Cold-Starting Circuit Question

[dasnoboarder]

Hey,

This winter I'm thinking of taking the cold-starting issues up again. When cold, first start of the morning is very rough, and when it does start, everything around is covered in a nice cloud of white/blue smoke. The engine starts perfectly when the wire on the thermostat is disconnected (forcing the glow plugs to run for their maximum duration), and the glow plugs run twice before starting. I'm thinking of connecting a circuit that runs to the dash, so I can disconnect the wire without having to get into the engine bay in the morning.

My plan is getting a normally open momentary push button switch (not many good normally closed around) and a relay to convert it effectively to a normally closed. When pushed, the relay will throw and disconnect the wire.

The question is, will the voltage going to the sensor be affected by this added resistance? E.g. will the sensor read a different temperature than before, causing issues?

Thanks for any help, will post a pic when finished if anyone's interested.

Andy.

[geeves]

could work but do remember disconecting this wire also advances the timing so it will run like a hairy goat under load and will overheat if ran for any time like that

[BUSHPIG]

ive just started haveing a problem just like this. my temp gauge not working and verry hard to start on cold mornings glow plugs turn on then straight of unless that wire on the thermo houseing disconected. does this run the gauge as well as the glow plug timer? if so where is the best place to get a new sender? i dont think ive ever seen a isuzu dealer round?

[dasnoboarder]

I'm not sure if it runs the gauge also.

I disconnect the wire, run the glow plugs twice, start it, and then reconnect the wire after about 10 seconds (only idles). The momentary switch would mean I would have to hold it while starting, and I couldn't accidentally knock it on.

Are the temperature sensors only for the cold-start system and temp gauge? No fuel or cooling systems would rely on them?

Bushpig, you could try a holden dealership and see if they can get you the part, or part number.

[BUSHPIG]

ah is holden the agent for isuzu. ill give em a ring tomorow.

[Kenneth]

A method I have used for reluctant starting is to use the fact that the glow plugs do not switch off when the indication light goes out. If you wait a while after the light goes out you will hear the timing relay click turning the glow plugs off. Then immediately try starting the engine.
The white smoke seems to me like one or more glow plugs faulty. Have you tested them?
Ken

[dasnoboarder]

I was trying to fix the hard-starting and smoke last winter, changed all the glow plugs and tested the circuits. Power does get to them normally for around a second. When the temp wire gets disconnected, power is there much longer, about 8 seconds. I hear the relay clicking when the glow plugs go on and off, and when I reconnect the temp wire after its started.

The longer glow plugs and timing advancing are supposed to happen automatically below a certain temperature, but I've only seen this happen once before. Maybe the automatic system is faulty, or just activates at temperatures a bit too low. Forcing the system to activate seems like a quick and easy fix.

[mulover]

I wouldn't have thought it gets cold enough in Auckland to worry about this

[dasnoboarder]

It's not too bad but we're getting low single digit temperatures some days. Driveway had a coating of ice last week, a few in the family got a fright haha.

[geeves]

First frost in Auckland for 5 years! It made national news with a dozen or more people complaining about the bitter cold. The cold start system doesnt activate on the 4jb1 untill below 5C measured in the thermostat housing. Mine starts like yours down to this temp but then starts fine down to the coldest we get in Wellington ever

[bedford4x4]

I don't know if you're still having trouble with your cold starts.

I had exactly the same trouble with my truck.

The issue is not the cold start system at all. The issue is injector timing, normally because the crankshaft sprocket for the timing belt is slogged out. This retards the timing, which means that the motor doesn't want to start. When you disconnect the wire on the thermostat, you are forcing the glow-plugs to come on for longer, true, but what causes the engine to start better is that by disconnecting that wire, the injector pump timing gets advanced for better cold-starting. This brings the timing back to somewhere approaching normal.

I would strongly recommend investigating the crankshaft sprocket. This is well-known for coming loose on these motors, often because ignorant mechanics don't torque them up to the right torque setting after changing timing belts.

The 2.8TD doesn't generally need glow-plugs. The cold-start system activates at about 0 degrees C., or below.

Regards,

Harry

[turnturn]

I can confirm that the 2.8 generally doesn't need the cold start system.
I rarely wait for the glow plugs to do their thing and this is in Dunners.
Mulover can probably confirm this from and even colder place (Southland) if he can remember back to when he was a Kiwi.
Dunners (Wingatui) is still getting the occasional frost.

[dasnoboarder]

Hmmm this is interesting...

The hard-starting only occurs when I try to start the car after it's been sitting overnight or more.

As said before, forcing the glow plugs to run and injector timing to advance make it start much easier.

When the car is warm (I don't do anything with the injector timing & glow plugs) it starts fine, car seems to run normally once started.

Would it be easy to tell if the crankshaft sprocket has moved? Or would you basically have to get in there as if you were doing the timing belt replacement?

I was going to get the injector timing advanced for better performance, but have had trouble in the past with mechanics not wanting to do it without specific values.

[BUSHPIG]

I don't know if you're still having trouble with your cold starts.

I had exactly the same trouble with my truck.

The issue is not the cold start system at all. The issue is injector timing, normally because the crankshaft sprocket for the timing belt is slogged out. This retards the timing, which means that the motor doesn't want to start. When you disconnect the wire on the thermostat, you are forcing the glow-plugs to come on for longer, true, but what causes the engine to start better is that by disconnecting that wire, the injector pump timing gets advanced for better cold-starting. This brings the timing back to somewhere approaching normal.

I would strongly recommend investigating the crankshaft sprocket. This is well-known for coming loose on these motors, often because ignorant mechanics don't torque them up to the right torque setting after changing timing belts.

The 2.8TD doesn't generally need glow-plugs. The cold-start system activates at about 0 degrees C., or below.

Regards,

Harry

im guessing you mean the keyway in the pully stuffed nt the crank its slef?

[dasnoboarder]

I was wondering how the crank pulley could go out of alignment with the crank too (because it should have the keyway thing), that's how I understood it as well.

Bedford, is a further explaination or photos of what you mean possible?

[geeves]

Check the torque on the large crankshaft bolt on the front of the engine. It should be about 150 foot pound. If this is loose the spacer behind the fan pulley wobbles and this wears the keyway in the spacer and sometimes also damages the crankshaft. (on mine the bolt fell right out). The cambelt pulley is bolted to the spacer.
As bedford says this is a common problem and the spacer is not cheap.

[BUSHPIG]

cool well i need to change my ac/ps belts and my steering box so ill have a look while im in there. man im gonna be stoked if thats what my hard start problem is and not wireing.

[geeves]

Also if you look at the bottom pulley while the engine is running it should run true. Any wobble also points to this problem.
On mine the only symptom of this was the pulley knocking on the timing cover No starting issues

[BUSHPIG]

yeh my one looks to be running true. but still worth maybe takeing it of and checking keyway and drive hub then a re torque'n it

[dasnoboarder]

My truck is starting much better now!

I got the crank pulley issue checked, thankfully that was all good. After that, I got the glow system checked, they said that it seemed the coolant temp sensor was faulty. (The one that you disconnect to force the glow plug system to run longer, on the thermostat housing). I was a bit unsure as I thought the sensor was either open or grounded. Anyway, they got a new genuine Isuzu part and it seems to have fixed the issues. One small blue puff of smoke when starting from cold, rough idling and cutting out has stopped.

Andy.