[Vwdiesel] Lusting after efficiency

Tue Jul 8 16:55:07 PDT 2014

What's the break-even point for a diesel to be switched off, over the excess fuel from a restart? For my QTD , I can increase fuel economy, if switched off for 
at least 30 seconds, say at traffic lights. Loading on the starter etc is dependent on number of turns to restart I would have thought.. My engine can restart 
in about a turn to about an hour, if it is hot!

This brings me to my question for this forum:

About 2 months ago my car developed a fault, that either hadn't been there before, or had just not shown itself:

>From cold it is quick to start. 
After a journey of a few miles, if hot car would not restart. 
No roadside jump leads, booster pack, or even ether, would start it. 
However, if left till almost completely cold it would then start normally. 
Directly powering glow plugs made no difference. 
Flow through the pump is about half litre per minute [Although can't say I've checked during the failure to start period]. 

Rebuilding engine revealed 2 pistons had aligned ring gaps. I decided to put in new rings seeing as I'd bought 2 spare sets. New rings seemed to cure it for 
a few weeks.
Then the refusal to start when hot returned. 
Cracking fuel lines seemed to indicate fuel getting to the injectors but possibly not much...
This was mentioned by 2 independent roadside mechanics. 
We jointly decided to check the stop solenoid. 

Removing the core brought about a cure, when car had cooled, but had still start minutes earlier. 
So it was interpreted that the solenoid was opening when cold, then shutting when hot, but only partially re-opening when hot, or still warm. 
Inspecting the solenoid core showed it to look like new, black and anodized, except for a wear[binding?] patch on one side.
When I got home, I put in a spare solenoid, and all was well again; restarts after trips were successful for a few weeks, until last week when after a 2 mile 
RUSHED trip I turned the car off for a couple of minutes and then it refused to start. 

I removed the core again, but it made no difference, so I called Rescue. The AA rescue man tried a near flat battery booster pack, and ether, but that didn't 
work, 
He didn't show any empathy, unlike the previous 2 guys, and said it was probably a tired old engine, and that we could spend, or as he put it "waste" another 
hour trying to start it; I insisted he take me back home. He asked if I wanted to leave the car! Crikey, I pay membership for a full relay service, why would I 
want to abandon my car? 
Problem started at 8.30pm, back home by 9.30pm, still not starting, but about 10.15pm tried again, and the car started straight up with a few turns, a cloud 
of smoke and then normal idling. 

Last night I went out for a 20 mile round trip with 2 x 20 min stops. No problems. 1 hour later I repeat similar journey. Stop for 15 minutes to pick someone 
up, and car almost starts, .but doesn't and then as per usual no signs of starting. I tried a few minutes later, but nothing. This time after 20 minutes, car did 
start, which is the quickest restart after a 'no start'!
It blew a cloud of smoke and then was happy to idle normally. Returned home.

Summary:
So car starts straight away when cold, but not when hot [pump hot to touch] 
It is not a lack of fueling to the pump, as it lifts 0.5 litre per minute. [not sure when failing to start, but I assume still so.]
Not glow plugs, as I have directly powered them up with a second battery during the problems with no difference.

The failure to start is usually commenced with a 'near' start, and then nothing, until it decides to suddenly start later after cooling down, so is it possible that 
the problem lies with the mechanism that gives beyond maximum fueling for startup and it is sticking when pump is hot, in it's idle, or running position?

Really sorry for the long post, but read slowly shouldn't take more than 2 days to read...

Mark

========================================
Message Received: Jul 08 2014, 03:19 PM
From: "Bryan Belman" 
To: "Tad" , "Mark Shepherd" 
Cc: "mailing list" 
Subject: Re: [Vwdiesel] Lusting after efficiency

GREAT summation.  I had not thought about those issues, I would agree, TDI would not make sense in a hybrid.  Possibly if they would let the motor idle 
and that defeats the purpose.  While sitting in a traffic jam, dead stop closed highway last fall, in 28F weather, my 1.9NA motor consumed almost a gallon of 
fuel in 1 hour of idling, but it was able to keep heat in the van since it was at road running temp.  An idling TDI in cold weather will not warm things up, but 
they could over come this with electric coils in the heater box.

All and all, it is not the best idea.

Bryan Belman, Pt. Pleasant, NJ
04 Jetta Wagon TDI PD BEW, 100hp, 5sp -- running :<)
04 Golf TDI PD BEW, 100hp, 5sp Tiptronic Auto -- running :<)
82 Diesel Westy 1.9NA 1Y -- running :<)
70 Type 1 Beetle -- Under Restoration forever:-) 

On Tuesday, July 8, 2014 1:17 AM, Tad  wrote:

(sorry, Atkinson, not Miller, and apparently the answer is yes. )

On Mon, Jul 7, 2014 at 10:09 PM, Tad  wrote:

> Doyt, interesting you don't mention it by name, but we have one too, and
> it's a good car.  Quite different from a VW diesel, but good in it's own
> way, and basically equivalent MPG.
>
> As for the diesel hybrid... I think there's a good reason we haven't seen
> one of those on the market.  For one, diesel wouldn't gain as much from the
> start/stop technology because it's far more efficient at idle.  Two, I
> suspect longevity issues from the stop/start due to, among other things,
> issues with keeping the system up to temp (which is hard enough in cold
> weather with a conventional diesel).  Third- cost.  The additional cost of
> a diesel plus the additional cost of a hybrid setup is a double-whammy.
>
> It makes me curious  though, is there such thing as a miller-cycle diesel?
>
>
>
> On Mon, Jul 7, 2014 at 5:36 PM, Mark Shepherd 
> wrote:
>
>> And then there is Stirling- Electric
>> If ever I found a Syncro Q, over here, I'd probably try make it electric
>> drive on the back with regenerative braking. Diesel powered with a Stirling
>> Engine recovery of the
>> exhaust...Germany did a 1.8 gasser syncro.
>> ========================================
>> Message Received: Jul 07 2014, 06:32 AM
>> From: "Stephen Kraus"
>> To: "Doyt W. Echelberger"
>> Cc: "vw fans"
>> Subject: Re: [Vwdiesel] Lusting after efficiency
>>
>> Diesel electric can beat it. VW was testing a 70 MPG diesel hybrid.
>> On Jul 6, 2014 8:21 PM, "Doyt W. Echelberger"
>> wrote:
>>
>> > Back in the eighties I pampered an overwhelming lust for efficient
>> > transportation by acquiring a 1985 Jetta TD. I drove it until a few
>> years
>> > ago, and then moved the turbo to a naturally aspirated diesel engine in
>> a
>> > pristine low mileage 89 Jetta chassis. Part of that long relationship
>> with
>> > the 85 Jetta involved learning as much as possible about diesel
>> technology,
>> > largely by conversing with people on this list. But I recently
>> encountered
>> > something that rivaled the diesel solution. And you might find it
>> > interesting. A rival car joined our family and returned a 47 mpg
>> > performance using regular gasoline, over the same roads that I've been
>> > clattering around on for almost 30 years.......and that equals or beats
>> all
>> > my diesel experience with efficiency. I was pleasantly surprised to
>> > discover gasoline/electric engine technology invading that space.
>> >
>> > It gives me more choices. I like both of them, and look forward to a
>> > diesel/electric hybrid at some point in the future.
>> >
>> > Doyt Echelberger
>> > 89 Jetta TD
>> > 2014.5 Camry Hybrid
>> >
>> > _______________________________________________
>> > Vwdiesel mailing list
>> > Vwdiesel at vwfans.com
>> > http://www.audifans.com/mailman/listinfo/vwdiesel
>> >
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>
>
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