ACSD tech/discussion (2 Viewers)

[Eurasiaoverland]

'Just get rid of the ACSD'. A common reply on the forum - if this is your firmly held opinion, you may not wish to read any further.

I'm not trying to persuade anyone to do one thing or another, just interested to discuss/learn about the failures. By failure I mean the shaft disintegrating. I'm not interested in leaks or the thermowax losing its properties.

I'm interested in these ACSD failures for a few reasons:
-I like the function and wish to retain it my engine, while understanding the risks of the shaft failing. There could also be arguments based on individual cirumstances for keeping it such as legal emissions control requirements, or just for originality's sake.
-I only heard about ACSD failure once I joined this forum. In terms of documented examples, I have only seen shaft failure in the 1HD-T. Understand that in Europe, where Toyota diesels are very common, these things were fitted to a whole generation of Toyota diesel engines (the vast majority of which would have been four cylinder engines), and I have never heard of them failing on UK based Hilux owners groups/forums, or in any reading about maintaining or overhauling Toyota injection pumps.

Now, I have two dismantled ACSDs here with which to make an observation. These are not from 1HD-Ts, but I believe the shafts are basically the same.

In the following picture are two ACSD shafts:
Left: a 14B ACSD (which went into production in 1988) from my 1994 15B-T engine.
Right: courtesy of @frankenyota, a 15B-F ACSD (which went into production in 1995).

Notice how the 1988 ACSD has a two piece shaft where the cam appears to be pressed/stamped onto the shaft. From what I have seen, it is this part that always disintegrates when the shaft fails. On the 1995 ACSD, the shaft appears to be turned from a single piece. A 'billet ACSD'! It also has a much larger cam, and a much larger washer. I would suggest that this has been done to prevent shaft failure, and that these design of shafts will not fail in the same manner.

Now, let's look at 1HD ACSDs (both photos taken from Partsouq website).

Firstly, the 1HD-T ACSD, 22790-17141, launched in 1990:

And the 1HD-FT ACSD, 22790-17840, launched in 1995:

So, the same design change that I documented in the 14B vs 15B-F ACSDs.

My question - has anyone got a documented case of ACSD failure on a 1HD-FT?

EO

 

[HDJ80L]

Interesting to see the difference of the 1990 vs 1995 variant, the later version certainly looks beefier.

I've read through a german LC forum (Buschtaxi) extensively prior to removing mine and only found one documented case of a shaft failure that damaged the injector pump and from what I found out that was on a 1HD-T. Seems to be extremely rare and likely connected to the earlier shaft design. The ACSD starting to leak however seems to be more common which is (imo) the main reason for people removing it and why there seems to be sort of a consensus among owners to get rid of it. If there was an official service schedule for that item I'm sure more people would check/replace rather than remove it.

 

[Squash]

If you live in a moderate climate this thing should last forever. On the other hand those of us who content with upwards of -30C should be concerned, as I do not feel Toyota engineering considered weeks of frigid weather.
I have removed 3 ACSD's from the 1hdt engines just because my first ACSD cost me some time and money, and lastly my 1HD-FT as a PM.
Again, let your climate rule.
Pretty certain that a convection heater and/or a Webasto system mitigate what little emissions benefit you receive from the ACSD.

 

[Eurasiaoverland]

Interesting to see the difference of the 1990 vs 1995 variant, the later version certainly looks beefier.

I've read through a german LC forum (Buschtaxi) extensively prior to removing mine and only found one documented case of a shaft failure that damaged the injector pump and from what I found out that was on a 1HD-T. Seems to be extremely rare and likely connected to the earlier shaft design. The ACSD starting to leak however seems to be more common which is (imo) the main reason for people removing it and why there seems to be sort of a consensus among owners to get rid of it. If there was an official service schedule for that item I'm sure more people would check/replace rather than remove it.

Thanks for your reply. Interesting data point to collect, also about the leaking leading to people replacing it. There's a single O-ring on the shaft which commonly wears, it's easy to replace, once you have the ACSD off the pump of course.

