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I'll be the first one to admit I am in kindergarten when it comes to this stuff. All new to me...
So... I've been reading about PWM... It seems that in one way or another it is controlled either by power or a positive lead,,, turned off and on by intermittent grounding OR always grounded and what is intermittent is the powering...
Either way,,, it seems (and maybe the 2003 PWM system is got its own approach) that grounding is a necessary component going into the appliance or solenoid... Am I getting this wrong?
Many of the things I am reading (and watching) says that the duty cycle(s) are controlled by alternating or intermittent powering and grounding.
There's no difference between XK8 and XKR from 2003 on the earlier XKRs had two pumps.
Cool. Thanks. I am grateful for these JTIS posts/images and will use them... I just wanted to make sure the information was specific to, and in reference to, the right year make and model... I have gotten information on the forum from well meaning folks,,, but the info they were sending was from a different year and make...
I'm going to dig into the JTIS... This is getting nutts, in some respects.
Are you saying that because the FPump isn't grounded, not doing work, voltage will flow thru that pump (not doing any work) and come out the other side? And that's what I'm reading with the test light? Admittedly, I did not unplug the connector at the upper rim of the gas tank. I back probed the wires. So, I was reading voltage that was coming into and going out of the pump?
Do you think if I unclipped the connector and took a reading from the downward side (sorry, I don't know the term) towards the FPM (and what should be intermittent grounding if the FPM or ECU was functional) get nothing. And, if I took a reading on the lead on the pump side I would find voltage still, the "open circuit" as you said?
I guess I need to understand that either or both the ECU isn't signalling ground, or the FPM isn't picking it up, or working...?
If I did ground the line that was supposed to be providing intermittent ground,,, full time ground,,, and the pump runs, will it cause all kinds ah unholy damage?
And again, I'm sorry for pushing back yesterday. I'm stubborn and way on the low sidebofba learning curve here.
Thank you for your explanation and help - now if I will just accepted the help, lol
This may be a silly question, but why can't a a regular pump be used in the circuit? If the fpm is regulating the normal on-off cycling of the pump to maintain a constant fuel pressure based on demand, why can't it do the same thing with a standard injector fuel pump?
I've never held one in my hands but you'd think you could replace just the pump component of the assembly and all would be fine.
This may be a silly question, but why can't a a regular pump be used in the circuit? If the fpm is regulating the normal on-off cycling of the pump to maintain a constant fuel pressure based on demand, why can't it do the same thing with a standard injector fuel pump?
I've never held one in my hands but you'd think you could replace just the pump component of the assembly and all would be fine.
I hear THAT... The only thing that I am/was and will be uncertain/conerned about is - well, you know that thing where an appliance will ONLY work rightly on a steady-ish 12v and won't respond well to millions of micro pulses over its life. It's a lot. There must be some engineering into that application... I ordered an aftermarket Walbro 255lph high pressure pump... $70 bucks. I'll secure it in the bucket and see how it rolls... My problem now is that I have to fix my pulse system... And I have NO idea, yet,,,,
I haven't done this in a very long time and am going from memory... You will need a proper multi-meter rather than a test light to figure this out.
If you disconnect the white plug in the middle of the harness that runs across the top of the tank you can check a couple of things.
Checking the pump driver side of the harness
With Key on, measure 1 pin at a time to chassis ground.
On the RED pump wire you should see +12V
On the RED-YELLOW pump wire you should see zero volts (or very near it)
On the zero volt pin, switch to resistance measurement and check resistance from RED-YELLOW to chassis ground. You should read an open circuit (or very high resistance).
If you turn the key to the CRANK position this should change from open to a low resistance.
If it works like this, then the pump driver and ECU are doing their job. What I have described is basically the same checks that Norri posted from JTIS.
Checking the pump side of the harness you can measure resistance through the pump. 1 lead on the RED and 1 lead on the RED-YELLOW. Through the pump you should see a resistance of a few ohms. If the resistance is very high, the pump is dead.
You do not need a "special" motor to use with PWM control. What I don't know is if there is anything designed differently in the pump mechanism itself to make them better to this type of flow control. I would assume that fuel pumps are positive displacement type and the flow is just a linear function of RPM, but I do not know that for a fact.
I haven't done this in a very long time and am going from memory... You will need a proper multi-meter rather than a test light to figure this out.
