"Future Heap Owner" (aperiodic)
08/11/2019 at 20:05 • Filed to: Hey maybe it’s not a terrible idea to put time and money into this truck, Gmt400, Chevy, Maintenance
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"Future Heap Owner" (aperiodic)
08/11/2019 at 20:05 • Filed to: Hey maybe it’s not a terrible idea to put time and money into this truck, Gmt400, Chevy, Maintenance | 1
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After I had finished most of my errands and chores for the day and gotten Ravna good and tired for the afternoon, I spent a couple hours working on the truck.
Dumbo mode engaged
If you don’t remember my post from last week, the background is that the truck doesn’t seem to be running well: it makes a weird noise for a few seconds after startup, and the old spark plugs don’t look ideal. In particular, it looks like oil is getting into the #7 cylinder somehow, but a lot of the plugs look sorta like the engine is running hot and/or rich.
Because I am very slow with automotive work, the only things I did were replace the spark plugs and, while the plugs were out, test compression on all the cylinders. Happily, the compression numbers are where they should be:
Driver Side
1: 150 psi
3: 140 psi
5: 150 psi
7: 140 psi
Passenger Side:
2: 140 psi
4: 140 psi
6: 140 psi
8: 150 psi
I tried to crank four revolutions on all cylinders, but I may have done five on the ones that showed 150. Either that, or other variance, or maybe the cylinder heads on those are gunked up with carbon.
One interesting thing I noticed is that, while I had disconnected the fuel pump fuse for the compression test, I did still hear the same weird noise it makes after startup while the engine was cranking (though it did not last as long as when starting). Does that rule out the injectors as the source of that noise? Or are the injectors still trying to do their thing even though there’s no fuel pressure?
Oh, and yesterday (after visiting three different stores and buying too much stuff) I finally managed to get the distributor cap off, and the cap rotor seem ...fine?
expect a little dirtiness
on this old a truck (though the distributor cap was replaced fairly recently (no more than four years ago).
I’m about to take the truck out for a short drive to see if it’s running any better. My main question for all of you is: what do you think I should do next to determine how oil is getting in the #7 cylinder? I think my next move will be to remove the valve cover on that side, take a look around, and replace the valve cover gasket, but maybe there’s another (easier) diagnostic step I can take before that.
Update: seems to be running pretty smooth and pulling fine. Dunno how accurate my butt dyno is in this heavy a thing, but knowing that when new it had less power than my Volvo, I think the power is in the right ballpark . It s till stalls trying to drive the power steering pump when doing hard turns at low speed. My blind hope for that issue is that a throttle body clean & rebuild will help.
Urambo Tauro
> Future Heap Owner
08/11/2019 at 22:38 |
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One interesting thing I noticed is that, while I had disconnected the fuel pump fuse for the compression test, I did s till hear the same weird noise it makes after startup while the engine was cranking (though it did not last as long as when starting). Does that rule out the injectors as the source of that noise? Or are the injectors still trying to do their thing even though there’s no fuel pressure?
Hm, I thought a quick peek at a wiring diagram would confirm, but I’m just more confused now. The fuel pump fuse is labelled “FUEL PUMP, PCM”, and disabling the PCM should keep the injectors from firing... but I’m also seeing another fuse labelled “INJEC TOR #1, INJECTOR #2, PCM”. So the PCM gets power from two fuses? Is that just a redundancy, or are different parts of the PCM powered by different fuses? I dunno.
Eh, my diagrams are specific to 1995 models, so they might not even apply to your truck here.. .