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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15674
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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My engine qa125a froze the exhaust manifold and now it spits

Customer Question

my engine qa125a froze the exhaust manifold and now it spits gas out of the carburetor while its running. it has no water in the oil. it has good compression.starts good idles good. but when you punch it it bogs out and spits gas out of the carburator
Submitted: 10 months ago.
Category: Boat
Expert:  Jason replied 10 months ago.

Hi Steve, my name is Jason.

What does the engine have for compression numbers?

Customer: replied 10 months ago.
180
Customer: replied 10 months ago.
all are between 173 and 180
Customer: replied 10 months ago.
I put in new plugs and there all burning rich there black
Expert:  Jason replied 10 months ago.

Got it. No you said you set the points. Did you do that with a dwell meter or a feeler gauge?

Customer: replied 10 months ago.
there electronic points
Expert:  Jason replied 10 months ago.

Pertronix?

Customer: replied 10 months ago.
I dont remember them being called that not sure what brand
Expert:  Jason replied 10 months ago.

Okay no problem. Did you double and triple check the firing order to make sure that is correct?

Customer: replied 10 months ago.
timed it perfectly 10 degrees above top dead center
Expert:  Jason replied 10 months ago.

Okay, compression and timing sound good. How old is the fuel itself, and have you tried running it on a portable fuel tank yet?

Customer: replied 10 months ago.
new fuel changed that too
Customer: replied 10 months ago.
changed the tank new fuel tank I've been busy
Expert:  Jason replied 10 months ago.

The next step is to remove the steel fuel line between the fuel pump and carb and replace it with some rubber line, a T fitting, and a fuel pressure gauge so you can see what fuel pressure is when under a load. Have you done that yet?

Customer: replied 10 months ago.
when i checked the compression I hooked up the gage and turned it over till i got the highest reading and waited for it to go down and it never did maby I missed somthing there
Customer: replied 10 months ago.
could it have to much presser int the fuel line
Customer: replied 10 months ago.
I havent done that but i checked the fuel pump
Customer: replied 10 months ago.
the longer it runs the slower it goes till it stops
Customer: replied 10 months ago.
its still getting gas
Expert:  Jason replied 10 months ago.

No, if anything it would be to little fuel pressure.

When troubleshooting gasoline powered carbureted engines there is a process that must be followed. And that process must be done in a certain order or else mistakes can be made. Each test is a simple pass or fail, either the test passes or it fails. The process goes like this.

1. Check compression

2. Check ignition timing

3. Check firing order (this is usually correct unless somebody was playing with the plug wires)

4. Check the fuel quality/run the engine off of a different fuel supply.

5. Check fuel pressure, it must be 3 to 7 psi at all times

6. check for vacuum leaks in the intake manifold

7. Rebuild or replace the carb.

So far we are at step #5. Fuel pressure can be low for other reasons besides a bad fuel pump. But either way, the engine will either have good fuel pressure, and you move on to #6, or it won't, and you have to figure out why.

If fuel pressure does end up being good then you move on to checking the intake for vacuum leaks. The easiest way to do this is to get some 6 in 1 foaming spray oil, you can get this from an Evinrude dealer or a Motorcycle dealer. This type of oil is like a WD40 but it foams up like shaving cream when you spray it. What you do is run the engine and spray the base of the carb as well as the intake to cylinder head gaskets and see if the oil gets sucked in or not. If it does, there is a leak.

If no leaks are found, and if all tests have been a pass to this point, then the problem is in the carb. It is either still dirty, or it's bad. Carburetors are a wear and tear item and they do wear out and go bad over time. The biggest issue with the carb is finding somebody qualified to rebuild it. Solex downdraft carbs are not a common carburetor, and only mechanics who have been around more than 20-25 years understand how they work. If the carb has been rebuilt by somebody qualified to do the work, and if it's still spitting gas out of the carb, then the carb would be replaced. What happens with carbs over time is they will start to leak internally. Fuel will start to leech through the metal over time and get into air passageways. This causes the carb not to be able to flow fuel correctly through it. Does that all make sense.

Expert:  Jason replied 10 months ago.

I don't know how you want to leave this but that is where you stand on your end and what needs to be checked. I think that should do it but I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.

Thank you
Jason

Customer: replied 10 months ago.
what could freezing the exhaust manifold destroy that would cause this just to ease my mind because thats when this all started and i watch the carb shoot gas in there while the engine slows down could it rack the intake
Expert:  Jason replied 10 months ago.

The freezing in the intake would not cause the issue you are having. The most common cause of the issue you are having is going to be a dirty or defective carb, however, before jumping to that all of the previous items on the list need to be checked first. The Solex carbs' are fairly reliable but they are picky about being clean, they have to be absolutely flawlessly clean, every jet, every port, every passageway. When I do Solex carbs in my shop I don't do them by hand, they go into an ultrasonic machine to be cleaned that way.

Customer: replied 10 months ago.
i have rebuilt the carb 2 times
Customer: replied 10 months ago.
its clean new jets I just dont know ill check the gas pressure but if the intake blows back maby ite a stuck rod or somthing
Expert:  Jason replied 10 months ago.

Are you qualified to rebuild Solex carbs? Have you been through carb school?

Customer: replied 10 months ago.
the school of hard knocks i climbed through every hole twice every port every jet
Expert:  Jason replied 10 months ago.

I've covered everything that can cause the engines symptoms, there isn't any other step or anything else to cover. Did you have any further questions for me on the issue?

Customer: replied 10 months ago.
what would cause air to blow back through the carburetor
Customer: replied 10 months ago.
or could cause it
Expert:  Jason replied 10 months ago.

I've spent the last hour going over every single thing that would cause air to blow back out through the carb. Were you not reading everything I have been writing?

Customer: replied 10 months ago.
no I missed that part
Expert:  Jason replied 10 months ago.

Please scroll up and re-read everything I have written, especially the reply time stamped 11:00 AM EST.

Expert:  Jason replied 10 months ago.

Did you get a chance to re-read it?

Expert:  Jason replied 10 months ago.

It looks like you read my answer without replying back or putting through a rating for me. Please keep in mind the website did charge you to speak with me, but they will hold your money and not credit me for helping you out if no rating is put through. If you have a problem with the ratings box or can not see it please let me know.

Thanks

Jason