MFI help!

[BK911]

Help!

I recently installed a 2.4E engine with MFI into my 72E Targa. I took it for a spin to get the engine to operating temperature and it ran rough. Adjusted the dwell and timing and took for another spin. The car ran great with the only problem being a slight hesitation around 2k rpm's.

This past weekend I decided to "tweak" the car to get up to 100%. Big mistake! I started with the 10 commandments. Everything was fine until it was time to measure the CO. That's where it hit the fan.

The CO level at 2500 RPM's was over 10. I adjusted the MFI pump until I got down to 2.5%, as per the check measure and adjust manual. Big mistake! Apparently there is a difference between part load and no load at 2500 RPM's! The car couldn't make it up my driveway!

I remembered something on Pelican about this so I did a search. Seems like the CO level should be around 7 at 3k RPM, and around 5 at idle. So I went back through all the adjustments until I got real close to these numbers. The car STILL won't make it up my driveway without riding the clutch. It feels like I am trying to start off in 5th gear or something.

The car idles nice, with nice throttle response throughout the RPM range. But under load it's a totally different story. Dwell is set to 38, timing is 35 BTDC at 6k RPM.

Anybody have any ideas on what to do now? I am thinking of putting on carbs! Please don't let me do this!

Thanks!
BK

[jluetjen]

The car STILL won't make it up my driveway without riding the clutch....with nice throttle response throughout the RPM range.

If it won't pull up your drive way - you have NO throttle response. How well a 4-stroke engine rev's without any load on it doesn't tell you anything.

First; I'd reset the MFI back to where it was when the engine was drivable.

Now; Have you downloaded and read all of the MFI data from Pelican's Tech Article section? Remember - the most important point in Bosch's tuning manual is the thing that they repeat the most: "Check - think - repair". The second most important point is that the ignition is the cause of problems far more often then the MFI.

If your CO is high, it is because the engine is running rich, even though it is running pretty well. Why? Does the car smell rich? Does is smoke a lot? What do the plugs look like? Do they all look the same? You've set the ignition timing, but have you confirmed the setting across the entire rev range? Does the rotor on the dizzy move freely?

Before you curse the wonderful MFI system be sure that you've eliminated all of the likely suspects. If you just decide to punt and swap on some Webers, you might not even fix the problem. Not to mention you'll never have the chance to experiece the joys of the MFI's instant throttle response!

[jstobo]

I couldn't tell where or what you were adjusting in your post. There are two CO adjustment screws on your MFI. One for part laod and one for idle. To adjust the part load, open throttle 7 degrees then brake to 2500 RPM check CO stop adjust. Obviosly you need to be able to read your CO while moving or on a dyno. After part load check idle CO and use that adjustment screw. Don't switch screws or you will really mess up the adjustmen. The part load adjustment is behind the allen screw and the idle adjustment is a push in hex machine screw toward the bottom of the pump. A hole for this adjustment should be in your engine shroud to get the adjustment tool in. I drove my 69E over ten years and never needed to adjust the MFI. From reading this board I think way too many people adjust the MFI first instead of last.

[Bob Spindel]

My suggestion:

The idle CO adjustment--the one in the center of the pump that has a spring loaded screw that must be accessed through the fan housing--has very little effect. Leave it alone for the moment.

The part-load, or mid-range adjusment, accessed by removing a hex hed bolt from the upper right side of the pump, and then turned by using a slim, 4" long screwdriver, has **huge** effects. I'd worry about that one.

One way to get it very close to ideal is to keep leaning out the mid-range adjustment until the car stumbles when going through that range, and then clicking back towrads rich two or three clicks. This will have you pretty close to ideal, and you can tweak a click or two either way from there. More than a half dozen clicks away from ideal, and your going to have very poor performance.

If you're not sure where you are now, just start leaning it out until it idles poorly, then richen 4 or 5 clicks. then go to the paragraph above.

It's not all that hard. It just takes a little time

[Paul Thomas]

Numero uno should be to check the pump timing. It sounds like to me someone richened it up big time to compensate for something, like the fact that the pump isn't injecting when it should be. Ask me how i know that.

Paul

[jkeyzer]

So that bit on the tech articles page about injection pump timing not making a difference is a bunch of BS?

Mine's a little off, maybe a few degrees, and I haven't gotten around to actually fixing it.

[BK911]

Gentlemen!

I appreciate all your advice and encouragement, but you guys were way off! Back to the basics? How about confirming the car IS in 1st NOT 3rd! 15 hours of going through the commandments over and over to find out it was the shift linkage. I never touched the shift linkage though. But I did remove the shifter and handbrake trying to fix the hand throttle. Apparently that made a difference. Do I feel stupid? YES!

But at least the car is fixed! One word, WOW!! The throttle response is simply amazing! 3rd gear from 2.5k to 5k rpm on twisties is better than any roller coaster I've ever been on.

Again, thanks for all the help. My experience just confirms that it usually isn't the MFI.

BK

[Paul Thomas]

Jeff,
When you are running 5000+ rpm consistently, like in a 917, the pump timing doesn't matter that much, but when you are cruising around like we do it matters a whoooole lot. I figured this out when my car had no where near the power it should from 2000 but would take off like a rocket at 4000+. The pump cam was way off.

Paul