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#1 2020-10-27 09:07:09

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

The mysteries of the DW8B engine

Well guys.
This is the start of a thread wich i hope will be long and educational. First up is something that has been bothering me for a while. I can't seem to find out anything about the purpose of the throttle pos sensor and the MAF sensor. Is the only purpose of these sensors emission control/EGR, or is it more to it than that? Is there some more advanced engine-control there somewhere?

Secondly I would greatly appreciate a complete diagram of the vacuum system of this engine.


2003 Citroen Jumpy 1.9D

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#2 2020-10-27 21:27:16

Shakes
Member
From: Exeter
Registered: 2016-03-24
Posts: 99

Re: The mysteries of the DW8B engine

Hi Jumpy Joe, I'll kick the replies off with this, which may or may not help. I'm running my DW10RHZ engine with the MAF sensor disconnected, and have been for several months now.  It was done to stop the excessive blasts of black exhaust smoke I was seeing under acceleration.

The effects of disconnecting the MAF have been: 
(1) no more smoke
(2) slightly higher fuel consumption
(3) annoying turbo lag at low revs

Whether the sensor needs cleaning, or whether it is incompatible with my engine variant, I haven't got round to investigating yet. It was an eBay purchase, and fits the hose fine, but clearly it wasn't doing a great job at maintaining the correct air/fuel mix to the engine. 

I plan to replace it with an OEM part soon....not particularly cheap in the UK.

Hoping to use my van for a Norway trip in the future!

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#3 2020-10-28 13:46:27

tee_cee
Member
Registered: 2016-03-18
Posts: 318

Re: The mysteries of the DW8B engine

The MAF sensor is related to the EGR. Since diesel engines take all the air they can get, the ECU can work out the theoretical mass of air. However when the EGR opens, the air intake will reduce, so the MAF is used to measure this difference. The ECU will use this information to fine tune the EGR position and injected fuel.

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#4 2020-10-28 13:54:58

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

Re: The mysteries of the DW8B engine

Thanks, Tee_Cee. So with the EGR vacuum tubes blocked off, the MAF is actually redundant?


2003 Citroen Jumpy 1.9D

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#5 2020-10-28 15:29:17

tee_cee
Member
Registered: 2016-03-18
Posts: 318

Re: The mysteries of the DW8B engine

Jumpy-Joe wrote:

Thanks, Tee_Cee. So with the EGR vacuum tubes blocked off, the MAF is actually redundant?

Probably not, if the MAF measures the intake air temperature as well.

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#6 2020-10-29 07:41:19

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

Re: The mysteries of the DW8B engine

Drove to work today, with the MAF unplugged... no difference, what so ever. Will check the TPS this afternoon, see if the voltage equals the one written on the tag.

Last edited by Jumpy-Joe (2020-10-29 07:44:23)


2003 Citroen Jumpy 1.9D

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#7 2020-10-29 18:35:26

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

Re: The mysteries of the DW8B engine

Checked the TPS, and it was at 1 volt on idle. It was impossible to get it up to 2,45 as the tag stated. Got it up to about 2 volts... So I will see after driving to work tomorrow.


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#8 2020-10-30 03:27:20

JohnDragonMan
Member
From: Derby, East Midlands, UK
Registered: 2020-06-02
Posts: 117
Website

Re: The mysteries of the DW8B engine

i had an old XUD 306.. it was really slow. it ended up being a blocked fuel filter. maybe worth looking into if its never been changed...


- JohnDragonMan
Notice: I have the tendency to void warranties, blow fuses, cause fires, and other fun stuff.
Words of wisdom: There's always user serviceable parts inside. Internally rust proof the sills! both skins!!. "Oh that shouldn't have happened".
My Crazy Mk2 2005 Dispatch Camper Project big_smile

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#9 2020-10-30 06:27:46

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

Re: The mysteries of the DW8B engine

Filter has been changed, and the air intake cleaned when I replaced the glow plugs.


2003 Citroen Jumpy 1.9D

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#10 2020-10-31 19:36:07

kenbw2
Member
From: Anywhere the van takes me
Registered: 2017-11-26
Posts: 633

Re: The mysteries of the DW8B engine

My understanding is that the fuel pump on the DW8B is electronically advanced/retarded, which I assume to be based on the input from the MAF sensor. Maybe worth considering that?


2000 Citroen Dispatch 1.9TD XUD9 Camper Conversion + full time home
1999 Citroen Dispatch 1.9D DW8 Disassembled Camper Conversion
1996 Peugeot 806 1.9TD XUD9 Spare vehicle
1998 Citroen Synergie 1.9TD XUD9 Snapped timing belt

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#11 2020-11-01 08:25:36

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

Re: The mysteries of the DW8B engine

Yeah. I am still learning about this engine. The pump is partially electric part mechanical controlled. But the electric part varies from car to car, and that makes it a bit difficult. Some has electric advance, some have mechanical, and I haven’t found out which I have yet. And if my engine has the needle lift sensor on one of the injectors or not... The one thing I do know, is the doesn’t run smoothly at medium load and medium throttle.


