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stuzbot Samba Member
Joined: March 30, 2018 Posts: 377 Location: Pining for the Puddles of Yesterday
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Posted: Wed Jan 02, 2019 12:51 pm Post subject: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Here's one that's been niggling at me for a while now:
Ever since I adjusted the timing on my injection pump...
[it was set at 1,6mm of lift when I bought it and the van sounded like a bag of marbles. Now set to 1mm and sounds great]
...I've had this intermittent problem where, sometimes, when I let in the clutch to change gear, or lift my foot off the pedal when stopped at lights, the engine revs don't drop. So that [in the case of being stopped at lights] the engine will be sitting revving at around 1200 or 1300 and I have to lift the clutch pedal a fraction to the biting point, whereupon the revs will drop back and idle normally at 900.
It only seems to happen in 1st or occasionally 2nd gear, when I'm travelling quite slowly and, the rest of the time, the rev counter is rock solid and bang on the 900 mark. Of course, it may be happening at higher speeds too but I just don't notice as the engine is revving quite high then, anyway.
I've checked the obvious, such as making sure neither pedal or throttle cable are sticking anywhere and the throttle lever on the pump itself springs back nice and strongly when I push it forward by hand and release it. So I'm at a bit of a loss as to what else to check now.
As I've said previously on other threads; my pump has undoubtedly been "fiddled about with" by PO as all the adjustment screws are missing their sealing paint and/or tags and [as mentioned above] the timing was off by a ridiculous amount when I bought it. Unfortunately, as this is a turbo diesel and the pump has an LDA on top [I'm still not sure exactly what that does!] there seem to be a lot more possible adjustment points on it than I'm used to from the normally-aspirated diesels I've always owned before. _________________ *****************************
Click to view image
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1992 VW LT35 2,4D [SOLD]
1993 VW LT35 2,4D [SOLD]
1992 VW T3 1,6TD Syncro [SOLD]
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?Waldo? Samba Member
Joined: February 22, 2006 Posts: 9752 Location: Where?
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Posted: Wed Jan 02, 2019 12:53 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Post a pic of the cold start side of the pump (block side - a pic looking into the space between pump and block) so I can see if your pump has the later fast-idle linkage. |
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stuzbot Samba Member
Joined: March 30, 2018 Posts: 377 Location: Pining for the Puddles of Yesterday
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Posted: Wed Jan 02, 2019 12:56 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Wilco.
It'll have to be tomorrow though. It's Dark O'clock over here now. _________________ *****************************
Click to view image
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1992 VW LT35 2,4D [SOLD]
1993 VW LT35 2,4D [SOLD]
1992 VW T3 1,6TD Syncro [SOLD]
***************************** |
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?Waldo? Samba Member
Joined: February 22, 2006 Posts: 9752 Location: Where?
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Posted: Wed Jan 02, 2019 4:40 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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It is usually simply the accelerator lever stop screw is too far out. On the older pumps that means that the idle is set too high. On the newer pumps, there are two additional screws for low/high idle so you can lower the accelerator lever stop screw (called the 'residual pressure screw") and then raise the idle to where it was previously.
Another potential cause that is more rare is one or more injector that is peeing a stream below break pressure. |
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stuzbot Samba Member
Joined: March 30, 2018 Posts: 377 Location: Pining for the Puddles of Yesterday
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Posted: Mon Jan 21, 2019 12:41 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Whoops! –that "tomorrow" turned into a bit of a spanish "mañana". I kept forgetting to get out there and snap some pics of my injector pump. It didn't help that the weather's been cold, grey and damp for about the past fortnight. Anyway, here she goes –from as many angles as possible:
_________________ *****************************
Click to view image
*****************************
1992 VW LT35 2,4D [SOLD]
1993 VW LT35 2,4D [SOLD]
1992 VW T3 1,6TD Syncro [SOLD]
***************************** |
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?Waldo? Samba Member
Joined: February 22, 2006 Posts: 9752 Location: Where?
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Posted: Mon Jan 21, 2019 8:51 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Your pump does not have the cold start fast idle setup. With pumps that do not have the cold start fast idle setup, 99% of the time, hanging revs are caused simply by the idle speed being set too high. What is your engine idle speed? |
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stuzbot Samba Member
Joined: March 30, 2018 Posts: 377 Location: Pining for the Puddles of Yesterday
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Posted: Tue Jan 22, 2019 4:02 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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?Waldo? wrote: |
Your pump does not have the cold start fast idle setup...
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Hmmm... so bang goes that theory then
?Waldo? wrote: |
With pumps that do not have the cold start fast idle setup, 99% of the time, hanging revs are caused simply by the idle speed being set too high. What is your engine idle speed? |
When it's idling normally, it sits bang on the line under the 1000 RPM one –so about 700 - 800?
When it's over-running, it usually only drops down to somewhere in the region of about 1200 - 1500 and sits there until I slightly blip the clutch pedal, at which point it'll drop back to normal and sit solid on the 700 - 800 line again.
