'90 Buick stalling, no start - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-19-2011, 03:18 PM   #11
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FP, KOEO was 42psi but slowly dropped to 40psi, specs are 40.5-47psi.
FP, KOER was 36psi, specs are 30-37psi.

Nothing wrong there that I can see, I didn't even try the vacuum pump as it appears to be fine. Squeezed the vacuum line during KOER and pressure increased as it should.

The diagram shows a Pump Prime Test Lead being one of two orange wires which doesn't make sense. There isn't two orange wire but only one but there is a red wire. All wires go into a harness with no test connector to put 12V directly to the pump. I'll have to check AllDataDIY to see it shows the location of that test connector

Here'* the current waveform for the pump, KOER.


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Old 08-20-2011, 05:37 PM   #12
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I had a thought. What if the EGR valve had stuck open for a bit and is now working properly? I couldn't find a EGR valve although several auto parts dealers list one for it.

Did some searching and although I find this odd, somebody states that some GM 3300 engines use a ERG valve and some don't! Another person state none do.
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Old 09-05-2011, 10:28 AM   #13
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Here'* two scope screens during a start/stall.

Red=EST from ECM
Blue=5V Bypass from ECM
Green=RefHi ICM output ECM
Yellow=1X Crank Position Output to ICM

The two needed outputs from the ECM have dropped and restarted during starting. Unless the ECM is losing power, it'* defective. Annoying since although ECM was replaced in '03/'04, it only has about 5K on it! Back then, the ECM was dropping the 5V Bypass only, IIRC.

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Old 09-22-2011, 01:34 AM   #14
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Update:

For anyone interested. The problem turned out to be bad injectors. One was almost a dead short which causes the ECM to shutdown and/or sometimes damages the drivers. The car started with that one left disconnected but the scope still showed a partial short which was another one on the other bank the read under specs. With that one disconnected also, it ran a bit rougher but the injector signal looked correct.

This is supposed to be a common issue with the injectors used on this engine. I'm waiting on a set of injectors now.
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