What Am I Missing? Zenith 1, Chuck 0

[ctaylor738]

Crew -

Got the 280S outside and running with my patented gravity feed direct to the carbs. Fuel pump dead. Blocked fuel return line since I thought floats should be able to deal with gravity feed.

Car will not run below 2000 RPM and runs very rough, with occasional backfiring through rear carb. Compression 150-160 on all cylinders. Changing balance of carbs had no real effect on running. Timing OK.

What am I missing?

Chuck

[DANTRCAV]

Oh Boy..

Symptoms of a world-class vacuum leak somewhere maybe? Good gaskets between the insulator plates, carb and heat shield?

Does your setup have the idle cutoff solenoids on each carb? If so, make sure they both work.

My 250C had your symptoms. One was a vacuum leak the other when the #4 fuse blew and killed the idle cutoff solenoids.

Dan

[ctaylor738]

This is a '69, no idle solenoids to worry about.

I have pluuged the brake booster hose.

The donor told me he rebuilt the carbs. I looked at the carb base gaskets and they appear new, but you never know ...

Chuck

[bachlauter]

What's the brake booster hose???

~Christy

[Mark V]

Its the large rigid hose that runs from the intake to the large round donut behind the master cylinder (brake booster). The brake booster is a vaccuum cylinder or diaphram that gives you a little extra power to push the brake fluid through the lines when stepping on the brakes. The reason he plugged it was to make sure a leaky booster isn't causing a vaccuum leak.

Mark

[cth350]

Christy,

It's the plastic hose that should be running from the back of the intake manifold, OVER the valve cover and going to the brake booster.

Silly question, but when you took off the valve cover on Sunday, was this hose there? It would have been in the way.

Not having it attached to the manifold, leaving the manifold open to the air would have an affect on the quality of running (but not the affect you are struggling with now).

-CTH

[ctaylor738]

Looked all around for a loose bolt or sign of manifold problem - no dice - it all looks good.

Pulled the top and fuel block off the rear and discovered that there was only a little bit of fuel in the bowl - the jets were dry. Float clearance good, valve not stuck.

Leads me to believe that fuel starvation is the culprit, and that gravity feed is not going to work, especially in the driveway which has a modest slope, lowering the front carb. The fuel return valve was also leaking, which was not helping the situation.

Looks like a peek at the fuel pump is in order.

Chuck

[cth350]

Now that it runs, the gravity feed isn't that much of a necessity, other than that your fuel pump is shot. Since you plan on doing an engine swap, you'll need to replace it anyway.

do you have the cap on the lawn mower tank? Perhaps it's not feeding gas well enough. Also, try a plumbing change...

Put a Tee in the line from your gravity tank and have it feed both carbs from the middle of the two carbs. Have the connection for the gas input tie back to the return valve, effectively eliminating it.

-CTH

[ctaylor738]

Right on! I am proceeding with version 2 of the gravity feed system. I am pretty sure the cap vent is OK, since the lawnmower always worked.

I am going to see if I can get pump to work if only because it is the old style with the screws, which looks much better than the new type with its pressed metal cover. I am somewhat dismayed that I passed up a NOS old-style pump on e-Bay for 10 bucks.

Chuck

[DANTRCAV]

Chuck:

I have a used fuel pump from another 71 250C that I picked up when the owner wrecked the car. It was worknig then (two years ago). You can have it for the shipping cost if you like. Let me know or e-mail me.

Dan

[cth350]

There are two different kinds of pumps for the old straight 6's. Look carefully at how they mount to the block. I doubt the M130 & M114 use the same style. One pump has a finger that is inserted into the block. The other relies on a finger sticking out of the block

-CTH

[ctaylor738]

But if Dan's pump came out of a 250C, it should fit a M130. Only one way to find out.

Cheers

Chuck

[bachlauter]

My '69 250 M114 has the mechanical lever type of fuel pump.



~Christy

[Mark DiSilvestro]

To whom it may help,
My 1972 250 has a 1970 M130 engine
and the old style 'screwed together' fuel pump bolted to the engine block with a right angle mounting adapter. The original 1972 engine and the one in my 1972 250C (Both M130) had a 'crimped together' pump bolted directly to the block with a thick bakelite spacer and no right angle mounting adapter. Hope this doesn't add to the confusion.
Mark