Compression Test

[dawson]

Tried to do a compression test today and discovered that my gauge doesn't have an adapter small enough for the tiny little plugs on my 09 vtec.

Has anyone seen any adapters that will go from a 12/14 mm gauge to a 9mm plug hole? I checked the part number listed in the service manual and it looks like the whole gauge, retailing for 300$+. Can't see that happening...

[YoshiHNS]

The HF gauge I bought had a bunch of adaptors with it. Maybe try an auto parts store?

[dawson]

Tried the local crappy tire with no luck. They're not really a serious store any more though. Had to explain what a tire iron was to the kid on the parts counter there last year. He'd never heard of such a thing. :o(

I'll try napa tomorrow and see if such a thing exists.

Thanks for the suggestion!

[gll429]

if you cant find one.. and you have tap set..

take an old spark plug and break the ceramic off.. and then break off the tang.. thead the inside of the plug to fit your hose.. or another adapter.. dont forget the o ring..

[dawson]

Turns out the plug hole is 10 mm. Oops. Dealer sells a hose with the right thread on one end and a quick release fitting that should work with my gauge on the other. They didn't have any in stock but it should be in this week. Will update when it shows up.

[dawson]

The adapter showed up, it was a 10" hose with the male 10mm, 1.0 pitch thread on one end and a quick release M type male end on the other.

Naturally, my guage uses a different style quick release, but I found an M female quick release at princess auto that would screw onto the 12 mm fitting of my gauge. End result is a hose about 20" long, which isn't quite ideal.

I warmed up the bike, yanked the fuel pump connector and all the plugs, and tested all four cylinders. They ranged between 60-80 psi, which is a bit to far off the 142-178 the service manual calls for. I'm still seeing some oil dilution happening, so the rings doing appear to be underperforming. My inspection camera is slightly too big to get into the cylinder, but I can see the top of the cylinders, which appear to be dark grey and granular looking. Very carbony.

The other thing that struck me as odd was how much force it took to rotate the engine from the back wheel. Tried a few different gears, but they all took a fair bit of effort to rotate the crank. I thought it should be fairly easy to do with all the plugs out, but maybe not? Only time I've turned an engine by hand before was with a breaker bar at the stator (inline fours), so maybe the transmission doesn't give as much mechanical advantage as I thought...

Any suggested next steps beyond tearing down to look at the piston tops/cylinder walls?

[V-FORE]

I would think the low reading is due to it being warm and due to the connectors are you checking with the throttle WFO?

[Cogswell]

Your OP didn't mention why you're doing a compression test on a fairly new engine. If you suspect a problem, a compression test will only confirm which cylinder has the problem, but not specifically what it is. Something you might consider would be a leakdown test, which will differentiate between rings, valves or head gasket issues.

[dawson]

Forgot to open the throttle. Rechecked two cyls, it went up to 90 on both. Engine is now cool. Shouldn't compression be higher when warm?

Cogswell, checking compression due to gas appearing in the crank case. Bike runs stupid rich, I think it's washing the cylinder walls and breaking down the oil seal around the piston. :o(

[Cogswell]

Interesting. Running extremely rich probably has something to do with sensors / actuators / injectors, etc rather than something mechanical. Can you post a photo of the plugs? If it's running that rich it will show up there. If it's all 4, then it's something common to all, like maybe the fuel pressure regulator or a pinched or dis-connected vacuum hose. If the thermostat is stuck open and the engine is running too cold, that also can cause problems. If it's just 1 cylinder, then it's something like an injector with some trash in it that's not allowing it to close properly, so fuel is being sprayed in constantly, etc. Maybe go over the airbox thoroughly and re-check all the electrical and vacuum hose connections and be sure that's all good. If you haven't done that previously, it's not too bad a job - just keep track of where everything goes and plug the throttle bodies with some lint-free rags before removal so nothing can accidentally get down one of them.

Here's an informative thread about running rich - a couple of the posts have some good diagnostic tips on troubleshooting the FI system, especially the FPR and a way to see if the injectors are leaking.

http://www.vfrdiscussion.com/forum/index.php/topic/72930-running-rich-how-to-fix/?hl=%2Bfuel+%2Bpressure+%2Bregulator#entry860322

[dawson]

Yep, we're on the same page. Put a PCV on last year, noticed the fuel in the oil, checked the FPR, fuel rail pressure, checked the injectors for leaks, put the bike back to stock less the PAIR and it's still over fuelling. Temperature seems to be okay in that it comes up to 106, fan cuts in, drops down to the 90s, repeat. Runs in the mid to high 90s on the highway. Although the display, ECU and fan control all run off different sensors so perhaps the ECU is getting a bad temp reading.

I've been thinking that the model of injector on mine flow more than the model used to develop the map so it ends up richer than designed.