If you disconnect the white plug in the middle of the harness that runs across the top of the tank you can check a couple of things.
Checking the pump driver side of the harness
With Key on, measure 1 pin at a time to chassis ground.
On the RED pump wire you should see +12V
On the RED-YELLOW pump wire you should see zero volts (or very near it)
On the zero volt pin, switch to resistance measurement and check resistance from RED-YELLOW to chassis ground. You should read an open circuit (or very high resistance).
If you turn the key to the CRANK position this should change from open to a low resistance.
If it works like this, then the pump driver and ECU are doing their job. What I have described is basically the same checks that Norri posted from JTIS.
Checking the pump side of the harness you can measure resistance through the pump. 1 lead on the RED and 1 lead on the RED-YELLOW. Through the pump you should see a resistance of a few ohms. If the resistance is very high, the pump is dead.
You do not need a "special" motor to use with PWM control. What I don't know is if there is anything designed differently in the pump mechanism itself to make them better to this type of flow control. I would assume that fuel pumps are positive displacement type and the flow is just a linear function of RPM, but I do not know that for a fact.
Hello Fulton, Thank You...
I hope you saw my attempt a making amends for my hard headedness, yesterday. I just couldn't pick up what you were putting down,,, as they say...
I will run thru these tests on Saturday...
A couple of questions.
On the red-yellow in the FPM direction... I will test with a DMM as well, but with a test light, if I connect the clamp to a hot source and CRANK,,, I should get light, at least a flicker? Because, as you described, low resistance will be the ability for power to flow, because the PWM is grounding? Do I have that right?
And - the big question...What the hell do I do IF the ECU and/or the FPM are not functioning? Next steps? What do you suggest?
This car has sat for a couple/few years after being partly underwater... In your experience, if I were to get the car running direct grounding the pump getting pressure to the rail,,, and charge starts flowing thru the car and she warms up,,, is it possible that some of these days will kinda come back to life and online? I know that when something goes wrong electrically ok no my xk8,,, it's like a cascade effect and it's not til I have a few drive cycles. Could this be that?
Anyways, thank you for you patience and for coming back to this. Really!
If you stick your test light in the connector with the two legs between the RED and RED-YELLOW wires, then you should see:
Switch the key ON --> light on for 2sec (priming)
Switch key to CRANK --> light stays on while cranking
If you run the pump at full 12V the fuel pressure will most likely be way too high, probably to the point that the car won't run properly. There is no pressure regulator in this system.
If you stick your test light in the connector with the two legs between the RED and RED-YELLOW wires, then you should see:
Switch the key ON --> light on for 2sec (priming)
Switch key to CRANK --> light stays on while cranking
If you run the pump at full 12V the fuel pressure will most likely be way too high, probably to the point that the car won't run properly. There is no pressure regulator in this system.
Will do, Fulton.
I hope I do see something like normal operation of the FPM. I haven't yet... With a known working pump installed, as designed, on key ON I have not gotten a prime interval. I usually don't have a helper but I'll have to figure it out. Small car,,, I'll have to scoot around back in the 2seconds to see light... I may also test to see if I rig my test light to a 12v source,,, the grounding pump control line will light up for the 2second interval at key on. Something's got to give.
I am a LONG ways away from driving the car. Loooong ways. I expect over fueling and high rail pressures. This will just be for idling, warm and getting her going under her own power. That's the hope, aim and goal. If she is not running RIGHT RIGHT, I can deal with that for now...
Always open to more, any and all suggestions and guidance
INFO RECEIVED FROM WALBO FUEL PUMP MANUFACTURER ABOUT,,,, WELL SEE BELOW...
I'M NOT SURE IF THIS IS OF ANY VALUE,,, BUT I THOUGHT I WOULD PASS ON A POSSIBLE ALTERNATIVE...
Hello
Walbro fuel pumps are not ECU regulated like your factory pump.
Your pump will have a power wire and a voltage signal from the ECU... where the ECU is acting...ALMOST like a fuel pressure regulator by demanding more or less fuel pressure depending on how much it anticipates the injectors are consuming.
Walbro fuel pumps can only work either on or off...and cannot be controlled like that by an ECU.
Deatchwerks pumps can be controlled in pulse modulated applications... and so can Aeromotive Pumps
12-18-2019 | 12:00 PM
