Past posts I thought you just advance the throttle on the second attempt to start the engine and it would start. Pumping the throttle with an MPI engine - the injectors are at the end of the line - throttle pumping has nothing to do with them spraying fuel like a CARB would. The ECM does and of course proper voltage and so on for the injectors to spray fuel - the JIST of it. That's why I am really curious to see if you leave throttle at idle setting and do not touch IT or move it - but cycle the fuel pump 5 to 8 times and then crank over the engine to start - I want to know what happens - if this starts the engine then possible fuel related issue / fuel pump/ check valve in the fuel pump or fuel boil off issue -

if no start on those attempts - advance the throttle on the next try - if it starts it is not a fuel related problem nor a vapor lock problem or fuel boil off problem. It is a sensor / or connection or a ground problem of some sort.

Sounds like a plan.. thanks again.

I pretty much was. Started cold and hot fine but if it sat a while after running it would start hard like you are experiencing. I pretty much tried everything else so I swapped coil packs and the issue went to the other engine. I spoke with mercury racing and they agreed that it was strange but it's been fine since the new coil pack went on.

Hey, ..... HI Five, ........ even if we cant diagnose the problem, your typing skills have greatly improved, good luck brutha

the ignitions coils in the later apps 0M953??? engine serial # and up were moved to upper back side. this help somewhat better against heat and heat soak compared to the past mounted.

I have brought up what has changed in your app and thought about some the things to double check and might help whomever whenever.

Asking how did you mount your sensors - questions are posted ?



Did you remove the throttle body for any reason ?

have you touched the throttle stop screw or adjusted it ?

Did you install a new gasket for the IAC and torque it correctly

Did you install the crankshaft position sensor and examine the SPACER that goes with it for the install. Was the spacer in perfect shape or a NEW SPACER installed ? VERY IMPORTANT HERE again very important.

Did you install a MAP sensor - if so make sure you did not damage the seal. And this sensor should lie perfectly flat on the mounting surface when installed.

coolant temp install - If I remember CORRECTLY should not exceed 2.5 turns when installing but might be wrong here. Sensor installed to seat the o-ring and do not over tighten. Also merc has always listed PST pipe sealant for the threads.

I know this 4 sure the MAT sensor is 2. 5 turrns MAX for the install and uses the same PST thread sealant on the threads.



Important INFO that might help.

The throttle plate adjustment is important here.

you have to remove the throttle cable off the stud and remove Flame Arrestor

You have to manually open up the throttle plate about 1/2 way and let it snap shut by itself. AFTER that there is 5 measurements that need to be taken with a feeler gauge thru the throttle body and throttle plate horizontal sections of the throttle plate - 3 top and 2 bottom positions with a feeler gauge to see measurements.

find the smallest gap with your feeler gauge in these 5 points of measurements. You are looking for 0.009 of inch clearance. If you do not have this - you have to adjust the clearance of the throttle plate against the throttle body by using the throttle stop screw. After the correct clearance is adjusted at the smallest section /position - open the throttle plate manual again half way and let it snap shut by itself - retest your clearance again with the feeler gauge to make sure it is correct - again at the smallest position section throttle plate clearance of your measurement like the first time go around still needs to read 0.0009 in.

Next is reinstall the throttle cable and flame arrestor. Hook up your scan tool and the run the engine reaching full warmed up normal temp. Next is - at IDLE SPEED fully warmed up engine you have to adjust the idle speed screw on the throttle body to a IAC duty cycle of 20 %. This is very important.

I took a lot of thought into this if all else fails in your testing - I think I have covered a lot that could possible help. Like I said before What has changed on your engine ? I thought of outside of the box thinking what could have possible changed here.

Still want to know about cycling the fuel pump not touching the throttle and then advancing it.to see what happens.

thanks BUP. my next step is to cycle the fuel pump and see what happens to figure out where to go next.

I know I wanted to get all that info I posted out of the way just in case if your issue remains because one of these days when it stops with the bad weather around here - I will have to get back to work non stop. Plus it was in my head and I did not want to forgot anything.

Cycling the key 5 to 8 times or even 10 times will tell a lot and if still no start but advancing the throttle and the engine starts will tell a whole lot as well.

So whats up with the triplet beast here ??? See I even put 3 question marks for the triplets.

Nothing to report yet. Haven't been able to get back out again yet.. You can be sure that I will report my results...

I did find one thing the other night when I was doing some other stuff, but I really don't think it has any bearing on the situation. It looks like some of the adel clamps that hold the fuel line down were stepped on and they are pinching the fuel line a bit. It probably happened when they put my engine back in this winter. I'm going to put new clamps down, but I doubt it has any effect on whats happening since it was also happening last summer.