Reply
 
Thread Tools Search this Thread
 
Old 18 July 2018, 15:28   #11
Member
 
Country: UK - Wales
Town: Pembroke
Boat name: Rapscallion
Make: Humber Destroyer 6.0
Length: 5m +
Engine: Yam 150 HPDI
Join Date: Jul 2006
Posts: 83
Tonight's update - and a theory to test........

New TPS is definitely under-reading (3.99 Volts at wide-open / corresponds to 75' open on YDS). I can't account for this as input voltage is correct (5.0 Volts), throttles are coming to within a mil or two of their stops and there's no lost motion in the shaft to the TPS........however the plot thickens.....
Running YDS engine monitor at idle and up to 1600 rpm in gear (fastest I can safely go on muffs), Oxygen sensor voltage is basically flat - wavers between 0.2-0.3 volts. So I have a theory..........
Fuel control must be closed-loop at at least some rev ranges (otherwise why would it have an oxygen sensor?), maybe open loop, based on engine speed and throttle position at others. If the Oxygen sensor were working, it would adjust fuelling at least in its closed-loop range, based on the O2 sensor, adjusting for any discrepancies in the TPS. However if the O2 sensor has failed, it will have to resort to open-loop fuel control, the only inputs it's got being engine speed and throttle control. If it thinks the throttles are only 75' open when they're infact 90', it'll under fuel, run lean and make less power - exactly what I'm seeing.

So, a few questions:-
  • Does anyone kow the fuel control strategy for these engines (open loop / closed loop and when it runs in each)
  • Does anyone know how to test the O2 sensor?
  • Does anyone have a spare O2 sensor (600 for a new one - kinda expensive to just try it)
  • Anything I've missed?

Also - one strange thing. When I do a "drop cylinder" test at idle via YDS, the engine speed increases when the cylinder is dropped (from 700 to around 1300 revs). It's exactly the same for all 6 cylinders. Anyone come across this before?

Incidentally fuel pressures are spot on at 5bar MP and 700psi HP

Tomorrow I'll be checking the resistances of all the injectors & coils as a basic check, however I can't find the resistance specifications in the Yam workshop manuals - does anyone know them?
__________________

__________________
Jon Tallis is offline   Reply With Quote
Old 19 July 2018, 06:19   #12
Member
 
Country: UK - England
Town: penzance
Boat name: not named
Make: ski boat
Length: 5m +
Engine: 150 HPDI
Join Date: Sep 2013
Posts: 212
I have the same engine, but I've thankfully not had to get in as deep as you've gone.
If nobody can give you stock answers then I can get measuring stuff for you
__________________

__________________
simonl is offline   Reply With Quote
Old 19 July 2018, 06:42   #13
Member
 
Country: UK - England
Town: penzance
Boat name: not named
Make: ski boat
Length: 5m +
Engine: 150 HPDI
Join Date: Sep 2013
Posts: 212

worth trying..


Good article https://www.thehulltruth.com/335856-post6.html
__________________
simonl is offline   Reply With Quote
Old 19 July 2018, 07:11   #14
Member
 
Country: UK - England
Town: penzance
Boat name: not named
Make: ski boat
Length: 5m +
Engine: 150 HPDI
Join Date: Sep 2013
Posts: 212
Quote:
Originally Posted by Jon Tallis View Post
New TPS is definitely under-reading (3.99 Volts at wide-open / corresponds to 75' open on YDS). I can't account for this as input voltage is correct (5.0 Volts), throttles are coming to within a mil or two of their stops and there's no lost motion in the shaft to the TPS........however the plot thickens.....
Running YDS engine monitor at idle and up to 1600 rpm in gear (fastest I can safely go on muffs), Oxygen sensor voltage is basically flat - wavers between 0.2-0.3 volts.
Have you tried depriving it of air, making the mixture richer to look for changes in the lambda sensor voltage?
__________________
simonl is offline   Reply With Quote
Old 20 July 2018, 16:35   #15
Member
 
Country: UK - Wales
Town: Pembroke
Boat name: Rapscallion
Make: Humber Destroyer 6.0
Length: 5m +
Engine: Yam 150 HPDI
Join Date: Jul 2006
Posts: 83
Adjusting the TPS at idle would definitely do that. Will try it tomorrow, you're right will definitely show up a non-functioning O2 sensor - if it runs closed loop at idle that is??

Quote:
Originally Posted by simonl View Post
Have you tried depriving it of air, making the mixture richer to look for changes in the lambda sensor voltage?
__________________
Jon Tallis is offline   Reply With Quote
Old 20 July 2018, 17:50   #16
Member
 
Country: UK - England
Town: penzance
Boat name: not named
Make: ski boat
Length: 5m +
Engine: 150 HPDI
Join Date: Sep 2013
Posts: 212
Quote:
Originally Posted by Jon Tallis View Post
Adjusting the TPS at idle would definitely do that. Will try it tomorrow, you're right will definitely show up a non-functioning O2 sensor - if it runs closed loop at idle that is??
I can't see that it would matter if it's closed or open loop for this test - it'll change the sensor output. Whether the ECU acts upon that is another matter...
__________________
simonl is offline   Reply With Quote
Old 22 July 2018, 09:30   #17
Member
 
mhb100's Avatar
 
Country: UK - England
Town: Swindon
Boat name: Ballistic
Make: Ballistic
Length: 7m +
Engine: Yam 250 Yam 15
Join Date: May 2007
Posts: 206
I thought the o2 did very little above 1500 revs, but my hpdi 250 does not have one. You have checked what I would have suggested as it's silky smooth both on tick over and at above 4000. If not I'd have suggested vacuum /throttle sync /tps, etc. You've done all the filters but what is YDS saying about your HP Psi. I'd take it for a spin and take some measurements. Hook up by removing trim switch so you can keep cowling on. I'll look in by workshop manual. Personally I'd go on the USA forum like the Hull Truth and marineengine. Com. There is an expert goes by the name of rodbolt (I think) who seems to know more than anyone else I know of, but not sure if still active.
__________________
mhb100 is offline   Reply With Quote
Old 22 July 2018, 09:32   #18
Member
 
mhb100's Avatar
 
Country: UK - England
Town: Swindon
Boat name: Ballistic
Make: Ballistic
Length: 7m +
Engine: Yam 250 Yam 15
Join Date: May 2007
Posts: 206
What Psi are your cylinders giving?
__________________
mhb100 is offline   Reply With Quote
Old 22 July 2018, 09:42   #19
Member
 
mhb100's Avatar
 
Country: UK - England
Town: Swindon
Boat name: Ballistic
Make: Ballistic
Length: 7m +
Engine: Yam 250 Yam 15
Join Date: May 2007
Posts: 206
When you changed mystery filters how many did you change? and did you change the ones in the injectors?
__________________
mhb100 is offline   Reply With Quote
Old 22 July 2018, 10:22   #20
Member
 
mhb100's Avatar
 
Country: UK - England
Town: Swindon
Boat name: Ballistic
Make: Ballistic
Length: 7m +
Engine: Yam 250 Yam 15
Join Date: May 2007
Posts: 206
Had a quick look on some other posts. If your coils, hp psi, cylinder psi, and fuel regulator screen (in top of vst) are all good, and your 100% sure your on all 6 cylinders then perhaps best to get the injectors tested and cleaned. I expect your throttle adj and reeds are all OK but that's all I can think of.
__________________

__________________
mhb100 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 20:15.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.