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hello guys please help with this; my car was slowly overheating not matter the speed and decided to change the thermostat only to find that it did not have one installed, after I ended installing the thermostat I tried to start the car and I got no fuel, I did not touch nothing electrical afaik, I have no fuel pressure on the fuel rail and I can't hear the fuel pump priming (like I could before) when I opened the switch to the run position; I disconnected the connector at the drivers side wheel well to test for voltage on the connector and cleaned the ground beside it.
I tried several times to get it to work, checked the fuses under the hood and switched relays with the horn relay to test.
I got 12 V directly to the fuel pump and it does work, I have it replaced like 6 months ago, I tested with a test light (small) if I got voltage at the connector under the wheel well when I open the switch and the illuminate for about 2 seconds and then shuts off but I can't get the fuel pump to prime.
I tested with this probe:
I hope you can help me guys!
Thanks
Did you try jumping terminals 30 and 87 at the relay socket ??...you need to test all 4 terminals on the relay socket also with a 12 volt test light...do you know how to do it ??
If you jump 30 and 87 and the pump runs you know that the "load" side of the relay is good...the "control" side is 85 and 86...the FP Relay Control which is controlled by the PCM is "power side switched" so to test that connect your test light to a good ground and if the test light illuminates when the key is turned on that signal is good...the last terminal is the ground for the control side so hook up your test to battery positive...is G105 is good the test light will illuminate.
One still needs to check out the control side of the relay...having the pump run when the load side is tested only checks half of the circuit !!
From what he said above, he was getting the two second commanded prime with his test light.
Why next step is to check the pressure.
He said something along the lines there was nothing at first with no pressure now there's the two second prime and he can hear the Fuel Pump Prime then nothing, but it has 12v at it after cleaning the ground.
So yea at this point I guess the best thing would be what exactly is the car doing right now.
If you jump 30 and 87 and the pump runs you know that the "load" side of the relay is good...the "control" side is 85 and 86...the FP Relay Control which is controlled by the PCM is "power side switched" so to test that connect your test light to a good ground and if the test light illuminates when the key is turned on that signal is good...the last terminal is the ground for the control side so hook up your test to battery positive...is G105 is good the test light will illuminate.
Im not very good reading schematics, but to clear out for me and others, if I connect my probe light to 85 and to ground the light should turn on and if I connect 86 to the + terminal of battery the light should turn on, correct?
Swapping the Relay out and getting 12v at the Fuel Pump rules out the Relay. I'd be checking pressure at this point.
This will be my next step after I try the tips C5 Diag is telling me to test first. I'll report back
30 is the 12v from Fuse #13
87 is the power wire to the Fuel Pump
85 is the Relay Coil Ground
86 is the Relay Coil 12v, that is the Green/White Stripe wire from the PCM
With that info you can see it on the Schematic. 85 and 86 might be the opposite of what I said but it's usually wired as 85 being the Coil Ground and 86 being the Coil 12v.
Try the test light in 85 to the Battery positve with the Key off, if it lights up that's the ground as I mentioned above.
86 is the Fuel Pump Relay Control from the PCM. With the Key on that is hot for 2-3sec then it's open unless the car is running. To check that would be the test light in 86 and the other end to the Battery negative, turn the Key on and see the test light light up for 2-3 seconds.
Again, could be opposite but 85 is usually the ground. Try what I said above.
Hook up your test light to B+ and touch it to 85...the test light should light the test if the control side ground (G105) is good...then hook test light to ground and when key is turned on test light should illuminate when hooked to 86...if you are starting to electrical diagnose your car you need a basic understanding of electricity and how to read a wiring diagram...and BTW DON'T jam your test light tip into the relay socket or you will have connection issues.
Yup need something thin like the blade on the Relay. I've used a thicker wire in the past, mainly a solid core copper wire for house wiring then hammered it flat to make good contact in that Relay Socket. Works good you clamp to it with the end of the test light.
I did what you and C5 Diag has told me and the light turned on both of the tests, I reconnected the relay inverted from the original position and I got fuel and started the car, I'm pretty sure I have an intermittent fault somewhere. I used a paper clip to insert it on the fuse box for this tests like indicated at first.
Thank you guys for your answers, I'll update the thread if I got more troubles or if everything is going right.
I did what you and C5 Diag has told me and the light turned on both of the tests, I reconnected the relay inverted from the original position and I got fuel and started the car, I'm pretty sure I have an intermittent fault somewhere.
It does not matter which way these Bosch style relays are inserted into the socket...they work either way.
It does not matter which way these Bosch style relays are inserted into the socket...they work either way.
Is very good to know!
if you are starting to electrical diagnose your car you need a basic understanding of electricity and how to read a wiring diagram
I expected to see the pin number that you posted on the picture (30, 87, 85, 86) on the schematics but yeah, I have little to no experience on electrical diag. I need to start reading to learn a little more I guess.
Thanks again guys!
Tom
I expected to see the pin number that you posted on the picture (30, 87, 85, 86) on the schematics but yeah, I have little to no experience on electrical diag. I need to start reading to learn a little more I guess.
Thanks again guys!
Tom
Bosch style relays follow DIN 72552 which is the auto electrical standard in their numbering of relays...30 is normally load side power and 86 is the coil side trigger...most OE wiring diagrams don't list these 4 numbers on their wiring diagrams.
Bosch style relays follow DIN 72552 which is the auto electrical standard in their numbering of relays...30 is normally load side power and 86 is the coil side trigger...most OE wiring diagrams don't list these 4 numbers on their wiring diagrams.
For whatever reason, GM only showed the corresponding relay numbers in the "Fuel Pump Electrical Circuit Diagnosis" schematic .......and only from 97-2000. The schematic disappears in 2001.
Yet another fuel problem
