changed pump ,sending unit,relay,fuse....but run a jumper from battery and the pump turns on....i will hot wire it for now on fuse....no power to relay now....would that be the ecm? im thinking so and how hard and how much of pain in the ass is the prom chips and computers or whatever?
@kenjackson1977 Do you have spark and injector pulse? Or does the engine run when you hot-wire the pump. All you said was the pump runs when you hot-wire it. I need to know to help you further.
@ScannerDanneri have spark....i can get it to start by pouring fuel in throttle body now.... i just bought fuel pressure regulator rebuild kit ....gonna try that...
@kenjackson1977 Don't do that, it won't fix it. Do this test: turn key on engine off (KOEO) find the purple /white wire coming off of the back of the distributor module connector. Connect a test light to battery positive and touch on/off/on/off/on/off this wire. The ECM should react by running the fuel pump (FP relay should turn on) and the ECM will also fire the injectors. Let me know the result of this test.
@ScannerDanner If the FP relay turns on and the injectors fire you need to replace the ignition module. I know, I know, "but I have spark" is what you are thinking. Listen, these modules will fail in that it will still control the coil, but not send the reference pulse (0-5v square wave) on the purple-white wire to the ECM. Without this signal the ECM will not see an RPM signal and will not fire the injectors and will not run the pump.
@ScannerDanner Another clue to this problem is when you first turn the key on you should still get a fuel pump "prime". This is the ECM turning the FP relay on for a second to bring fuel pressure up. After this "prime" the ECM will NOT turn the FP relay back on until it receives an RPM signal (on the purple-white ref. wire).
If you do not have a "prime" happening when you first tune key on, then we are barking up the wrong tree. I can still help you though.
@ScannerDanner i turn key on i dont even see power on at the fuse or pump relay on firewall when on the test light...yet pour fuel in and starts hmmmm im stumped buddy.
@kenjackson1977 If you have no power at the pump fuse then you have a fusible link problem. I believe these are attached to the starter battery post. Maybe you left one off when you did the tranny or you connected one to the wrong post. All fusible links must go to starter battery post. The post that has the positive battery cable.
@ScannerDanner ok man i totally 100% appreciate it and your time. I will look tomorrow and trace the fusible link and see what i can find. Ill get back to you with results as you've been helpful as s.o.b to me. I have no clue haha but learning quickly from your shared knowledge i should donate or buy this book?
@ScannerDanner ok....i rebuilt the fuel pressure regulator... did not fix the problem. So took the clip off back of distrib. and put light on the box with purp/white white wire did it 3 times and nothing cycled nothing happened. I went to junk yard grabbed 35.00 computer...changed the prom to from old one to the junk yard one nothing happened....wants to start but isnt...pour fuel in throttle body and starts right up..still no pump kicking on...
Having a problem with my 1991 chevy 4x4 350...ran good..lost the tranny...changed the tranny then no fuel pump turning on..so change the relay...change the fuel pump...and still nothing grrr...what order does the electronic fuel system go on these? Would the oil pressure switch being bad make the relay or pump not have power? or would it be computer? I unplugged the battery not sure it would throw a code as to why no fuel pump or relay juice..??? any help people??? thanks.
@kenjackson1977 First is watch my fuel pump electrical circuit designs video. This will answer your question about the oil pressure switch. Second is do you have spark? Third is do you have injector pulse? Answer these and watch that video and I can help you more.
@ScannerDanner Ok ,watching your video now...im not sure if i have spark i will check tomorrow on that. What is Injector pulse? Ill keep in touch i have a pile of money into this truck now haha ...much thanks for your time.
This a good example of a real tech working on the field,also you can check ground chassis trough the pin # 4 of the OBD II DLC, but as i mention before this is nice job done technically,thanks for sharing.
Excellent excellent case study.. I was baffled in the beginning with the heater in the mix of things, that really through me a loop. Shared ground never cross my mind. Wiring digram interpretation is really key to figuring out what is going on within a circuit.
@fivefortyeye540i Thank you, this one was a little tricky to film. There are so many different directions I could have taken this. Hopefully it was clear and not cluttered with too much info.
Paul, you just keep amazing me !!! when you know how to use your equipment , there is nothing you cannot fix ....thanks for the awesome lesson again..
@ScannerDanner That sounds a lot like a quote from Isaac Newton. It went like this, "If I have seen farther, it was by standing on the shoulders of giants...." I love that quote, and I love standing on shoulders, ha ha.
Why is that backup circuit from the oil pressure switch there?
@spelunkerd Nice, I have never heard that quote. I like it too. The oil psi switch is simply there as a backup in case the relay fails. Of course the other side of that oil psi switch runs the oil psi gauge or light, so it serves two functions. I don't know why GM felt the need to backup the FP relay. No one else is doing that. Seems like a waste of copper wire to me. They must have had a lot of problems with this circuit early on?
