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'84 V6 Cologne Engine


wadehilts

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Hello all,

I recently rebuilt my dad's 1984 V6 2.8L Cologne Engine. It is the carbureted variant. The original engine got to 210,000 miles before we decided it was time to rebuild when it was leaking oil like crazy.
In the process of rebuilding the engine, I replaced the carburetor with a re-manufactured one (but the original starter motor is still going strong! Amazing).

I am having some problems with the drive-ability of the car, and I suspect it is a fueling condition. My prime suspect is the accelerator pump. Here are the symptoms:

When the truck is at a stand still, if I tip in the accelerator lightly (like you would when slowly pulling out of an intersection) the engine starts to die - seemingly like it is going lean. After this brief lug, the engine jumps back to life and runs fine. This is extremely aggravating and dangerous as there is a big risk of stalling if the driver isn't careful.

A similar scenario will occur when I am on overrun (throttle closed) and lightly apply the throttle.

My initial theory was that the accelerator pump was failing to richen the fuel mixture, as this seems to be a textbook example. However, I wasn't able to determine exactly how to adjust the accelerator pump. The lever that actuates the pump has 3 different positions that it can be set to. I adjusted it to the position that depresses the pump diaphragm the most at it's idle position, thinking that might squirt more gas. No dice.
It's my understanding that these later model carburetors had fairly sophisticated designs to meet emissions, so I was wondering if anyone has any experience with this problem and can point me in the right direction for adjusting anything to fix it?

Thanks,
Wade
 


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BLOODBANE

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did it ever back fire through the carb (new one)? If it did it could possibly be the power valve on the carb (they are famous for this, at least mine was( They can cause the problems you are describing. Its a crappy system trying to mix carbs with computer. If its working its great, but when something goes wrong it flat out sucks. When I did my V-8 swap I pulled all the computer.

This is in no way the absolute answer and someone else with probably chime in with some other things to check.
 

wadehilts

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I haven't had any backfiring issues, but I'll do some reading on that power valve. Thanks for the pointer. You're right, the computer-carb mix can be quite confusing and convoluted!
Wade
 

AndyB.

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Do you still have the original carburetor, or did you turn it in as a core? Did you set the float level, idle speeds (all three), and adjust the idle mixture? Is the computer giving you any error codes?

At first read, it could be a low float.

The accelerator pump rod adjustment has three holes, numbered 4, 3, and 2. The correct position for your carb is #4, which is the hole highest on the lever.
 

wadehilts

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I do not have the original carburetor, it was returned as a core. I have not adjusted the carburetor, although I had a shop do some repairs and adjustments to the car after I botched the valve clearance setting on the rebuild. It passed DEQ after the shop fixed the bent pushrod (whoops!) and adjusted the carburetor. They at least adjusted the idle speed and mixture to a level sufficient to pass emissions.

That being said, I don't want to blindly trust some mechanic I don't know. I believe I have the Chilton manual somewhere, does that go over the carburetor adjustment?
From what you described of how to adjust the accelerator pump, I think I did it backwards (the lowest hole on the lever). It was originally in the middle hole. I'll try changing that this evening and see if it makes a lick of difference. How is the float adjusted?

I'll look into reading some error codes from the computer.
Doing some more reading on this forum, I'm tempted to do the CFI conversion from a 3.8L... Although I am a little confused about how the ECU from a 3.8L engine is supposed to deliver a proper amount of fuel to a 2.8L engine. I would think that the injector size would at least need to be decreased, right? Or does the ECU have a strong reliance on O2 sensor feedback? I can't imagine how else it would know to deliver only 70% of the fuel a 3.8 would need!
Ok, ok I'm getting ahead of myself here. I'll focus on getting the carburetor working first. Any additional tips/literature would be appreciated!
Thanks!
Wade
 

wadehilts

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Update: (fixed!)
Thankfully, it was just the accelerator pump position that was the problem! Moving the arm to the highest position on the lever solved the issue. The truck drives much smoother now, and is back to it's old self... well I guess better than its old self because for its first 210,000 miles it burned a pint of oil every tank of gas. The intake runners leaked oil right out of the factory. I made sure not to make the same mistake when I rebuilt it.
 


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