hesitation

[artron9]

My 52 v8 was running rich with #51 jets. Dropped two sizes to#49's. I'M getting a slight hesitation when I start to accelerate. I adjusted the fuel mixture with my vac gauge and increased the idle speed to about 600 rpm in Drive. Would the drop in jet size be the cause?

[51 MERC-CT]

Sounds more like the accelerator pump needs attention (longer stroke position).
If it's an automatic, the idle speed in neutral should be closer to 500 RPM or less.

[artron9]

Hi Merc 51, I thought the hole nearest the throttle shaft was for hot temperature and the far hole was for cold weather? Should I try the far hole(longer stroke)? Thank you!

[51 MERC-CT]

Originally Posted by artron9

Hi Merc 51, I thought the hole nearest the throttle shaft was for hot temperature and the far hole was for cold weather? Should I try the far hole(longer stroke)? Thank you!

Yes, by all means try the longer stroke position. (it is possible that the pump is defective)

[artron9]

Thanks 51 Merc-ct, I moved the position to the right(cold setting). Noticed some improvement. Will test it again tmrw and let you know! I appreciate our input!

[51 MERC-CT]

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Originally Posted by artron9

Thanks 51 Merc-ct, I moved the position to the right(cold setting). Noticed some improvement. Will test it again tmrw and let you know! I appreciate our input!

If you did notice some improvement then it appears that the accel. pump needs to be corrected as it is not supplying enough fuel shot off idle which can be the cause of hesitation.

[artron9]

Thanks 51Merc-CT
I rechecked the pump and lubed it. Pump seems ok. Did not check the squirt though? Still have the hesitation. Maybe I should put the #51 jets back?

[drolston]

Originally Posted by artron9

Thanks 51Merc-CT
I rechecked the pump and lubed it. Pump seems ok. Did not check the squirt though? Still have the hesitation. Maybe I should put the #51 jets back?

Check the squirt in both barrels before you change jets. Weak stream means accel pump plunger loose fit, or blocked passage.

[51 MERC-CT]

Originally Posted by artron9

Thanks 51Merc-CT
I rechecked the pump and lubed it. Pump seems ok. Did not check the squirt though? Still have the hesitation. Maybe I should put the #51 jets back?

No amount of lubrication will fix a faulty accel. pump, it needs to be replaced if faulty.

[artron9]

Thank you both for your suggestions! i have a new plunger coming!

[Pete F.]

Check the vacuum and than check the power valve setting.
With the fatter jet you didn’t need the extra fuel on acceleration but now since the mixture is leaner you need fuel enrichment till your up to speed. If the power valve is opening to late you will get hesitation.


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[artron9]

Thank you all: I have decided to go back to the #51 jets. Hesitation is gone? again, I appreciate all of your concerns!