backfire then big miss

[Doc]

I have a 50' Gibson houseboat with two crusader 350's (454cc engines). My port engine is driving me bonkers. It started backfiring when I would give it any gas (while under load, just idling would not make it backfire). However if I just moseyed along at idle speed it worked fine. So, I changed the points and plugs. Same problem. Then this weekend I traveled 15 miles up river to a sternwheeler festival (idle speed the whole way) and all was fine for the trip up. After sitting all weekend the darn thing would not start. When it did start I had to be giving it lots of throttle and it would miss horribly and backfire.
I had to piggy back a ride down river with another 50' houseboat. Not a good way to end a GREAT weekend.
What would you try next?
Any guesses as to what the issue might be?
Thanks in advance! http://www.speedwake.com/upload/images/smilies/biggrin.gif

[mla2ofus]

I'm assuming these engines have distributors.Check the inside of the distributor cap,Greg. Sounds like you have some tracks formed which let the spark travel to other contacts that it shouldn't go to.
Mike

[Bt Doctur]

cracked dist tower, carbon cracked cap

[Doc]

Are you saying the distributor shaft might be cracked? I replaced the distributor cap and rotor ...not sure what a carbon cracked cap would be. :confused:

[Bt Doctur]

on the coil,the tower is where the wire goes from the coil to the dist cap.
if you ever open up a old cap you`ll see like #2 pencil lines between the contacts or a ragged lightening bolt pattern.

[dreamseeker]

hook up a timing light and check you advance.

your timing should be advancing to the inxrease in rpms i believe up to 30 at 3000 rpms

if it isnt then the advance needs to be cleaned and lubed or repalced

you may have vacume adcance but most cases it is mechanical on boats

hope it is this simple

[Doc]

on the coil,the tower is where the wire goes from the coil to the dist cap.
if you ever open up a old cap you`ll see like #2 pencil lines between the contacts or a ragged lightening bolt pattern.

Ahhh, okay. Thanks Ed. :D

hook up a timing light and check you advance.

your timing should be advancing to the inxrease in rpms i believe up to 30 at 3000 rpms

if it isnt then the advance needs to be cleaned and lubed or repalced

you may have vacume adcance but most cases it is mechanical on boats

hope it is this simple

Getting at it tomorrow if it doesn't rain. I hope it's simple too. Thanks for the suggestion.

[Doc]

Well ...we hit a snag. It didn't rain but we didn't work on the boat. The mechanic / man with the compression checker, timing light and all couldn't make it today. No biggie. We are going to shoot for mid week to do an initial analysis.

[OhioTC18]

You have a month to get it running right :beer:

[Doc]

Yeah, I know Jerry. :hide:
I don't even want to mention this 'issue' in the houseboat party thread.

[dreamseeker]

hey doc
was just wondering how you made out and if your problem is resolved
wayne

[Doc]

I have an update.
Last Saturday: Compression check is good. :thumb:
Tried to put in electronic ignition. Didn't have the right modules. Wait until Weds.

Wednesday: Installed electronic ignition. No joy.
had to put in new plugs just to get it to start.
Check timing and it's right on.
Horrible miss and backfire still.

Today (Saturday) put on new spark plug wires. No joy.
Pulled the Carbs on both motors. Both have a good bit of dirt and a rebuild was strongly recommended. So now they are being rebuilt.
They will be reinstalled next Weds.
Keep your fingers crossed.

[mla2ofus]

Doc, by backfire do you mean out the exhaust or back thru the intake.
Mike

[Doc]

Doc, by backfire do you mean out the exhaust or back thru the intake.
Mike
Out the exhaust.

[Doc]

These engines have run cool since I got the boat. Avg 120 degrees operating temp. I'm guessing there is not thermostat in the motors. I'm also suspecting running so cool could cause the carbs to gum up. I'm not a mechanic and guessing. Are my guesses valid?

