help needed: 502BBC engine problem
#1
Registered
Platinum Member
Thread Starter
Join Date: Sep 2010
Location: Cologne, Germany
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
help needed: 502BBC engine problem
Hi,
I rebuild over the winter my 502 EFI engine. after refit in the boat it starts very good idle perfect and run up to 2800rpm or 40% throttle position, then it suddenly struggle, sound as a few cylinders are missing, no chnace to overrev this. if I take back the throttle the engine run fine again. it happens all the time under same condition. I checked
-fuel pressure (35psi)
-ignition timing (10 in idling)
-air fuel ratio (perfect)
the problem is the same if I rev the engine without gear in.
Had somebody a problem with the ignition module in the Deöco HEI distributor? If the problem happen the ignition timing jumps from 32° suddenly to 11°.
Hoping for help, no more idea what I could check :-(
Daniel
I rebuild over the winter my 502 EFI engine. after refit in the boat it starts very good idle perfect and run up to 2800rpm or 40% throttle position, then it suddenly struggle, sound as a few cylinders are missing, no chnace to overrev this. if I take back the throttle the engine run fine again. it happens all the time under same condition. I checked
-fuel pressure (35psi)
-ignition timing (10 in idling)
-air fuel ratio (perfect)
the problem is the same if I rev the engine without gear in.
Had somebody a problem with the ignition module in the Deöco HEI distributor? If the problem happen the ignition timing jumps from 32° suddenly to 11°.
Hoping for help, no more idea what I could check :-(
Daniel
#3
Registered
Platinum Member
Thread Starter
Join Date: Sep 2010
Location: Cologne, Germany
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
thanks for your reply. I torqued the bolts of the rocker arms with 60nm as described in the Merc manual, did you think a bit less torque helps?
#4
Registered
Join Date: Feb 2009
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
The rocker arms are non-adjustable, you have installed them correctly. I sounds like you have a scan tool, look to see if this is caused by knock retard to the ECM timing. Might try replacing the knocksensor, but they rarely go bad. I have seen worn shaft bushings in the distributor do bizzarre things to the timing, but I think your on the right track with the ignition module. Good luck.
#5
Registered
check the firing order....had a small block that a friend redid and ran like you described...asked him a few times on the plug wires...after messing with it for a long time found 2 wires crossed..idled fine, no backfire....but would not turn RPM