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DIESEL engine increase RPM when clutch is pushed+neutral
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Kfumer
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PostPosted: Fri Oct 29, 2021 8:28 am    Post subject: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

Hi everyone, hoping someone out there can help me with an engine issue.

Quick backstory, I got a 1.9T diesel engine installed in my 1989 Vanagon. The previous engine was a 1.6T

When I received the engine from the mechanic in Greece, it seemed fine. I then drove to Germany and started noticing that when I would push in the clutch and took my foot off the gas, the engine would skyrocket and Rev. This never happened on the highway.

I shipped the van back to Canada and now the engine has the problem almost every time I drive.
I took it to a busy mechanic and we quickly made sure it is not the throttle cable getting caught.
He suggested that I just turn off and on my engine when I'm at a red light or longer stop, because it now almost never is able to sit in neutral without the engine racing up.
Similarly, between gears the engine races.
It dies back down when I depress and let out the clutch.

Any and all advice back would be apprciated! I have looked on various threads for week and dont see something that has helped so far


Last edited by Kfumer on Mon Nov 01, 2021 3:19 pm; edited 1 time in total
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danfromsyr
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PostPosted: Fri Oct 29, 2021 9:43 am    Post subject: Re: Engine continues to increase RPM when clutch is pushed+neutral Reply with quote

check the spring return on the injection pump throttle lever..
add an 'temporary' additional return spring to verify it's behavior.
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CdnVWJunkie Premium Member
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PostPosted: Sat Oct 30, 2021 8:16 pm    Post subject: Re: Engine continues to increase RPM when clutch is pushed+neutral Reply with quote

This sounds like diesel runaway.
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crazyvwvanman
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PostPosted: Sun Oct 31, 2021 8:42 am    Post subject: Re: Engine continues to increase RPM when clutch is pushed+neutral Reply with quote

Yes, the word DIESEL should have been included in the subject line.

That would get the attention of more people in the know.

It can still be added.

Mark
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DuncanS
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PostPosted: Sun Oct 31, 2021 9:36 am    Post subject: Re: Engine continues to increase RPM when clutch is pushed+neutral Reply with quote

Try running it without any oil and see it it still does it. Joke, but sounds like it's running on the oil. Serious and needs immediate attention. Agree with diesel runaway.

Duncan
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Kfumer
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PostPosted: Mon Nov 01, 2021 3:18 pm    Post subject: Re: Engine continues to increase RPM when clutch is pushed+neutral Reply with quote

danfromsyr wrote:
check the spring return on the injection pump throttle lever..
add an 'temporary' additional return spring to verify it's behavior.


The mechanic also checked the spring return and it seemed to be in fine shape and pulled back the lever...
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Kfumer
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PostPosted: Mon Nov 01, 2021 3:20 pm    Post subject: Re: Engine continues to increase RPM when clutch is pushed+neutral Reply with quote

crazyvwvanman wrote:
Yes, the word DIESEL should have been included in the subject line.

That would get the attention of more people in the know.

It can still be added.

Mark



Thanks Mark, I changed the title
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Kfumer
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PostPosted: Mon Nov 01, 2021 3:23 pm    Post subject: Re: Engine continues to increase RPM when clutch is pushed+neutral Reply with quote

DuncanS wrote:
Try running it without any oil and see it it still does it. Joke, but sounds like it's running on the oil. Serious and needs immediate attention. Agree with diesel runaway.

Duncan


Thanks for the response Duncan
Because it mostly runs fine, I have actually been driving it for a couple of months. At first it would do the runaway thing once a week, and now it is happening every other time I drive

The mechanic suggested I just turn the van off at red lights or long stops...and not to have my foot on the clutch, holding it at the moment of release. That is the only way the engine stops revving like crazy. When I'm 'just' about to give it gas and let the clutch out completely.

Is runaway diesel a thing that happens often with these vans?
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?Waldo?
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PostPosted: Mon Nov 01, 2021 3:29 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

If you can turn it off with the key when it is revving, then it is *not* diesel runaway. You say you can turn it off, so it is clearly not diesel runaway.

It sounds like simply your 'residual pressure' screw on the injection pump is too high. It is the screw the accelerator lever rests on when at idle. Post pics of your pump, though, as it might be different depending on the pump model. Be sure to get the cold start lever in the pics.
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Kfumer
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PostPosted: Mon Nov 01, 2021 4:02 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

?Waldo? wrote:
If you can turn it off with the key when it is revving, then it is *not* diesel runaway. You say you can turn it off, so it is clearly not diesel runaway.

It sounds like simply your 'residual pressure' screw on the injection pump is too high. It is the screw the accelerator lever rests on when at idle. Post pics of your pump, though, as it might be different depending on the pump model. Be sure to get the cold start lever in the pics.


Thanks for the response.
Yes it does not continue to rev as soon as I shut it off. When I turn the van back on it sometimes starts revving up again, but from low RPM. It does not continue where it left off.

Its funny you comment on the cold start lever...it turns out the shop who put the new engine in did not attach the cold start lever. So the fact you mentioned it, could be the problem!

Attached are the pictures. I should mention that the blue hose just goes nowhere. I'm not an engine person at all so have no idea where it is going or what it is for

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.
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?Waldo?
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PostPosted: Mon Nov 01, 2021 4:34 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

Definitely check to make sure your accelerator cable is not binding and that the accelerator lever on the pump moves freely.

Your pump is a JX (1.6TD Vanagon) pump. Glad I asked for pics. There are not independent idle and residual pressure screws.

Try this... loosen the 10mm locknut, rotate that screw 2 full turns CW, tighten the locknut.

The idle will be lower. Hopefully not too low. Hopefully that cures the revving.
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ndorian
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PostPosted: Mon Nov 01, 2021 4:40 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

Blue hose probably went to a boost gauge. Isn't the cold start cable lever down lower though?
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?Waldo?
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PostPosted: Mon Nov 01, 2021 6:00 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

The blue hose should connect to the intake manifold inlet flange. There should be a small nipple there to attach to. That is what causes the boost fuel enrichment. With it connected and the boost fuel enrichment functioning properly, you will gain a decent amount of max power.

The cold start lever not being connected will be an issue if you ever try to start in colder weather. On the IDI engines I prefer to use it with a cold start even in hot weather.
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ndorian
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PostPosted: Mon Nov 01, 2021 6:11 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

I pretty much always (have to) use mine. Sometimes forget to push it back in for a while. Could you leave it pulled out all the time?
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RolandD
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PostPosted: Tue Nov 02, 2021 4:24 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

What does it do with the clutch out in neutral?

Roland
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Kfumer
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PostPosted: Wed Nov 03, 2021 10:32 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

RolandD wrote:
What does it do with the clutch out in neutral?

Roland


with the clutch out in neutral it still revs up to a scream. I have to put the clutch in, find a gear, and then slowly let the clutch out to calm it down...very strange
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?Waldo?
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PostPosted: Thu Nov 04, 2021 8:23 am    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

...lower the idle and report back.
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RolandD
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PostPosted: Thu Nov 04, 2021 7:43 pm    Post subject: Re: DIESEL engine increase RPM when clutch is pushed+neutral Reply with quote

OK, try what waldo says, or disconnect the throttle linkage. If it still runs fast, Waldo is right.

Roland
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