[dreamseeker]

backfiring through the exhaust imo in most cases in the timing

has the mech checked the timing chain for play and may have jumped a tooth

[Doc]

backfiring through the exhaust imo in most cases in the timing

has the mech checked the timing chain for play and may have jumped a tooth

If the carbs don't fix it that is where we are going next. Started with small things first (points, plugs, plug wires and now carbs) ...probably spending more than I would have had to but the carbs needed done anyway.

[OhioTC18]

If the carbs (with new gasket) doesn't fix it, check for a vacuum leak. Another possibility is a clogged fuel filter.

[dreamseeker]

you know it is possible you dropped a lifter or have a frozen lifter or valve spring

i would pull the valve cover and see if all are working right

pull the plugs and turn the engine by hand and see if all your valve open and close properly

you may want to do a compresion check to be sure you dont have a cracked valve

[OhioTC18]

According to a previous post, compression test was good. Hopefully all cylinders were checked. At first I was leaning toward a cracked exhaust spring but if compression is good, that rules that out.

[waybomb]

You can still have a great reading with a valve partially opening. I'd suggest pulling the valve covers. It's not that hard.

[Doc]

You can still have a great reading with a valve partially opening. I'd suggest pulling the valve covers. It's not that hard.

Thanks for the info Fred. I thought a good compression check eliminated that but ...now we have something else to check if the carbs don't fix it.
:thumb:

[mla2ofus]

Doc said he changed the distributor cap and that's the only thing I can think of to cause this if the compression is good.
Mike

[Doc]

Yep, new distributor cap.

[waybomb]

If he has a wiped cam lobe, or a bent pushrod, or abad lifter, the intake valve or exhaust valve will still open enough to let the air in and out easily during a compression check. The cylinder with the bad valvetrain may even have higher indicated compression.

A compression check is only good for things affecting compression - like rings, bad valves, bad headgaskets, cracked head, cracked block, etc.

[Bt Doctur]

Doc, do this test and let us know
Remove the dist cap ,use some way to SLOWLY rotate the motor to "0" mark on the timing tab. .Using some form of an indicator mark the position of the rotor. (closepin, coathanger, welding rod, pipe cleaner etc.).
Leave this in place. rotate motor in reverse rotation and see how many degrees of rotation untill the rotor moves.
A good timing chain and or gears will have very little degree difference.
if you move it 1-3 inches of harmonic balancer rotation before the rotor moves ,suspect timing chain and sprockets are badly worn.

[Doc]

Thanks for the tips guys. Very useful info. We're back at it Weds. I'll post the results.

[OhioTC18]

Less than 2 weeks.........tap tap tap...........:waiting::hide:

Just teasing ya
Sorry I know you're frustrated.

[dreamseeker]

dumb question

are you sure you have the correct dis cap

seems things got worse since you replaced.

[Bt Doctur]

I don`t see it mentioned but did this develop AFTER you worked on the dist cap?
What rotation is the affected motor. could you have used the firing order of a standard rotation on a rev rotation motor? I know, I know, but is the firing order correct for the motors rotation?

[Doc]

Good thoughts Bt Doctur!!!

But this started before we touched anything. It had ran fine last season, but had trouble at the end of the season when I was taking out. It had sat for 45 days at that point. Then when I launched in late May I had trouble starting. Played with points and got er going. She ran semi okay but he backfire started when I gave it a little throttle. 1800 rpm. Changed plugs and she fired right up. All seemed good, then when under load running down river and reved up she backfires. But I could idle okay. Changed points. Again, all seemed okay. But under load she still backfired. We idled most of the 15 miles upriver to Marietta for the sternwheeler festival. After turning off up there I could not get her started back up. If I held the throttle up at 15 to 1800 rpm it would keep running but it was backfiring and sputtering so bad that I shut it down. Hitched a ride back with a friends houseboat and got to work on her. That's how we got to the point of where I started this thread.
Long way of saying I don't see how the plug wires could have been switched for the firing ......we didn't mess with those.

