Great video Mario. I agree, a failed RC test could easily send you into a wild goose chase. This is a good point you made because it isn’t talked about often.
Thank you for the time and trouble of posting this valuable educational video, yes often the gremlins can be miss fueling or water in the tank, or cheap fuel sourced from unreliable sources (junk yard) customers are not always very upfront or truthful in dissecting the core issues that could be resolved fairly quickly, i cannot understand why some car owners will use any narrative to sway the diagnostic procedure, misguided by a degree of vagueness and in asserting ignorance hoping that will bring about sympathetic results and a cheaper price! 🤔
It amazes me how people manage to do that (fill a gasoline car with diesel). The size difference of diesel and gas nozzles prevents people from putting diesel in a gasoline car. But as the saying goes, "If you make something idiot-proof, someone will just make a better idiot"
Here the importance of following notes. I now write down down all possible possibilities when diagnosing no start and go thru them chronologically. Sometimes you just forget... Nice tip
Great video, definitely something to keep in the back of your mind. I could see that being overlooked very easily. And would not be a fun rabbit hole to travel down! Thanks for all the great content. I’ve learned so much from your videos, keep it up man!
Mario, thanks for your video, great info on the cylinder walls getting washed down. Had a BMW come in.. So much time spent on it.. If we could get it running, it actually ran fine after warming up.. The way it was figured out that there was diesel in the gasoline was by accidentally spilling a little bit of it on the ground and realizing that it wasn't evaporating...
I see a lot of gas in diesel (vs here was diesel in gas) and a couple things I have seen when the two are mixed. Gas obviously has a stronger smell so you can smell it when it is not supposed to be there. If you put a little of the mixture on your fingers (just a drop or two) it will be a little oily. Where straight gas will not and straight diesel will be really oily. Lastly put about a teaspoon of the mixture on a workbench, when it spreads out you can watch the gas evaporate out of the mixture and you will be left with just diesel fuel. That will give you a good idea how contaminated the system is.
What a great video it shows that you never know what a customer is capable of and the never ending things that can enter in to diagnostics thanks for sharing.
New subscriber. Older DIYer but just learning scopes. Have many years of mechanical background but but self teaching with techs like yourself,Paul Danner, Keith Defazio, SMA, Cody diagnostics, PHD Ivan leading the way. Thanks for sharing. Artie 👍
agreed....and when you go down that wrong path you never forget....in my automotive journey whenever the vehicle is changing symptions right in front of you it is best to take 2 steps back and really think about whats going on...
Customer questions 1 have you recently refuelled 2 how much fuel 3 do you have the receipt. Misfuel is massive effective questioning minimising Diag time.
Mario! que buen video en definitiva esas son algunas experiencias que dejan marca y nunca se nos olvidan, me había tocado gasolina y agua y provoca falla, pero gasolina y diésel no. Gracias por compartirlo!!
I've experienced cylinder wash a couple times. I also used brake clean to try to start a car i pulled the engine apart and had to throw the pistons away because it welded the rings in the grooves
this is the very reason I use external fuel supply on drivability issues.....very simple to rule out fuel as an issue or in your case, the main issue!....great vid Mario.......
hope you don't think I'm coming across as a "know-it-all" but in reality fuel quality is one of the most overlooked items....I just had a early ford 3.0L (flex vehicle) with positive fuel trims..and not really running constant....took a good fuel sample and did a alcohol content test (10% water, 90% fuel from vehicle) well it was at 40%....enough said.....once again great vid
billmck12345 if you don't mind me asking, what is your method for running on external fuel? I've diagnosed fuel misfires by running the cars on fuel cleaner through intake but sometimes can be a pain since the one I use has inconsistent spray.
So if diesel washed down the cylinder wall, and it actually ran like that, was there any immediate critical damage caused to the engine or fuel tank? How did you handle the fuel system?? Did you, or COULD you directly jump power to the fuel pump with the fuel line off, running a hose from the pump to a fuel can to pump out the old gas? Did you have to remove the tank to clean it? And what work did the engine need afterwards besides new oil?
