----- Original Message -----
From: "Jeanne Lacourse" <cckw@mediaone.net>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Wednesday, May 02, 2001 11:50 PM
Subject: [MV] M151 engine problem Suggestions?
> My M151A2 (AKA Piece of S*) did something today that it did late last
year:
>
> I had just had it inspected and was about a mile away and was pulling a
> moderate hill at about 40 in 3rd. All of a sudden it seemed to lose power
> and the temperature rose to over 220 degrees. It then started to pop back
> thru the carb. I though maybe I was running out of gas and pulled out the
> choke which seemed to help. A little past the top of the hill, everything
> returned to normal.
>
> Suggestions?
>
Depending on the prevailing conditions, the elusive carb icing can cause
just this, spitting back is commensurate with a very weak mixture which
burns very hot indeed, possibly overheating spark plugs which serves to
exacerbate the effect.
Pulling the choke would roughly redress the balance of the mixture but limit
the total mass of mixture the engine can pass.
Icing is virtually impossible to find since almost immediately the engine is
stopped to investigate the tiny amount of frost, usually formed at the main
jet spray system, is immediately thawed by engine heat.
As described it would seem the conditions were just adequate to cause
freezing at high volume flows, ie., working hard at moderately high revs, as
soon as the carb flow demand and therefore the level of vaporisation cooling
dropped slightly the effect disappears.
Other things that may cause similar effects are incorrect heat rated plugs
which may begin to glow under heavy load and ignition mis-timing which can
have the same effect.
Richard
Southampton - England
This archive was generated by hypermail 2b29 : Tue Jun 05 2001 - 23:18:30 PDT