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Discussion Starter #1
Apparently this is my first post, i could have sworn I'd posted here before, oh well.

So after a stator change early this summer, I finally got to fixing other problems with my cx500 turbo.

After searching around a lot, I can't find anyone with the same problems as me.

I get overboost, the boost meter doesn't go up or down with any sort of twist of the throttle, it can idle or you can ride it, the result is the same slow ( about 10 minutes) crawl to overboost with flashing turbo light. You can turn the key off and unplug the battery and the overboost will still be there. I can open the wategate with some vice grips and the boost doesn't go down. The only thing that brings in down is sitting for about 24 hours not running.

I've tried quite a few things already and i don't think its a case of a stuck wastegate. I've had the exhaust off and put high temp penetrate on the wastegate, it's freed up and seems to work well.

Okay so not the wastegate (at least sticking anyway). I pulled the computer from the tail to see what kind of codes its showing as some people on this forum suggested on other posts. No codes, none... it sits there flashing turbo on the dash and the computer doesn't relay any faults. I checked all the sensors and they seem to be without problems, the connectors have the correct voltage and the vacuum lines seem to be intact.

I'm at a loss. The bike pulls like a stabbed rat at about 5000 rpm so I'm 99% sure the turbo is working, it also doesn't go into limp mode when the turbo light is flashing indicating overboost.

Any suggestions would be helpful.

- Scott
 

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The big clue here is the flashing turbo light. That has to be root caused and resolved first before moving on. That is a fairly simple circuit fortunately. Its basically your PIGN sensor/ wiring/vacuum line and the Ignition control box. See the attachments below from the FSM. Start with the static gauge test. Disconnect the red 3 wire coupler under the RH side panel and turn the key on. The boost gauge should show red segments indicating over boost. Next hook that back up. apply a vac/pressure gage to the sensor replacing the line going to the intake. (You did connect it to the correct port on the intake right? After the stator replacement? Should go to the port labelled "4") You should be able to key on and again and get the correct results in the table below by applying vacuum/pressure. My guess is your PIGN sensor is bad or the line going to it is not hooked up correctly OR has a restriction. Check that you have vacuum to it! If all is well, it may be the spark control unit. let us know what you find.

Your comment about a 24 hr sitting is interesting. Since the sensor is vacuum/boost operated, it should go to atmospheric as soon as the engine is off. If it is showing anything else, it makes me think the vacuum line is restricted/ plugged in incorrectly or a bad sensor. Just a thought.

Note - The ECU has nothing to do with the boost indicator - separate systems. The FUEL SYSTEM lamp is all about ECU issues. That lamp should come on every key cycle for about 2 seconds and go off. Also, the ECU has no historical memory. Once you key off - it resets completely. You must check for codes after the issue has occurred but before keying off.

Note - looks like the site is still having issues posting pictures again. Check back in a few days for them to show up. I sent JC a message.


Normal voltage idle .43 to .83v (output)
Normal voltage engine stopped 1.09 to 1.29

man1.JPG man2.JPG man3.JPG man4.JPG
 

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Discussion Starter #3
The big clue here is the flashing turbo light. That has to be root caused and resolved first before moving on. That is a fairly simple circuit fortunately. Its basically your PIGN sensor/ wiring/vacuum line and the Ignition control box. See the attachments below from the FSM. Start with the static gauge test. Disconnect the red 3 wire coupler under the RH side panel and turn the key on. The boost gauge should show red segments indicating over boost. Next hook that back up. apply a vac/pressure gage to the sensor replacing the line going to the intake. (You did connect it to the correct port on the intake right? After the stator replacement? Should go to the port labelled "4") You should be able to key on and again and get the correct results in the table below by applying vacuum/pressure. My guess is your PIGN sensor is bad or the line going to it is not hooked up correctly OR has a restriction. Check that you have vacuum to it! If all is well, it may be the spark control unit. let us know what you find.

Your comment about a 24 hr sitting is interesting. Since the sensor is vacuum/boost operated, it should go to atmospheric as soon as the engine is off. If it is showing anything else, it makes me think the vacuum line is restricted/ plugged in incorrectly or a bad sensor. Just a thought.

Note - The ECU has nothing to do with the boost indicator - separate systems. The FUEL SYSTEM lamp is all about ECU issues. That lamp should come on every key cycle for about 2 seconds and go off. Also, the ECU has no historical memory. Once you key off - it resets completely. You must check for codes after the issue has occurred but before keying off.

Note - looks like the site is still having issues posting pictures again. Check back in a few days for them to show up. I sent JC a message.


