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Hond 225 3950 max rpm

Garygin

Garygin

Regular Contributor
Ok I ready to jump off a frieking bridge.
First I just replaced ALL the fuel filters. New fuel tank, new IAB vacuum diaphragm , new fuel line cut solenoid valve. I just rebuild the whole out drive , service bulletin #56 , all gaskets seals bearings , water pump, and checked every fuel line, and vacuum hose. So yesterday I started it up idled beautifully.
Ran it up to 3950 rpm. And that was it. It sounded like it hit a rev limiter. The only thing I found that I had hooked up wrong was the vacuum line from the fuel regulator to the vacuum tank . I had the one with the check valve on the wrong one on the vacuum tank.
Today I tore into it. Took out the vst. Took the whole thing apart . Checked everything. Here’s what I found I put 12 volts to To the high pressure pump
And nothing, no click no spinning ,NOTHING. I checked resistance between the two terminals on the HP pump and it said open line. I checked the voltage at the 2 pin connector. Turn the key on and you should have battery voltage for 2 seconds. I had 5.7 volts. Then I checked it again later and it was under 2 volts so please tell me what the hell am I supposed to look at now. I really don’t want to go to a Honda dealer. I’m the type of person who doesn’t like to get beat by not being able to figure something out. I don’t give up.
Please HELP!
Thank you all ,
Gary
 
Hi,
I will try to help but I can only tell you what the wiring diagrams say as I've never worked on a 225.

The fuel pump circuit is a bit complicated because it goes through the main relay..

Most of your fuses are all powered by a single lug on the fuse box. That is a location that would be subjected to corrosion. Taking all the wires off there and cleaning everything up for good contact would be a good first move. But disconnect the battery first because that lug is hot directly from the battery.

Check the condition and contacts of the #2 10 amp fuse. It's also a good idea to check them all really.

The #2 10amp fuse feeds power to the main relay through a White wire with black stripe (W/bl). That wire travels first through a 4 pin connector and then on to a 2 pin connector before entering the main relay. Be advised that corrosion or loose pin to socket contact at either of those connectors could cause your low voltage. Sometimes wiggling them or unplugging and plugging back in while testing the voltage at the pump will reveal an issue there.

The White black (W/bl) wire enters the main relay to supply power to an internal set of contacts. When the key is on, the contacts close and deliver power through the contacts and back out of the main relay to a Blue/red (Bu/r) wire. That is an excellent location to check voltage as it could indicate as to the condition of the contact points inside the main relay. Back probing is required though because the plug has to stay connected.

The Bu/r wire goes through the SAME two pin connector that the W/bl wire does and then goes on to the positive terminal of the HP fuel pump.

Your loss of voltage could be occurring anywhere along the route just described and even though most problems like this are found at connection points, it could also be a partially broken wire that you just.can't see.

That's why I advocate using a test method called Voltage Drop Testing to find problems like these. It's not hard but takes a little reading to learn it.

I also would like to know where you are putting your ground lead during your test because, if you are using the other socket of the 2 wire connector with the black wire at the pump, change that to a different ground point. Preferably directly to battery ground if your leads will reach. Poor grounds rob voltage just the same as positive connections do.

I hope this helps you find the issue and I'm always happy to discuss it.

Good luck.
 
Thanks so much. I’m am looking at it right now. One question why would I see voltage drop when I check the terminal that feeds the hp fuel pump in the 2 second test. I never had 12volts. First it was 6 then later in the day I checked it again and it was .6. I did use a good ground when checking this. Also the engine ran great the day before but wouldn’t go Over 3950 rpm that’s when I decided to take everything apart and start checking everything. Thanks so much for your help because I’m totally lost now.
Gary
 
Ok, I followed your instructions line by line. You won’t believe this. I found one of my test leads was bad. Used a different one everything is working . I wasted so many hours I don’t even want to tell you. Thank you!
One other question. When I took this apart yesterday I noticed when I had it apart before I inadvertently hooked the vacuum line from the fuel regulator to the wrong place on the vacuum tank. Would this prevent the engine from going over 3950 rpm.
Thanks again
Gary
 
Ha ha! The bad test lead thing has burned me (and thousands more) a couple of times. So frustrating! Glad you caught that.

I'm not sure about your question.

I do see that the fuel pressure regulator is "T"d into a vacuum line to the vacuum tank via a check valve. It and the MAP sensor share that "T". So putting unrestricted vacuum to them both would possibility change the way they function.

But another thing I think might have happened is that the IAB solenoid is connected via an unrestricted vacuum line. So, if you somehow got the IAB line hooked in to that check valve it could have interfered with how the baffle in the manifold was working. That's just a guess though. I honestly don't know.

So it runs ok now that you've switched everything back to the way it was?
 
I haven’t finished it … grandkids came over. I have it almost done. I did notice that the service manual shows two different routing for the vacuum lines . The schematic on boats.net looks like the right one . I do have the unrestricted vac. hose hooked up correctly. I’m wondering if the IAB solenoid might be bad. Would you know how to check it? The only thing I haven’t checked is the fuel pressure. But I honestly don’t think that is it , because it is flawless up to 3950 rpm. Thanks so much for your help . You saved me a lot of time.
Gary
 
3950 RPM is the RPM 's where the IAB baffles are supposed to activate and change the air intake profile of the engine. See attached. It is also the RPM's where the V-tec (variable timing) kicks in. Both are controlled by vacuum. So it looks like you have a vacuum problem somewhere.

HOWEVER! Neither of these conditions - Stuck IAB or V-Tec not activating - , should limit RPM's to 3950. What I suspect may be happening is that when rpm's hit 3950, and either the V-tec solenoid or the IAB solenoid kick in, you are losing vacuum across the board. I have no idea how to test that. Maybe Professor Jimmy (JGMO) does.
 

