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30 backfiring at my last straw

jrod1540

Contributing Member
alright i have done it all and

alright i have done it all and after my boat sitting for three weeks i go to take it out and its backfiring im thinking last i took it out there was a bad storm that hit me got a lot of water it boat.

So draine 50 bucks worth of gas
change fuel filters
check timing
check plugs for spark
replaced exhaust manifold due to i found a crack in mine (which i thought would fix this problem when it occurred the other day before i found crack)

prior to manifold replacement rebuilt the carb (2bbl Rochester)

SOOO i get this horrible popping backfiring noise through the carb like its not burning all the fuel
boat goes about 10mph

then yesterday i take it out still doing fiddled with the timing while on the water kinda helped but not really.
then took it out and it got to like 25 and it would kick in and out of popping noise backfiring as i was going O this was at 3/4 throttle if i flowered it it got worse... HELP ANYONE AND EVERYONE IM GETTING SO SICK OF THIS MOTOR .


i took so video on the water to but not sure how to up load if some one knows help me out it will give you a better understanding i hope
 
"change dis, cap with all that

"change dis, cap with all that water if it had a small crack that will make it miss fire"
 
I would also throw in some gas

I would also throw in some gas line antifreeze or dry gas or whatever you call it in your area because it still sounds like water in the gas.
 
yea i put some of that stp gas

yea i put some of that stp gas treatment in with the new gas i think that might have been what maybe helped it.. the cap and plugs look pretty new. how do i check for a crack and if so can you pick them up at local hardware stores.


ALSO NOTE

with the backfiring noise it sounds good after 1500 rpm or so if i have it on the muffs with the linkage popped off.but under load it is very noticable....
 
i was reading another thread o

i was reading another thread on the 4.3 backfiring and not idling right... saw talk about siphon hose and its components how do i check this guy out
 
"antsiphon valve is on the gas

"antsiphon valve is on the gas line going to the fuel filter then to the carb. Take it out and blow through it if you can only blow through it one way it is good.

How to check cap is take it off and look real good at it look for very fine lines ( carbon tracks ) or run the engine in the dark and look very close at it it looking for sparks or small lighting like sparks jumping from post to post.

Or across the side of the cap.
Hope this helps.

Frank
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ok found a chip on the bottom

ok found a chip on the bottom of the distributor cap which was causing it to wear out the taps thus thinking it was mis firing and causeing a fuel overload giving the backfiring


Question boat shops are closed today really want to try the boat anyone know if there is an auto parts cap that will fit???

tried to get one but it was a no match

a part # or manufacturer would be great i saw on the parts that DELCO makes one but cant find a part number
 
alright so i put the new cap o

alright so i put the new cap on today and still the same old backfiring spraying gas out of the top of the carburator ....

I lost i dont know what else to check i did notice a little bit of smoke come from the manifold vent or i think its called the pcv or something could this be related.....also should i check the coil it starts right up fine but its like its just not burning all the fuel up and is really bad under load???


anyone got any ideas beside taking to someone to work on...
 
also if someone has a manual i

also if someone has a manual i would really really like it if you could paste the trouble shooting if there is one for this backfiring problem...
 
"What kind of engine is this.

"What kind of engine is this. ( I can see a sick one
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I would do a comp,check. It sounds like could have a bad intake valve. Not real sure how that would happen.

Frank
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"
 
"Normally a look at the spark

"Normally a look at the spark plugs would identify which cylinder.
If no difference, then it is a common problem, and I would guess timing totally out as first guess. Next might be a general lean-burning.
Could You post a pic of the spark plugs?"
 
i took all plugs out earlier a

i took all plugs out earlier and the one that looked a little bad i rearrange and no difference i put the pictures with labels up this afternoon
 
"I could be wrong but I don&#3

"I could be wrong but I don't think the plugs will show this. Because the plug where the bad valve is,is still fireing thats the popping sound you are hearing. And the gas is being pushed out the top of the carb with the comp because the valve is not stopping it. To safe a lot of time do a comp check. Take a close look where that bad plug was.

Frank
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yea i keep thinking its a valv

yea i keep thinking its a valve problem but im no longer at home im back at school an no longer have a compression tester with me is there a kinda not as accurate way to check
 
also i was wondering if i migh

also i was wondering if i might have a bad coil.. is it possible to have a coil that works good at idle but doesnt underload...or doesnt give enough power
 
"I don't know of a way to

"I don't know of a way to check compression with out at tester. And I don't think it is a coil. A coil would be a miss fire. The popping sound is the compressed gas burning and some going back up the intake and out the carb. Because the vale is not closed or part of it is gone.

If this was mine I would go get a comp tester. and check it They can't cost that much I don't think.

Frank
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ok pulled the plugs replaced t

ok pulled the plugs replaced them 1 and 4 look burnt out 2 and 3 look fouled so i thing i have problem in either 2 or 3??? started it up for a second and i could still hear the popping noise coming from the carb....

also i forgot to mention that in june i had the head checked for cracks and had valves reconditioned and one exhaust valve replaced and new valve seats in all of them thats why im hesitant to think it is a valve issue....


Also i noticed yesterday when i got gas that in the past if i pump gas in at full speed the breather spits gas out but yesterday when i pumped at full speed nothing.... could the breather be something to check and if so how do you test it
 
morton would you still like me

morton would you still like me to post the pictures of the spark plugs.... cause at this point ill try anything anyone tells me to... also frank i did a compression test right after i put the head back together by end of june... it was between 132 140 in the cylinders the specs say 130
 
"Recheck Your valve clearance.