So it definitely seems like the problem is with the revs sometimes not dropping all the way back down to where they should, rather than the idle speed being too high to start with because, when it does drop down all the way to the idle speed, it's always rock steady and always bang on that line.
I'm mostly seeing this in stop-start traffic in town, where I'll rev slightly to inch forward a bit snd then drop the clutch to stop again and find that the revs don't drop back down –or sometimes do drop down but do so really slowly. I'm sure it happens other times though, when it's just not so noticeable as, on the odd occasion when I'm running quite slowly in normal traffic, I'll lift my foot off the accelerator and the van will keep travelling at the same speed. It's almost like having cruise control.
As I said though, it only happens at slowish speeds and lowish revs. Maybe there's a sticking point in that band somewhere between 1000 - 2000? Or maybe it's just that, at higher speeds there's more tension on the throttle so it snaps back down harder?
I'm at a bit of a loss as to what's causing it. As I said, nothing seems to be physically sticking anywhere along the route from accelerator pedal to throttle lever. And the levers on the pump all feel pretty springy and snappy too. _________________ *****************************
Click to view image
*****************************
1992 VW LT35 2,4D [SOLD]
1993 VW LT35 2,4D [SOLD]
1992 VW T3 1,6TD Syncro [SOLD]
***************************** |
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zuhandenheit Samba Member
Joined: June 27, 2008 Posts: 846
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Posted: Tue Jan 22, 2019 6:25 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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I think it would be interesting to see what happens if you set the timing back to 1.6. Maybe the timing change is the direct cause, maybe it's incidental -- e.g., something was disturbed in the process of changing timing, and maybe it's a red herring. |
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CohPro Samba Member
Joined: January 14, 2019 Posts: 6 Location: UK
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Posted: Tue Jan 22, 2019 7:17 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Throttle cable is routed incorrectly and looks to be over adjusted as the levers don't look to be going back to their stops. |
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?Waldo? Samba Member
Joined: February 22, 2006 Posts: 9752 Location: Where?
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Posted: Tue Jan 22, 2019 9:03 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Yeah, something is hanging up the cable. You want the routing to be as relaxed as it can be. Try going under that hose rather than over it.
Also, get an anti-vibration clamp over the 4 metal lines or they will work harden and crack from the engine vibrations. |
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stuzbot Samba Member
Joined: March 30, 2018 Posts: 377 Location: Pining for the Puddles of Yesterday
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Posted: Tue Jan 22, 2019 9:51 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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zuhandenheit wrote: |
I think it would be interesting to see what happens if you set the timing back to 1.6... |
I have wondered that, in passing, myself. But the engine sounded so rough back then and sounds so much better now that I think I'd rather put up with the sticky throttle than go back to that again
CohPro wrote: |
Throttle cable is routed incorrectly and looks to be over adjusted as the levers don't look to be going back to their stops. |
?Waldo? wrote: |
Yeah, something is hanging up the cable... Try going under that hose rather than over it... |
Interesting. Can you point out on one of the pics where you think that's happening. I'm not near the van at the mo but I don't think the cable isn't as near that hose [assuming you mean the fuel hose] as it maybe looks on those photos. And I'm 99% sure it is resting against the stop. Again the photos might be misleading.
I could be wrong though. I think I may have re-routed some pipes while replacing the leak-off pipes. So that sounds like a hopeful avenue to explore.
?Waldo? wrote: |
Also, get an anti-vibration clamp over the 4 metal lines or they will work harden and crack from the engine vibrations. |
On the never-ending todo list! _________________ *****************************
Click to view image
*****************************
1992 VW LT35 2,4D [SOLD]
1993 VW LT35 2,4D [SOLD]
1992 VW T3 1,6TD Syncro [SOLD]
***************************** |
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CohPro Samba Member
Joined: January 14, 2019 Posts: 6 Location: UK
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Posted: Tue Jan 22, 2019 9:59 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Cable goes over coolant hose not under.
Just disconnect the cable and see if it behaves properly. |
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?Waldo? Samba Member
Joined: February 22, 2006 Posts: 9752 Location: Where?
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Posted: Tue Jan 22, 2019 10:48 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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stuzbot wrote: |
Interesting. Can you point out on one of the pics where you think that's happening. I'm not near the van at the mo but I don't think the cable isn't as near that hose [assuming you mean the fuel hose] as it maybe looks on those photos. And I'm 99% sure it is resting against the stop. Again the photos might be misleading.
I could be wrong though. I think I may have re-routed some pipes while replacing the leak-off pipes. So that sounds like a hopeful avenue to explore.
