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454XL Won't start after replacing cap, rotor,and plugs

kevin_z

Regular Contributor
1995 454XL (MSTS) 860 hrs. Replaced risers and start engine to get warm to re-torque riser bolts, Started up fine. I then replaced spark plugs, cap and rotor. Went to start and backfired bad!! Double checked wires. All is fine. Put old cap and rotor and same thing, no start. Rented a spark tester, and good spark on all 8. Unplugged MSTS to check timing. Almost 8 degrees off. HOW? Moved distributor to timing marks. Re-connected MSTS and tried to start. Worse back fire now.
 
When you unplugged the MSTS did you plug in the jumper and connect it to a 12VDC source before checking the timing ? Dees sound like criss crossed ignition wires - which you have rechecked. With the MSTS unplugged - and the engine timed correctly - the engine should run fine.
 
I did not use a jumper connected to a 12v source. Will try that today.

Question?? Can I use a sierra ( 18-517-1) ignition module to replace the Crusader (CRU 38068) Sierra is almost half price.
 
Yes, Sierra 18-5107-1 will replace CRU38068, CRUR116014, or CRU7243110. With a little bit of research you can also find a GM part (specifically for marine aps). Before you change out your ICM, recommend you have it bench tested at AutoZone - no charge.
 
Swapped ECM from port engine. Same thing, Stbd no start, port no problem. Did not know AutoZone did ECM testing. I did not remove the ignition module. The bolts are rusted and not ready to tap.

Any other ideas??
 
Swapped ECM from port engine. Same thing, Stbd no start, port no problem. Did not know AutoZone did ECM testing. I did not remove the ignition module. The bolts are rusted and not ready to tap.

Any other ideas??
 
If you have good spark the next culprit to investigate is fuel. Is your fuel pump running while the engine is cranking ? If you put the trans in gear and turn the key to start, does the fuel pump run even though the engine is not cranking ?
 
Yes. Fuel pump is running. I replaced the ignition module today. found a GM one at local O'Rileys. Still no start. Back fire through carb. Advanced timing a lot and now back fire through exhaust. Is the next step to remove distributor and look at gear and distributor pick up???? This engine was rebuilt 3 yrs ago. Again, all I did was replace cap, rotor, and plugs.
 
The most likely scenario is something was upset when the ignition parts were changed. The timing should not have been effected. A failed ECM, ICM, ignition coil, or pickup coil are unlikely. Just for clarity; did you change the ignition wires one at a time or all at once according to the firing order and rotor direction realizing the firing order on the left and right engine are different ? Since the distro cap was changed, are you sure the right wires were on the correct terminals ? The presentation is classic mis-wiring. BTW the correct GM ICM is Part Number GM10482830.

The timing can be adjusted two ways 1) with jumper (CRU98073) plugged into the 4-wire ICM port and the pigtail connected to 12 VDC or 2) leaving the MSTS plugged into the 4-wire port AND disconnecting the single MSTS wire at the quick disconnect (located below the left exhaust elbow).

HTH
 
Port and Stbd engines are left hand rotation. I determined that because when I look at the belts and pulleys, both engines are turning clockwise (right). I can not see the flywheel. Firing order I'm using: 1-8-4-3-6-5-7-2.

After this rain passes, I am going to remove plugs, turn crank over by hand until #1 is TDC.

OUESTION: When #1 is TDC, where should the rotor point? Towards #1 cylinder or #1on distributor cap?
 
When #1 is at TDC (on the compression stroke) the rotor must point to the distro contact that is connected to the #1 plug. To be sure you are on the compression stroke, take out the plug and feel the compression build. If there is no pressure building you are on the exhaust stoke.
 
2X on the root cause being the wires...only other things that come to mind are the rotor or cap not being aligned/seated correctly...
 
Guys..

I am away off here and probably not much help.

My engines are 350's but I couldn't get one started....we found that the wire at the tach at the helm had worked off.
Cleaned up the wire, reconnected and the engine started...(we had changed everything electric prior to finding this problem up front (1991 Crusader 350's.)
 
FIXED!!!! I removed plugs, attached compression tester on #1. Rotated crank by hand until #1 was TDC on compression as indicated by compression tester gauge. The rotor was pointing to what I thought was # 4 on distributor cap. Reinstalled plugs, re-did plug wires, and BOOM, started right up. Lesson learned: Port and Starboard engines are not the same even if they are both left hand rotation. Also learned, don't start replacing parts (ing module) until sure that's the issue!
 
Good on ya !! Nothing like that manifestation of rapture when a problem engine finally fires up. Concur with your "lessons learned". Good job.

FL Panhandle
 
2X on that!!

Now that both engines are 'right', make sure you document their 'features' in your log book...may also want to clearly mark your #1 wires' positions ....
 
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