replay to the last question first? Also i was sucsesfull In sending the payment and adding a 5 dollar tip. Thanks again for everything. ron
Sorry I missed your previous question. If you respond then pay, the question does not come up on my list. The ECM gets power from two different fuses. One has power all the time (ECM B) and the other has power only with the key on (ECM I). The ECM only turns on after receiving the signal from the ignition switch. The constant power from the ECM B fuse keeps the memory alive in the computer when the key is off.
Customer: replied 6 years ago.

Hi david. Thanks for the email. ok great. Well. let me tell you what has happend from the begining and see what you think. Im driving down the road. everything is fine. Then bamm!! engine shuts off... Coast to the side of the road. Crank crank crank.....Nothing... Minute later... crank crank crank.... Nothing. Couple minutes later.. crank crank bamm engine starts..ok.. Drive a mile. same thing...Then get it started again. Idle for 30 seconds. Engine dies. couple minutes later. Get it stated again. drive 4 miles and get it home in the driveway.. let it idle for a couple minutes.. Then it dies... wait a couple minutes. It starts and idles for a while. During that time. I pull the fuel pump relay. engine dies. Put it back it. crank and engine starts and idles.. ok. I turn it off and leave it til the morning. Next morning. go out and it starts and idles for a while. I hook up a timing light and hook it to #1 plug wire and set it off to the side. Pull fuel relay still dies. Put it back in starts and runs. Then after 2 minutes it dies again. So i zip tie the trigger on the timming light and point it tword the cab so i can watch it. As i crack the engine it flashes everytime that plug fires. ok. Im getting spark but when i put my ear to the gas tank filler neck. I dont hear the pump buzzing. So i turn off the ignition switch for 20 sec. Turn it on. Dont hear the fuel pump run for 3 seconds like normal... But the timing light still flashes when i crank the engine. ok. Then all of a suddon. it stops flashing when cranking... And hasent flashed when cranking since. and... i also took out the relay. And put a test light to that green and white wire and grounded it. I was told when you turn on the ignition the green wire should get power from the ecm for 2 seconds and then turn off. But it doesnt get power now at all. for no seconds. and no spark at the plugs. And no power to the pink wire at the coil when key is turned on. I thought the dist. control module took a dump. and maybe thats why the ecm wasnt sending out the 2 second power pulse to the green wire at the fuel relay to trip it. cause it wasnt sencing anything from the control module. And thats why i wasnt getting any more spark to the plugs. But then i descovered no power to the pink coil wire now. ... so i thought. .. Maybe a bad ignition switch was taking everything out and causing all the problems?? Thats why i asked about the power to the ecm. I thought maybe if the ignition switch was bad. Thast why it wasnt sending power through the green wire to the relay... Im sorry its such a big email. Im hoping to can make sence of it and let me know what you think. or be able to ask the question you need to in order to figure it out. I am a car guy. I have many older cars. GTOs firebirds camaros and mopars. and have restored them. So im very at home working on the cars. Just dont have knowledge of the computor stuff like this./ Like you do. thanks again ron

p.s. When the relay was out i did jump the orange wire that has power to the grey wire and the pump came on. So it seems the pump itself is cool.

Try connecting a jumper wire from the positive battery terminal to the pink wire at the coil and see if the engine starts. Let me know what you find. I will check back tomorrow morning. Getting late tonight.
Customer: replied 6 years ago.
Hi dave. Sorry about the wait. ok. I did what you said. And im surprised at what happend.. IF i did it correctly. ok here it is. The connector at the coil was to tight for me to back probe the pink wire to hook up the 12v from the batt. So i unpluged the connector and stuck a paper clip in the socket where the pink wire goes that comes from the harness. I put a test light to the other 3 termanals on the coil. (theres 4) Pink and white on one side. And pink and white on the other side leading to the control module. All 4 had power when i hooked up the jumper. But i couldnt plug the connector back on to the coil from the harness while the jumper was in place. So i cranked it and no spark.. My timing light is still hooked up liek a describes and no flashes. But the fuel pump is still not coming on yet. So i took out the relay. And jumped the orange wire (always has power) across to the grey wire and the pump came on and stayed on. Then cranked. No go. Still wont start. I totaly thought it would. Ive jumped power to the coil many times on my older cars the same way. So what do you think now? thanks ron
Customer: replied 6 years ago.

p.s.. does the connector fro mthe harness to the coil have to be on the coil or can it be off with power just to the pink wire like i had it? maybe thats why? That white wire needs to be on there for some reason? if so. I can redo the test and figure out some way to have the connector on while testing.