?Waldo? wrote: |
Also, get an anti-vibration clamp over the 4 metal lines or they will work harden and crack from the engine vibrations. |
On the never-ending todo list! |
I assume what is happening is that when the accelerator lever on the pump is moved just a small distance, the return spring does not exert enough force to consistently return the lever to its proper stop location. That could be caused by resistance in several locations, including the cable, the accelerator lever shaft/bushing in the pump, the front accelerator pedal/lever assembly. Most likely culprit is the cable.
CohPro wrote: |
Cable goes over coolant hose not under.
Just disconnect the cable and see if it behaves properly. |
JX was not offered in North America so I'll take your word on the stock routing. Looking at online images of the JX, the pics seem to be split with ~1/2 over and ~1/2 under the coolant hose. Whichever way kinks the cable less would exert less stress on the cable and would be preferred regardless of whether or not that routing is stock. |
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zuhandenheit Samba Member
Joined: June 27, 2008 Posts: 846
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Posted: Tue Jan 22, 2019 11:00 am Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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Quote: |
[quote="stuzbot"]
zuhandenheit wrote: |
I think it would be interesting to see what happens if you set the timing back to 1.6... |
I have wondered that, in passing, myself. But the engine sounded so rough back then and sounds so much better now that I think I'd rather put up with the sticky throttle than go back to that again
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Right, I just meant as a test.
But anyway it's almost certainly the cable! |
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outcaststudios Samba Member
Joined: February 09, 2015 Posts: 1732 Location: Maine
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Posted: Sat Sep 19, 2020 2:45 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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the routing of the throttle cable:
does it always need to travel through the hole in the firewall with the rubber bushing? when i place my replacement diesel throttle cable cable through that way , its too short. i found that if i ran it the way the OP has it run here, i get JUST enough to be ale to clip it without moving the throttle arm. i dont like this configuration becasue now there is diagonal play that couses the movement to be restricted and so you have to push very hard on the peddle to engage. then it revs up super fast becaseu the tension is restricted. so my question is: are there two different length replacements availabel? for US vs. Euro markets? and is thee another area to look for hangups. as far as i can tell ive checked everything front to back. thanks. oh and also if there is a better thread to ask this in let me know i spent about an hour in search trying to find the right one and didnt want to make a thread. _________________ '88Doka JX td
'69 westy
(rip)couple bugs
(rip)three type III"s
(rip) '81 vanagon
a bunch of french stuff,and 9 motorcycles.
https://www.thesamba.com/vw/classifieds/detail.php?id=2573791 |
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Zeitgeist 13 Samba Member
Joined: March 05, 2009 Posts: 12115 Location: Port Manteau
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Posted: Sat Sep 19, 2020 2:55 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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I have a stock diesel accelerator cable in my mTDI van, and I cut out the entire firewall, so the cable just runs freely up to the pump. So long as it's free and not resting on something it shouldn't, I don't see any reason why it can't bypass the firewall and just mount directly to the pump bracket. _________________ Casey--
'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik? |
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outcaststudios Samba Member
Joined: February 09, 2015 Posts: 1732 Location: Maine
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Posted: Sat Sep 19, 2020 3:52 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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hmm. that's good to know. i'll have to move it around and find a spot that is better geometry. _________________ '88Doka JX td
'69 westy
(rip)couple bugs
(rip)three type III"s
(rip) '81 vanagon
a bunch of french stuff,and 9 motorcycles.
https://www.thesamba.com/vw/classifieds/detail.php?id=2573791 |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9920 Location: Orbiting San Diego
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Posted: Sat Sep 19, 2020 4:23 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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There are 2 different length diesel throttle cables used in the US (and more in the rest of the world)
81/82 diesels have the engine and tranny mounted in a similar position as aircooled vans did, as far as front to rear position.
In 83 diesels the tranny and engine were moved back a little, to a similar front to rear position as wbx would also share. This happened mostly to allow the new longer 5 speed tranny to fit.
So diesels from 83-on use a cable 35mm longer than 81/82 do.
The longer cable part number is 251 721 555S
(short cable is 251 721 555C)
Tthe above numbers are for 2wd LHD vehicles like the US models.
Mark
outcaststudios wrote: |
..... so my question is: are there two different length replacements availabel? for US vs. Euro markets? ..... |
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outcaststudios Samba Member
Joined: February 09, 2015 Posts: 1732 Location: Maine
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Posted: Sat Sep 19, 2020 4:37 pm Post subject: Re: 1,6TD JX –Sometimes Revs Not Dropping When Easing Off Throttle |
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let me guess, the earlier cable is shorter by about an inch and some change? to me it looks like the later cable is what i need, if that is the longer of the two, as you said they moved the location of the arm back so that would make sense.
*edit* LOL i didtn see that you say the exact length 35mm above im getting old and yes its about the difference. _________________ '88Doka JX td
'69 westy
(rip)couple bugs
(rip)three type III"s
(rip) '81 vanagon
a bunch of french stuff,and 9 motorcycles.
https://www.thesamba.com/vw/classifieds/detail.php?id=2573791 |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9920 Location: Orbiting San Diego
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