Guys, I am really stuck and I hope someone here could help me identify what is causing this problem:

I have just replaced my water pump and related gasket. I initially had an issue where the first new gasket failed and the coolant drained down in to the sump. I sucked all of the oil and water out of the sump, replaced the engine oil, replaced the water and coolant: all good so far.

The 351c fired up immediately. Once the choke closed and the engine idled in park, it began to splutter somewhat. When revving the spluttering decreased quite a bit but not entirely. The exhaust smells different too, almost too rich. Perhaps unburnt fuel?

Does this sound like an ignition problem? I am at a total loss. Thanks in advance for any help or suggestions.

 

The choke should have opened a bit once the engine starter, not closed, as you stated. The sputtering and rich smell could be because the choke is closed.
Try manually opening the choke plate and see if the problems don't go away.

Sounds like there is an issue with your choke and/or the choke pull off.

Roger Carter

 

Hi Roger, thanks for the suggestion. As its an automatic choke, could that explain why the problem is intermittent (ie, the choke opening and closing)?

 

A choke that is not working properly, whether automatic or manual, could cause the problems you describe.

First, let me say this: There are numerous people on this site that will tell you to "remove the automatic choke and install a manual choke and all your problems will be over". I am not one of those. A properly assembled auto choke will work just fine and give years of trouble free service.
If you choose to replace your auto choke with a manual unit, that's fine. Go for it. If you want to address the problem and confirm your auto choke operation, follow along.

Now you have to answer the questions, "Is your auto choke working properly?" and" Is it really the cause of the problem?"

With the engine cold, that is not run for 8-12 hours, pop the hood and remove the air cleaner. If the choke is properly adjusted and working properly, the choke plate should be about 1/2 way closed.
Now, open the throttle all the way and let it close. Do this once, only. The choke plate should snap fully closed. Opening the throttle allows the spring mechanism on the choke assembly to close the choke plate and set the fast idle.
Once you confirm the choke is properly setting you can start the truck, leaving the air cleaner off. It is best to have someone help, so you can stay under the hood, watching the choke operation.
As soon as the truck starts, the choke plate should open part way, and the truck should be running at fast idle. If the truck won't run without "revving" it, a problem is indicated, though not necessarily a choke problem. If the truck continues to run, the choke plate should slowly open to it's full, wide open posistion. This could take 5-10 minutes. The enging should still be at fast idle. Once the choke plate is fully open, "blip" the throttle once and the truck should drop to it's normal idle.

Do this test and post the results. Remember, the engine needs to be cold to perform this test and get meaningful results. That means one, maybe two shots at it a day.

Good luck.

Roger Carter

 

Hi Roger, thanks for the detailed instructions. Its much appreciated. Will give it a crack today.

 

One other item regarding the choke plate. When all is working correctly, spring pressure holds the choke plate in place, whether cold, warm or somewhere in between.
When cold and the choke is set, the choke plate should be closed, and should snap shut if opened. Likewise, when warm and the choke plate is open, it should snap open if you try to close it.
At no time should the choke plate flop loosly.

RC

 

Hi Roger, I followed your instructions precisely. The choke did not snap shut after opening the throttle.

 

What Carb do you have on it? Sounds like a linkage issue of some sort.

 

x2

Are pictures available?

One quick check would be to see if the choke cap in indexed properly. For now, set the index mark on the choke cap to the center, or largest mark, on the choke housing. Do this by loosening the three small screws that hold the choke bail and cap in place. Do not remove the srcews, just loosen a couple turns, enough to allow the choke cap to rotate.
If all is well with the choke assembly and linkage, the choke plate should be in the fully closed position and held there by spring pressure when the imdex marks are lined up. If not, we will go to the next step.
Also, by rotating the choke cap you should be able to see the choke plate open and close.
Remember, with any of these choke "tests" to do them on a cold engine and be sure to release any tension on the choke mechanism by opening the throttle a bit then letting the throttle close.

Question. When you did the previous test did the engine act the same as you originally posted?

RC