The connector needs to be plugged in to the coil for the engine to run. The pink wire supplies power to the coil and the white wire is the trigger wire from the ignition module that causes the coil to fire. Both need to be connected to the coil in order for it to run.
Customer: replied 6 years ago.
Hi dave. ok. I figured out how i can do it with everything pluged in. i will try it and let you know what happens in a bit. ron
Sounds good.
Customer: replied 6 years ago.
Hey Mr. dave. ok. Hooked it all up and the engine started. with jumpers across both pink and white wires. But only cause i poured gas in the throttle body. So it only ran for 2 seconds. But it did start up. I did it again and it started and ran for 2 seconds. Thats because even though im jumping the orange and grey wire on the realy and making the pumped run. I guess its not running the pump good enough to start or run the car on its own. Even though it was before all this crap. and when i take everything out and hook it all back up normal. Using the ignition switch. No 12v to the coil. ron
You may not be getting power to the injectors as well. My suggestion at this point is to replace the ignition switch;
Customer: replied 6 years ago.
hi dave. Ok. Im going to replace the ignition switch. Once i do that in the next couple days. I will email and let you know if i get power to the coil. After that if it works. I guess we can move onto the fuel relay problem. thanks for your help. ron
Customer: replied 6 years ago.
hi dave. I got an ignition switch. And i got a new control module for the distributor. Actualy i had one. Just so you know. But its raining here right now. So i have to wait a bit to put on the ignition switch. So while im waiting to do that. Should i try checking the injectors for power or pulses? if so how? thanks my friend. ron
Just unplug the connector at the injector and use a test light to check for power on one of the wires with the key on. If you do not have power at the injectors, then there is no sense in checking for pulse. Just continue with the ignition switch replacement at that point.
Customer: replied 6 years ago.
you got it boss. Itsraining still. So as soon as it stops i'll do that and let you know what happens. thanks ron
Looking forward to hearing the results.
Customer: replied 6 years ago.
Hi dave. Guess what? it stopped raining this afternoon so i got out there with a replacement ignition switch. Let me tell you what i did. Hopefully your familer with how a 95 chevy truck is set up. Theres a bulk head connector under the dash. The ignition switch and turn signal switch wiring coming down from the top of the collum plug into that. So i disconnected it. (the ignition switch and turn signal switch wiring all clip together to make one big connector that plugs into that bulkhead socket) I took the new ignition switch and just pluged it into that bulkhead connector. Then took a screwdriver and put it in the slot and turned it like the key normaly would to the on possition. LOLOL All the dash idiot lights came on. The gauges moved. And that green wire at the fuel pump relay got power for a couple seconds. LOl so i thought. oh boy.. I went out to check the pink wire at the coil and it had power!! So i went in and turned the switch to start and the engine cranked and bamm!!! It started and ran. LOL So i turned it off. Unpluged it. Pluged the old swtich back in. Nothing. Just like before. took it out. Put in the new one. Everything worked!! So i guess the ignition switch was bad and most of the trouble. I had a suspition of it but you confirmed it!!!!! Thank you my friend. ok so. While it was running. I pulled the fuel relay and it still died. So i guess i'll jumped the oil switch and if it still runs. You think its the oil switch?? and i have a couple more questions. Do i need to try tipping you some more money again? thanks ron
The ignition switch did fix the starting problem, that is good. The oil pressure sending unit does need to be replaced if pulling the fuel pump relay still causes the engine to die. No need for more money. You have already paid and given me a tip. Thanks. Let me know if I can help you further.
Customer: replied 6 years ago.
Hi dave. ok. Im going to start tomarrow on that damm oil switch problem. But let me tell you some things before i start. to see what you think. When the car original died while driving. I did get a servise engine code 54.. Book said low voltage at fuel relay. What does that tell you? also. since the car is running with the relay in. can you tell me how? meaning what is the realy doing and how is the power to the pump getting through the relay. which wires? So i can understand it. thanks my friend. ron

The ECM (computer) is what turns the relay on. The relay is just an electromagnetic switch. The relay has a coil (electromagnet) that is turned on by the computer. This causes the contacts of the switch to close. The switch is fed power by the ECM B fuse and the other side goes to the fuel pump.


