Changing Distributor Cap and Rotor, throw timing off?

[enginesilo]

My engine (5.0 GXI-B Fuel Injected) is having some running issues so I figured I would start with changing the distributor cap, rotors, spark plugs, and the wires. How difficult is it to change the distributor cap and the rotor? Seems like it's only a few screws holding the cap on, and then does the rotor just pull off the metal shaft, or is there a screw holding it on or something? I'm worried about throwing the timing off, is it safe to remove the cap and pull the rotor directly upward to remove, and install the new one in the same spot?

Any tips on how to go about changing it? My plan is to number the spark plug wires well, draw myself a diagram, and then get to work. What order is common, do you remove the cap, and then remove one wire at a time and replace with a new one until all the new wires are on the new cap, and the old cap and old wires are all gone? Any tips on what is best procedure so I keep track and get it done successfully will be great.

 

[alldodge]

The distributor cap for your motor gives folks trouble quite often. Not saying it is the issue but many carry a spare because they can look great but have issues. Many call it a crap cap

To remove, remove screw holding cap and lift up.
Rotor is removed the same way by removing 2 screws
Replace both in reverse order and your done.

I would replace the cap and rotor before anything else unless you just want to.

You might be able to replace the cap without removing the wires off the cap prior. If unable to do this, just replace one for one. The cap has numbers on each port, 1 thru 8 and coil. You shouldn't need a drawing, unless all wires are removed before reinstalling.

Plugs on the motor are 1, 3, 5, 7 on the port side, and 2, 4, 6, 8 on the starboard side. The pic below is a V8 same as yours and firing order is the same, but has a different distributor. This is just to show which cylinders are on which side

 

[enginesilo]

The distributor cap for your motor gives folks trouble quite often. Not saying it is the issue but many carry a spare because they can look great but have issues. Many call it a crap cap

To remove, remove screw holding cap and lift up.
Rotor is removed the same way by removing 2 screws
Replace both in reverse order and your done.

Thanks for the help, this is building my confidence to give it a go. So far I have fuel separator, cap, rotor, and possibly plugs and wires in the plan. Sure am hoping it fixes the issue. If it doesn't I'll start a new thread and share the exact symptoms. In a nut shell it started to idle a little rough, and wouldn't rev over 3000rpm's, and now hardly wants to start. Hoping its something simple.

 

[alldodge]

Sounds like the cap

 

[enginesilo]

A quick update. So the boat wouldn't start when I tried it early in the day. At night I returned with a fuel separator and a remote gas tank with fresh gas. Was able to get it to start with the throttle all the way down. Still has that miss feeling in idle, but it does idle nice and low. I tried to pull a spark plug wire at a time but it was hard to tell a difference in the engine sound. I let it run a while and it ran fine. If I try to rev it quickly it hesitates for a second but then revs up normal. Still think its cap and rotor?


I have a distributor cap and rotor arriving today, along with a fuel pressure tester gauge and plan to go down and do the following:
-Spark Test just out of curiosity to see if some plugs aren't firing
-Check fuel pump pressure (High and Low)
-Change Distributor cap and rotor

Then based on how its running i'll probably do the following based on symptoms remaining:
-Check Compression
-Change Spark Plugs
-Change Wires
-Take off flame arrestor and look inside (No clue if there is anything even to see in here but figured why not look)

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Did I miss anything? Any sensors to unhook and check to see if there are running/symptom changes (MAP, Etc?)

 

[Scott Danforth]

start with the cap and rotor

 

[enginesilo]

start with the cap and rotor

You guys both called it! I checked for spark and all 8 tested with spark, but I could tell some were weaker than others. Took the distributor off and all the points inside were full of chalky crud. Put the new one on and the engine starts up quickly time after time. The real test now will be to do a test drive at high rpm's. Hoping to do the test ride soon.

Should I bother with changing the spark plug wires or plugs if it runs like it should during the test drive? I'm thinking I may run it as is and keep a set of spark plugs on hand for when I do a baseline compression test just to get an idea of where the compression is when I got the boat.

Thanks again

 

[Scott Danforth]

change the plugs too

then get a second set of plugs and a second cap and rotor to keep on hand.

change the cap and rotor every 2 years

 

[alldodge]

I wouldn't change the wires unless other issues show up