On Oct 8, 2008, at 12:23 PM, Peter Merle wrote:
This engine has been driven has been using WVO for arround 12000 km .
It is
using a 1micro filter. He has another W123 300D also on WVo and its
been
going for arround 32000 km now without issues.
What gets damaged in the pump? Surely it would be terminal and not
intermittant.
Thanks
Peter
Peter,
I have a number of clients that run/have run WVO. One has amassed in
excess of 80k miles on WVO and is only now beginning to show signs of
problems, while others traveled only a few thousand miles and ended up
with damaged IPs. The viability of running WVO is only as good as the
conversion. Most conversions do not heat the WVO to a high enough
temperature (min. 160 F) and this is the number one cause for IP
failure based on my experience. The viscosity of properly heated WVO is
close to that of cold diesel. As temperature of the WVO decreases its
viscosity rises at a near exponential rate. Our IPs were designed to
operate with fuel having a viscosity lower than that of cold diesel,
i.e. warm diesel. It was never expected that these IPs would be
continually running cold diesel; it would only see such until the motor
reached running temperature and was able to warm the fuel. If in doubt,
feel your spin-on fuel filter after a 20 minute drive,, it will be
downright warm, even without an auxiliary fuel heater. Given this, my
hypothesis is IP failure is a question of when and not if when running
WVO.
I owned a Euro 300td, non-turbo OM617. It saw WVO under the previous
owner's tenure (+/- 10k miles) and the oil was not sufficiently heated.
That motor would often, not always, suffer hard starting when hot and
an intermittent miss, only at idle, hot and/or cold. The miss was
without rhyme or reason with the exception it was more prevalent at
higher ambient temperatures. However, once running, it exhibited
excellent power, textbook fuel economy, and did not miss off idle. All
of this running diesel. I replaced the IP with a known good unit and
all the problems went away. Of course, I did my homework to verify the
rest of the motor and fuel system was sound before proceeding with the
IP.
However, the majority of the MB diesels I have come across with an
intermittent miss at idle either have defective fuel injector(s) or a
cylinder with out of spec compression on one or more cylinders (be it
due to rings, valves, etc). It would be foolish to conclude a faulty IP
based on your symptoms without doing further diagnostic on the motor.
In conclusion, the IP issue can be intermittent based on my experience.
MB IPs seldom fail catastrophically and without warning. Almost always,
they show signs long before complete failure. As to what fails in the
IP, there are a myriad of possibilities. Truth is, it really does not
matter, as IPs are meant to be serviced only by those with the
equipment and experience necessary to repair them. IPs are not meant to
be repaired by the general mechanic or the casual DIYer (outside of
delivery valves and seals, the feed pump, and oil servicing for the M
pumps with self contained oil systems). Proper diagnosis and repair of
the IP requires a calibration bench among many other things. Some
things are best left to the professionals. There are only two outfits
in the US I would trust my IPs to.
Mathieu
www.oldworldauto.com
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