Running really bad - Page 3

rob6773 · 10-10-2009, 09:08 PM

I changed the power valve and got rid of the hesitation. It is running somewhat better. The bog/stumble is cleared-up.

The rpm dip on deceleration is still there.

I ran it without the throttle hooked up and working the carb by hand the rpm still dips on acceleration. Someone suggested it may be fuel supply, so I hooked up the throttle, reved it up and when it went to stall shut the key at that second, opened the fuel sight and found adequate fuel in the primary bowl. That should be proof enough that fuel supply is good.

I also opened up the idle screws a lot and it did not help.

I have non-marine holleys sitting around so I am going to try one on this thing tomorrow to see if it still does this.

rob6773 · 10-11-2009, 12:28 PM

I tried another holley and it is still doing it. It seems is like it dropping to 4 cylinders for several seconds after reving-up. At normal idle 1000 and below it stalls. With a 1200 rpm idle it will stay running, it dips to 800 and recovers in about 4-6 seconds.
I am pretty sure I had this problem with the last distributor. I am going to put the my digital snap-on timing light on it next to see if it is loosing spark or having some weird drop in timing. The springs/limiters are set in this disrtibutor so it can have alot of timing at idle, I set it for 21 idle, 33 full.

rob6773 · 10-11-2009, 03:57 PM

It was the #$%^ing coil! It was doing wierd stuff on the timing light and I saw some skipped blinks on my spark testor also. So I changed the coil (took out a MSD blaster 2 and replaced it with a blaster 3 I had around) and at first it did not want to idle, made some adjustments and had it idling @1K rpm and it was only dipping 100 rpm w/no threat of stalling. I also noticed that the 12 degree limiters in the distributor were allowing 15 degrees of advance so I modded them to I only have 9 degrees of advance now. I have 25 degree at idle and 34 total. I want to take it tomorrow.

Here are the three things that caused all the trouble-
1) old gas
2) bad power valve (from backfires)
3) weak coil

mrfixxall · 10-11-2009, 08:35 PM

Do you have a msd 6? box? you wont get a accurate readings with the snapon digital timing light..the mark bounces around.

rob6773 · 10-12-2009, 08:12 AM

The MSD box was disconnected back in August. When I thought the boat had ignition problems I had changed the distributor and unhooked the box. With more than one thing wrong this was a very hard diagnosis. I've been working on cars a long time and can't remember figuring a running problem to ever be this bad. Boats are more difficult.

rob6773 · 10-12-2009, 10:43 PM

Wound-up brought back by Seatow, the boat was running OK, pretty fast, but we ran out of gas. It had 8-9 galloon and we were only out about an hour. I think this 454 is using more gas the 502 we had because I have a double pumper on it and the last one was vacuum secondary. It is empty for winter. I flushed it out on cam2 purple, fogged it, and left the tank empty.