View Full Version : What might cause a dry Carb?
I'm having a problem with my Baja. It has a 454 (7.4L), normally runs perfect. It ran fine, then out of nowhere would not start. Checked and it is getting plenty of fire. Checked the carb and it's dry. Primed the carb with a little gas and she fired right up. Ran fine, I ran it for 1/2 hour, then it started up enough for us to get 100 yards from the dock then it died. Same problem. Primed the carb and it ran just fine.
I plan to change the water separator and the fuel filter, since those need replaced anyway and are the cheapest fix.
Have any of you heard of a fuel pump going out that would act that erratically? Any other ideas what might be wrong?
It has a Mechanical fuel pump. I talked with a part time marine mechanic he said he has never seen a fuel pump on a boat go bad. http://www.forumsforums.com/3_9/images/smilies/eek.gif Surprised me. But would a fuel pump that is going bad work once you prime the carb?
The boat is a 1989, so it's close to 20 yrs old. I have had it the past 10 years, and it has run perfect all that time, until now.
The 2nd time this happened we went about 15 miles. Stopped for dinner, so it sat an hour or so. Started it up to head back home, get about 100 yards from the dock just idling getting stuff arranged before taking her up, and plunk ...it just dies. I had not given it any gas, it was idling fine and sputtered and died. I was able to get it started for 2 seconds but then it would die again, even with me pumpiing the throttle.
The more I type about it the more I'm afraid it's the fuel pump that is a bear to get to (ofcourse). Baja did not consider the mechanic when it put this boat together (force 235).
Fred mentioned a birds nest or blocked vent on FF when I posted this question ...and I've checked all that. Vent is clear.
Verado275
02-05-2008, 05:50 PM
Who ever told u that fuel pumps don't go bad that is dead wrong. Allthough fuel pumps dont go bad as often they Do go bad. Best wy to check a fuel pump is the about ofg psi ts putting out or vaccum its using to suck the fuel from the fuel tank say there is a clog in a fuel pick up in the tank from debris that would cause a high vaccum at the fuel pump. And can cause the diaphragm to prematurely wear. What can happen is when u are boating the piece of debris can get sucked up into the pickup in the tank and get into the anti-siphon valve. Then when u shut the boat off the piece will fall back into the tank and when restarted it may take awhile for it to get sucked back up. Also Anti siphon valve can seize (never seen it but heard about it) causing a stall or no run state. Easy way to check is to install a remote fuel tank illiminating the boat fuel tank and take it for a ride if it don't stall your good to go.
OhioTC18
02-05-2008, 07:01 PM
I've had mechanical fuel pumps go bad on different cars (not a boat, I know, but the fuel pump issue could be the same). The diaphragm could have a rupture in it and cause symptoms such as this. Is there a way to put an inline electric pump in the system?
Who ever told u that fuel pumps don't go bad that is dead wrong. Allthough fuel pumps dont go bad as often they Do go bad. Best wy to check a fuel pump is the about ofg psi ts putting out or vaccum its using to suck the fuel from the fuel tank say there is a clog in a fuel pick up in the tank from debris that would cause a high vaccum at the fuel pump. And can cause the diaphragm to prematurely wear. What can happen is when u are boating the piece of debris can get sucked up into the pickup in the tank and get into the anti-siphon valve. Then when u shut the boat off the piece will fall back into the tank and when restarted it may take awhile for it to get sucked back up. Also Anti siphon valve can seize (never seen it but heard about it) causing a stall or no run state. Easy way to check is to install a remote fuel tank illiminating the boat fuel tank and take it for a ride if it don't stall your good to go.
It ran fine for a few days in between of the problem. You might be onto something with the tank and the anti siphon valve. That same part time mechanic said he could punch out the anti siphon ball ....didn't sound like a good option to me, but what do I know.
I've no clue where I'd get an auxilary tank that could run me long enough to be sure the problem was solved. I'm probably missing something. :confused:
Thanks for your reply Marc!!!!!!!!!!!!!!!!! :tiphat:
I've had mechanical fuel pumps go bad on different cars (not a boat, I know, but the fuel pump issue could be the same). The diaphragm could have a rupture in it and cause symptoms such as this. Is there a way to put an inline electric pump in the system?
I don't know about that Jerry. Maybe Marc will chime in on this. Thanks for the suggestion. :thumb:
waybomb
02-05-2008, 08:16 PM
Usually if the diaphragm breaks, you'll get gas in the engine oil. Is your engine oil above full? Smell it.
You don't need an electric pump. If you do decide to replace your fuel pump, make sure you install a marine fuel pump that has it's vent line running back up to the air cleaner. A vent line to the engine room, and a bit of spark, could cause some excitement.