Good video as usual. Can you tell me if an inexpensive 20 MHZ, dual trace oscilloscope can handle most of the diagnostic work that you do for a home mechanic? There's one at h-tt-p://w-w-w.multimeterwarehouse.c-0-m/YB4328f.htm for only $260.
@CoolasIce2 Im not sure, I'll look into it when I get a chance. I think any scope is better than no scope but then again there is some crap out there.
@CoolasIce2 I just checked out that scope. It is an old analog scope. It will do want you want but you will have problems with "glitch" captures because there is no play back. I would recommend you go on ebay and buy a used Vantage (not pro, unless you can afford it)). It is a graphing multimeter and will get you by for awhile. Plus the data base in the tool is unmatched in this field. I have had students pick them up for around $200
This guy is freaking GENIUS!!!!
contagiousFX 3 weeks ago
excellent video@!
contagiousFX 3 weeks ago
changed pump ,sending unit,relay,fuse....but run a jumper from battery and the pump turns on....i will hot wire it for now on fuse....no power to relay now....would that be the ecm? im thinking so and how hard and how much of pain in the ass is the prom chips and computers or whatever?
kenjackson1977 3 weeks ago
@kenjackson1977 Do you have spark and injector pulse? Or does the engine run when you hot-wire the pump. All you said was the pump runs when you hot-wire it. I need to know to help you further.
ScannerDanner 3 weeks ago
@ScannerDanner *I have spark...not sure how to test injector pulse?
kenjackson1977 3 weeks ago
@ScannerDanneri have spark....i can get it to start by pouring fuel in throttle body now.... i just bought fuel pressure regulator rebuild kit ....gonna try that...
kenjackson1977 3 weeks ago
@kenjackson1977 Don't do that, it won't fix it. Do this test: turn key on engine off (KOEO) find the purple /white wire coming off of the back of the distributor module connector. Connect a test light to battery positive and touch on/off/on/off/on/off this wire. The ECM should react by running the fuel pump (FP relay should turn on) and the ECM will also fire the injectors. Let me know the result of this test.
ScannerDanner 3 weeks ago
@ScannerDanner If the FP relay turns on and the injectors fire you need to replace the ignition module. I know, I know, "but I have spark" is what you are thinking. Listen, these modules will fail in that it will still control the coil, but not send the reference pulse (0-5v square wave) on the purple-white wire to the ECM. Without this signal the ECM will not see an RPM signal and will not fire the injectors and will not run the pump.
ScannerDanner 3 weeks ago
@ScannerDanner Another clue to this problem is when you first turn the key on you should still get a fuel pump "prime". This is the ECM turning the FP relay on for a second to bring fuel pressure up. After this "prime" the ECM will NOT turn the FP relay back on until it receives an RPM signal (on the purple-white ref. wire).
If you do not have a "prime" happening when you first tune key on, then we are barking up the wrong tree. I can still help you though.
ScannerDanner 3 weeks ago
@ScannerDanner its not priming when i turn key on....pour fuel in it will start....
kenjackson1977 3 weeks ago
@ScannerDanner BTW this is the kind of stuff that I teach in my book.
ScannerDanner 3 weeks ago
@ScannerDanner i turn key on i dont even see power on at the fuse or pump relay on firewall when on the test light...yet pour fuel in and starts hmmmm im stumped buddy.
kenjackson1977 3 weeks ago
@kenjackson1977 If you have no power at the pump fuse then you have a fusible link problem. I believe these are attached to the starter battery post. Maybe you left one off when you did the tranny or you connected one to the wrong post. All fusible links must go to starter battery post. The post that has the positive battery cable.
ScannerDanner 3 weeks ago
@ScannerDanner ok man i totally 100% appreciate it and your time. I will look tomorrow and trace the fusible link and see what i can find. Ill get back to you with results as you've been helpful as s.o.b to me. I have no clue haha but learning quickly from your shared knowledge i should donate or buy this book?
kenjackson1977 3 weeks ago
@kenjackson1977 lol, or course you know I agree with that, but either way I will still help you
ScannerDanner 3 weeks ago
@ScannerDanner ok,going to go do this test i will get back to u in few hours thanks a bunch.
kenjackson1977 3 weeks ago
@ScannerDanner ok....i rebuilt the fuel pressure regulator... did not fix the problem. So took the clip off back of distrib. and put light on the box with purp/white white wire did it 3 times and nothing cycled nothing happened. I went to junk yard grabbed 35.00 computer...changed the prom to from old one to the junk yard one nothing happened....wants to start but isnt...pour fuel in throttle body and starts right up..still no pump kicking on...
kenjackson1977 3 weeks ago
Having a problem with my 1991 chevy 4x4 350...ran good..lost the tranny...changed the tranny then no fuel pump turning on..so change the relay...change the fuel pump...and still nothing grrr...what order does the electronic fuel system go on these? Would the oil pressure switch being bad make the relay or pump not have power? or would it be computer? I unplugged the battery not sure it would throw a code as to why no fuel pump or relay juice..??? any help people??? thanks.
kenjackson1977 1 month ago
@kenjackson1977 First is watch my fuel pump electrical circuit designs video. This will answer your question about the oil pressure switch. Second is do you have spark? Third is do you have injector pulse? Answer these and watch that video and I can help you more.
