[Vwdiesel] Cold Start 1... Hot Start 0

[Mark Shepherd]

Interesting thought, but I don't think that the vane pump is failing when hot, otherwise it would show up whilst actually running, and it doesn't seem t o, as it 
accelerates normally, and idles normally, and runs at high speed normally.
It's just that turning off when hot, immediately creates the issue [or not]. 

It would be interesting to check internal pressure, whilst problem exists, but that would entail cranking pressure only, and would need to be compared with 
cranking pressure with artificially induced non start cranking. 
Probably easier to compare flow through pump outlet, with non start, and induced non start.

I think the problem lies with one of the levers attached to the leakoff sleeve on the high pressure piston. I'm not an expert in pump workings, but I feel I 'm 
about to become one! Rationally, if a pump is running in normal mode, which is fairly lean at idle and sticks in this mode when hot, when switched off, and 
does't default to starting enrichment mode when hot cranking, that would kind of account for the near starting, but not quite achieving it. Idle on my car is 
about 800 to 850rpm, but cranking achieves 300rpm at a guess, which may be insufficient to maintain momentum at that fueling level.

Mark

========================================
Message Received: Jul 09 2014, 02:49 PM
From: "peter blake" 

To: "Mark Shepherd" 
Cc: vwdiesel at vwfans.com
Subject: Re: [Vwdiesel] Cold Start 1... Hot Start 0

Mark,
I use a small electric fuel pump to feed the bosch pump.It doesn't put out much pressure; less than
7 pounds, but it prevents your situation from even developing. Perhaps the vanes in your pump are
worn or for some reason don't pump enough fuel when they are hot. I'm interested in what you 
finally figure out. Keep the list posted.
Peter
--------------------------------------------
On Wed, 7/9/14, Mark Shepherd  wrote:

Subject: Re: [Vwdiesel] Cold Start 1... Hot Start 0
To: vwdiesel at vwfans.com
Date: Wednesday, July 9, 2014, 5:54 AM

Thanks for all the replies. 
I have driven it without the solenoid plunger, and it's not
failed with it out, yet, but, having said that, after that 2
mile run, in a rush last week [perhaps making 
the pump hotter than normal], I took the solenoid plunger
out after restart failure, but it made no difference when
hot, and the AA man came about half an 
hour later, and it was still out, with the pump luke warm,
and his initial tentative use of Ether, and then generous
direct squirts beyond the filter, failed to get 
the engine to go beyond a stutter. 

Stalling the engine with the clutch is not much fun,
especially as it has a clutch that has been slipping
recently. It needs replacing, but I've forgot which size 
is already in it!

Today I did an 8 mile trip, broken up in the middle with an
hour and a half stop. No issues. Returned home, stopped the
engine counted to 10, and tried a 
restart. No problem. The trip was quite leisurely paced. 
I think that the issue occurs when engine is slightly
pushed, and then it seems to remain, until cool. I suppose
most journeys such as going to work, visiting 
friends, or a lengthy shopping spree etc and this fault will
not show itself. Forcing the glowplugs on with a jump did
not cure it. 

Thus I'm now down to the apparent low volume of fuel in the
fuel lines at hot start-up. 
The solenoid has now been discounted, and that leaves fuel
supply at startup. Fine when cold but, not when hot, maybe
when warm. 

I cannot see the vane pump being an issue as it is fed
diesel from the tank, with no recycling at the fuel filter.

It really must be linked to the special lever mentioned in
books, that holds the spill-off sleeve over and beyond
maximum fueling, for driving.

Compression likely not great, but certainly better than it
has been for many of the 7 years or so of driving this
engine!
Constructive comments welcome, even rude ones might be worth
a look Lol

Regards,
Mark

Mark

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