Hey guys, I'm a newbie and glad to see there is someplace like this around. Came across it while trying to find info on a problem......

I have a 90 cbr. riding into work the other day and it dies on me. Feels like I had run out of fuel. Pushed her back home and after investigating a bit, I figured out there is nothing coming out of the fuel pump. Looking through my clymer manual, it appears that I should see fuel flow by simply turning the ignition on? Is that true?

In any case, put a voltmeter to the black lead coming into the fuelpump relay and it reads 12.4V; looks good. checked continuity between the relay and fuel pump, it's ok. Then checked between the relay and the spark unit; that looked ok. I was all ready to go buy another fuel pump when a friend suggested I try hooking my fuel pump directly to a 12V source. And surprise, it pumps like a champ. so I went back and checked the voltage on the 2 wires coming off the harness (that connect directly to the fuel pump). With just the ignition on, I get 0.0V. When I push the starter, it gets eratic and I can't read it, but never gets over about 7.5V.

This one has me stumped, since I'm not clear on what the relay does. But since the voltage coming into the relay is good, could it be a bad relay?

Sorry for the long-winded explanation, but I'm hopeful someone on here has seen this before, or has some idea of what else I might check?
thanks for the help.
greg

 

Had the exact same problem on my F3. Was the regulator/rectifier. When it got hot it wouldnt put enough power out to keep the fuel pump running. I thought I had a broken fuel pump but when I checked it was perfect. Replaced the RR and has run fine ever since.

Goodluck.

 

me too. got an 87 f1 and i thought the relay was bad, so i got another one and to no avail the same problem. just replaced the reg/rec as well($220 btw) and had carbs celaned, still getting some kind of throttle issues but no more problems with the pump.

 

you're basically confirming what I thought it might be. I went back and charged up the battery, then started the bike. While it was running I watched the voltage at the battery terminals. It slowly dropped from 13.3V down to about 11.9. Once it hit 12V or so, the fuelpump stopped working, and the bike shut off about 30 seconds later. The thing ran for about 20 minutes total.

Is there a way of testing the reg/rect and the stator to confirm that this is the problem? I looked through the clymer manual, but the tests they describe don't make any sense. And it passes them all (If I'm even understanding what they describe)

 

Its bad mate, I guarantee it. I would just spend the $30-$40 and get another one from Ebay but if you really want to go through it theres a tutorial here:

http://cbrworld.net/forums/thread/140473.aspx

Also keep in mind that your RR won't charge your battery if you just let the bike idle. Its need about 5000rpm or so. One more thing, I've been told its bad to let your bike sit and idle for 20 minutes. Not sure why, but might want to investigate before doing it again.

 

i did the same tests from the clymer manual and they all read that it was still good, but to no avail it was bad.

 

hmmm........just came back from the honda shop. They tested my R-R and said it looked fine, but I don't buy it. Logically, if I have the correct voltage going into the the thing, and it's only putting out 6-8V, then that has to be the weak link in the chain. But then again, electricity is only 1 step away from magic, so who knows. Either way, I think I'll start by replacing that (guy at the shop was even confused because he had seen them go bad so often, he was convinced that it was the RR when I described the problem). If a new one doesn't fix it, it's back to the drawing board.

 

dont feel bad i have been working on my bike for 2 months and still having problems. no bike=angry me. and yes you are right, electricity is 1 step away from magic, and the carbs...well they are black magic.

 

just thought I'd close this out in case anyone searches for this in the future and finds this post.

Turns out it was the RR. It passed all tests, and appeared to be fine. It was putting out between 5 and 7 volts, which because it is on a series circuit with the battery was totally screwing the whole system. The new one I installed reads .8 - 1.5 V as the engine is revved, and seems to charge the battery without any problems that I've found so far.

Like I said...electronics are MAGIC!!

 

Ok,

I had this problem with the R/R before, but totally unrelated to fuel pump, When installing the rr, make sure the all the wires to the rr are fresh and look good, if not cut the connectors and install new one on then, i used the gold plated female and butt connectors,alsomake sure u use dielectric grease.Before I did this, my rr was pushing out very low voltage at 5k rpm,after, it was pushing out 14 v at 5k rpm, these bikes are old and wiring is a big engineering flaw on them. The f3 has very skinny wires on the places that require a higher guage or thickness of wires to handle the voltage output, also the coil wires that connect to ecu are the same.