Cold start

C

cmariner32

Member
exMember
Joined
Jan 20, 2002
RO Number
7269
Messages
802
'89 Crusader 454's with Rochester 4bbl carbs. Last year I replaced the carb, fuel pump, all the lines, and fuel tank pickup tube to solve a primarily cold start issue that expanded to out of gas issue while running. This season and primariliy within the last 6-7 weeks, I would have to shoot some ether down the carb in order to get it started. There would be no fuel injected from the accelerator pump when I would pump the carb linkage otherwise. As soon as it started with the ether, it would continue to run and restarts the rest of the day would be fine. The old carb had no choke mechanism when I bought the boat and the screw into the manifold to mount the old bimetal choke coil had been broken off in the manifold. When I installed the new carb, it too didn't have the choke mechanism and I figured that just pumping the throttle would make up for the issue of no choke and it worked fine after the installation of the carb. That has worked fine until this summer when the old issue resurfaced. . Yesterday, I tried something different. Instead of shooting ether into the carb, I closed the choke plate and within seconds of cranking, it started! I'm thinking that a vacuum needs to be created by the closed choke plate in order for gas to be drawn out of the fuel bowls and into the venturi. Why the accelerator pump resevoir isn't filled with fuel during cranking and injected into the venturi is a question that I still have. Can anyone clue me in to what may be going on? Is installing the choke mechanism the only way to solve this issue? Opinions, advice and thoughts appreciated.
 
What time period between shut down for the day and next startup.

Possible causes...Is fuel evaporating from the float bowl or is fuel leaking from the well tubes.

Q-jet doesn't need choke. I removed even the choke pivot rod. just needs a few pumps to richen the mixture.

If it takes a while to fill the float bowl on cold start, it's a good thing by allowing pre-oiling the top end before firing up.
 
quote:
Originally posted by jtybt15

What time period between shut down for the day and next startup.

Possible causes...Is fuel evaporating from the float bowl or is fuel leaking from the well tubes.

Q-jet doesn't need choke. I removed even the choke pivot rod. just needs a few pumps to richen the mixture.

If it takes a while to fill the float bowl on cold start, it's a good thing by allowing pre-oiling the top end before firing up.

Click to expand...


+1
 
look down the carb after shut off and see if fuel is leaking inside. steam rising from a hot carb is a sign of leakdown.
 
The OP said that pumping the throttle didn't help, but choking did. Seems to me that his original diagnosis is correct and that the problem is with the accelerator pump. Possibly a clogged passage or bad seal? Short of a carb overhaul I don't know what to do about it though.

If re-installing the choke mechanism works, why not?
 
When your accelerator pump is working and injecting fuel before start, it was enriching your mixture as a substitute for the chock. On warm days that should be ok. To test your accelerator pump: After an overnight setting, and before turn on, remove the air filter and look into the throat. Activate the throttle. You should see 2 squirts of fuel injected. If not, turn on ignition, wait seconds for the fuel pump to fill bowl/AP, and test throttle again. If still no fuel squirts, the accelerator pump is not injecting and the chokc is missed. I would also look for vacumn leaks.
 
the accelerator pump cant pump what is not there.
 
The accelerator pump may work since you say engine operation is normal after eventual starting, but as Charlie suggests the Q-jet welch plugs may be leaking to drain the bowl so the pump has nothing to pump. The fix for that is open the carb , and epoxy back in the welch plugs. ( Google " epoxying q-jet welch plugs " .) However , I would have suspected that would have resulted in a rich/flooded condition better started with open choke and open throttle.

I would also drill out the soft plain steel broken screw in the intake manifold and replace the thermostatic coil choke mechanism since you report manual choking was effective. I used to replace that coil choke device at east every 2 yrs on my old carbed Crusaders and had to drill out the screw a couple times, easy. If necessary, just tap and use a bigger SS screw.
http://www.boatered.com/forum/topic.asp?TOPIC_ID=150932

You ...may.... also have a bad anti-siphon valve on your tank allowing drain back.
 
You must log in or register to reply here.
Back
Top