Discussion:
Backfire through intake system

Hello, wondering if any of you Komatsu guy's can help. I have a FG50 with a Nissan TB45 propane engine that periodically backfires through the intake blowing the air cleaner cap off. This only occurs under high revs when lifting,never when travelling.
I have went through the basics (fuel spark wires cap rotor plugs timing valves etc) but can't seem to pin point it. it doesn't throw a code and only seems to do it once a shift (once is to many) regardless of operator. This unit is run very hard though.

Any thoughts would be appreciated.
  • Posted 11 Aug 2010 07:06
  • Modified 11 Aug 2010 07:07 by poster
  • By FORKLIFTCHICK
  • joined 11 Aug'10 - 16 messages
  • Alberta, Canada
Showing items 1 - 6 of 6 results.
Common cause 4 this is lpg set too rich and check inline flow valve not open 2 far
  • Posted 25 Jan 2020 22:07
  • By Firerescue
  • joined 25 Jan'20 - 9 messages
  • New Zealand
Bryan
Gary & Frank are good first choices. They both have been known to cause the backfire issue you are speaking about. After cleaning out the distributor, double check your timing as well. If all else fails, pull the head and send out for a rebuild. We have seen bad/leaky valves in hard run trucks do this too.
  • Posted 27 Nov 2010 22:33
  • By Jeff
  • joined 8 Feb'07 - 60 messages
  • Georgia, United States
I have found if the unit is in very dusty conditions, due to the dist cap is vented,it picks up dust under the rotor button cover.(three screws holds it down).Remove and blow out the pickup.( gets its timing from crank sensor)Good Luck
  • Posted 14 Nov 2010 03:49
  • By frank_a
  • joined 14 Nov'10 - 1 message
  • Georgia, United States
Check the camshaft, had the same problem and found one of the camshaft lobes had worn down causing valve to stay closed.
  • Posted 27 Aug 2010 18:32
  • By catlover
  • joined 19 Apr'09 - 4 messages
  • Victoria, Australia
Thanks Gary but weve tried that.
  • Posted 12 Aug 2010 00:34
  • By FORKLIFTCHICK
  • joined 11 Aug'10 - 16 messages
  • Alberta, Canada
I had the somewhat of the same problem. try replacing the MAP sensor.
  • Posted 11 Aug 2010 07:17
  • By GaryE
  • joined 19 Nov'09 - 3 messages
  • California, United States

Post your Reply

Forkliftaction accepts no responsibility for forum content and requires forum participants to adhere to our rules of conduct. Click here for more information.

If you are having trouble using the Discussion Forums, please contact us for help.

TCM FHD105Z
Yokohama, Japan
Used - Sale
Mobicon 2T
Coraopolis, Pennsylvania, United States
New - Sale
Global Industry News
edition #1237 - 3 July 2025
While innovation and new technology are evolving at what seems to be an ever-increasing pace, the need to capture the data (telemetry) from this tech, and the ability to utilise it (telematics) for efficiency and cost savings, is one area attracting more and more attention ... Continue reading
Movers & Shakers
Jeannette Walker Jeannette Walker
CEO, MHEDA
President, European Rental Association (ERA)
Chief marketing officer, JLT Mobile Computers
Chief executive officer, East Penn Manufacturing
Global Industry News
edition #1237 - 3 July 2025
While innovation and new technology are evolving at what seems to be an ever-increasing pace, the need to capture the data (telemetry) from this tech, and the ability to utilise it (telematics) for efficiency and cost savings, is one area attracting more and more attention ... Continue reading
Upcoming industry events …
October 6-9, 2025 - Detroit, MI, United States
October 6-9, 2025 - Detroit, MI, United States
November 14, 2025 - Melbourne, Australia
Fact of the week
The use of "hello" as a telephone greeting is attributed to Thomas Edison. He is said to have suggested it as a simpler alternative to other greetings, such as "Do I get you?" or "Are you there?".