I had a customer replace a 750,000 engine put it together same problem I went in Turns out bad fuel Recommend every one have a hydrometer in there box to test fuel I did a video showing the test device Great video mario
Great information thanks, yes i have seen this before only just last week i got call out to a workshop that i car went in for just a service when they went to start the car it crank very slow on a low battery it got wash down and we had almost no compression the fix was put oil down the cylinders and then the car started and after a few minutes the car was ok . This all happened because of a low battery. So yes your right be very careful with Relative Compression test .
Hey mario. I had a vw tdi fuelled with petrol/diesel mix. Wasted time on loads of test till i did a leak off and the fuel was yellow. Wish i had of videoed it. Cheers dave
SUPER MARIO DIAGNOSTICS /// ,,, when one or more pistons are NOT giving any compression. What would be the problems on the cars engine? /// Do you have to replace the piston or the actual engine block is cracked inside that piston cylinder and have to replace the whole engine block?
Cylinder wash would kill some compression but can it kill all of it?And diesel can wash the same way as gas? Diesel is "thicker" than gas so it should keep the compression and maybe seal those rings even better? The car will not run because it will wet those plugs and even if were dry it can not ignite diesel anyways. Sometimes is very hard to detect fuel contamination especially if you are not familiar with diesel. The fuel in the dipstick was from lots of cranking and the fuel would leak down past the rings at rest.If this car is gdi than would make the spraying of fuel worse if it ran leaner at start up. The thing is that it was not 100% diesel so maybe thats why you had irregular compression values. You didnt show the values on each cylinder.Were they low or some of them higher than spec? Hope you like my comment.Really like your videos and im learning a lot with them. Thanks Mario.
How do you do a relative compression? Did you disable fuel or ignition? It would be nice to see how you got those results to either see what the problem is.
I disconnected every injector. Not sure i understand your last statement. I was about to check fuel pressure since it ran with alternate fuel. When i saw green gasoline come out, i took a sample and confirmed that it was diesel.
Super Mario Diagnostics so even with injectors disconnected the compression was bad “relative”. I guess a lot of diesel in the oil too. Thx a lot for this good information. I have run across contaminated fuel but have never done a relative compression whit it. I will next time. This got me curious.
Yes an change was necessary as well. Compression was erratic between all cylinders depending on sealing. At times it would idle perfectly, other times crank no start. Definitely was interesting, a plena vista. Hey, thanks for watching buddy and taking the time!
I think I would've been caught going the wrong way on that one. Good job of staying in the diagnostic funnel. I think I'll subscribe to your channel. 😉
Excellent video, another variable, great tips Mario! Can you put link to related video in your description for us? I'm going to watch it, but it's nice to have quick link, because I'm slow...lol! She's got power now baby, rockin' the diesel!
We cleaned out the tank, flushed out the line, cleared out the cylinders, did an oil change, and it was good to go. Luckily no rods were bent, no misfires afterwards, he got very lucky! Thanks for watching!
This was very interesting. In the early days of unleaded fuel, the pump nozzle, and the car filler port, were a smaller diameter, preventing putting leaded fuel in an unleaded car. Do diesel pump nozzles have something similar? Thank you for sharing. Did I just give my age away? Haha
They aren't federally mandated. But at this point it's hard to say exactly whether it was the pump nozzle or filler neck that allowed for this to happen
Super Mario Diagnostics yes I did but I like to try to guess ahead of time and you and Ivan always throw me curvs I do enjoy your videos very informative
The waveform represents the compression of each cylinder. This would suggest a mechanical fault since there are two cylinders with low compression compared to the other two. If you were to look at a good engine, you'd see even, uniform compression strokes.
@@SuperMarioDiagnostics yes that I see and understand. But there's 2 high peak And 2 low peak . Indicating 2 cylinders having a lower compression then the other 2.. but I guess you have to hear it cranking to determine if it really ran ruff and having cylinder imbalance issues.. thanks for the great diagnosis. Good call. Keep it up.
Yes, he does have a video where he gets a compression reading from one cylinder, and divides the amperage by the psi. So x amps per psi. Then using that he fills in the rest of the compressions based on their individual amperage. Not meant to be a precise calculation though, he does mention
@@SuperMarioDiagnostics ScannerDanner has videos on relative compression, but I can't find the "psi per amp" video :( Are you sure it's not Matt's video (first result searching "relative compression test psi")?