Many marine mechanical pumps are rebuildable. You'll know it is so because there will be a circle of screws holding the bottom on. Kits are cheap.
But the frist thing I'd check is the little fuel filter at the inlet to te carb. Wen you do remove it, you should be able to freely blow through it. If there is resistance to your air, you can bet that's the problem. There is usually a spring behind the filter. And look which way the filter comes out, so you put the ew one back in the same way.
And use two wrenches - one to hold the filter nut and one for the fuel line itself. And when you put it back together, you should snug everything up by hand before you put a wrench to it.
Wannafish
02-18-2008, 09:34 AM
"Usually if the diaphragm breaks, you'll get gas in the engine oil. Is your engine oil above full? Smell it."
I have had this happen on two different boats - it can and does happen.
"And use two wrenches - one to hold the filter nut and one for the fuel line itself. And when you put it back together, you should snug everything up by hand before you put a wrench to it."
Gee Fred...you HAVE done it the other way once, haven't you? :respect:
waybomb
02-18-2008, 09:40 AM
"And use two wrenches - one to hold the filter nut and one for the fuel line itself. And when you put it back together, you should snug everything up by hand before you put a wrench to it."
Gee Fred...you HAVE done it the other way once, haven't you? :respect:
My first car was a 68 GTO I bought when I turned 16. I knew NOTHING about cars, but I was determined to learn. Twisting fuel lines and cross threading carburetor fuel filter housings are just two of many many tasks I gained "experience" on. You should have seen my first brake job.
It pains me to watch my kid, a 19 year old know-it-all, make similar mistakes. But I guess that's how you learn.
Wannafish
02-18-2008, 09:52 AM
You should have seen my first brake job.
That memory gave me a chuckle. My first car was a 1967 Volswagen bug. I had to bleed the brakes on the back - of course the bleeder screw broke off so to town I went and got a new brake (wheel) cylinder. Tried taking the line off - dang it - busted off at the fitting. Didn't have time nor money for a new brake line so I got this great idea - lets braze it shut!
:bash: Wish I would have had someone around that day to not listen too!
Long story short - ever seen a flame thrower??
Had my buddy step on the brakes to see if it was sealed...nope! Not quite! Shot a 30' stream of brake fluid that ignited when it hit the red hot end of the brake line. Um, needless to say, I won't be doing that again. (At least not in THAT garage!)
Hmmm. Maybe there's a reason my wife's favorite saying is:
"You're too smart for the dumb shit you do."
:rofl: Funny Rick. :D
When I winterized the boat I changed the oil so ....I'll have to run it some before i can check the level and gas smell.
Speaking of the spring and carb filter, where would I get a shop manual for 454 marine engines? I have two crusader 454's in the houseboat and one mercruser 454 in the baja. I'm thinking the shop manual would be similar for both setups.
waybomb
02-18-2008, 10:35 AM
Speaking of the spring and carb filter, where would I get a shop manual for 454 marine engines? I have two crusader 454's in the houseboat and one mercruser 454 in the baja. I'm thinking the shop manual would be similar for both setups.
My favorite store - E-Bay!
Wannafish
02-18-2008, 10:35 AM
:rofl: Funny Rick. :D
When I winterized the boat I changed the oil so ....I'll have to run it some before i can check the level and gas smell.
Speaking of the spring and carb filter, where would I get a shop manual for 454 marine engines? I have two crusader 454's in the houseboat and one mercruser 454 in the baja. I'm thinking the shop manual would be similar for both setups.
Actually, all you have to do is watch the oil level. 15 minutes of running will raise the level to the top of the dipstick (and you'll scratch your head and say "How the heck did that get in there?"). It doesn't give off a real strong smell of gas, but there is a slight smell. If the wind is blowing you probably won't be able to even smell any gas.
Any decent boat store - or even West Marine - should have the manuals in stock. Both boats engines should be nearly identical, with the possible exception of cam, carb., and heads.
Kewl. I just got the 2008 HUGE West Marine Catalog. Perfect timing. :D
Wannafish
02-18-2008, 10:57 AM
Back to the title of this thread.
Check your fuel line. It's possible it is slightly rotted and sucking air. When you "prime" the carb, the engine starts and runs faster pumping more fuel and overriding the small hole in the fuel line. Yes, it is possible for a line to suck air but not leak fuel. Look for weathered/soft spots.
Good thought Rick. We did check the line and didn't see any problem spots.
UPDATE: We had great weather here for the 2008 Memorial day weekend and I was able to run the Baja Friday, Saturday, Sunday and Monday. I had to prime the carb every day but Monday.
