1989 Quadrajet 4 barrel with inconsistent start up isses...

[rhillman75]

I have a 1989 Regal Ambassador 233xl with a 5.7 Mercruiser with a Rochester Quadrajet. Full rebuild was finished 1 year with phenomenal results. My biggest issue and the cause of scratching my head is that sometimes when starting whether cold or warm, it either starts right up or I have to crank it 2 or 3 times and let it crank for up to 2 seconds. When it sits at the dock for upwards of a week, sometimes I can return to it and it will start right up without pumping the throttle. Same scenario another week later and it requires up to 2 to 3 pumps before it will start. The only issues when the engines is warm are at times I need to pump the throttle or crank 2 to 3 times. Some have told me to pump it no matter if the engine is warm or cold. I have had 3 rebuilders re-check each others work and all specs are within tolerance and it has a new float. They have offered a refund, but a refund won't solve the issue. Does anyone have this style of carb and if so, what characteristics have you seen from yours? The idle mix screws are at 2 turns out from seat position and the idle screw is 2 turns in from throttle lever contact. These are the 2 settings that the carb was at prior to rebuild. Thoughts???

 

[Rick Stephens]

Idle mixture screws should be adjusted to the motor, when warm, for best mix, not for what it used to be set to. And if you have the choke set correctly it should not need pumping, IMHO.

I have some of the same inconsistentcies, I store and work on the boat in my shop at 3600 ft elevation. I use the boat at 1600 ft or lower. Having a choke, let alone setting the choke is mostly irrelevant at the higher elevation since the boat runs rich at home. So I have to reset all those in the water if I want it right.

My point isn't that you have elevation issues, only that the carb needs to be properly adjusted. It doesn't sound like it is correct right now.

One other nice resource is the Mercruiser shop manual for your boat will have full carburetor servicing section for the Roc carb. My experience has been that most mechanics are not even close to being good carburetor technicians. They can do the routine, but actually doing deeper adjustments is beyond their scope of knowledge. Real carburetor techs are rare beasties.

Rick

 

[TyeeMan]

A lot of Merc initial idle jet settings are 1 1/2 turns out from the seat. Once the engine is at operating temperature, working on one jet at a time, slowly turn the jet in (leaning it out) until the engine starts to stumble, then slowly back the jet out (making a richer fuel/air mix) until the engine starts to stumble. Find a mid-point between rich and lean and that will be your final setting. Follow suit with the other jet.

Idle speed should be done in the water with boat secured to a dock, in gear. I believe you will need to disconnect the throttle cable from the carb to achieve proper idle setting. Then adjust the barrel on the throttle cable so the throttle cable will easily attach to the carb without using any force.

 

[harleyman1975]

I am a skeptic so please bear with me. Just because you paid for it does not mean it was A) done right and B) that there wasn't something missed. A q-jet is a marvelous thing when working right, next best thing to fuel injection some say. It has a few little check balls and hidden passages that can malfunction or get plugged or leak. It is possible to rebuild this carb and use all the pieces but put the wrong check ball in the wrong place and it will work some of the time and not all the time. Follow me? Sounds like this is the road you've been down. If it was me I would try a new, not reman, but new carb. This would eliminate the possibility of human error and worn cores. If you still have the same problems then at least you know it is not the carb itself. Not the cheap solution but isn't your time on the water worth the expenditure?