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#12 2020-11-05 17:53:54

vaz2121
Member
From: Glasgow Living:~ SW. Scotland
Registered: 2015-08-31
Posts: 1,012

Re: The mysteries of the DW8B engine

Jumpy-Joe wrote:

Yeah. I am still learning about this engine. The pump is partially electric part mechanical controlled. But the electric part varies from car to car, and that makes it a bit difficult. Some has electric advance, some have mechanical, and I haven’t found out which I have yet. And if my engine has the needle lift sensor on one of the injectors or not... The one thing I do know, is the doesn’t run smoothly at medium load and medium throttle.

I'm led to believe apart from all thats been said about EGR that the MAF also does signal the ECU with air flow and temp to determine air density along with TPS info to determine fueling unlike an HDI it's minimal input on a DW8.............
Usualy it's a wire on 3rd injector on these I believe it on the 4th .......... last injector nearest G/box.............

On our 306 with DW8 ............It's Bosch pump rather than the Lucus/ Delphi thats on Van plus being 5 yrs older No electronics at all.................
I also feel that the 306 starts easier and runs smoother/better than the van and has covered more than twice the milage of Van

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#13 2020-11-05 18:33:58

Casper
Member
From: East Lothian
Registered: 2015-12-20
Posts: 1,681

Re: The mysteries of the DW8B engine

kenbw2 wrote:

My understanding is that the fuel pump on the DW8B is electronically advanced/retarded, which I assume to be based on the input from the MAF sensor. Maybe worth considering that?

Does the MAF kick in instantly? Reason i ask when cold my van is a judders when taking up drive. Almost the same feeling you get with a contaminated clutch. Wondering is a wee MAF clean or replace may cure it. Only way i can cure it is take up drive like i stole it. Once warm it seems great.

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#14 2020-11-06 03:30:02

vaz2121
Member
From: Glasgow Living:~ SW. Scotland
Registered: 2015-08-31
Posts: 1,012

Re: The mysteries of the DW8B engine

Casper wrote:
kenbw2 wrote:

My understanding is that the fuel pump on the DW8B is electronically advanced/retarded, which I assume to be based on the input from the MAF sensor. Maybe worth considering that?

Does the MAF kick in instantly? Reason i ask when cold my van is a judders when taking up drive. Almost the same feeling you get with a contaminated clutch. Wondering is a wee MAF clean or replace may cure it. Only way i can cure it is take up drive like i stole it. Once warm it seems great.

My van is fitted with a Wax Stat with a cable running off it.............

Although Both the 306 and a 26 yr old mk3 golf Ive got are on Bosch pumps and are different to the Lucus/Delphi set up.... In operation the wax stat on them should  essentially do the same thing............. The Wax Stat on 306 has never apparently worked in all the time We've owned it.........
I say apparently It's not always noticable that you've got a few extra revs at idle until enough heat builds up............

Wax in the stat when Cold is thick gloopy/solid and in turn triggers/turns on extra Fuel/Timing and revs and as heat builds in engine the wax becomes more liquid and reduces the extra fuel and revs ETC at idle a bit like back in the day with a choke on a carb fed egine............

I have no idea if there is any influence from the ecu where cold running is concerned on the DW8/B .........


On the Bosch pump {No electronics} anyway this only applies up to approx 1200 RPM after that all is supposedly normal............

Although after 7 yrs use with my Ex before my eldest Daughter got it and  then it's return to me ...........
God knows who got to F*** about with it  But I reset the Wax Stat and a Few other pump settings as it drove/Run like a bag of S***...............

My van is much the same as yours when cold.............
On occasion I'll get a little shudder when taking up clutch ........Mostly noticeable if on a incline...........
but Ok when warmed up or hotter days.......... I've  just put it down to age...........

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#15 2020-11-06 12:08:14

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

Re: The mysteries of the DW8B engine

Quite a few checking points... This morning I drove straight off with cold engine... shuddered badly. Started up again after 3 hours, still shuddering... drove 500m and stopped. Started up again after 5 minutes and drove off. No shuddering and felt like all the power was back. This is strange... Could it be something electrical?


2003 Citroen Jumpy 1.9D

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#16 2020-11-27 12:37:43

Jumpy-Joe
Member
From: Norway
Registered: 2020-08-17
Posts: 27

Re: The mysteries of the DW8B engine

Found the connector for the needle lift sensor the other day... Had a little bit of water in it, so I dried it up and sprayed some electronic cleaner in it. No change in how the van runs, so I decided to unplug the sensor while the engine was still running... Well it seems that the sensor is functioning... the enginge had a bit of a fit with the sensor unplugged. tongue  So I am none the wiser...
Where is the plug for the advance solenoid? It will be the next to check out...


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