260 problem

[Bob A]

I have a 96 260 EFI with a63 ecu. The motor has a stumble from start of pass to about 500 ft of wide open pass where it finally cleans up. #2 piston is completely clean when I pulled heads. I have already replaced injector and that did not remedy problem. I have not yet had time to go further into diagnosis. Any suggestions? Thanks.

[Jay Smith]

Bob ,
Could be low speed windings on your stator or change that # 2 coil around to another hole it make be a weak coil that just cannot fire that rich charge of fuel off . Be sure and do the no brainer things like change plugs. Did your motor just start this ? And did your motor come with a digital box and your MAP air senser air barb in the plenium behind the ECU the correct size. Some guys when they retrofit a digital to take the place of an anolog they miss changing that barb and that can make one lazy off the get go...

Check for stopped up in line fuel filter that can make one act crazy ( use a 33093 WIX as a replacment for the BIG $ mercury one )



Jay @ JSRE

[us1]

One other thing, check the #2 injector for straight lining. The unatomized fuel will not burn correctly and will wash the piston clean also causing the motor to run poorly.

[Ziemer]

I also have a 260 that is terrible out of the hole and will not turn up over about 6700. I just put new plugs in it, all new bleed line and also cleaned the line and barb off the ECU. I have a digital box A42. It feels like it's getting too much fuel at takeoff. If I put the petal to the floor it's worse than if I gently ease into the throttle. Also at speed, there's no difference in RPM's when the throttle is wide open to when it's about 1/4"-1/2" off the floor. Also, this weekend I heard a flutter at about 4500 RPM's. Wasn't exactly sure what it was, possibly a bad reed??? Anyway, would like to hear any progress that you guyts figure out, because my problem sounds similar.

Thanks.

[Greg Moss]

you have bleed lines on an EFI motor? You should have bearing lube lines and that is it. What do your pistons look like. Do you have just one that is clean or all of them?

[Ziemer]

I haven't pulled the heads yet, so I don't know how clean any of the pistons are. However, I checked the plugs after running the new ones a couple of times and they were pretty black and somewhat wet. All six looked about the same. I read Bob A's original post again and my problem is a little different. Mine does not wanted to get out of the hole, and it won't turn up. The lines I replaced are on the left side of the block in between each of the injectors, and another that runs off of the horn. Also, the fuel filter is new, the fuel pump is new and I'm running the high performance Mercury oil ($82.00 for 2.5 gal.) good stuff at 40:1.
Tomorrow night I'm going over to my fellow weekend mechanics house and we're going to try a few things. I think we will start with the ECU and work from there. Any suggestions???

Thanks.

[Greg Moss]

i would try checking the temp sensor first. It is on the bottom side of the block across from the injectors

[UROSKEE]

My 260 is doing the exact same thing as yours. Please keep us informed as to what you find. I would appreciate it greatly!!!:D

[ChrisH]

Man, find someone else to buy your oil from! Somebody's hittin' you for full retail!

[Ziemer]

Thanks for the concern, however I don't pay that much for my oil, I just wanted to make sure that everyone new that I was running the good stuff and not just the premium plus rather than the performance oil.

UROSKEE, do you have the orange and blue wires jumped together that come off the main harness that leads to the ECU. There is a set of three wires that should lead off the main harness that go to a plug that should be to nothing. Two of the wires should be orange and blue. If they're not jumped, it will cause the motor to be slow out of the hole.

This was the first thing we looked for on my harness, however, I don't have the orange and blue wires off the main harness and none of the people I mainly deal with have ever seen a 260 without the secondary harness. So what we are going to do is find a different harness and jump them together to see if that's my problem.

Anyone with any comments please feel free to jump in.

Thanks.

[us1]

The orange and blue wires are for the TPI. If you don't have them in your harness you already have the digital wiring harness and are all set. The A63 can actually control its richness through the TPI harness if hooked up correctly. If you just jumper the orange and blue without the right potentiometer you will through the injector pulse width for a loop. It will either run supper rich or lean though the whole fuel curve. Be careful I don’t think that is your problem. Not sure if the same function is possible with the A42.

[Jay2002]

Check the tee in the return hose after the regulator. It has a small hole in it to bleed fuel off of fuel rail and it can get clogged not allowing fuel to return to tank along with fuel flowing thru the regulator.

[UROSKEE]

If the wires you asked about are indeed for the TPI, I probably have them because I have an analog ecu. I was going to buy a digital ecu to try and cure my problem, but you already have a digital ecu and are having the same problem I am. Therefore I was hoping your fix, when you find it, will work for me as well. Thanks.

[UROSKEE]

oops - forgot to ask - What year is that 260?

[Ziemer]

Mine is a 1996 260 with a digital A42 box. I don't have an external TPI so those wires on mine would go to nothing if I had them.

If you have a TPI and your wires are connected to it, then that won't be your problem.

I should have some more answers after this weekend, I hope.

[Ziemer]

I'm still not sure what my problem is; however, do some 260's not have the external TPI plug and some do?? We haven't seen one that doesn't have the empty plug off the wiring harness except mine. Even my friends 99' Drag has the empty TPI harness that he jumped the two wires on.

I had the heads off this weekend and the heads looked perfect, no nicks or dings and they have never been cut. Also the top left and right pistons along with the bottom right were fairly clean, not much carbon build up. The remaining had decent amounts of carbon on them(about the size of a silver dollar). All six pistons cleaned up perfect and the cylinders looked fine. (still all nicasil.)

The injectors are original and I think I'm going to replace them anyway, to be on the safe side.

It didn't run great this weekend, problem almost seemed worse than before.

Electrical or Fuel??? That is the question.
Thanks.

[Ziemer]

Checked the temp sensor and it seemed to be fine, also my ECU has two pins that go to nothing into the wiring harness. Are these the two that lead into the TPI sensor plug??

[us1]

The TPI terminals have pins digital or not. The digital ECUs should come with a wiring harness without the TPI plug in. Those three clean cylinders could have straight lining injectors