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TOPIC: Volvo n12 injection timing

Volvo n12 injection timing 07 Nov 2019 06:36 #204066

  • wedgetail84
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Anyone know how to check the injection timing on an 1990 N12 a td122 in it (intercooled)? It over revved, backfired and died in a cloud of white smoke.

I’ve triple checked for air, intake and exhauSt blockages and all it does is crank with clouds of white smoke but not even a hint of a fire. It’s getting fuel to injectors, and heaps to the pump. The pump drive shaft appears good, to tight and no sign of slippage. It will fire with aerostart. Starting to get desperate I want to check the injection timing - assuming it’s go timing gears so don’t know how it could be out but not sure where else to look right now...

Anyone got any ideas?

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Volvo n12 injection timing 07 Nov 2019 11:15 #204070

  • Blackduck59
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Over revved, how much over rev and for how long? White smoke says timing off, bad injector/s, bad compression or poor fuel supply
Possible valve damage from the over rev. What caused the over rev?
Steve

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Volvo n12 injection timing 07 Nov 2019 12:05 #204071

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Blackduck59 wrote: Over revved, how much over rev and for how long? White smoke says timing off, bad injector/s, bad compression or poor fuel supply
Possible valve damage from the over rev. What caused the over rev?
Steve


I'm with Steve. Pull the Rocker cover Off & check for bent pushrods & valves..

Just my 2 cents worth..
"Be who you are and say what you feel...
Because those that matter...
don't mind...
And those that mind....
don't matter." -

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Volvo n12 injection timing 07 Nov 2019 16:57 #204076

  • wedgetail84
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Thanks guys. Ended up finding it should be timed at 19* BTDC. Pump drive had slipped on the timing gear shaft and had become 20* ATDC. Apparently not uncommon for these TD122Fs - the earlier N12s had a Keyed shaft but they used to break to break the key... Reset it and runs good as ever.

Why it over revved is a different issue... has an IP issue where when it reaches full operating temp and when pushed fairly hard it develops some rather nasty habits - mostly reduced power and it keeps pulling for about 5seconds even not touching the throttle. If at this stage you hit the clutch the revs go through the roof. It’s an occasional use farm truck and the manager hadn’t wanted to fork out for pump work, but I think he might finally be rethinking this...

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Last edit: by wedgetail84.

Volvo n12 injection timing 07 Nov 2019 22:34 #204081

  • Blackduck59
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Any idea of what pump is on it? Tags on it or a pic or two.
Cheers Steve

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Volvo n12 injection timing 08 Nov 2019 05:54 #204084

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It’s an in-line, I think Bosch. I’ll get some numbers off it today

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Volvo n12 injection timing 08 Nov 2019 21:00 #204098

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Blackduck59 wrote: Any idea of what pump is on it? Tags on it or a pic or two.
Cheers Steve

Do you know these pumps Steve? Numbers are:

Bosch
6(?)50 00358 A19(or 8)6
0 401 846 827
PE6P120A320RS317

Thanks

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Last edit: by wedgetail84.

Volvo n12 injection timing 08 Nov 2019 22:27 #204102

  • Blackduck59
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Not up to speed on those, looks like a P pump with 12mm plungers. Think the early versions had their own lube later ones were hooked up to the engine oil supply. If there is an oil line coming from the block then it is engine lubed, if not may need to check the oil levels in the pump and governor.
Sounds a bit like the governor is hanging and with the reference to doing this when hot sort of suggests lack of lube.

Spent the whole day trying to sort out a Bosch VE on my Cummins, finally figured a spring in the governor assembly may have disappeared, at least I finally got it running now just need to up the fuel to it.
Cheers Steve

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Volvo n12 injection timing 09 Nov 2019 21:07 #204120

  • mammoth
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It may be one of the later engines which had an "injection timing adjuster" which fits in line with the pump drive line. The function of this device is to advance and retard the injection timing similar to a distributor in a spark ignition motor. Has springs'n stuff inside it so that could be your problem. As in a distributor static timing is your starting point.

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