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Chevy Blazer Oil Pressure problem

17 messages,  Last post on Nov 05, 2009 at 2:19 AM

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#11 of 17 Re: 1991 S10 Blazer Blowing 25A AC / Heat fuse [jlflemmons] by rfletcher Aug 06, 2009 (7:42 am)
Replying to: jlflemmons (Aug 05, 2009 8:21 pm) The 12V line was shorted to ground.The 12V line leaving the evaporator pressure switch goes to a connector, which does not appear on the diagram in the manual, where a second line is spliced in. One 12V line to the contacts of the compressor control relay, the second to the control module and back to the relay solenoid. The connector also contains a circuit ground wire. I can only assume that the problem was in the connector because the short disappeared as soon as I opened the connector and never came back. I removed the wires in question from the sleeves, in both directions, looking for damaged insulation but found none. I will also assume, as Murphy so eloquently states, the problem will come back and at the worst possible time. Most likely, when my wife is out shopping in 95 degree weather. I shudder to think about it. This sort of issue came up in a general discussion page elsewhere on this site. The question was, why are there never problems, in this forum, with the ECM. As I remember, the opinion was that the trouble is almost always in the peripheral circuit and the ECM is so well hidden that a stupid mechanic, such as myself, can't damage it. Well, I tried really hard.   Thanks Replies to this message: jlflemmons (Aug 06, 2009 8:47 am) rfletcher (Aug 06, 2009 11:45 am)
#12 of 17 Re: 1991 S10 Blazer Blowing 25A AC / Heat fuse [rfletcher] by jlflemmons Aug 06, 2009 (8:47 am)
Replying to: rfletcher (Aug 06, 2009 7:42 am) Good catch, hope it is a longterm fix. It may be that just moving the connector around cleared a short somewhere down stream in the harness. Connectors [Usually] don't short, but stranger things have happened.   Regarding ECM failure, they are very rare. As any failure can cripple the car, a lot of attention is paid to these, and typically they are built using MIL-SPEC parts. Higher temp ratings, greater voltage tolerance, etc. The second generation S series ECM has a heat sink mounted to it. I have been told that many of the ECM that are replaced will test good. Either a harness problem, or bad contact in the mating connector. In a manufacturing environment, these are very easy to test and confirm good before installation. Replies to this message: rfletcher (Aug 06, 2009 11:45 am)
#13 of 17 Re: 1991 S10 Blazer Blowing 25A AC / Heat fuse [jlflemmons] by rfletcher Aug 06, 2009 (11:45 am)
Replying to: jlflemmons (Aug 06, 2009 8:47 am) Thanks, and I agree on the fault clearing that way. It's going to be a lot of trouble but I think that I should take a more extensive look inside the two sections of harness at least near the connector. It's working fine now, but a truck with almost 200K miles probably has arteries that look a little like mine.   I need to correct myself on accessing the ECM. It was not the shelf under the dash but the kick panel below that was removed. Still a miserable job, out and back in. Also, the other wire in the connector was not circuit ground. Still more reason to look further down the line. Intermittent problems can make you crazy.
#14 of 17 gauge probs by allen30 Aug 16, 2009 (9:43 am)
I have a 99 blazer the gas gauge doesnt read right {just what ever it wants to).`Oil gauge reads according to rpms, speedometer moves up some while in park as to rpms. Is the a bad ground? Replies to this message: norblazer (Nov 05, 2009 2:19 am)
#15 of 17 high oil pressure 99 blazer 4.3 by odaat Oct 03, 2009 (12:13 am)
recently when i start the engine i hear a slight ticking noise from the engine,and the oil pressure climbs to 60, (it is normally40) /after a few miles the pressure will return to normal / speculation is perhaps the oil pump is bad, or i should try a different viscosity oil perhaps 5w/30 / anyway this is a baffling problem, do you have any suggestions, thanks Replies to this message: jlflemmons (Oct 03, 2009 6:48 am)
#16 of 17 Re: high oil pressure 99 blazer 4.3 [odaat] by jlflemmons Oct 03, 2009 (6:48 am)
Replying to: odaat (Oct 03, 2009 12:13 am) What are the outside temps? Not likely the oil pump, try an oil change with Castrol or Valvoline 10W30 and AC Delco PF52 (high capacity) filter.   How many miles on the engine?
#17 of 17 Re: gauge probs [allen30] by norblazer Nov 05, 2009 (2:19 am)
Replying to: allen30 (Aug 16, 2009 9:43 am) My sisters '91 Blazer does the same thing. The gauge kinda act like a RPM gauge. Did you find out what your problem was?   Her also seem to just stop for no reason. It will stumble and die. A day later it's fine again like nothing has happened. It seam to come and go. Sometimes she can only drive for like 5min before it start to stumble and want to die. Others it will be fine for a week.

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