3 replies to this topic

[DothaDoo]

I recently bought a 2003 Sportster 4tec, non SCIC. Not sure on the hours, but it does have a few issues. Everything associated with the MPEM for the radio, 12v outlet, blower, etc. is not functioning. The blower was working, but that was it and I replaced all the other fuses bc they appeared to be blown. Now nothing will work without blowing. I have read there can be a problem with the rectifier but I need to know what and where to check.

The engine runs fine and GPS tops out about 49mph with just me in it, and about 42mph with two 200lb guys. I expected it to hold it's speed a little better than that, but is that normal for an 03 155hp? Also up to around 3k RPM there is a slight surging of maybe 1-200RPMs. I changed the plugs and oil, but there was no change with the surging. Other thoughts i have include fuel/air filter, but I haven't checked or replaced them yet.

Last known issue is the fact that it is taking on a little water from an unknown source. I let it sit and it did not seem to be taking on water, but when I ran it for about 20 mins it took on a gallon or so. I ran it with the engine compartment open but did not see anything that was suspect. I inspected the hull for any cracks in or around the hull, but everything looks good. I can tell it has had this problem for a little while bc the engine compartment has some algae growth from sitting water. I really would not worry about this too much if the bilge was working, but that goes back to paragraph one. I know this is a pretty long post, but any help would be greatly appreciated.

[YuCrew]

DothaDoo, on 01 January 2011 - 09:55 PM, said:

I recently bought a 2003 Sportster 4tec, non SCIC. Not sure on the hours, but it does have a few issues. Everything associated with the MPEM for the radio, 12v outlet, blower, etc. is not functioning. The blower was working, but that was it and I replaced all the other fuses bc they appeared to be blown. Now nothing will work without blowing. I have read there can be a problem with the rectifier but I need to know what and where to check.

The engine runs fine and GPS tops out about 49mph with just me in it, and about 42mph with two 200lb guys. I expected it to hold it's speed a little better than that, but is that normal for an 03 155hp? Also up to around 3k RPM there is a slight surging of maybe 1-200RPMs. I changed the plugs and oil, but there was no change with the surging. Other thoughts i have include fuel/air filter, but I haven't checked or replaced them yet.

Last known issue is the fact that it is taking on a little water from an unknown source. I let it sit and it did not seem to be taking on water, but when I ran it for about 20 mins it took on a gallon or so. I ran it with the engine compartment open but did not see anything that was suspect. I inspected the hull for any cracks in or around the hull, but everything looks good. I can tell it has had this problem for a little while bc the engine compartment has some algae growth from sitting water. I really would not worry about this too much if the bilge was working, but that goes back to paragraph one. I know this is a pretty long post, but any help would be greatly appreciated.

[YuCrew]

Interesting set of problems.  I personally would not suspect the MPEM.  If this were my problem, I would disconnect the radio and blower and bilge.  Then I would use a continuity meter to confirm the hot is somehow getting grounded.  If so, I would disconnect the ground to all three devices (pretty easy to do at the terminal strip) and run a new ground to each or reconnect the grounds wires one by one to figure out which one is short to the hot 12V.  Let us know how you progress or what you find.  I'd focus on isolating and solving one at a time but it sounds like you're got a common fault.  Good luck.

[bobber]

I don't know about taking on water, but your performance matches mine - I own a well-maintained since new, 2007 Speedester 150 with the 155 hp, 4Tec.