diesel engine knock on cold start goes away after like 3 minutes

[somerandomguy1]

Here is a video tour of the denso ve

 

[somerandomguy1]

Here is a video tour of the ve pump:

 

[somerandomguy1]

This morning I decided to try adjusting screw no. 1 from the pic i had posted earlier in this thread since screw no.2 elevated the rpm way too high. Bingo!

It appears that screw no.1 is the fast idle, idle up,or cold idle screw as I adjusted it to raise the cold idle to where the knocking went away and afterwards the rpm didnt go sky high!

It appears that screw no.2 is the hot idle, normal idle, and screw no.1 is the cold idle.

I think this happened when i went to the electrical repair shop to see why the alternator wasnt charging the battery, which is a story for another thread, and one of the dudes told the other guy to adjust the idle to see a change of volts on the multimeter and then the dude said no not that one the other one referring to the idle screws. So that guy probably adjusted the cold idle mistakenly too low. Thanks to all you guys for the help, i appreciate it.

Well I will check tomorrow morning again to see if it stays without knocking on cold startup.

 

[somerandomguy1]

The mechanic checked the glow pligs with a continuity tester and all 4 received voltage from battery.

It appears as previously noted by mk732 that the automatic cold start device is vaccuum operated. The mecanic tested the vacuum automatic cold start mechanism by blowing into the hose and the it accelerates idle when activated, so the vacuum automatic cold start mechanism functions properly.

It appears i was wrong screw no.1 is cold idle operated by vacuum device.

Mechanic says that there is an electronic card or computer that receives signal from coolant tempertature sensor and if cold sends a signal to a solenoid valve to blow into / open the vacuum cold start device which increments idle speed to warm up engine quicker.

Screw no.2 is regular hot idle.

I then turned on the a/c to see if rpm would go up as before and they didnt, the mechanic noticed though that the rpms didnt go back down after turning off a/c. It appears the same solenoid that operates vacuum cold start device also accelerates the idle when the a/c is on and decelerates the idle when the ac is turned off.

It appears that the vacuum hoses to the solenoid that accelerates and decelarates idle depending on a/c operation were not correctlly installed more exactly switched up. Mechanic switch the vacuum hoses to the solenoid and idle cycles back to regular level when a/c is turned off.

 

[somerandomguy1]

Mechanic adjusted valves and saw engine cold start. The fast idle didnt turn on. The fast idle screw was adjusted properly. The vacuum fast idle device is operational as it idles up and down correctly with a/c operation.

That only leaves two other possibilities,
1. the solenoid that activates the vacuum idle up device to increase idle, would be weird because the solenoid works well with a/c and activates vacuum idle up and idle down mechanism with a/c opeeation.


2. The electronic controller device or cpu that receives the signal from coolant temp sensor and activates the solenoid to activate idle up when engine is cold to get engine warm faster. Thing is i dont know where this device is. I did see what looked like a electronic device under the stick shift that said diesel something. I will take a pic and see if i can post here. Dont know if this is cold start electronic controller.

 

[Popsy]

Before attacking the engine control unit, check if temperature sensor is still ok and connection to ECU Is good.
Also is the small air pump (for lack of better word) turning on (to control the vacuum idle control system) on cold start?
These vaccum mechanisms have a tendency to go bad with age, sometimes a tiny leak is enough to render the whole system insufficient, and when you blow in it it somewhat works).

As a hack, if the injection pump is controlled by a cable, you can tighten that cable a bit more, and adjust the hot idle accordingly, or play with the vacuum valve thing to effectively have the engine always on high idle when cold.

 

[somerandomguy1]

Mechanic said there are 3 temperature senders. 1 for the imstrument cluster. 1 for the rad fan and ac condensor fan and 1 for the electronic control device which supposedly controls the glowplugs, the ac idle up and the cold start idle up.

The sensor for instrument cluster is ok.
The sensor for the rad fan and condensor fan is ok.
The sensor for the electronical control device would be ok i assume because the glowplugs operate correctly accordimg to engine temperature.

The solenoid for the vacuim device operates well with the idle up vacuum device as it idles up for ac and idles down when ac is turned off. Why doesnt i operate well with the cold start idle up?

Perhaps the connection for the electronic control device to the solenoid for the vacuum cold start device has an issue.

How would i hack vacuum idle up device to get cold start idle up?

I am glad that the fact of the matter is that the cold start engine knock went away with the idle, valve and ip adjustments, so it doesnt have an automatic temperature dependant cold start idle up function,well, i can live with that.

I will see if i can troubleshoot the automatic cold start vacuum idle up function to get it to switch on and off.

I will post later the post valve adjustment cold start video.