I too think that failure is pretty unusual, and it's my opinion that it gets hyped up a bit on this forum. I think this is down to diesel Land Cruisers being unusual in the USA and people are keen for any knowledge on keeping their expensive imports running. But that is just my opinion, not really useful.

I also think the shaft failure is a 6 cylinder phenomenon, the 6 cylinder rotary pump will subject the ACSD to 50% more cycles of the rollers running over the cam ring compared to a 4 cylinder, and when the ACSD is engaged (engine cold) the cam on the shaft is what hholds the roller ring in place. Perhaps there is also an element of the frequency of vibration contributing to fatigue of the ACSD cam on 6 cylinder engines.

Cheers!

 

[Eurasiaoverland]

If you live in a moderate climate this thing should last forever. On the other hand those of us who content with upwards of -30C should be concerned, as I do not feel Toyota engineering considered weeks of frigid weather.
I have removed 3 ACSD's from the 1hdt engines just because my first ACSD cost me some time and money, and lastly my 1HD-FT as a PM.
Again, let your climate rule.
Pretty certain that a convection heater and/or a Webasto system mitigate what little emissions benefit you receive from the ACSD.

I don't really see the connection with climate - the ACSD will be engaged on any cold start, whether the ambient temperature in -30 or +30. Or are you saying it will be engaged for longer as it takes a bit longer for the engine to warm up? It should be taking coolant from the block and so not waiting for the thermostat to open, but of course that still leads to a longer warm-up.

 

[Squash]

Force over time, repetitive cold and hot cycles. Eventually something has to give.
I recall a -36C morning and pure cold start, pretty certain that the ACSD was maxed out.
Not taking that chance again.

 

[HDJ80L]

I remember seeing this post as well looking for information, from a FB account called "Diesel Australia".
Looks like this is from an early design ACSD as well

 

[Eurasiaoverland]

I remember seeing this post as well looking for information, from a FB account called "Diesel Australia".
Looks like this is from an early design ACSD as well

View attachment 3989041

I wonder if they have seen a broken 1HD-FT ACSD, or whether they just assume they are the same. Also, I don't think the shaft failure has anything to do with the wax capsule.

I agree, it looks like the 1HD-T type ACSD with the pressed on cam. All the pictures of failures I have seen look like this. Looks like stress cracking around the joint of the shaft and cam to me.

 

[OGBeno]

I wonder if they have seen a broken 1HD-FT ACSD, or whether they just assume they are the same. Also, I don't think the shaft failure has anything to do with the wax capsule.

I agree, it looks like the 1HD-T type ACSD with the pressed on cam. All the pictures of failures I have seen look like this. Looks like stress cracking around the joint of the shaft and cam to me.

We are working on a JDM -FT with a blown up ACSD and metal shards throughout the IP.

 

[Eurasiaoverland]

We are working on a JDM -FT with a blown up ACSD and metal shards throughout the IP.

Any pictures of what happened to the ACSD?

 

[GreenPump]

Of the truck with ACSD I've owned:

3x toyota hilux with the 3L engine- acsd never failed or leaked, I deleted from my LN106 when I rebuilt the pump.

2x 80 series with 1HDT, one began to leak, rebuilt pump & deleted, other still has it.

1x 80 series 1HDFT, no leaks or issues, still has ACSD.

The 80s which have internal glow plugs and a fuel heater start better in deep cold, regardless of ACSD. We only see a week or two below -20F, and most of us are parking in a garage, using a circulating heater, and a anti-gel additive at those temps.

Maybe the risk of shaft disintegration is blown out of proportion, yet with these trucks the benefit is negligible, so most people will opt to remove even if risk is small. Also, I personally dislike the added bloat of the ACSD parts, I find it ugly.

 

[OGBeno]

Any pictures of what happened to the ACSD?

IP shop has it and they are removing and rebuilding pump.