Got to talking to a local marine mechanic (retired) and after describing the problem to him and some of the possible solutions he eliminated the anti siphon valve saying that if that were the issue then when there was a call for lots of fuel it would fail causing hesitation and possible engine dying. I can run at half or full throttle without issue.
He said it sounded like a carb issue. This was Sunday. I just so happened to have brought some STP carb cleaner with me to add to the gas that same day. So I added the treatment and I still had the problem, but not as often. Monday all was well most of the day but just idling she started coughing and then died. I was able to start her back up and by pumping I was able to keep her running. This did not work (pumping vigorously) prior to adding the STP. I shut off and drifted a while and later it started up just fine. After taking off it started hesitating again but giving it more gas kept her running. Like I said earlier, until the STP was added I was not able to save the stall no matter how much I pumped the throttle.
....So, I'm thinking we are on to something. I plan to pick up some gum out and spray it into the carb later this week. But I'm looking for other ideas if you all have any of what else I might need to do to fix this issue.
TIA!!!!!
edit to add:
The majority of the time when it coughs and dies I am at idle or just starting to take off. Once up and running I've never experienced the coughing / dying out issue.
Bt Doctur
05-27-2008, 11:53 AM
accel pump not working, might be time for a rebuild
accel pump not working, might be time for a rebuild
I don't know what the accel pump is. Is it part of the carb? The boat & carb is 19 years old, and has 1300+ hours on it.
Bt Doctur
05-27-2008, 03:38 PM
a internal part, take the flame arrestor off, look at the carb and have someone pump the throttle a few times. you should see a healthy squirt of gas every time you move the handle
waybomb
05-27-2008, 05:34 PM
Does this engine have a Rochester carb? Some versions leak through a plug installed during manufacture. It's a common problem. Everything is fine until you let it sit for a while. All the gas leaks out of the bowl area.
But it does sound like the accelerator pump. Pull the carb and have a local shop rebuild it. While it is off, have them turn the carb over to look for signs of a leaking plug. They can fix that at the same time.
Not sure if it's a Rochester carb or not.
Was talking to someone else about this earlier this evening. The subject of a new or rebuilt carb came up. Would I be better off replacing the carb or rebuilding it?
What are the advantages either way.
Any idea on the cost of new or rebuilt carbs?
I don't know of a shop around that would rebuild it. What kind of shop would you look for?
Found carbs here:
http://bpi.ebasicpower.com/c/MER7A-IB/Carburetors+for+Mercruiser+Inboards
Carburetor, 4 Barrel, Mercruiser 454 V8 with Spring Choke (http://bpi.ebasicpower.com/pc/CPIMC31/MER7A-IB/Carburetor%2C+4+Barrel%2C+Mercruiser+454+V8+with+S pring+Choke)
Part Number: CPIMC31
Weight: 11
Price: $329.00
Quantity in Basket: none
Remanufactured Marine Carburetor for Mercruiser 330-340 HP GM 7.4L Big Block V8 with remote choke
Rochester 4 BBL 4MV Remote choke
MIE 330 Serial # : 4623115-5889913 MIE 340 7.4L Serial # 5889914-D715493 Mfg. # 1347-8288A1 OEM # : 17080560
waybomb
05-27-2008, 07:40 PM
I bet your local marina could rebuild it for 125 or less if you remove it. I usually do my own stuff, but a few years ago, my Carver was having carb issues. Not having the time to go out get the rebuild kits, get my bucket of hydroseal, rags, parts bucket, etc, I had my kid remove both engines' carbs and bring them over to the marina next door. 200 bucks later, my hands were still clean, my clothes were not stinky, and the carbs were back to like-new.
bdavis
05-27-2008, 11:26 PM
UPDATE: We had great weather here for the 2008 Memorial day weekend and I was able to run the Baja Friday, Saturday, Sunday and Monday. I had to prime the carb every day but Monday.
Got to talking to a local marine mechanic (retired) and after describing the problem to him and some of the possible solutions he eliminated the anti siphon valve saying that if that were the issue then when there was a call for lots of fuel it would fail causing hesitation and possible engine dying. I can run at half or full throttle without issue.
He said it sounded like a carb issue. This was Sunday. I just so happened to have brought some STP carb cleaner with me to add to the gas that same day. So I added the treatment and I still had the problem, but not as often. Monday all was well most of the day but just idling she started coughing and then died. I was able to start her back up and by pumping I was able to keep her running. This did not work (pumping vigorously) prior to adding the STP. I shut off and drifted a while and later it started up just fine. After taking off it started hesitating again but giving it more gas kept her running. Like I said earlier, until the STP was added I was not able to save the stall no matter how much I pumped the throttle.
