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Discussion Starter · #1 ·
2004 RC51, tore the bike down in Feb. After extensive rehab tried to fire it up Sat and no go. The bike ran at teardown. Here is what I have done so far:

Tip over sensor and relay function properly.
ECU swap, no different result.
Fuel pump primes/pressurizes as it should.
Fuel pump relay clicks as it should.
No blown fuses.
No dash codes.
Bench tested injectors, they work.
Brand new plugs that are dry as a bone upon removal after attempted start-up.
Starter relay works + brand new battery.
Everything is properly plugged in according to repair manual.
Ran code clear function in green diagnostic port per manual.

Found residual fuel in throttle body hard lines and fuel line. Seems as though fuel is getting to injectors but nothing is happening.

Previous owner did flapper and pair mods.

Thanks for any suggestions. If you need me I'll be pulling my hair out.
 

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Big Thymer
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Is there a Power Commander plugged into it? I'd eliminate that from the mix if there is.
How extensively was the bike torn down? I ask because the front injector wiring harness (two wires) get damaged very easily if the frame is muscled off the engine with the harness and t-bodies still on the engine. It's only one of four injectors, sure.
 

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Discussion Starter · #4 ·
No Power Commander. I did do a frame swap and left everything intact. I tried to be as careful as possible on the change over but its something I can check.

The injector problem is hurting all four simultaneously it appears. There is no fuel anywhere.

When I pull the plugs after a start attempt they are dry as the day I installed them. No residue in the tb's either, no fuel smell in the pipe. If I had an injector clogging issue wouldnt I get a little bump/pop when I tried to start it?

When I bench tested them I put some carb cleaner in and juiced 'em. They spray!
 

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2 things come to mind........ Has the crank pick up been replaced or damaged? If replaced i've seen folks put them in backwards. Obviously the bike wont fire if either one is the case. A faulty converter can cause a no start issue. Try swapping out with a known good unit if you have access to one. Have you tried running the bike on ether yet? Also, double check the connectors between the main and sub harness. Look for good solid contact(it'll click together) and make sure no wires are loose in the connectors themselves. Been a while since i've been behind the coolant overflow bottle but is there some connectors behind there on the sp2 as well? Probably nothing but should be easy to double check. The manual shows how to test pulse at the injector so if you are getting signal there then your problem is the injectors themselves. If getting the wrong reading, or none at all, then its electrical. There are a couple sensors on the TB assembly, or around it, and was wondering if you had triple checked everything up under the TB's? Could be as simple as a slightly loose wire within a connector.
 

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Discussion Starter · #6 ·
Just probed the ignition pulse generator (crank sensor). Absolutely positively no voltage when i hit the starter button. The manual recommends a peak voltage tester of which i do not have. Am I ruining the test by not having the right voltage tester?
 

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You don't have to have the Honda peak tester. I've been able to read everything i need to from a regular store bought digital meter. I've diagnosed 2 bad cps (one bad and the other installed backwards) using my meter, but for the life of me a can't think of which setting i used. Have you tried to start the bike on ether yet; or any other starting fluid....carb, map sensor, etc. cleaner? I take it you have the airbox off, right? If you get it to fire up then we can rule out everything with ignition. That'll narrow us down to injectors themselves or electrical having to do with the injectors. Something else to consider. Might want to double check the fpr/fuel pressure return valve. Granted i've never seen a bum one not allow any fuel into a cylinder, but if stuck wide open maybe, "maybe", there is a chance that fuel pressure can't build up to go through the injectors??? Not sure if wide open it would simply allow the fuel to return to the tank unabated. Its probably not this, but i'm just trying to think out loud here about every possible contributor no matter how unusual. To check this out you'll want to disconnect the return fuel line to the tank and run it to a large container. Turn the bike on and flip the starter switch but don't push the starter button yet. When the fuel pump cycles on see if fuel comes pouring out the return line. Don't think its supposed to do that. Someone else may need to chime in here to correct me if i'm wrong. Also, you've double check to make sure the fuel line isn't getting crimped and the proper vacuum hose in on the FPR, right? Hate to send you on a few goose chases here, but without the bike in hand its having to go through a few steps to fond the culprit. Trying to get you to do the easy and simple stuff first before swapping out parts.
 

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I had something similar after a fairly long lay up. The bike cranked fine but wouldn't fire. The spark was there, the fuel pump primed and there was fuel at the injectors but the plugs looked bone dry after repeated start attempts. In the end I just primed the fuel rail and then applied 12 volts directly to the front cylinder injectors for a very short time. Put everything back together and tried to start the bike again. Bike fired up on one cylinder and then after a couple of minutes picked up to both cylinders. Ran like crap for about 5 minutes but once some fresh fuel got through and the motor warmed up it was back to normal. I put it down to either the injectors sticking closed or gum blocking the holes. Either way it worked for me.
 

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Discussion Starter · #10 ·
Gentlemen,

Thank you for all your suggestions and help. The culprit has been identified. Bad Ignition Pulse Generator(Crank Sensor). Swapped it with a used one from my buddy's RC parts collection. Bike thundered to life on the first try!
 

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