2002 88B fuel injected, when I fill up the gas tank, the engine runs very rough, almost as if it has a fuel lock. Makes no difference if I put in 1 gallon or 4. Generally, when the bike is hot, it is at its worse. Will clear up after about 2 to 3 miles. Will not clear itself just sitting and running or letting things settle after fill up. Will idle, but will just barely run under load, generally when you roll on the throttle, it will cut out, catch, cut out cough etc. etc.
Anyone have any idears? Thanks, JC.

 

Two things come to mind here. First, if this is happening after fueling is there a possibility of something in the tank getting stirred up and covering the fuel pipe? Second it is not uncommon for intake leaks.

 

Just some thoughts................

I'm not a professional wrench but I read a lot on this forum and read AIM magizine and have seen some issues as you describe:

The EFI system and ECM relies on several inputs to make a rational decision about fuel, air, timing, spark etc. You have crank position, manifold pressure, tempeture and throttle position sensors to deal with.

Could be the tempeture sensor since you mentioned the problem to be worse when warm. The sensor starts out cold on first run, heats up with the ride, maybe gets a little warmer immediately after stopping/shuttion for fueling. After running a few miles the sensor may cool down a bit and get back in line. Bad data to the ECM will cause problems.

Since the bike runs well otherwise, I wouldn't suspect the manifold air pressure sensor, althought anything is possible.

Could be the fuel pump. They will usually let the vehicle idle but fails at higher RPMs and higher fuel demand. This would causing stalling etc. But since the problem goes away after a few miles the pump may be OK. Probably not the fuel filter for the same reasons.

Another thought would be if the tank is a vented or non-vented unit. Maybe a negative (or positive) pressure in the tank is hindering the fuel pumps ability to function. After a few miles of sloshing the fuel around it may clear itself or something.

I read an artical in AIM about a 2001 FLHRI with some Screamin' Eagle parts etc that would pop/spit/chug at certain RPM ranges. The guys checked everything; timing, spark, fuel systems, changed parts etc. Their problem was the throttle position sensor. It is basically a variable resistor, much like a volumn control on a radio, atttached to the throttle body. This sensor sends different resistance values to the ECM at different throttle positions. The ECM uses this data to determine how much fuel to send and when to send it based on all the the sensors mentioned at the begining of this post. You can check the TPS with an ohm meter by disconnecting the leads and placing the meter leads across the wires. Note the reading. Then move the throttle through the full range several times and note the readings. Each time the thottle closes fully you should see approximately the same readings. Also look for steady increase and decrease as you move the throttle. The sensor could have some dead spots or shorts. Bad data to the ECM will cause problems.

Just some thoughts................

Good Luck

 

In reply to possible tank problems, within the last year had the pickup tube replaced inside of the tank. We don't think that is a problem. Generally, if the intakes leak, the bike would back fire and pop. My wife's King did that and we changed the gaskets it went away.

I tend to agree that the temperature is the problem. Hot engine and running would cause the fuel in the tank to warm up, then when gassing up, introducing cool or cold gas causes a problem for the ECM. Don't know how to address that. Also have tried the loosing of the gas cap and such all to no avail.

Thanks, JC.

 

Could it have nothing to do with fuel and more with heat sink?

maybe the voltage reg, coil, or ecm getting hot when you shut it off and no air goes over it.
Once it cools a while, all is ok again?