'05 3.0L Alpha - fuel pressure drop during accel

[aspenorange]

i have an '05 3L alpha - i played with it myself, but the fiance asked to bring it to a professional to get it fixed faster. well they just started throwing parts at it, so i took it back because i can do that myself without a labor charge. so.... i can run at idle and if i move the throttle REALLY slow (once the engine is at temperature) i can get up to high rpms without it stalling out - if i throttle normal the engine stalls. the only helpful thing the mechanic said to me was that the fuel pressure was low (i'm assuming he means during accel). i have the TKS system and carburetor. what pressure should i be running at and what pieces affect the pressure - they replaced the fuel pump assembly so it's not that. any other ideas? thanks!

 

[Don S]

Re: '05 3.0L Alpha - fuel pressure drop during accel

Fuel pump pressure is probably not your problem, if it was, you wouldn't be able to run at high speed.
The carb is the problem, and that TKS carb is about the worst thing ever put on a 3.0L engine.
Those things run so lean to make the EPA happy, that you can't hardly give them gas. and you may never get it better than a slight hesitation.
I have extended the accelerator pump for maximum flow, and adjusted the idle mixture richer in order to get them to work better.
He ended up finally taking it to a Merc dealer and was getting Merc involved in it. (We couldn't do warranty as we were not a dealer).
That was last year, he still hasn't got it fixed the way it should be.

Here is the manual for the carb you can download, may help a bit. http://www.4shared.com/document/SNqPsoNI/Service_Manual_41.html

 

[aspenorange]

Re: '05 3.0L Alpha - fuel pressure drop during accel

Thanks don - the manual link was a huge help to understand our system. i was concerned by what the mechanic said with the low pressure so i put a gauge on myself and you were right it wasn't low at all - it ranged between 8 to 9 psi. Unfortunately I'm only running for a min or less and the engine stalls out, I can rev it hard but it still stalls itself out real quick. These symptoms are new after i got it back from the mechanic, something is getting worse and the only thing i can think to point my finger at is the carb. i did tweak the idle screw and the linkage, but i need a special tool for the mixture screw.

 

[Bayliner175xt]

Re: '05 3.0L Alpha - fuel pressure drop during accel

Fuel pump pressure is probably not your problem, if it was, you wouldn't be able to run at high speed.
The carb is the problem, and that TKS carb is about the worst thing ever put on a 3.0L engine.
Those things run so lean to make the EPA happy, that you can't hardly give them gas. and you may never get it better than a slight hesitation.
I have extended the accelerator pump for maximum flow, and adjusted the idle mixture richer in order to get them to work better.
He ended up finally taking it to a Merc dealer and was getting Merc involved in it. (We couldn't do warranty as we were not a dealer).
That was last year, he still hasn't got it fixed the way it should be.

Here is the manual for the carb you can download, may help a bit. http://www.4shared.com/document/SNqPsoNI/Service_Manual_41.html

Hi Don S i don't spose you would have the link for a Rochester twin barrel carb on a 2003 - 3.0 !!

 

[Don S]

Re: '05 3.0L Alpha - fuel pressure drop during accel

Merc stopped using Rochester carbs back in the 80's, they went to the Mercarb, looks like a Rochester at first glance, but there are differences.
The manual that covers that carb is #26, you can find it up in the Adults Only sticky under Merc Info.