Re: LT31 1986 DW jerking at 2000-2300 rpm


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Geschrieben von emilio da roma am 01. Februar 2021 21:50:38:

Als Antwort auf: Re: LT31 1986 DW jerking at 2000-2300 rpm geschrieben von Tiemo am 01. Februar 2021 14:58:16:


Does this also occur at standstill, with gearbox in neutral, if you rev up? Does it stop, if you shift to neutral at the speed it occurs at?
If it occurs only in rolling condition, it might be caused by tyres which are out-of-round.

It occurs when the engine and transmission are engaged and when the engine "pulls", it's like.

If it is also uccuring at standstill by reving up the engine, it must be a part of the engine.
1. Maybe ELAB (stop valve) has a loose electrical connection or broken wiring, which ca be testet by checking voltage at its terminal (test lamp, multimeter). Power supply must be uninterrupted at all speeds. If wiring is suspicious, try powering it by external wiring.
2. Also maybe there is air in the fuel system, which can be seen as bubbles rushing through the opaque tube between fuel filter and injection pump when engine is running. If there are bubbles, fuel filter may be clogged or fuel hosing is leaky. If there is air lashing back into the tube, when the engine stops, injection pump itself may be leaky at its shaft seal.
3. Annother cause might be a loose timing belt, which can be found by checking its tension: For the front belt try twisting it between thumb and forefinger, it may not be turnable more than 90° by normal hand force. For the rear belt, it may not be pushable more than half a thumb by normal hand force.
Ciao,
Tiemo

Hello Tiemo, thanks for your message.
The defect is not similar to a misfire, and not like someone repeatedly turning off and on the ignition key: rather it is as if I repeatedly raise and lower the accelerator pedal only a few millimeters, so as to cause a pitch-like oscillation of the vehicle. It occurs when the engine and transmission are engaged and when the engine "pulls". Revving the engine in neutral (or with a gear engaged and clutch depressed) seems to be good as usual. I'll check both belt tensions and air bubbles on the transparent tube. Injection pump has been refurbished by Bosch about 1 year and 7000 Km ago. Injectors have never been replaced nor tested.
Ciao!
emilio



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