The low voltage code most likely set because of the failing ignition switch so I wouldn't get too worried about the code. Replacing the oil sending unit would be a good idea.

Customer: replied 6 years ago.
Hi dave. Thanks for the replay. I have another interesting question for you.. I was told and read that if you put 12v to term. G (the lower left port) on that diegnostic plug under the dash. with the car off. The pump should come on. They call that port a pump test.. But when i do that. Nothing happens. On the wiring diagram. They show that port going to the fuel relay. The red wire on the relay socket. So i see how that would work. cause in the diagram of the relay. That red wire goes from the diognostic port to the relay. and in the relay it goes to the grey wire down to the pump.. So i thought what the hell. So i got my meter out. Put one probe on the G term on the dionogstic port. And the other probe on the red termimal on the pump relay. Thinking it would beep making continuity. But it did not.... So im a thinking wrong? Is it NOt wired like that? The truck still starts up and runs. Im just trying to fix everything thats wrong while i can. And learn at the same time. Thanks for your time ron

The fuel pump prime connector is located under the hood. It is a single red wire and should be near the underhood fuse panel. It does not go to the diagnostic connector under the dash.


Customer: replied 6 years ago.
Hi dave. Well damm. No wonder that wasnt working.. When i jumper the A and B port there. Thast what flashes the servise light to get the codes. Like the chiltons book says. ok. So do you know what that port G does? It does have a wire going to it. Im also going ot work on the oil switch today too. And i will let yea know what happens. thanks ron

Rechecked schematics and the red fuel pump wire may go to terminal F at the diagnostic connector. See diagram below. The wire at terminal G is the programming wire for the keyless entry system, jumper the A and G terminals together to program the keyless entry remotes.



Customer: replied 6 years ago.
Hi dave. yep. oil switch took a shit. Jumped it and the truck ran after i pulled out teh relay. So got a new one. But i cant get a wrench on it firmly to lossen it. So unless i buy that damm special socket for sending units. Its almost like i have to pull out the dist. Or at lest lossen it and turn it a bit. As long as i get it back close to where it was is that ok? Or no? I know old cars thats how you adjust the timing. But i think these cars its done by the comp. You just have to have it close to where it was? what do you think? thanks ron
You can move the distributor but you will need to put it back where it was. Make a mark on the base of the distibutor and on the intake manifold, then line the marks back up when you are done.
Customer: replied 6 years ago.

Hi dave. ok. Well. I did something you might have done in the past. LOl I took the wrench and cut it in half. LOLOL So it cleared the firewall. I got the switch out without having to move the distributor. Put the new one in. Bingo. runs when you pull the relay. But i dont think the switch was bad. What happend was one of the prongs in the switch was bent over. Like it didnt quite line up when the plug was put on. And when the plug got pushed on. It just bent it out of the way. Not leting the orange and grey wire connect when oil pressure went up. who knows. It might have been that way the trucks whole life out of the factory. So that was the problem with that. So everything works great now. Thanks for all your help bud. ron

P.S. When i need help again.. Or if i have a friend that needs help. Is there a way to come on this site and ask for YOU to pay and work with?

Yes, you can request me by name if you need me in the future. You can even include my name in the title of your question. I will be glad to work with you again.
Customer: replied 6 years ago.
hi dave. ok great. I hope i wasnt to much of a pain or hard to understand. LOL thanks again. Im sure i'll have a handfull of more questions at some point. ron
You were great to work with. Have a Happy New Year and let me know if I can help you any time.
Customer: replied 6 years ago.
hi dave. How are you? thought id let you know the truck is doing good. The problem is gone. Life is grand again. LOl I do have another thing going on with the egr system. This was happening before the problem you helped me on. I was wondering if you might be able to help/ And do i have to start a new thread and send more money? thanks ron
I should be able to help you with this as well. No need to start a new question, just click Accept when you are satisfied with my answer. Let me know what it is that you are having problems with and we can take it from there.
Customer: replied 6 years ago.
Hi dave. ok great!!!. well. Heres the low down.. I was driving on the freeway one day and all of a suddon the servise engine light came on.. ok.. Pulled the code. was the 32 code. ok. So here is what ive done so far. replaced the egr solinoid with a new one. I checked the egr valve. It moves freely. Put vacuum to it. As i pump up the vacuum. it slowly opens. I can leave vacuum on it and it stays put for how ever long i have vacuum on it. When i release vacumm it starts to close. So i THINK the egr valve is working correctly. That how i always tested them. vacuum hoses are good. I also tested the map sencer. Hooked the meter up to it. got 5v. Hooked up the vacuum pump. for ever 5lbs of vacuum i incressed it. The volts droped 1 v. The book said thats correct. Unless its wrong or i did it wrong.. So.. What the heck?? also. The light ONLY comes on at freeway speeds. Never driving on the streets. And once in a while it doesnt even come on while on the freeway. But usualy it does. What happens is i'll get on the freeway. And after driving for about 10 minutes. It will come on. (the light) So what do you think? Please dont tell me the egr passage way in the manifold is very common to plug up and thats usualy the problem. LOL thanks ron

