Thread: What year is this 4bd1

Originally Posted by steveG

Lack of torque down low was the issue Rijidij had with his 4BD1T before he tweaked the boost compensator. Pretty sure he posted up a good thread on what he did to sort it out.

IIRC the issue was the compensator was holding off the fuelling too much and resulting in much less low down that my 4bd1+t with the NA pump.

Steve

Originally Posted by Dougal

He took it off IIRC.
I've got a thread somewhere on making an internal stop for the boost compensator to set off-boost fuelling independently from the preload adjustment.

Small changes (0.2mm) make a significant difference.

You can see what I did here.........Boost compensator, how does it work ??

Cheers, Murray

So is the cold start enrichment momentary a few seconds or minutes in duration ....is it needed ....could it be used via a pull cable?

Originally Posted by Adrian18

So is the cold start enrichment momentary a few seconds or minutes in duration ....is it needed ....could it be used via a pull cable?

Until the revs pick up and the governor unhooks it.
Factory it's on the same cable pack as the stop cable, but you could do a pull and release cable.

I've never had anything to do with IP's with the pictured type of cold start enrichment, though I did have a VW Golf that had that style. The golf had a manual push/pull cable on the steering column, but was disconnected at the IP and I never used it.

The procedure for cold start enrichment for the IP on Isuzu's is to fully depress the accelerator, and hold it there, before starting. The control rack travels a lot further when the engine is stopped. When the engine fires the governor moves the torque cam to prevent that extra travel.

I imagine the above procedure will still work if you disconnect the cold start cable, but I haven't managed to find any diagrams that show what is happening inside the governor with that style of enrichment.

Originally Posted by Bush65

I've never had anything to do with IP's with the pictured type of cold start enrichment, though I did have a VW Golf that had that style. The golf had a manual push/pull cable on the steering column, but was disconnected at the IP and I never used it.

The procedure for cold start enrichment for the IP on Isuzu's is to fully depress the accelerator, and hold it there, before starting. The control rack travels a lot further when the engine is stopped. When the engine fires the governor moves the torque cam to prevent that extra travel.

I imagine the above procedure will still work if you disconnect the cold start cable, but I haven't managed to find any diagrams that show what is happening inside the governor with that style of enrichment.

Here is how mine works:
When the key is switch to "on" the stop cable releases and the cold-start cable (a seperate item) pulls and then releases. Latching the rack in the cold-start position internally. It does this every start.

On the Isuzu trucks this might have been wired to a switch on the accelerator pedal so it only did it when the accelerator was also pressed. The wiring on my cable pack has been butchered. The NPR with a 4BC2 here has the same setup as mine, but not butchered. I should check it some-time.

Internally there is only one stop for the cold start to latch to, but intermediate cable adjustment also has an effect. Presumably from enough stiction in the mechanism that the latching notch isn't the only stopping point.
I have mine set so when the engine is warm it starts clean, but when cold there is a puff. It starts reliably down to ~-10C and I don't have glowplugs hooked up. I do have a very good 24v direct drive starter.

Originally Posted by rijidij

You can see what I did here.........Boost compensator, how does it work ??

Cheers, Murray

That's right, still fitted but set internally to disable any de-fuel.

Originally Posted by Dougal

Here is how mine works:
When the key is switch to "on" the stop cable releases and the cold-start cable (a seperate item) pulls and then releases. Latching the rack in the cold-start position internally. It does this every start.

On the Isuzu trucks this might have been wired to a switch on the accelerator pedal so it only did it when the accelerator was also pressed. The wiring on my cable pack has been butchered. The NPR with a 4BC2 here has the same setup as mine, but not butchered. I should check it some-time.

Internally there is only one stop for the cold start to latch to, but intermediate cable adjustment also has an effect. Presumably from enough stiction in the mechanism that the latching notch isn't the only stopping point.
I have mine set so when the engine is warm it starts clean, but when cold there is a puff. It starts reliably down to ~-10C and I don't have glowplugs hooked up. I do have a very good 24v direct drive starter.

My stop cable device (from another truck, not originally with my engine) also had the cold start cable until I removed it because it served no purpose (my IP doesn't have that facility).

AFAIK when the accelerator is released, engine stopped or running, the control rack is pulled back to reduce fuel. So from your description I wonder how the control rack gets to the enriched position. This rack position is further in than full load and on the rack limiter.

The following diagrams might help with the procedure I described in an earlier post. The first is the governor assembly. The second is the parts around the torque cam.

When the IP is stationary the idle spring pushes the lower end of the tension lever forward, and the top end back. This movement is greater than when the engine is idling.

As the top of the tension lever goes back it pulls the torque cam around to the start position.

Now the function of the torque cam is to limit the maximum forward travel of the control rack (toward maximum fuel). There is a spring on the control rack that pulls it in the increased fuel direction. The top of the sensor lever is engaged with the control rack and the bottom hits the profile of the torque cam when the accelerator pulls the control lever to maximum load/speed and shifts the floating lever.

When the IP is stationary the torque cam is in a position where the tip of the sensor lever moves into the notch at the bottom of the torque cam, if the accelerator is fully depressed. As soon as the engine starts and the accelerator is lifted the torque cam is rotated so the notch is out of way.

Originally Posted by Bush65

AFAIK when the accelerator is released, engine stopped or running, the control rack is pulled back to reduce fuel. So from your description I wonder how the control rack gets to the enriched position. This rack position is further in than full load and on the rack limiter.

If I remember correctly, the enrichment cam on the back pulls the rack back and it locks in position with a pawl in a notch. It is the governor that unhooks the pawl and lets the rack return.

But it has been ~6 years since then.

If this is the case, it appears they were able to get the accelerator cable to do the same job on post 88 4BD1T engines.