It's going closed loop at the usual 76 degrees, so all that part is working.

VTEC is working as well, and not operating below temp, so I guess the ECU is getting a temperature after all.

I rarely get more than 200 km per tank, but I do a lot of short city trips. Exhaust smells like fuel.

All four plugs are rich looking. I changed them out last year when I returned to stock, new ones look just like the old ones. Think I have pics of the old ones in my gallery, having trouble navigating there on my ipod at the moment.

Thanks for the tips, will check all the vacuum lines tonight.

[kaldek]

The other thing that struck me as odd was how much force it took to rotate the engine from the back wheel. Tried a few different gears, but they all took a fair bit of effort to rotate the crank. I thought it should be fairly easy to do with all the plugs out, but maybe not? Only time I've turned an engine by hand before was with a breaker bar at the stator (inline fours), so maybe the transmission doesn't give as much mechanical advantage as I thought...

Yeah it's a hard engine to turn from the wheel. Remove the right-side engine cover inspection bolt and turn the crank using a 14mm socket.

Yep, we're on the same page. Put a PCV on last year, noticed the fuel in the oil, checked the FPR, fuel rail pressure, checked the injectors for leaks, put the bike back to stock less the PAIR and it's still over fuelling.

Tell me what's the power like at WOT - pretty good, feels fine or feeling like it's being held back?

[dawson]

Thanks kal, good to know that it's not just the desk job catching up to me.

Bike feels sluggish to me. Need second gear to get to 100 kph, recently long stretch to let it run and it topped out well below the advertised maximum. I had the side bags on and wasn't lying on the tank, but it didn't feel like it was even trying to pull anymore.

[kaldek]

OK so if it's sluggish even at WOT and high rpm then it's definitely being massively over fuelled and the problem is not, say, your MAP sensor. At WOT, the ECU is Alpha-N and ignores the MAP sensor, so the fuel metering at that point is controlled purely by:

• Cam Pulse generator for injector timing
• Throttle Position sensor (The "Alpha" in Alpha-N)
• Ignition Pulse Generator for Engine rpm (The "N" in Alpha-N)
• Fuel trimmed by:
  • Engine Coolant Temperature (ECT)
  • Intake Air Temperature (IAT)

How to test your ECT: Check VTEC activates. If so, ECT is working because ECT controls whether VTEC will work or not (65 degrees C).

How to test your IAT: Unplug it. Ride around ignoring the FI code caused by a disconnected IAT and see if the bike runs better

Cam pulse generator and Ignition Pulse generator failures are rare to the point of being unheard of. I replaced both of mine while tracking down problems and the changes made no difference.

What were the results of your Fuel pressure test and how did you go about it?

[dawson]

Fuel pressure was at 37 psi, the manual specs 38 i think? I got the hollow banjo from my dealer, brazed a Schrader valve into the end and hooked my fuel gauge into that.

I'll give the IAT a shot, but shouldn't it default to its richest setting when it doesn't receive a signal from that sensor?

Some of the sluggish could be from a plugged catalytic converter, when I may have. Seems to me that smelling fuel at the pipe doesn't happen with a good one. Could be an excuse to get headers....

[Cogswell]

Excessive unburned fuel that ignites once it hits the cat can melt the substrate and obstruct it, but the cat itself won't cause the fuel smell. It's still the over-fueling issue causing that. Cats don't die, they're murdered.

Just curious how the pressure test was done - sounds like at the connection under the fuel tank or ? Too bad Honda makes it difficult to test the regulated pressure without a special tool.

Since a lot of things have been eliminated, and presuming you eliminate the IAT sensor per Kal's suggestion, can you backprobe the TP sensor and measure the output voltage as the throttle is rotated (small paperclips work great for backprobing the connector)? Key on it should be between .4V and .6V throttle closed and 4.2V and 4.8V at WOT. If the TPS is faulty (or loose?) it could be sending the ECU a signal that the throttle is further open than it truly is, with the ECU then commanding inappropriate injector pulse durations. TPS's usually fail with use, but there aren't many things left. If everything checks out, it wouldn't hurt to go over the connections to the ECU and look for any loose or faulty connections.

[kaldek]

I'll give the IAT a shot, but shouldn't it default to its richest setting when it doesn't receive a signal from that sensor?

No it defaults to an assumption of 28 degrees C.

Fuel pressure was at 37 psi, the manual specs 38 i think? I got the hollow banjo from my dealer, brazed a Schrader valve into the end and hooked my fuel gauge into that.

That's the correct way to measure it and the pressure looks fine.

I should add, it's worth trying another bike's ECU. If your bike doesn't have HISS, you can just do a temporary swap-out of any 2006+ American bike. Only takes as long as it does to get the side fairing off and back on again.