diesel engine problem

djb85

I have a problem with an injector pump in a diesel engine, the car won't start when it's hot.

As far as I know when the engine is hot the thermostat tells the engine to fire using the injection pump and not the glow plugs. Is there anyway for the engine to always start using the glow plugs even when the engine is hot by bypassing or altering the thermostat?

Any help is greatly appreciated!

Row

What Make ,model, year,engine is it...??

djb85

Row wrote: »

What Make ,model, year,engine is it...??

It's a 1995 VW Vento 1.9 Diesel. AFAIK if I disconnect the ECT it should assume the car is cold and fire the glow plugs all the time? Problem is I don't know where this is....

Row

Does this also control the cooling fan...:eek:
If you check the glow plugs (ignition on) with a multimeter when the engine
is cold/hot for 12volt may tell you if the ECT if it working correctly.

Maybe its nothing got to do with the pre-heating....Maybe its fuel related as fuel gets less viscous when warm.....
Ron.

djb85

New glow plugs have recently gone in. I've disconnected the ect sensor and glow plugs are activated now no matter what the temperature of the engine. Would you think leaving this unplugged could cause any problems other than probable increased usage and wear of the glow plugs?

Anyone any more knowledge than me on this?

Fishtits

Sorry for being vague but I've come across this before, something about a valve somewhere.

Go see a VAG specialist, If memory serves me right its a fairly simple fix, nowt to do with glow plugs.

Good luck.

peasant

On my (much) older diesel there is a temp sensor that tells the glow plugs to come on or not. Sometimes this is faulty. Unplugging the sensor will have the glow plugs come on every time, but not constantly as they are controlled by a relay which switches off after about 30-40 seconds.

So, on the old diesel unplugging the temp sensor does no real harm ...no idea though what the effect on a modern ECU would be.

kermitpwee

djb85 wrote: »

New glow plugs have recently gone in. I've disconnected the ect sensor and glow plugs are activated now no matter what the temperature of the engine. Would you think leaving this unplugged could cause any problems other than probable increased usage and wear of the glow plugs?

Anyone any more knowledge than me on this?

Ask on vagdrivers.net those boys will know for sure.

djb85

I've gone with leaving the temperature sensor unplugged so the glow plugs are always activated!

Seems to have done the trick but hopefully doesn't cause any other side effects...
Thanks for the help.

Slidey

AFAIK there is a 4 pin temp sensor that is just held in with a clip.

Will have a look at dinner time for you.

djb85

Slidey wrote: »

AFAIK there is a 4 pin temp sensor that is just held in with a clip.

Will have a look at dinner time for you.

Yeah your bang on there, i removed the clip, but wondering if it would do any harm leaving this off?

Slidey

The small plastic clip is all that holds that sensor in.

There is just an o ring on it to keep it in place if it is the one I am thinking of.

With it off the cold start on the pump will be permanently on so your fuel use will be slightly up. Probably cheaper in the long run to fit the sensor.

djb85

Quazzie

Wasn't there a connection between glow plugs on old VW and the door pin switch that activates the lights in the car.
I think the original idea was that the glow plugs started upon opening the door and then they didn't need as long when ignition was turned on.

When the door pin switch failed (as they often did) the glow plugs stayed on constantly.

I remember fixing these about 4 or 5 times a winter back in the late 90's

Max Power1

djb85 wrote: »

file://byrne/Desktop/Derek/S5030442.JPG

lol

djb85

Apologies for making a mess of the upload... first time I've attached a photo.

The photo is of the ECT in the VW - Vento. As I've said I've disconnected this and hot start problems are no longer. However I don't know what other uses this plug has...I'm sure its not there just as a trigger for the glow plugs.

Slidey

It will as already pointed out control the cold start plunger on the pump some diesel pumps are retarded/advanced depending on the engine temperature.

They really aren't that dear and fitting them takes seconds, if done when the yoke is cold you will barely lose any coolant.

djb85

Maybe I'll just take it to a mechanic. I don't really know enough about it.

As far as I can make out the problem isn't the sensor. That's working fine. The problem is when the engine is hot and bypasses the glow plugs its relying on the injector pump which cannot develop enough pressure to get the injectors to open.

However, when glow plugs are used to start (hot or cold) there is no problem. No point in me spending € on a new pump as this car is only going to be on the road a couple more months.

Slidey

Nah dude, you have gotten confused somewhere along the way.

Glow plugs will not help the injectors open and do nothing when the engine is hot. They are used to heat the air in the combustion chamber to ease starting when the cylinders are cold.

If you are having problems starting it may be caused by the temp sender.

I had a Golf that used to be hard started when hot. It turned out to be the starter. When it got hot it would be turning slower and leave it harder started.

djb85

Slidey wrote: »

Nah dude, you have gotten confused somewhere along the way.

Glow plugs will not help the injectors open and do nothing when the engine is hot. They are used to heat the air in the combustion chamber to ease starting when the cylinders are cold.

If you are having problems starting it may be caused by the temp sender.

I had a Golf that used to be hard started when hot. It turned out to be the starter. When it got hot it would be turning slower and leave it harder started.

So it could be the pump,temp sender or the starter. I don't want to go spending a lot on this car as it's on its way out anyway.
As I said it's starting fine now with the temp sensor disconnected permanently and activating the glow plugs even when hot. So I might just leave it at that assuming leaving it out cannot do too much damage only to decrease mpg.

Slidey

IMO it would be worth changing the temp sensor. It ain't mad money and you will be able to change it yourself in a minute.

Just get a new 'O' ring with the sensor, pull out the clip you see in the picture that is facing towards the head and pull the sensor out and push in the new one. A little bit of grease will help on the new one in.

If needed then all you have to do is top up the coolant but if you are quick you shouldn't need more than a cup full

martinr5232

Did you get the timing belt done recently is it possible that the pump timing is out.

I would try advancing the timing a fraction anyway.