[Bt Doctur]

pull the valve covers and inspect. maybe you hung a valve from storage, or cracked a valve spring. Had something similiar with a V6. turned out we had decent compression readings but the inner spring of an exaust valve was busted, caused the valve to float a bit sucking in water mist from the exaust.

[dreamseeker]

doc from all you discribe brings me back to timing advance

idles fine and smooth and your timeing is dead on put at rpms it backfires and runs rough

run the engine at idle and check your timing then raise your rpm as you raise your timing should also increase or advance till it is about 27 to 30 degrees avanced. You should be able to see this easy with a timing light

you avance is mechanical and not vancume in most cases on a boat engine and the linkage in the bottom of the distributer could be rusted and broken

[Doc]

Update:
Reinstalled the carbs: no joy.
Swapped carbs from starboard motor "just in case": no joy.
Checked all valves: no problems there
physically checked timing chain no problem there.

Checked and found out we could swap distributors with the starboard motor to try. Dang if the starboard motor which had been running fine now had the backfire and popping problem. So it appears it's the distributor.
Ordering one today and should have it installed by Monday or Tuesday. I feel better already. What a dilemma.

[Doc]

Less than 2 weeks.........tap tap tap...........:waiting::hide:

Just teasing ya
Sorry I know you're frustrated.

Whew! Told ya we'd be ready. Now we just have to get a new distributor in. :whistle:

[OhioTC18]

Could have been lobes worn down, shaft worn or bent or advance system faulty.

Glad to see you have it nailed down.

[Doc]

Glad to see you have it nailed down.

ME TOO!!!!!!!!

[dreamseeker]

glad you found the trouble and will be back in the water soon
wayne:fishing:

[mla2ofus]

You know,Doc,this has brought back a problem I had w/ a Dodge 318 in a p/u. It had points and if I set them @.017" like the book said it would do the same thing you described w/ your engine. If I just closed the points a few thousandths,.013" IIRC, it would never skip a beat. I always attributed that to wear in the shaft bushings. It's been 30 yrs so I guess that's why I didn't recall it when your problem started.
Mike

[Doc]

Thanks guys!

Had the test drive today. All is GREAT.

The mechanic put in the new distributor and made the port engine purr. GREAT! :applause:

Then he puts the old good distributor back in the starboard motor. Trouble. It would not run right. It appears both distributors where wore out. The old distributor did not want to work with the electronic ignition we had put in hoping to fix the original problem. So now we have two new distributors and both run perfect. Whew. What an ordeal.

Like you said Mike. We could tinker with the points and keep it going, sometimes. From last summer through this past summer that's how I kept it running until it died the begining of Sept. It was done until the distributor was upgraded.
On the way I got new plugs, electronic ignition, wires, cap, rotor, and had the compression checked, timing belt checked, valves checked ........ All is good but but it was a long way to get there. :D :beer:

[blondebullfrog]

Good to hear Greg! When's the get together again? BTW, I figured out Blondie and I can get on here from work!

[OhioTC18]

Good to hear Greg! When's the get together again? BTW, I figured out Blondie and I can get on here from work!

Actually WE have not heard or seen it run yet :rofl: Just Doc.
We all met up last night and will get together today at noon to make a trip up the river.

[OhioTC18]

Those twin Crusader 350's purred along all day long.:wave:

[Doc]

That's awesome Jeremy. We expect to see you guys on FF again then. :thumb: :D
Thanks for the check in call last night. :D

Yep Jerry they sure did purr. Feels so good to be back in the saddle again. :D

[blondebullfrog]

Good to hear! It sounds like everyone had a great time. I wish blondie and I could've come!

[Doc]

We missed you guys. You would have had a great time I'm sure. :thumb:

Yesterday we cruised to Marietta even. Not a problem at all. The engines are running purrrrr fect. :D