Blazer code 439 440 where to look

RONALD SCHWARZ

MEMBER
1988 CHEVROLET BLAZER
150 MILES

88 blazer will show service engine soon light when running down road. Truck will start to stall and lights go out. Will do this on and off a half dozen times. Dosen't quite die, but when I pull over to check it, it will not start. No service engine soon light, no nothing. Will take a bit and start. Book states trouble shoot the two circuits (439 & 440), but I don't know where they are located. Any help on this would be appreciated. Everytime I think I fixed the problem, it reappears. Or if your familiar with this problem and know a fix, that would be great. Thanks for your time on this,

thank you
ronald

2 Replies

JACOBANDNICKOLAS

MECHANIC
109,787 POSTS

It could be a vacuum leak, fuel pressure issue. What trouble codes did you get. WIth the OBD 1 they should be two digit codes.

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Sunday, October 16th, 2011 AT 12:45 AM

RONALD SCHWARZ

MEMBER
2 POSTS

Sorry was out of town, my obd is not giving me any codes.I have been reading the repair books from the auto store and they say check the (439 & 440) but they do not say where they are at.
This is what I have tried since I got home
Did the fuel filter, old one was good-no dirt. Check plugs and they are
good.
But still dosen't explain the lights going off and on and the
times the truck won't start, no electrics anywhere, but will crank the
engine. No headlites, interior lights, no stereo. Period. But the engine
will crank over with the key. And sooner or later it will start
any suggestions
thank you