hot start question

Hi,

My 1500D starts instantly from cold after the glowplugs have switched off, but if the engine is warm it needs to churn for a couple of seconds before it fires and starts with a puff or smoke.

Is there a simple way of making the glowplugs heat even if the engine is hot, simply to speed up starting and reduce the wear on the starter motor?

Any ideas?

Robin

You can take the wire off the temp sensor on the gearbox end of the head and this will give you the maximum 30-45 seconds of heater plug but once it's warm you shouldn't have trouble starting it??

Is the timing set up right?

blans said

You can take the wire off the temp sensor on the gearbox end of the head and this will give you the maximum 30-45 seconds of heater plug but once it's warm you shouldn't have trouble starting it??

Is the timing set up right?

Hi,

I've never touched the timing, as it runs so well. It restarts instantly when the engine is hot if you've just switched off - the problem is if you leave it for more than a couple of minutes, but not long enough for the engine to cool.

A friend who knows a lot about diesels said, like you, that I should disconnect the engine temp sensor to let it preheat every time.

Maybe I should check the timing, but that's a bit scary on a diesel, isn't it? I was so careful not to move anything when I changed the timing belt…

So it should start instantly when hot too - that would be nice.

Robin

timing could be an issue for this

but my issue with hot starting is that the diesel in the fuel line after the filter and the pump drains back to the tank alittle,
this is cause by leaks in the pump seals and other bit (nothing to worry about)
but it ment it had to crack a few times when hot

simple none return valve sorted it in the fuel line

jellybelly said

timing could be an issue for this

but my issue with hot starting is that the diesel in the fuel line after the filter and the pump drains back to the tank alittle,
this is cause by leaks in the pump seals and other bit (nothing to worry about)
but it ment it had to crack a few times when hot

simple none return valve sorted it in the fuel line

Ok, that's easy to fix, but wouldn't the symptoms be the same when cold? My car starts instantly from cold…

Robin

mine only does it when hot

think the main course it the pump shaft seal when hot allows air in when cold it doent

that what i read a while ago

Just ordered a non-return valve (£4.15 on ebay)

I'll keep you informed,

thanks again,
Robin

Ok, just a quick update.

The non-return valve didn't seem to make a difference, neither did shunting the temp sensor to lengthen pre-heat time, but a new battery made things better, for a week or so. After being stranded after a fuel fill-up and the engine not firing at all I decided to have a look at the starter motor, which was not that fast.
The engine restarted easily with a push to get me home, and a scrappy provided a Golf 2 TD starter motor, which is physically smaller but does the job.

I opened it up, cleaned the commutator and admired the brand-new look inside, greased the greasy parts and fitted it.

Since then the engine starts much more easily from cold and instantly from hot.

Thanks to all!
Robin

Hey Robin,
Ours seems to do this too. It starts as you would expect cold but after running and being warm it reallt struggles to get going. The starter motor sounds fine but obviously slows after a long time of trying to start with the battery taking a hit.

Did replacing the starter definitely fix this issue for you?
When ours does eventually restart it coughs out some smoke and runs fine!

STurbo said

Hey Robin,
Ours seems to do this too. It starts as you would expect cold but after running and being warm it reallt struggles to get going. The starter motor sounds fine but obviously slows after a long time of trying to start with the battery taking a hit.

Did replacing the starter definitely fix this issue for you?
When ours does eventually restart it coughs out some smoke and runs fine!

Is this an automatic?
Have you replaced your main ground cables Battery to frame and frame to engine?

The reasons I ask is that on a old starter they can get weak spin when they are warmed and not spin the engine fast enough for spontaneous combustion to occur.  This can be caused by weak old ground cables, if yours are still OEM replace them out of hand your electrics will than you for this.

If it is a automatic or manual even you can install a heat soak relay to the solenoid pick where you use a relay to bypass the ignition switch start wire to the solenoid, and go from the battery to the solenoid, and not from the battery to the ignition switch, to the Starter so you are shorting the run of wires and such.

Replace the starter bushing if you hang a new starter, you
can press it out either using the screw and slid hammer method or using bread to force the bushing out.

Once you install the heat soak relay you will be amazed at how much your starter likes it, and you will be taking the high amp current load off the ignition switch.

Pressing bearing out with bread.
https://www.vwvortex.com/threads/pressing-pilot-bearing-out-with-bread.9563213/?post_id=116422616#post-116422616

Installing a heat soak relay.
https://www.cabby-info.com/files/ignition/InstallingHot-startRelay.pdf

lastly you may want to learn all there is to know about glow plugs, as there are 2 styles Pre-82 and post 82.
Pre 82 used a wait-forever plug.
Post 82 used a seven second plug.

The differences are the Plugs, and the relay for time duration.
I will tell you after changing over from the wait forver on my 81, to the 7 second ones at 130K miles, I found that I should keep one spare plug and the 2 wrenches that it takes to remove the number 4 plug in the boot.
The Diesel engines can loose a glow plug they burn out,  usually one at a time and until the 4th one goes you can usually start your engine.
Once the last one goes your engine will not usually start.  Carrying a spare GP and the Fuse (40 amp flat) one for spares can save you a tow.

Everything you wanted to know about glow plugs and the circuits can be found here:
https://vincewaldon.com/category/volkswagens/how-tos/

https://www.4crawler.com/Diesel/CheapTricks/GlowPlugs.shtml

https://www.4crawler.com/Diesel/CheapTricks/index.shtml

Hope this helps, I did drive my 81 from 1980-2000 with only 360k miles on it.
 

Thanks again Briano, 
It's a 1978 diesel manual. 
The previous owner took to a local mechanic who was stumped. But may not have known these tricks. 

No idea when the plugs were changed etc so would that be a good place to start? Still go for the 7 second ones?

I'm struggling to confirm exactly what engine I have as the previous owners also replaced that with the old one blown head gasket. I am picking up the old engine soon so that might have the dual wire oil pressure sensor from my other post!

If you go to the 7 second ones you will need the 7 second GP relay..  They used to make an upgrade kit.  don't know if it is still avail.

Blocks have the 15D raised casting on the back side of the engine nearest to the tranny.

I would go over the grounds and maybe the starter as that is the usual issue as well as installing the heat soak relay.  

You Starter may be worn out, and possibly you could have it rebuilt.  But get a new Bushing.

Hey Briano,

If i do the heat sync upgrade - can i keep the glow plugs and relay that i have existing?

Do you have any links to the 7 second plugs and relay upgrade? Or an example of the upgrade kit? I cant seem to find anything online.

How does the 7 second relay work? My understanding is the 7 second plugs get to a glow faster - but do they glow for the same duration as the wait4ever plugs and are shut off by the same temp sensors?

You would have to buy a new relay for fast glow, then add new 7 second GP's.  that is all there is to it.  I don't know if kits are available any more.  

They glow hotter and are lit for 7 seconds, then you can start your car.  But be warned, they will go out one at a time with no issues starting but when the last one goes you have to have.it towed, or if you follow my advice carry a spare GP and the 3 wrenches it takes to remove the number 4, and then you can motor on.  Then you can replace the other 3 later on in the week.

The 7 second ones last fro 7months to 1.5 years, where as my 81 used the same wait forever plugs for about 135K miles before I had to replace them.  Well I replaced them with another engine because a new to me timing belt stripped 3 teeth, and put the pistone through the head.    But I did source another 1.5 rabbit for 500 bucks with only 130K on it and swapped it into my car, and I owned it for another 10 years and total of about 350K miles on the different engine and frame.