Engine runs rough while activating my timing light but run fine when light if inative

[payitforward]

Hey Guy's

I'm hoping someone could help me with a crazy problem with my timing light. Every time I push the timing light button to set the time the engine starts to run rough and will die unless I let the button go...... so, i do the same thing to engine #2 no problems and timing is set. Please help I've had four Volvo Penta dealer look at with no help. 1999 7.4GI PBYCCE i just had it rebuilt.

 

[Fun Times]

Engine runs rough while activating timing light but runs fine when light is inative?

Engine runs rough while activating timing light but runs fine when light is inative?

Hi there payitforward, that does seem like an unusual problem. I went ahead and started a new thread of your own for you vs tacking onto the end of someone else thread per iboats policies.

Just to confirm, what engine model and year do you have?

Also as a starting point, what have the four dealers mentioned to you as a theory thus far? And of course what have they tried?

 

[Grub54891]

Re: Engine runs rough while activating timing light but runs fine when light is inati

Re: Engine runs rough while activating timing light but runs fine when light is inati

A bit of a reach-but is the coil hooked up backwards? Try switching coils from the other engine,see if the issue switches. If it does bad coil.
Grub

 

[alldodge]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Hey Guy's

I'm hoping someone could help me with a crazy problem with my timing light. Every time I push the timing light button to set the time the engine starts to run rough and will die unless I let the button go...... so, i do the same thing to engine #2 no problems and timing is set. Please help I've had four Volvo Penta dealer look at with no help.

What kind of timing light and what kind of engines? Also are they both the same year and model, no one has replaced one of them?

 

[Bondo]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Ayuh,... 'n Where are ya attachin' the timin' light's leads,..?? (+), 'n (-),..??

 

[payitforward]

Re: Engine runs rough while activating my timing light but run fine when light if ina

sorry...

1999 7.4GI PBYCCE
Rebuilt three months ago with about 4 hours on it. My boats down in Long Beach and the mechanics just want to charge you $125.00 an hour for to go over the basics you learn in high school. The mechanics had no clue they didn't even know how to time it. I got frustrated and bought a computer and shop manuals and started doing it my self. I have changed ever part from one motor to the other one at a time, including the upper plenum. still no changes! I tested the fuel system all the way to the gas tank. I had the alternator checked, Changed the coil. This motor was running good until it was rebuilt! Do to being water locked.

 

[Grub54891]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Sounds like you have your bases almost coverd. Have tou checked/cleaned every ground and hot terminals completly? Did the engine get painted @ the rebuild? Could gave paint where there shouldnt be. Saw one one time the owner painted it,including the spark plugs. Ran like crap till we pointed out the paint on the plugs.
Grub

 

[alldodge]

Re: Engine runs rough while activating my timing light but run fine when light if ina

As Bondo asked, where are you connecting the + and - for the timing light?

Is your timing light inductive or one that goes in-line?

 

[payitforward]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Craftsman advanced timing light. I connected it to the positive on the starter and grounded to engine. Also, connected to positive and ground on back of alternator. Same result! So, I removed the battery cables from engine and added a new battery with new cables directly to motor. Same result!

 

[alldodge]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Craftsman advanced timing light. I connected it to the positive on the starter and grounded to engine. Also, connected to positive and ground on back of alternator. Same result! So, I removed the battery cables from engine and added a new battery with new cables directly to motor. Same result!

Defiantly a weird one. You start the timing light and the engine starts to die. The timing light is pulling very little current to run, so for it to cause an engine to miss, I would look at wires and connections. It pulls very little juice but causes a miss. With the engine running what is the voltage reading at the battery?

 

[K-2]

Re: Engine runs rough while activating my timing light but run fine when light if ina

swap the #1 plug wires on your engines and see if the problem also switches engines. How old are the plug wires?
I think you have a bad plug wire and the timing light is sending that spark to ground.

 

[Scott Danforth]

Re: Engine runs rough while activating my timing light but run fine when light if ina

I would put the clamps on the battery. if the problem keeps persisting, I would also try a borrowed timing light

 

[payitforward]

Re: Engine runs rough while activating my timing light but run fine when light if ina

14.4 Volts when running... I will swap the wire this weekend.

 

[Walt T]

Re: Engine runs rough while activating my timing light but run fine when light if ina

It's either a ground issue or a timing light. Doesn't sound like a ground issue but I would never assume anything with a weird problem like this. As Mr. Danforth said, try a different timing light.

 

[skydiveD30571]

Re: Engine runs rough while activating my timing light but run fine when light if ina

It almost sounds like the timing light is backfeeding through the spark plug wire and interrupting smooth spark signals. No clue how that could happen though. I'd be trying out a different light.

 

[alldodge]

Re: Engine runs rough while activating my timing light but run fine when light if ina

The thing that gets me is if you ground out one plug wire on a 7.4 this would not normally kill the engine. The timing light is moved to the other engine and there is no problem. I think the key is somewhere in the engine was just rebuilt. I'm thinking something along the line component was not installed/connected correctly. Maybe a ground or other wire was left off and the timing light is causing a feed back because of it like you mentioned skydive.

 

[payitforward]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Ok, looks like I had a bad set of wires..... changed them and issue with timing light is gone. Motor is still running rough at idle and risers are new and running real hot. could I have the timing off?

 

[Scott Danforth]

Re: Engine runs rough while activating my timing light but run fine when light if ina

if the risers are running hot, there is no water getting to them.

 

[alldodge]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Ok, looks like I had a bad set of wires..... changed them and issue with timing light is gone. Motor is still running rough at idle and risers are new and running real hot. could I have the timing off?

Agree with Scott: Will ask, are the elbows (risers) getting so hot you can't touch them without getting burned, or hot enough you can't keep your hand on them?

 

[payitforward]

Re: Engine runs rough while activating my timing light but run fine when light if ina

Yes they get HOT you can't hold on to them. The exhaust and elbows, raw water pump and circulation pump are brand new. I checked every part of the water circulation and it's got water flow. Can timing cause this? I hooked a water hose directly to the exhaust manifold hose and the the one side ran cool.