| Electronics > Beginners |
| Is this a bad sensor or are my O-scope settings off? |
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| McKay420:
--- Quote from: Gregg on April 19, 2018, 06:17:18 pm ---If you have variable valve timing, it may be oil pressure activated. The reason the timing chain was mentioned is both noise and blips on the scope. A camshaft isn’t unidirectional; the valve springs reacting against the lobes can give it counter rotational forces that may cause less than stable signals on a cam position sensor. In other words, looseness in the timing chain can cause increasing rotational variations in the cam. With as many miles on the vehicle as you stated, the timing chain cannot be in the best shape. Moisture in the exhaust may be normal combustion byproducts that collect in the exhaust system until it has a few highway miles and is fully warmed up. Most likely you are seeing oil smoke due to the diluted oil going through the intake valve guides (and maybe the piston rings). With so many miles, the valve stem seals are not doing a very good job and the intake manifold vacuum just sucks the oil in. There are ways of changing the valve stem seals without removing the cylinder head. You may want to go for slightly heavier weight oil and get rid of the seafoam before you put any real load on the engine. Fram filters may not be the best choice; Wix or Delco are the best for the $ although Fram does make some premium ones that are OK. Rock Auto is a good source of parts of all kinds but with shipping sometimes some things are cheaper locally. --- End quote --- Valve seals makes sense since I just pulled my PCV hose and there it's full of oil, even after changing the valve cover gaskets and detail cleaning the valve covers and PCV valve and surrounding areas. Well it's not really a PCV valve in this case, I would call it more of a PCV restrictor, since there isn't an actual valve, but just a hole. Are you talking about using compressed air to keep the valves pushed up or isn't there another method where you just have to find TDC on each cylinder before you undo whatever holds the valves in? Woudn't that be the nut/bolt in the middle of the rockers? I guess I can probably figure that out on my own since I have an AllData subscription, but I don't think they have alternate methods for doing things like valve seals. I may actually decide to just go with a complete rebuild this summer before I start buying too many individual pieces that would usually be included in a rebuild or I'm gonna end up wasting money. A rebuild kit is only $450 which seems pretty reasonable. Not sure if it comes with pistons though or if I even need them. How many extra miles does a well done rebuild usually get you if somehow the body and suspension or other components don't wear out first? --- Quote from: mikerj on April 20, 2018, 12:15:16 pm ---A faulty crank sensor can not stop the engine turning over (i.e. being cranked by the starter) unless it's physically fallen into the flywheel and jammed it. It will prevent the engine running of course. --- End quote --- Don't some vehicles disable the fuel pump in the abscence of an RPM signal? In this case, it would crank, but not turn over for even a second. I never had a no crank problem. It was a crank, no-start. |
| mikerj:
--- Quote from: McKay420 on April 21, 2018, 06:33:26 am ---Don't some vehicles disable the fuel pump in the abscence of an RPM signal? In this case, it would crank, but not turn over for even a second. I never had a no crank problem. It was a crank, no-start. --- End quote --- Cranking the engine is turning it over. |
| McKay420:
Yeah I guess that makes a little more sense. I always get that mixed up. Ok so my engine would turn over, but it wouldn't fire. |
| tautech:
You imply it's an injected motor and the fuel rail pressures required are such that an electric fuel pump is normally used. Most vehicles they can be heard rattling away until required rail pressure is reached when the key is turned on. In such a motor if all things that normally support combustion are OK it's either no ignition spark or no injector pulse that would stop an engine from firing. Or in the case of an ECU with various sensors either a crook ECU or faulty sensors. |
| McKay420:
Well when my engine wasn't firing, I couldn't hear the fuel pump prime. If I take a paperclip when this happens and jump from socket 87-30 where the fuel pump relay goes, the pump starts up no problem. I have since replaced the fuel pump (for a bad check valve) and have not had this issue. Today, however, I used the old pump to make an injector rail tester and noticed that the amperage was only around 1.5a. When I measured the amperage of the same pump while it was in the vehicle (used multimeter to jump 87-30) and got 7-8 amps. What is normal for a fuel pump? It seemed to hold pressure fine today on my rig when it was running, but I think the most I saw it go to today was 2 amps. Anyway, we're getting quite far off topic from my original question. The no-start has not happened in a couple months. I rigged a can of carb cleaner to each injector using fuel lines and shrink tubing to adapt the size. I sprayed each for at least 20 seconds and at least half of them had a bad spray pattern and the other half were literally PERFECT. So perfect I did not feel the need to take pictures or anything. After being sprayed, the other half slowly opened up to I'd say 95% quality spray pattern. I also flow tested them after that. Specs for my injectors say 33lb/hr at 50psi (flex fuel). This comes out to 41.6g every 10 seconds. I wired a rocker switch to control the injector, with the fuel pump constantly running on the same power supply circuit. Pressure held steady at 52 psi during testing. Each injector was tested 3 times and an average was taken. Here are the results: 39, 40, 38, 39.5, 40, 36, 41, 40. As a percentage with all injectors added together, They are working at 95% efficiency, which should roughly account for 5% of the 15% fuel trims. I also replaced the O-rings. Before reinstalling, I dumped a can of Seafoam on the pump while it was running in order to fill each injector with Seafoam. Let rail sit full of seafoam for 30 minutes and was slowly pulsed out of each injector. As I write this, I have not started the vehicle yet. Injectors were not kept in the same order as taken out. I will report back if any of this helped anything, but that would be quite the shock. |
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