Monday
Mar102014

HD fuel system, engine control module (ECM), and idle air control (IAC)

HD fuel pump assembly part label sm[3/10/2014; updated 3/16/2014] Well, the fine gentlemen at Jockeys Cycle are still sleuthing for the cause of my engine's problem(s). I took the bike for a test ride early last week and it was actually running worse than before: very low power and a great deal of misfiring. I don't blame the guys at Jockeys; it's like I told them, if it was a simple problem, I wouldn't need them. (They're quickly developing a fondness for carburetors, by the way.)

Complete fuel pump system smWhen I returned from my test ride, Kevin pulled the rear plug and it was clear that the rear cylinder was running very lean. This was in spite of the computer connected to the ThunderMax module indicating a relatively rich fuel-air mixture. I'm thinking that the ThunderMax ECM is basically saying that on the assumption that the fuel system is delivering as it's supposed to, then we have a good fuel-air mixture. Unfortunately, the computer is like me at work: I can tell someone to do something, but if they're incapacitated, then I can holler at them all day long and it won't make much difference.

In addition to poor engine performance, I’ve been getting unacceptable fuel mileage on my bike for a year or more: 28 mpg city and 32 mpg highway, on a good day. Also, the bike would not idle smoothly when started cold. Thus I’ve been on a quest to diagnose and repair the problem(s).

I decided to start by having Kevin replace the fuel pump and fuel filter (HD 62897-01B). This followed my experience last fall with a dead fuel pressure regulator, where I took my two-wheeler to the Harley-Davidson dealership in Durham to have them replace it--which took them three weeks! (That whole experience turned out to be a real adventure. Please refer to my blog post about that for details.)

It happened that there was another 2006 Electra Glide Classic with similar mileage (~90K) at the dealership with a failed fuel pump at the same time my bike was there. The whole experience made me curious about the entire fuel system.

Given that I plan on riding more than 15,000 miles in 2014, including an 8,000+ mile ride to Banff, Alberta and Portland, Oregon in July, I want to be sure I do everything I can (afford) to avoid any catastrophic failures while on the road. In addition to the fuel pump, I asked Kevin to replace my fuel filter, but it turns out that the fuel filter is part of the Fuel Pump Assembly, and one cannot change the pump and filter independently of one another. (Refer to the illustration above/right. Click on it to display a larger image.)

Fuel pump assembly top view smUntil now, I had never seen the fuel pump assembly for my bike. It’s a real Rube Goldberg-looking thing; like something Dr. Seuss dreamt up. I couldn’t resist taking a picture and posting it here. It’s the craziest looking part on the bike—and it’s all hidden inside the gas tank!

[In the photo at left, you can see HD Fuel Pump Assembly, which includes the pump itself, a mounting bracket, and the fuel filter--the pad protruding out at the base.]

So, Kevin and Jim put everything back together and tuned the new ThunderMax engine control module (ECM) but could not get the cold idle to work. When you started the bike cold, for example, first thing in the morning, it wouldn't idle without lots of help manually working the throttle for 2-3 minutes. These guys were about to rip their hair out until they isolated the problem to the Idle Air Control (IAC) [HD 27658-06]. (Refer to the photo below, right.)

With the old ECM and Power Commander module, the IAC—with its worn spring—didn't appear as a problem. But anyone who has experience working on complex systems knows that when you replace one part of the system, it can reveal problems in other parts. Replacing the IAC did the trick. It's likely that the "stepper motor" was failing on the old unit.

Combining the fuel pump replacement with additional tuning of a newly-installed ECM has turned out to be quite a learning experience. I'll post an update when the guys at Jockeys have figure it all out.

As always, keep the shiny side up.

-The Long Rider

 

Tip: Record your mileage and fuel consumption when filling up so you can calculate your fuel mileage. If you’re getting low mileage, you’ve got reason to begin an investigation into an engine problem.

 

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Reader Comments (1)

My car gets better mileage than your bike... :)

March 10, 2014 | Unregistered CommenterLisa

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