Pagoda SL Group
W113 Pagoda SL Group => General Discussion => Topic started by: Naj ✝︎ on May 22, 2003, 03:17:30
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Do injectors tell tales like spark plugs do?
I removed 4 injectors with carboned up tips/nozzles and two tips were shiney clean. Car misfires over 4500rpm. Think I have eliminated ignition problems.
Comments?
naj
naj
'Kloines Scheisserle'
65 230SL
68 280SL
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has the injection pump been rebuilt? i ask only because that seems to be the weak link in my system.
Douglas Kim
New York, NY
#018260
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Douglas,
Car was bought without history, but I suspect not in the recent past.
Car starts fine and runs okay upto 4500rpm.
Pump rebuild: I hope not.
naj
naj
'Kloines Scheisserle'
65 230SL
68 280SL
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I have it on good authority that these particular injection pumps rarely go bad. So it would perhaps be better to source a used one off a sedan at a breaker yard (for $250?) than to go for a full rebuild. I also understand that there is a relatively inexpensive basic service (replacing seals and springs, cleaning etc) that can spruce up the FI pump without going through the all-inclusive (and rather expensive) total rebuild. Maybe the general tune of the engine is out of spec (valves, linkage, mixture, fuel delivery/pressure etc) but knowing Naj this has all been checked out. Any chance of a head gasket leak?
white 1969 280 SL
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Hello naj,
The injectors are positioned in the intake port in the cylinder head, above the intake valve. They will not be an indicator like a spark plug. In addition I have never seen them be the source of a high speed misfire. A ignition coil can misfire at high rpms and be perfectly fine when cold or at lower rpms. Spark plugs that are new but have been run too lean or rich can also cause high rpm problems. The ignition wires and the resistor ends themselves should be checked with an ohm meter. Make sure the distributor rotor is correct some are close but wobble and do not fit correctly. Check the distributor advance springs by twisting the rotor, it should move clockwise then spring back. The engine must have the correct fuel pressure to run especially at high rpms when the demand is greatest. Bad ignition condensors are hard to diagnose but fairly inexpensive to replace. Try the cheap fixes first.
Check your valve adjustment and valve timing. If too tight, maybe some escaping exhaust gases are the cause of this carbon on the injectors?
Good Luck!
Joe Alexander
Blacklick, Ohio