....So, I'm thinking we are on to something. I plan to pick up some gum out and spray it into the carb later this week. But I'm looking for other ideas if you all have any of what else I might need to do to fix this issue.
TIA!!!!!
edit to add:
The majority of the time when it coughs and dies I am at idle or just starting to take off. Once up and running I've never experienced the coughing / dying out issue.
Sounds like you're going through the same problems as me. My 40hp yamaha ran excellent last year being only a month old. It was fogged before being stored for the winter. I put new plugs in it, a can of fuel cleaner to the gas etc. but she still won't idle for long and bogs down when accelerating. All I have to do right now to get it up to speed is quickly back off the throttle and nail it again and it'll get up and go. I could see a problem like this hapenning on an oldr motor but this thing is new. Getting furstrated.........any ideas???
Sounds a bit different than my issue Brian. Feel free to start a fresh thread to talk about the issue. It might be noticed more in a thread of it's own.
New rebuilt carb runs around 300. Taking the carb out and having the mechanic rebuild it costs 100 (parts and labor). So I'm off to remove the carb and deliver it to the boat repair shop.
Wish me luck.
OhioTC18
05-28-2008, 06:29 PM
Wish me luck.
Good Luck Doc. But yes, that probably will fix it.
Good Luck Doc. But yes, that probably will fix it.
The guy rebuilding the carb said the same thing Jerry. 90% chance this will fix the issue.
OhioTC18
05-29-2008, 06:05 PM
BTW, I never owned a Rochester carb that did NOT have an accelerator pump problem at some point.
Got the carb reinstalled today. All is good so far. I only tested the boat at the dock, but should be able to give it a real test tomorrow.
The weather forecast is good for tomorrow but ify for Saturday, so we're going to get in some boating tomorrow for sure. :thumb: :D
Crums
05-29-2008, 10:46 PM
Glad to here you got it back together and it. We're going to try to get down early enough to get in the water before dark, but you know how it goes. We'll give you a call on our way. Good luck with it, call us if you need a tow in and I'll take off from work early(haha).
The carb didn't fix the problem.
If I start up and rev at 1500 to 2k for a little bit, no problem. If I start up and go straight to idle and then take off sometimes it works, sometimes it falls on it's nose. If I pump vigorously I can prolong it but eventually it dies. A squirt of gas to the carb and I'm back in business.
What are your thoughts on what might cause this?
Bt Doctur
05-30-2008, 11:08 PM
Doc, try running on a outboard tank to eliminate a tank/fuel delivery issue.
Let us know the results.
Doc, try running on a outboard tank to eliminate a tank/fuel delivery issue.
Let us know the results.
I've considered that but am not comfortable with how I could accomplish that.
In talking about the issue I know how we can change out the anti siphon valve at the gas tank ... but local logic says that if it was the anti siphon ball it would likely interrupt the flow of gas when demand for gas increased. I can be cruising at 3000 rpm and go full throttle without incident. No hesitation or cough or anything. She runs as expected.
Would / could a fuel pump problem possibly be the issue?
One suggestion was to make up a line w/ gauge that would show fuel pressure reading. This is also over my head ...
I'm leaning towards fuel pump or maybe the anti siphon ball.
Care to take a guess which you think it might be?
waybomb
06-10-2008, 08:56 PM
They're both relatively cheap. Go for the easiest first.
Here's another thought. How hard is it to replace the fuel lines from the tank to the pump? Ive heard of the alcohol in gas these days damaging hoses. I've heard of at least one guy that leaned out his engine because of a collapsed hose, alegedly made spongy by the alcohol in the fuel.
I've heard of another possibility, and actually this happened to another owner of a Baja just like mine. Carb leak down.
I thought rebuilding the carb would have fixed the carb leak down issue but now I'm not so sure of that.
Have any of you heard of this problem? Does it sounds like a potential culprit for my issues?
waybomb
06-13-2008, 11:04 AM
I've heard of another possibility, and actually this happened to another owner of a Baja just like mine. Carb leak down.
I thought rebuilding the carb would have fixed the carb leak down issue but now I'm not so sure of that.
Have any of you heard of this problem? Does it sounds like a potential culprit for my issues?
See post 20. The rebuilder should have corrected the issue is your carb is of the type from that vintage.
You're right Fred. I just got off the phone with the shop where I had the carb rebuilt. He checked the fuel pressure and it was 2 to 3 pounds max. He replaced the fuel pump and now it's reading 7 to 8 pounds constant. :thumb:
I think we are back in business for our little go fast. I plan to give her a good test run this weekend. :thumb: Now if only the weather will cooperate for a change. :D
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