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  • Honda 225 Intake Air Bypass.pdf
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Ha! I was just about to post "I wish chawk_man would chime in"!!

I have the pdf manual but I don't have a computer so trying to read this stuff on my phone isn't very easy for me because of the small print combined with small screen.
I'm looking into it but it is going to take time.

I do see that the solenoid gets grounded by the ECM but I'm not certain about where the voltage is sourced or if it's 12 volts or not. The manual I have is just very difficult for me to read.
 
Chawk. Thanks for your input. It is always appreciated. If you remember I posted pictures of a vacuum diaphragm I had modified
To fit since you cannot purchase one from Honda. So that is new. I Have replaced almost everything.
Jgmo . Whatever you find please let me know. The service manual is really missing a lot of information. I think it just covers the basics. Service manuals I’ve used in the past describe where parts are located , color coded , how to test, how it is laid out, and such. Just wanted to say thanks to you guys for being such a great help. I hope I can pay it forward.
 
Well I ran it in a tank of water today . 3950 rpm and the same thing. Just like a rev limiter. Any suggestions would be very much appreciated.
Gary
 
Is it missing or coughing when you hit the 3950 rpms? If not, consider checking and adjusting the throttle linkage. See attached.

That file may have been too big to post. See pages 3-18 thru 3-21 in the Helm shop manual.

Many years ago I was having throttle problems, all looked good at the main throttle lever, BUT on the top of the engine there is another throttle pully - see page 3-18, first diagram. The lock nut had come loose and was totally out of spec.
 
Hi Gary,

Haven't forgotten about you.

I don't know but it really would be a very strange "coincidence" that the rpms freeze at the exact same (3950) revs that the IAB is supposed to come online. Curious and curiouser.

The wiring diagram does say that the bypass solenoid is on switched ignition power so I  AM confident that you could simply unplug it and apply 12 volts and a ground to test it.
If it will allow air to flow when powered, the solenoid is good.

You will probably want to test it on the engine while it is running first though. That would require either observing the movement of the diaphragm at 3950 rpm or connecting an automotive vacuum gauge in place of the diagram and seeing if you have vacuum at 3950.
I'm guessing that you should see approximately 15 to 18 inches of mercury but I don't know. I read through specifications, operation and troubleshooting sections of the manual but didn't see anything on that.

Are you positive that the vacuum tank is getting and holding vacuum?

I mean, there could be a problem with that check valve. If it leaks back to the intake manifold, it will likely "empty" the tank as soon as the throttle is increased significantly.

That might be the first thing to verify when looking at this system. I don't know. But if the vacuum control portion of the system checks out then my guess is either with the linkage or inside the intake.

Wish I knew more but it's hard not having ever touched one before.

Here's hoping you already figured it out and I typed this up for drill.
 
Hi Jgmo!
Well thanks for doing all of that research. It sounds like I have a few more things to check. The vacuum tank I’m most curious about. I really don’t know if it is getting vacuum, and if it is holding vacuum. The next I was going to check was is it getting vacuum. I was away so Ii haven’t had a chance to look at it. The other thing you said about the vacuum tank holding vacuum, I didn’t even think about that. How would I test for that? I think the check valve is ok. When I blow air through it, it will only go one way.
I will run through these tests and let you know what I find.
Thanks. You have been a great help.
Gary
 
Well, I'm not sure blowing through the check valve is a valid test but
...maybe?

If the tank holds vacuum you could simply unplug the check valve from the engine and then pump down the tank with a Mityvac. But, if the tank leaks, you either need to seal it, replace or use a different method to verify the check valve works properly.

I've got a big glass jar with a screw on lid that I used to use to vacuum evacuate and then add oil to the crankcases of walk in store cooler compressors. I just drilled 2 holes in the lid and screwed in and silicone sealed two flare connectors for vacuum hoses. Held vacuum really well.


A similar and smaller rig could work well for holding a vacuum to test this by using a mayonnaise or pickle jar. Then just substitute a couple of barbed fittings instead of flared to connect tubing from the check valve and to your vacuum gauge.

With that, you get a "real life" simulation to test the valve AND it could also help facilitate testing the vacuum tank to make sure that it holds vacuum if access to the tank while it's mounted to the engine is limited.

Now that I read all this back to myself it seems a bit "over engneered" to check that check valve but that's just how my brain is wrapped at the moment.

It's just that, if I were having this problem, I would want to make dang sure I took the time to verify this stuff functions correctly before moving on to the next thing.

Hopefully you will come up with a simpler approach than mine.

Good luck.
 
Wow! That is alot for my little brain to process this early in the morning. The check valve you are talking about, is that the one that comes from the fuel regulator? I will follow as directed, and keep you posted.
Thanks again ,
Gary
 
Yeah, I over complicated my thoughts. Sorry if I gave you a headache.

Well, that check valve is shown on the vacuum diagram to "T* off of the vacuum line for the fuel pressure regulator. So yes, it shows they are "connected".

But just want to point out though that both the FPR and MAP both get unrestricted vacuum from the intake manifold and NOT through the check valve.

I mention this because I initially read the diagram wrong. The vacuum tank is the ONLY thing "protected" by the check valve.
 
Ok . This is what I found so far. The IAB is opening at idle, which is really confusing me. I have vacuum from the line with the check valve which I think is correct. I assume the check valve is supposed to make vacuum in the vacuum tank. When I shut the engine down I pulled one hose off the vacuum tank and you could hear it suck air in . So I’m assuming this is correct. I wish I knew how the system worked so I could sorta trace each vac. line and check it as it goes from connection to the next. Let me know what you think .
Happy Fathers Day,
Gary
 
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