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Old 09-08-2014, 02:42 PM   #1
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Join Date: Jan 2013
Location: LaSalle ON
Default B21FT Impulse Relay Function


I have a 83 240 turbo with the original b21ft in it and I was wondering how the impulse relay works during warm starts.

Referencing the green book it says "during warm starts the impulse relay is engage after approximately 1.5s. It then gives a 0.1s pulse of injection with a 0.3 second interval"

My question is how long does it perform this pulse on / off cycle?

The reason why I am asking is during operation in warmer weather (80F+) I noticed that after starting the car stumbles for a few seconds (like 5 - 10 sec) at idle then it runs perfect. Normally this occurs for a relatively short period of time but last Friday we had a very warm day 90F+ and this bogged idling occurred for even longer almost like 30 sec. This condition only occurs after the car has been sitting for about an hour and a half after I have been driving it and does not occur when my car has been sitting in the parking lot all day at work.

My thought was that the thermal time switch is telling the the cold start injector to fire when it doesn't need to but after reading the description of the impulse relay I think it is related to it.

Any help would be appreciated.
1983 242 Turbo w Tremec T5 152,000 km's B230FT LH2.4

2019 VW Golf R w 6 Speed w 1320 kms NEW DD

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