Normal voltage idle .43 to .83v (output)
Normal voltage engine stopped 1.09 to 1.29

View attachment 170753 View attachment 170755 View attachment 170757 View attachment 170759
I checked the position of the Pign sensor hose and it is correct, and i tend to agree that the continuation of overboost once the bike is keyed off and then back on seems to suggest a restricted hose. Once those photos come up I will do some testing.

Does the Pign hose have a small check valve in it like the P1 sensor? I have the correct size hose to replace it if that would rule out an obstruction.

All my fault code checking was with engine running as to be sure I wasn't clearing any.

Thanks for the help, I will report back once I've tried a few things on the Pign sensor.
 

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I tested the pign today. Also checked the hose and found nothing plugging it.

I unplug the sensor and keyd on: got 1 bar of boost and no flashing turbo. Tested the voltage and got .22 volts with key on between all 3 wires. 6.6 volts between pink and green/white, 12.6 volts between green/white and balck/white while at idle.

Funny thing is as long as you leave the red plug unhooked it doesn't build boost but it also doesn't misbehave in any way, no fault codes, no flashing turbo, nothing. Aonther strange thing is that the boost indication doesn't change with the red plug unplugged between key on and key off.

So I hooked up a Vacuum/pressure guage and applied varying amounts of vacuum and pressure with key on and while at idle with no results, just the same slow building of boost over the 5 minutes of testing with the end result being flashing turbo sign.

So I think it's safe to say that the pign sensor is bad, but my worry is that the boost hangs around even when the senior is unplugged. Does this indicate a bad ecu or ignition unit?

Also is it unsafe to drive it while it is in this state? I have some other problems I need to diagnose but I need to do some short trips to do so.

Thanks for all the help. Who knew old turbos were so complicated. ?
 

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Another update. I watched some old vedoes on YouTube about testing the sensors and computer.

Seems as though I can't get any response from the computer. It's doesn't trip any faults at all but I also don't get correct readings from the pign sensor. At the very least the computer is not functioning properly.

I tested to see if the computer was getting power and it is, so I don't think it's a harness issue.

After all the repairs I've done already I'm too deep to give up now. I've ordered a set of sensors off eBay, all 4. I also found 2 computers (one in a junk yard, and one off eBay) the one off eBay looks like is has a bit of damage but hopefully one of them will work.

I also took all the Jets out of the chamber the vacuum hoses attach to and cleaned them out they seemed fine.

Parts should be here in a few weeks, in the mean time I'm going to get tires installed and get the thing inspected and reg.

I'll update once parts arrive.
 

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Excellent report back. Thanks for staying with it. These old beasts can be cantankerous - but once you get it sorted, I think you will find things will settle down. These early fuel injection designs lacked good diagnostics - same issues that plagued their automotive counterparts. Keep your changes logged in a journal with the results written down. Make only one change at a time. If you go shot gunning about - it can be an endless circle. I always tell myself - "its a machine made by men - it can be repaired by men. And I am at least as smart as they were :)"
 

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Update

So i received my ebay cpu and 4 sensors.

I installed the cpu first seeing as the old one worked but gave no codes or even a start up test W light. The ebay cpu gave a code Solid W plus flashing 0: which according to my manual is a pb sensor open circuit or shorted signal wire. However the ebay cpu won't make the bike run also there is still the constant turbo red bars and warning and the fuel warning light does not go out.

So i replace the old pb sensor with the new one, check for obstructions in the vacuum line and test. On testing I no longer get the W and 0 code however the bike won't run with the ebay cpu and the turbo warning is still lit. If I plug in the old cpu the bike runs fine but still has turbo warning.

So since I have all new sensors I replace all of them, one by one testing each time with the ebay cpu and old cpu.

In the end there was no change, I have all new sensors and two cpus, no obstructions in the vacuum lines. I even pulled the battery to reset everything each time I tested.

The ebay cpu still shows the fuel warning light but gives no other codes to go by and still has the turbo overboost issue and won't run much at all.

The old cpu doesn't show the fuel warning light, gives no codes (never did), still has the overboost issue and runs very good, goes up and down the road great.

I noticed that the boost gauge goes up slowly even when the bike isn't on. I know this is weird, but could it be the actual boost gauge that is faulty? I have no other tests to do currently and am mostly left with what I started.

- Scott
 

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If the boost go up slowly, and the sensor is ok, then check your grounding and over all wire harness. It looks like the voltages your measuring are not what the computer is seeing.
 

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And most important - make sure both your cylinders fires... on high idle (1500-2000) yank out one spark wire at a time and make sure the engine is still running (though dropping 300-500 rpm). A cx500tc running on one cylinder would sound just like you described: weak and the turbo won’t kink. No warning lights either.
 
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