15

This engine is equipped with a voltage regulator. Depending on the exact construction of the regulator a reverse current would be disastrous, especially the high current from a starter battery


10

Why not just put a wrench on the crankshaft? Ignoring the electrical repercussions, I fear damage to the starter, too. Besides, if the starter on this tractor uses a sprag clutch (and probably most other designs), it wont engage backwards, anyway.


9

You just hold the rubber ended bit against the plug hole whilst cranking the engine. No, it does not blow out of the hole due to pressure build up. This is how such a unit is designed to be used. The different designs of tube allow use on different designs of engines, choose the one which feels most appropriate to the vehicle you are testing.


8

Looks like the starter drive is the typical spring loaded drive gear that engages when the starter motor turns in the "forward" direction, then disengages if the engine starts running and overdrives the starter gear forcing it to disengage. So if you run the starter motor backwards, the starter gear won't engage at all, and the starter will just spin. And ...


6

I use pressure transducers to test for cam sync problems. And other problems. Cam sync problems are seen on the waveform in a section called the exhaust ramp. The middle of the ramp moves back and forth as the valve timing changes. It is easy to see if you know where to look. Training in what to look for is required. It is a bit like interpreting ignition ...


5

You cannot assume just because it starts it has good compression. It can have minimal compression and still start and run just fine. That minimal compression is going to be different for every engine, so you'd have to look up the specifications for the exact engine you're looking at. The deal with it is, the more compression the better it will run (make more ...


5

I'm not familiar with your engine, but on the VW TDI engines quite a bit of oil can accumulate in the intake, particularly in the intercooler. The last time I did the timing belt I found about 100 CC of oil in the intercooler. I'd never though to clean it out before so I don't know how long the oil had been accumulating. I also don't know what circumstances ...


5

Regarding loss of compression The loss of compression can be explained by the evidence of oil in the cooling system. The usual way the two fluids mix is when there is head gasket failure and/or warpage of the cylinder head. In the case of cylinder head warpage, the head does not seal some of the combustion chambers completely, which results in low ...


5

Analysing in cylinder pressure waveform is extremely useful in developing combustion strategies in OEM R&D environments and also for diagnosing lots of issues. I have taken picture and its explanation from a Snap on product catalogue which I thought was well explained. A—Ready Position — Piston has stopped at TDC — Cylinder contents are compressed ...


5

Even if there are no polarity-sensitive electronics to damage and the starter motor was able to engage, it is unlikely that the motor would rotate backwards anyway. Most car starter motors (in fact all that I have worked with) do not use permanent magnets, instead opting for coils for the stator. I suspect the same may be true for your lawn tractor. ...


5

A compression test will only give you a general idea of engine health It WILL NOT help you to understand if there is gunk buildup in the engine It WILL NOT tell you if you have a specific issue with your valves or rings It WILL give you an idea of whether you have good compression or not. A compression tester will give you an idea of whether you cylinder ...


4

It is good to check first if the coolant in the radiator has oil droplets inside, and if the oil (most of the times using the dipstick) has water inside. Then with a compression test you will be able to tell if the piston rigs are still ok, if the valves are sealing the chamber properly. However in order to understand how good or bad the motor is, you will ...


4

Most accurate way to diagnose plugged exhaust (not severe) or chain stretch is to compare to known good waveforms on same engine and year. Like any other diagnostic tool of this type it takes time and experience to do it without comparing to good waveforms. Another good tool in conjunction with compression tool you describe is looking at oscilloscope ...


3

So searching the Internet, I've found some conflicting opinions, with an occasional person saying either that cold leak down tests are completely invalid, or that cold numbers will be two to three times warm numbers. Some people relate the numbers to how big your ring gap is: I just did a cold test on my fresh off the dyno engine, over the past 20 yrs I'...


3

It should be at the beginning of the Chapter 2 portion which covers General engine overhaul procedures. Whether it's in 2B or 2C or subsequent sub-chapters will depend on how many engine options there are for any specific vehicle. When you find the section on the overhaul procedures, it should be locate under the "Specifications", with a sub-heading of "...


2

If you attempted to run the engine with the valve train improperly aligned, you may have caused valve damage to your head, as this is an interference motor. This would definitely affect your ability to produce a lot of compression within the cylinder during testing and could be the reason why it's not running. Unfortunately, about the only way you'd be able ...


2

Does my hypothesis sound reasonable? What doesn't sit well with me is that the engine has already been cranked a lot (when the cylinders were flooded). Regardless of whether the engine started, shouldn't that be enough to relubricate the walls? Compression can be lost through: curvature in the cylinder head leaky head gasket leaky valves gaps between the ...


2

Compression tests certainly have their uses - I wouldn't go so far as to say they should be a routine part of the car buying process, unless you have reasons to suspect an issue or you're buying an RX-8. A small loss of compression could easily be present without causing a misfire and could produce a feeling of sluggishness or being down on power. The ...


1

As is said here 2-Stroke Squish & Compression Testing The Best Way to get a Valid Compression Reading A) Within 5 days of a normal “operating cycle - Engines that have sat for a long time may have excess oil that has leaked in from somewhere. The added ring sealing offered by this excessive oil presence can greatly increase the normal valid ...


1

This is only a partial answer: You could narrow down your diagnosis by comparing the volume of both heads. If both volumes match, then the new head is fine and your problem lies somewhere else. How to measure the volume of a cylinder head. Remove head. Attach spark plugs and valves, without rocker arms or camshafts, so that all the valves can be closed. ...


1

This could be caused by any number of problems. The most common are probably: Stuck or burned valves Blown head gasket Burned piston Damaged piston rings and/or cylinder wall Is there any other history of this vehicle that might give some more clues? But before you do anything else, please double-check your compression tests. I find it odd that there ...


1

A compression test is a useful diagnostic aid. It's definitely wrong that all compression-related issues manifest themselves as something that can be seen or heard. It's very possible to have low compression due to worn components (such as rings) that will reduce the power output of that one cylinder without being obvious during a drive. By doing a ...


1

It's not that likely to be the head gasket, if it is you'd have oil leaking into the coolant or vice versa, plus lots of white smoke coming out of your exhaust. More likely it's worn rings or your valves aren't seating properly, and I can see from your wet compression tests that it's worn rings or cylinder walls. The reason I say it's rings is that the wet ...


1

A compression test is a proxy for "there's a problem" but you'll probably need to go and do a leak down test to identify specifically what's the problem. As stated above these tools are helpful in identifying problems with the core of the motor - how effectively will the pistons, rings, valves, etc function or is there excessive wear or damage. There are ...


1

I have owned many VW diesel cars since 1977. Runaway in the IDI engines was more common than in the TDI engines. In general, runaway is from the ingestion of oil, normally pooled in the intake manifold (IDI) or somewhere in the intake system like the intercooler on TDIs. This is for VW, and I am sorry, I cannot address your specific car. When runaway ...


1

I did some searching on IATN and found known good pressure waveforms that are identical to my after repair captures. Unfortunately I can't post them here. It turns out that hump is completely normal. After doing more captures on different cars with VVT I've found that most waveforms are unique to some degree. I guess the same can be said about non VVT ...


1

Your piston rings are worn. This is allowing oil into the combustion chamber so it's being burnt off... Typically accompanied by a sweetish smelling exhaust and heavy gas smell in oil itself. And the reason you didn't need to step on the gas when the compression was checked is because the spark plugs shouldn't of been working... This it wouldn't have helped ...


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