12HT engine on HJ60 jerks on low speed

Submitted: Friday, May 24, 2013 at 13:12
ThreadID: 102389 Views:2659 Replies:6 FollowUps:5
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I have recently installed rebuilt 12HT engine on HJ60 with its turbo. I have notice when I am driving at low speed the engine jerks high and low resulting in high and low speed jerks. Is this normal with this engine? Is there a way to fix this problem?
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Reply By: philldeb - Friday, May 24, 2013 at 13:50

Friday, May 24, 2013 at 13:50
Your fuel system could be sucking air
AnswerID: 511749

Follow Up By: Naveed Merchant - Friday, May 24, 2013 at 16:51

Friday, May 24, 2013 at 16:51
Phil... i forgot to mention this happens on high gear such as on 2nd gear when running on low rpm. Seems to work OK on 1st gear
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FollowupID: 790027

Reply By: Ross M - Friday, May 24, 2013 at 16:56

Friday, May 24, 2013 at 16:56
The accelerator/throttle response on a 12HT is far more sensitive to ANY movement of the arm on the pump than a 2h ever is.
My wife could never drive my HJ61 for exactly that reason. Couldn't control it.

The fluctuations may be because the cable pull is in to close to the pivot on the pump arm or the cable outer isn't in an ideally located path and is being affected by slight engine twist at lower speed.

Just 1mm of pull on the cable will give an instant result in throttle setting.

Ross M
AnswerID: 511761

Follow Up By: Naveed Merchant - Friday, May 24, 2013 at 17:16

Friday, May 24, 2013 at 17:16
Is there any solution perhaps any modification that i can try attempting its
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FollowupID: 790033

Follow Up By: Dave B ( BHQ NSW) - Friday, May 24, 2013 at 17:26

Friday, May 24, 2013 at 17:26
I have got a piece of sponge rubber underneath my accelerator pedal to stop that exact problem.
It is far easier to drive now with a slightly heavier pressure needed on the pedal.
Without the sponge rubber there I would get whiplash with the car surging just driving down the road over a few bumps.

cheers
Dave
'Wouldn't be dead for quids'

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FollowupID: 790034

Follow Up By: Ross M - Friday, May 24, 2013 at 18:32

Friday, May 24, 2013 at 18:32
Naveed Merchant
Make sure the cable pull is at 90degrees to the pump arm otherwise it is flicking the throttle open and not smoothly applying it.
Also try moving or fitting another ball end further out from centre on the pump arm.
Of course, check you can get full throttle but it shouldn't be a problem.

Ross M
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FollowupID: 790039

Follow Up By: Naveed Merchant - Saturday, May 25, 2013 at 01:23

Saturday, May 25, 2013 at 01:23
Dave

I have the same problem on 2nd gear whenever there are road bumps while driving on low RPM.

Ross: I will see if the cable pull is at 90% to the pump arm and will also see if I can try moving or fit another ball end further out from centre on pump arm with full throttle setting on the pedal
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FollowupID: 790080

Reply By: Batt's - Friday, May 24, 2013 at 19:23

Friday, May 24, 2013 at 19:23
maybe a heavier return spring
AnswerID: 511770

Reply By: Gregory M - Saturday, May 25, 2013 at 11:15

Saturday, May 25, 2013 at 11:15
Hi Greg here,had the same problem,I moved the accelerator cable where it attaches to the arm of the injector pump further out,I even put a longer arm on it from memory,to increase the travel distance of the cable,other wise I couldnot drive it off road ,it would kangaroo ,problem solved,.....Great car.
AnswerID: 511802

Reply By: Naveed Merchant - Sunday, May 26, 2013 at 22:05

Sunday, May 26, 2013 at 22:05
Thank you so much... I will talk to my mechanic to make attempt with all above suggestions..
AnswerID: 511899

Reply By: Tim HJ61 (WA) - Saturday, Jun 01, 2013 at 22:18

Saturday, Jun 01, 2013 at 22:18
There is no commonly accepted resolution to this problem. People try all sorts of things. We just get used to it.

I use the hand throttle when walking over rocky ground or other places where I need even speed.

Dave B ( BHQ NSW) is one of the more creative solutions I have heard of.
Ross M's is one of the more technically interesting solutions I have heard of.

If you can resolve this problem, let us all know!

Tim
AnswerID: 512345

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