PicoScope 7 Automotive
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Checking inlet metering/ SCV/ volume control valves
Checking inlet metering/ SCV/ volume control valves
Hi,
I fit a lot of Inlet metering/ SCV and volume control valves to different vehicles, I have been using fault codes, slow fuel pressure readings and verifying the signal to diagnose but I am not completely confident that I am always making the correct diagnosis. Are there anymore tests that I could carry out to verify failure? i.e excess duty/ frequency or high amp draw and if so what figures should I expect? I am talking generally speaking as I have replaced ones on Bosch and Denso and systems recently on Ford, Toyota, Vauxhall and Mitsubishi vehicles.
It may not be a one size fits all diagnosis but i'm just wondering if there is anything I can do additional to be almost certain of the cause of the fault.
I fit a lot of Inlet metering/ SCV and volume control valves to different vehicles, I have been using fault codes, slow fuel pressure readings and verifying the signal to diagnose but I am not completely confident that I am always making the correct diagnosis. Are there anymore tests that I could carry out to verify failure? i.e excess duty/ frequency or high amp draw and if so what figures should I expect? I am talking generally speaking as I have replaced ones on Bosch and Denso and systems recently on Ford, Toyota, Vauxhall and Mitsubishi vehicles.
It may not be a one size fits all diagnosis but i'm just wondering if there is anything I can do additional to be almost certain of the cause of the fault.
Re: Checking inlet metering/ SCV/ volume control valves
As with many things we as tech's deal with there is probably only one simple answer. 
"Known Good's" "Known Good's" "Known Good's" "Known Good's" and even more "Known Good's"
You Say:
Preferably upload the "Known Good's" to the Waveform Library and job done!
Kev.
"Known Good's" "Known Good's" "Known Good's" "Known Good's" and even more "Known Good's" You Say:
There is your opportunity! Every time you fit a new one, scope it to within an inch of it's life. that way you will get to see the differences between the faulty one that you tested to start with, and the new shiney one you replaced it with.
Preferably upload the "Known Good's" to the Waveform Library and job done!
Kev.
Re: Checking inlet metering/ SCV/ volume control valves
Ok will do but what should a known good show against say a sticky or slow to react solenoid? I.e high duty, current flow?
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scottpitcher22
- Newbie
- Posts: 1
- Joined: Wed Mar 18, 2015 2:49 pm
Re: Checking inlet metering/ SCV/ volume control valves
Check if the valve is normally open type or closed. If normally open disconnect it and see if the pump can generate full pressure and scope how quickly via rail pressure sensor. If it’s normally closed ground the control wire, if it’s ground controlled and do the same test. If they build full rail pressure and quickly, your fuel supply is good, your pump is good, likely the imv.
If fuel pressure does not build to full pressure or quickly, you can get dummy imv to replace the imv to act as a known good fully open imv. If full fuel pressure is then generated quickly then you have a faulty imv. if it doesn’t you need to test the rest of the fuel system.
If it’s a concern of uneven idle (Renault 1.5dci comes to mind) I scope imv control and current with rail pressure. If rail pressure fluctuates use a math channel to graph duty of the imv to prove the pcm correcting the pressure via imv. Confirm good fuel supply, confirm injector leak back, Quick test as previously mentioned to ensure fuel pump can supply full rail pressure which confirms imv is at fault.
That’s just what I’ve learnt and I’m no way an expert on diesels
If fuel pressure does not build to full pressure or quickly, you can get dummy imv to replace the imv to act as a known good fully open imv. If full fuel pressure is then generated quickly then you have a faulty imv. if it doesn’t you need to test the rest of the fuel system.
If it’s a concern of uneven idle (Renault 1.5dci comes to mind) I scope imv control and current with rail pressure. If rail pressure fluctuates use a math channel to graph duty of the imv to prove the pcm correcting the pressure via imv. Confirm good fuel supply, confirm injector leak back, Quick test as previously mentioned to ensure fuel pump can supply full rail pressure which confirms imv is at fault.
That’s just what I’ve learnt and I’m no way an expert on diesels
Re: Checking inlet metering/ SCV/ volume control valves
Look at what it is commanded to do and what it is doing.
Scope the Power supply, Duty Cycle, Current Draw and FRP Sensor.
I like to drive them with a PWM Emulator, you will need to convince the ECU that it is not unplugged if you emulate it.
Re: Checking inlet metering/ SCV/ volume control valves
Ok so how fast should I expect to see a change in fuel pressure once a higher duty/ demand from acc pedal is applied?
Re: Checking inlet metering/ SCV/ volume control valves
Burt
You can create a larger demand on the HP System using an emulator or as Scott has outlined. Full pressure build up should be almost instant. Within a second.
Using the ACC is a good way to do the test but not the Best !!Ok so how fast should I expect to see a change in fuel pressure once a higher duty/ demand from acc pedal is applied?
You can create a larger demand on the HP System using an emulator or as Scott has outlined. Full pressure build up should be almost instant. Within a second.