The egr passage does not normally stop up on this engine. With the engine running, pull open the diaprhagm on the egr valve and see if the engine rpm drops. If it does, the passage is clear.


Next test, connect vacuum pump to egr valve and apply vacuum. Start the engine and immediately observe the egr valve and vacuum gauge. Reading should drop and the egr should move to the closed position. If it does not, then ther is an internal passage in the egr valve itself that is clogged, this will require replacement of the egr valve.

Customer: replied 6 years ago.
Hi dave. ok. I understand everything except the last part. what i have is a mity vac hand pump. So your saying to disconect the vacuum line at the egr and hook up my pump and put some vacuum on it? Then start the engine and the valve should close and the reading on the gauge drop? I dont think im fully understanding that test. can you tell me if im following it correctly? Because im used to if the egr is held open at idle. The engine wont run. thanks ron
You are understanding correctly. This particular egr valve uses exhaust backpressure to close the valve. If you apply enough vacuum to open the valve, once the engine starts the valve should close.
Customer: replied 6 years ago.
hi dave. ok. Yes ive heard about that type of egr valve. I was told it has 2 vacuum ports. Is that correct? Or no. Because I beleave mine only has one. A line runs from the front of the throttle body over to the egr seliniod, The from that to the egr. let me know thanks bud. ron
These types only have one vacuum port. They have an internal passage that feeds exhaust pressure to the backside of the egr valve to push it closed.
Customer: replied 6 years ago.
ok my friend. I understand now. I will do the test as soon as i can and let you know what happens. I did forget to mention something else thats going on. And it might have something to do with this. or help you.. at freeway speeds. When i go to pass someone and hit the gas. Under firm excelleration. it does a stumble miss kinda thing. till either it kicks itself out of overdrive or Im cruising at a higher speed. Does that tell you anything? ron
The miss at freeway speeds when accelerating may be due to bad plug wires. This should not be connected to the egr fault.
Customer: replied 6 years ago.
Hi dave. ok. I did the test. Im totaly baffled. LOl your going to love it!!.. ok. I'll try to explain good. I took my pump and applied vacuum to the egr valve. as soon as i started pumping. The diafram moved. The vacuum needle would go up while i squeesed the pump. When i released it the needle would go back to zero. BUT.. The diafram in the egr valve would stay where it was at. So i repeated this prosses. A couple times. each time the same thing would happend except the diafram would be higher up but still maintaning its possition. Then once it was open all the way. And couldnt open any more. THEN the needle would stay up in the numbers once i released the handle. And each time i would pump. The needle would stay higher. So thats that part. So what i did was get the egr to stay open at about half way. I started the truck. It ran nice and smooth at idle. So i thought .ah. it closed itself like you were saying cause of that pach pressure set up thing... But when i got around the truck to check it. it was still half open! And idleing prefect!!! So THATS where im baffled. Cause im used to a car dieing when that egr valce is open at idle... So.. what do you think? thanks ron 1995 chevy truck 1500 5.7 auto.
If the engine still idles well with the egr valve open, then the egr port is likely clogged with carbon buildup. This is not common at all on this engine, but must be what has happened. remove the egr valve and clean both ports under the valve. You may need to use a piece of stiff wire and some carburetor cleaner spray to clear the passages.
Customer: replied 6 years ago.
Hi dave. Yea i was thinking the same thing.... Should i take off the throttle body and see about cleaning any ports on that side as well? or use that opening to vacumm up what i break loose? thanks ron
The egr port should open into the manifold below the throttle body so this should at least give you a way to clean up the debris. A wire coat hanger works well to dislodge the carbon buildup.