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Zeniths won’t accelerate

s2willdo

Donation Time
Scratching my head on this. Car ran fine. I replaced the transmission so ended up removing the exhaust and intake. Didn’t remove carbs from intake. When I put it all back together the car starts and runs when accelerator is pushed to the floor but the rpms don’t increase.

I made sure I’m timed correctly, new gas, new fuel filter. Tomorrow I’ll follow all the instructions to sync the carbs but I wonder if someone has an idea off the top of your head.
 

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Gary T

Gold Level Sponsor
I have seen before that the accelerator pump in both carbs can sometimes stick and not return after depressing the throttle. They are made of brass and are similar to a piston. They have a close fit in the bore and inspection could reveal whether or not they are sticking.
 

alpine_64

Donation Time
I'm wondering if you have a big vac leak at the intake manifold... The gasket may not have seated or sealed.. The car would start and idle but make a deep gruff sound that slows down when you accelerate... Try spraying starting fluid around the manifold to head joint and see if idle speed increases
 

beamdream

Gold Level Sponsor
Scratching my head on this. Car ran fine. I replaced the transmission so ended up removing the exhaust and intake. Didn’t remove carbs from intake. When I put it all back together the car starts and runs when accelerator is pushed to the floor but the rpms don’t increase.

I made sure I’m timed correctly, new gas, new fuel filter. Tomorrow I’ll follow all the instructions to sync the carbs but I wonder if someone has an idea off the top of your head.

Do the throttle plates open when you push the pedal down?
 

bernd_st

Bronze Level Sponsor
Valid point. Check the throttle rods for proper connection. Sometimes the clamping part on the throttle pedal inside the car under dash comes loose resulting in insufficient opening of the butterflies. Asking myself why you need the T- piece in vacuum line. Normally only straight connection to the dizzy is there...
 

absunbeam

Platinum Level Sponsor
Agree with beamdream. Maybe running on one carb, had a pin fall out on the connecting rod and would not get any RPMs over 2K.
 

s2willdo

Donation Time
Thanks for your help. Still not running.

1) Engine starts but doesn't idle when when I release the gas pedal. I have to keep the pedal on the floor to have it idle. But it only runs for 15 seconds at about 1,000 RPM
2 Throttle plates open all the way when the pedal is depressed in the car
3) Instead of spraying starting fluid, I blew cigar smoke through the vacuum tube to check for leaks. Smoke only came out of the throats of the carbs. I think the smoke would come out of the intake gasket that way. Am I wrong?
4) I loosened #3. Then backed both of the #2's out until they were not touching. Seated both #1's.
5) Then backed the #1's off 3/4 turn counter clockwise. Ran the #2's in 1 1/2 turns after they started touching. Then tightened #3.

Overall I'm getting the same result, starts, runs 15 seconds with the pedal on the floor then stops. There is no crazy sputtering like it's out of time, just a sort of rough running. These are WIP-2 carbs.

Thoughts?
 

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beamdream

Gold Level Sponsor
Can you see fuel spraying into the carb throat(s) when you open the throttles ?

Not sure that your smoke test would achieve much as you wouldnt have enough pressure or volume below the throttles to see a leak out the
manifold joint.
 

alpine_64

Donation Time
To test a vac leak breathing smoke into the carbs will not tell you anything. You to spray fluid on the joint at the manifold and head .. If there is a gap it will be drawn in and idle speed will increase.

The manifold beimg separated will cause it to draw more air and overly lean the motor.

However if the motor is not even able to idle it sounds like something else.
 
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oLD lIMEY

Donation Time
Could you by chance restricted the exhaust some how? Seen it before colapsed inner exhaust, wont rev up no power. This was not on a Alpine.
 

jfcroni

Donation Time
If plug wires were disturbed....maybe back on wrong.

++ On the exhaust clog... It happened to me once.
 

s2willdo

Donation Time
I’m at a point where this should be an intake manifold leak as you described.

1) Exhaust pipe - I feel good pressure coming out of the tail pipe
2) I checked timing and point gap again.
3) I sprayed starter fluid on the manifold but it didn’t help. But I still think there’s a leak
4) car still only runs while gas pedal is on the floor
5) Vacuum gauge stays on zero. When the engine dies gauge goes up to about 5 before it stops.

Since I replaced the head pipes with stainless steel headers from Rick I’m thinking that’s the problem. I only used the one gasket he gave me. I had taken off two gaskets. Maybe I’ll try using those. Has anyone got opinions on using a gasket sealer here.
 

65beam

Donation Time
I installed a Falcon stainless exhaust on the Harrington. I had similar problems. I found that the triangle flanges on the section for #1 and #4 were holding the intake out from the head. Using a feeler gauge I found that I could stack several blades and slide them between the head and the intake. When I compared it to an original exhaust piece I could see the difference in the thickness of the flanges. A little machining was needed to eliminate the leak. some bending of other pieces was needed before everything fit. Runs good now.
 

Alpine 1789

SAOCA President
Diamond Level Sponsor
I fought vacuum leaks almost every time I had to remove the intake manifold, until I started smearing Hylomar on the gaskets. I know some recommences against this, but it has worked for me.
 

s2willdo

Donation Time
Thanks for all the advice. I removed the intake and put a sealer on the gasket. Still doesn’t run. I’m going to take a break on this for a couple weeks. Feeling a bit defeated.
 

hartmandm

Moderator
Diamond Level Sponsor
Stock fuel pump? Fuel level in glass bowl look good? Have you manually primed the pump?
Tried leaving the gas cap off as a test?

Mike
 

Bill Blue

Platinum Level Sponsor
You've checked the timing, was it ever far off? I'm wondering about the possibility of timing chain jump.

Bill
 

Thor 1211

Silver Level Sponsor
Stock fuel pump? Fuel level in glass bowl look good? Have you manually primed the pump?
Tried leaving the gas cap off as a test?

Mike
I'm with Mike, sounds like a fuel pump/delivery problem. It will run for 15 seconds on the main jet until it empties the float bowls. I bet if you could check the fuel level in the float bowls after it conks out, there wouldn't be any gas in them. I'd crank the engine to check the delivery at the fuel pump and see what the output is. If you took the manifold and carbs off as a unit you may have created a problem when you reconnected the fuel line. I haven't worked on Zeniths for a long time but I have kinked and pinched many a copper fuel line sometimes under the connector where you can't see it.
 
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