ScannerDanner 1 month ago
@ScannerDanner Ok ,watching your video now...im not sure if i have spark i will check tomorrow on that. What is Injector pulse? Ill keep in touch i have a pile of money into this truck now haha ...much thanks for your time.
kenjackson1977 1 month ago
@ScannerDanner now on this what does the ECU stand for? Is that computer?
kenjackson1977 1 month ago
Hi there,
This a good example of a real tech working on the field,also you can check ground chassis trough the pin # 4 of the OBD II DLC, but as i mention before this is nice job done technically,thanks for sharing.
Quetzalcoatl09 1 month ago
we dont need a obd2 or lab scope man u have a computer in ur head lol
hp11208 2 months ago
@hp11208 LOL.
ScannerDanner 2 months ago
Thnx man that will help me at my auto tech school
roro560v8 2 months ago
Excellent excellent case study.. I was baffled in the beginning with the heater in the mix of things, that really through me a loop. Shared ground never cross my mind. Wiring digram interpretation is really key to figuring out what is going on within a circuit.
fivefortyeye540i 2 months ago
@fivefortyeye540i Thank you, this one was a little tricky to film. There are so many different directions I could have taken this. Hopefully it was clear and not cluttered with too much info.
ScannerDanner 2 months ago
Paul, you just keep amazing me !!! when you know how to use your equipment , there is nothing you cannot fix ....thanks for the awesome lesson again..
CHIBA280CRV 2 months ago
@CHIBA280CRV Thanks, but I take no credit. Any ability I have is from above
ScannerDanner 2 months ago
@ScannerDanner That sounds a lot like a quote from Isaac Newton. It went like this, "If I have seen farther, it was by standing on the shoulders of giants...." I love that quote, and I love standing on shoulders, ha ha.
Why is that backup circuit from the oil pressure switch there?
spelunkerd 2 months ago
@spelunkerd Nice, I have never heard that quote. I like it too. The oil psi switch is simply there as a backup in case the relay fails. Of course the other side of that oil psi switch runs the oil psi gauge or light, so it serves two functions. I don't know why GM felt the need to backup the FP relay. No one else is doing that. Seems like a waste of copper wire to me. They must have had a lot of problems with this circuit early on?
ScannerDanner 2 months ago
@spelunkerd Backing up the FP relay can't hurt. I'll take it. My '87 Cutlass Ciera has the same layout
CoolasIce2 2 months ago
@ScannerDanner That is the first time I've heard someone give credit to the real source (The Lord) of they're knowledge.
Thanks again for sharing that knowledge with us new techs.
God bless.
TRcustomengineering 2 months ago
@TRcustomengineering No problem and than you for your comment. I have nothing and can offer nothing outside of Him.
ScannerDanner 2 months ago
The next step is to find out who the s.o.b. is who removed that nut from a previous repair.
CoolasIce2 2 months ago
Excellent! Love these video's! Keep them coming!
dreamer2355 2 months ago
Good video as usual. Can you tell me if an inexpensive 20 MHZ, dual trace oscilloscope can handle most of the diagnostic work that you do for a home mechanic? There's one at h-tt-p://w-w-w.multimeterwarehouse.c-0-m/YB4328f.htm for only $260.
CoolasIce2 2 months ago
@CoolasIce2 Im not sure, I'll look into it when I get a chance. I think any scope is better than no scope but then again there is some crap out there.
ScannerDanner 2 months ago
@ScannerDanner OK Thanks.
CoolasIce2 2 months ago
@CoolasIce2 I just checked out that scope. It is an old analog scope. It will do want you want but you will have problems with "glitch" captures because there is no play back. I would recommend you go on ebay and buy a used Vantage (not pro, unless you can afford it)). It is a graphing multimeter and will get you by for awhile. Plus the data base in the tool is unmatched in this field. I have had students pick them up for around $200
ScannerDanner 2 months ago
@ScannerDanner OK Thanks. I'll look into that.
CoolasIce2 2 months ago
Brother, you keep out doing yourself. Amazing. God bless
Viper81766 2 months ago
Great video as always!
ExoVCDS 2 months ago