"Recheck Your valve clearance. Did You do it Yourself, or the workshop?
As for spark plugs there are two 'types' to be used.
Champion RV8C -was the original one, but is mainly for 'hard' driving. It was later changed to RV15YC which improves idling. Which ones are You using?"
 
i had a friend of the family w

i had a friend of the family who has worked on boats a long time come over and do the valves adjusments in early june and if worked great up until i sat it up for a few weeks

the spark plugs im using are actually neither im using some Delco R45t which worked fine in the past

prior to a full understanding of the timing i was playing with it a little which i think could have some how possibly thrown it over over several attempts to try to fix it im going to buy a timing gun tomorrow and re set it and see if that corrects the problem and if not thats one more thing cancelled out...
 
"Using AC Delco's web page

"Using AC Delco's web page and cross reference, this is what I came up with:
Cross reference from Champion RV15YC4:
CR42TS SPARK PLUG, AR CR43TS SPARK PLUG, AR R42LTS SPARK PLUG, AR R42TS SPARK PLUG, 02 R42XLS SPARK PLUG, 04 R42XLS SPARK PLUG, 06 R42XLS SPARK PLUG, 08 R42XLS SPARK PLUG, 12 R42XLS SPARK PLUG, AR R42XLS SPARK PLUG, AR R43TS SPARK PLUG, AR R43TSK SPARK PLUG, 02 R43XLS SPARK PLUG, 04 R43XLS SPARK PLUG, 06 R43XLS SPARK PLUG, 08 R43XLS SPARK PLUG, AR R43XLS SPARK PLUG, AR R44T SPARK PLUG, AR R44TS SPARK PLUG, AR R45TS SPARK PLUG,

Cross reference from Champion RV8C;

R43T SPARK PLUG, AR R44T SPARK PLUG,

That indicates You might be using a too 'hot' plug.
As You indicate that this happened after the boat was sitting for some time, it might even indicate a stuck valve lifter. Back to: check valve adjustment/lifters."
 
just talked to the guy that or

just talked to the guy that orignally did valve adjustment and he gave me some advice on adjument aswell im going to try it first thing tomorrow evening ill post the results...


and im glad i actually went to get the new spark plugs today i almost a 100 percent sure i got the Ar44t this time ill check those as well i know i didnt get the same ones described earlier
 
"To get the adjustments right:

"To get the adjustments right:
Take out the spark-plugs and off valve cover. Turn the engine by hand slowly until You see one of the cylinders 'change from exhaust to intake. ( The exhaust rocker will come up and the intake rocker will start to go down. If on cyl 1 You will even have the ignition marking at TDC.
Your firing order is 1-3-4-2.
If/when #1 changes -adjust cyl 4.
Loosen the nut a couple of turns and be sure You have a decent play. Slowly tighten down while You are rolling the push-rod between two fingers.As soon as You feel the slightest resistance (no play)-stop. Then tighten another 3/4 to 1 turn. Be very careful to determine the 0-play, it is easy to tighten too much if You are not used to it.
Next cylinder (after #1 changing) will be #3 -You adjust #2.
Then #4 -adjust #1, finally #2 -adjust 3.
You do not have to start at Cyl 1, I did it just as an example. Just follow the sequence.
Turning the engine manually might not be that easy as there is no nut on the vibration damper. Sometimes You may use the nut on the alternator and hope the belt does not slip too much, sometimes it is needed to put some screws into the puller holes in the damper and use a bar."
 
alright let me get this strait

alright let me get this strait first i set my timing to 4 BTDC

now as for the valve adjustment... after i bring cylinder 1 to TDC to the according adjustments to both valves

then i rotate engine and next cylinder to reach TDC will be 3 right cause thats the firing order and then 4 and then finally 2 each time i roatate the engine after i have made the adjustment for the previous cylinder correct???
 
"It will be a 180 degree turn

"It will be a 180 degree turn of crank shaft between each adjustment, a total of 2 turns for all adjustments.
Note that there are 2 TDC situations for each cylinder:
1: Compression/firing (when You set Your timing)
2: Change from exhaust to intake. (where You adjust the valves)
Between these to there is one turn of the crank shaft, or 1/2 cam shaft turn.
If You compare the valves changing with the position of the rotor in the distributor, You will notice that when cyl 1 is in overlap (changing ), the rotor will point at cyl 4 in the distributor."
 
alrigth know its been a while.

alrigth know its been a while... so kicking myself for not doing the first thing i should off and many of you suggested.....CHECK THE COMPRESSION.. i had just redone that so i didnt think that was it..

found out after no compression in cylinder 2 and 3 that i had a blown headgasket missing a chuck of gasket inbetween 2 and 3 and a little warped head


getting head resurfaced and got the new gasket

however when i was inspecting the head exhaust valves 1 and 4 where almost white in color... previously i had change the plugs with some auto ones that seemed a little bit longer..

so do i just have to hot of a spark?

P.S. thanks for everyones input atleast now ive got everything else set right ha
 
maybeb i can help . the only t

maybeb i can help . the only time an engine will pop through the intake is if it is firing at the wrong time . make bouble shure youre wires are not bleeding inductivley.make shure they are seperated frome each other and if they have to cross each other make shure it is at a 90 degree angle . if it isnt the cap or wires then it has to be valve timing or a flat cam .it is important to make shure the valves are closing all the way but it is also important to make shure they are opening all the way. pull your dipstick make shure it doesnt smell like gas .i wish i could hear the popping noise there is a distinct diference between a back fire caused by ignition and one caused by a mech problem. if it doesnt miss at idle and misses like a machine gun udner a load it is a cam or cam timing problem .something else to consider is a collapsed lifter some engines with hydrolic lifers may not oil well and can cause the valves to float or not open far enough.have fun
 
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"<font color=""aa00aa""><font face=""verdana,arial,helvetica""><font size=""+2"">

Jerod Parr sounds like a hot name!
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