Jim Grant's Tech Tips
Chevy Silverado, Propane Back-fire
Q:
I run my Chevy Silverado
1500 with a 4.3 engine on propane. The engine sometimes gets blowback
in the air intake. The last time it damaged the air intake. I have heard
this can be a common fault on some propane conversions. What can I do
to stop this?
- Dave A.
A:
That is a problem on
many newer vehicles that are converted to operate on propane. Part of
the problem has to do with the new style intake manifold designs. The
newer manifolds have long passages called runners that the air entering
the engine travels through. Also the newer style intake manifolds are
designed to manage/optimize air flow to the engine. The fuel injectors
introduce fuel just as air enters the cylinders. With propane, it is mixed
with the air as it enters the intake manifold. With long paths for the
air and propane to travel you have created the near perfect conditions
for a lean backfire as the throttle is first opened. When this happens
it can ignite the air & propane as it enters the intake manifold.
This creates a propane torch, which does great things to the plastic and
aluminum used in todays intake manifolds. If this condition is a common
event on your vehicle then something isn't installed correctly; you have
ignition, fuel control or engine problems. A tech working on these systems
has to know his/her stuff to rid your truck of this problem. A lot of
people install these systems, but it is few and very far bewteen that
know how to optimize their operation. Once the system's working right
it's better than gas, real clean and the engines go/last longer.
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