Cap and rotor question? Backfire?

[NAM75]

99 Response. 5.7 EFI TBI.

I changed the cap and rotor today. Why would some of the posts in the cap and the plug wires look corroded and others look ok?

 

Edited September 12, 2023 by NAM75

[oldjeep]

Just now, NAM75 said:

99 Response. 5.7 EFI TBI.

I changed the cap and rotor today. Why would some of the posts in the cap and the plug wires look corroded and others look ok?

 

Because life is unfair?  

Did you replace with a cap/rotor with brass contacts - or a car type aluminum set?

[NAM75]

I bought the new one from discount inboard marine. It’s brass. 

Wasn’t sure if there might be a reason or just random??
 

[Bozboat]

15 minutes ago, NAM75 said:

I bought the new one from discount inboard marine. It’s brass. 

Wasn’t sure if there might be a reason or just random??
 

Brass mo better less corrosion

[NAM75]

Cap and rotor didn’t help. New plug wires coming tomorrow.

It seems to do it if i throttle up harder. It also does not seem to be coming from the exhaust but under the  motor cover.

Maybe fuel related?  I’ll change the high pressure fuel filter too.

Would clogged fuel injectors cause this. About 700 hours and I don’t think they have been cleaned.

Thanks Crew! 

 

 

 

 

 

 

[justgary]

21 minutes ago, NAM75 said:

It seems to do it if i throttle up harder. It also does not seem to be coming from the exhaust but under the  motor cover.

What is "it?"  Your question was about corrosion under the cap....

[NAM75]

Sorry…I’m getting a slight pop, like a backfire when I throttle up. Seems to be under the engine cover and not the exhaust. 

Seems to happen more often if I’m heavy on the throttle up. 

[justgary]

3 hours ago, NAM75 said:

Sorry…I’m getting a slight pop, like a backfire when I throttle up. Seems to be under the engine cover and not the exhaust. 

Seems to happen more often if I’m heavy on the throttle up. 

How old are the plug wires and plugs?  You mentioned crud on the wire terminals, and resistor wires do age poorly.  Consider changing them if they are more than ten years old.

[NAM75]

5 hours ago, justgary said:

How old are the plug wires and plugs?  You mentioned crud on the wire terminals, and resistor wires do age poorly.  Consider changing them if they are more than ten years old.

Spark plug wires are probably 6-7 years old. The ends are pretty cruddy. Next on the list. 

[JasonK]

Have you ever cleaned the throttle body of carbon?

My dist cap contacts don't have the same amount of corrosion, but they all have some. Not sure why some are more/less corroded.

A bad fuel pump regulator could cause a backfire.

I don't know if bad injectors would cause a backfire. My injectors have 1,750 hours and no problems.