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Loss of oil pressure after distributor work?

So I worked on my buddy's GM 2.8, replacing the pickup coil in the distributor because the insulation on the original was rotting off in tatters. Took me

40 minutes to get the dang thing engaged with the hexagonal oil pump drive shaft when reinstalling the distributor. Started the motor and the lifters clacked like crazy. I shut it down after about 10 seconds. Turns out his oil pressure guage is non- functional, I'll be fixing that problem this next weekend, but I'm trying to figure out how I might have disabled the oil pump on this engine, if that is indeed what has happened. The hex shaft fits into a relatively tight hole through the block casting to the oil pump proper, the length of the shaft and the oil pump design is such that there's no place for the shaft to go down, and the distributor will not seat into the block completely unless the shaft goes into the distributor gear. Hmmm....

With the experience I gained rebuilding my motor, which is identical to his, I'm about 100% confident that the oil pump is working correctly. I can't see any way for the distributor to not be driving the oil pump. The only scenario I can think of is that when I pulled the distributor (which intersects one of the two lifter oil supply galleries in the block) the oil drained back into the engine and left lots of air in the system. Maybe the

10 seconds or so that it idled wasn't enough to charge the system completely?

I'm headed back out to work on it tomorrow after work, and to add heat sink grease to the module (previous installer put the module on dry?!?!).

JazzMan

Reply to
JazzMan
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Drain back of the upper gallies is not gonna cavitate the pump. I'd be pulling it back out for a look. . If you bumped it with the key to get it to seat, you may have sheared something . If you turned the engine by hand and you felt it seat . I'd be scratching my head too. Does the hex shaft have a pin in it ?

Reply to
Akacguy6161

You can get the engine priming tool at autozone from their loan-a-tool.

-Bruce

Reply to
Bruce Chang

Started it up again today and let it idle for a few seconds, the clattering went away. I had manually turned the engine while trying to seat the drive shaft, and apparently this pushed all the oil out of the lifters. Anyway, got that problem fixed only to have another one rear it's ugly head. Car was running fine, then started having an intermittent miss. Then the idle jumped to 1500, the IAC counts locked at 36 and the ECM lost control of the idle. MAP high pressure and MAP low pressure codes both set. I swapped MAPs, no change, and used a MityVAC in conjunction with my scan tool to verify both MAPs seem good. Pulled the ECM fuse for 3 minutes, codes didn't clear. Hmmm. I think the missing is causing a false rich condition, the ECM is driving it lean. One possible clue is that on occasion if you apply brakes, even if already at a dead stop, the idle will fluctuate. Maybe a bad brake booster. Another clue is that when I had the distributor out to replace the pickup coil I discovered that the last person to work on it had put the module in dry, no thermal grease. It's been run like that for at least two years, and maybe the module is bad. Sigh. These intermittent driveability problems with multiple scenarios are going to drive me nuts.

I haven't hooked up my fluke to monitor O2 directly yet, but with a false rich condition I don't expect that the O2 will tell me anything meaningful. The next time the problem occurs I will pinch off the vacuum booster line and see if the problem clears. Otherwise I will try swapping in a known good module.

JazzMan

Reply to
JazzMan

Sounds like a vacuum leak.

A miss would cause a false lean condition. When a cylinder misfires, you have (roughly) 15 parts air and 1 part fuel injected into the exhaust for each misfiring cylinder. The O2 sensor is just that, it detects oxygen levels not fuel levels.

It could confirm the lean condition in the exhaust and would let you know if the mixture is locked lean or intermittent.

Reply to
saeengineer

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