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Author Topic: 78 Holley 5200 running rich  (Read 4302 times)

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Offline 74WagonMeadowGreen

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78 Holley 5200 running rich
« on: December 31, 2011, 11:14:22 PM »
My 78 Pinto with 2.3 and 4 spd just failed emission testing (required in Colorado). I got readings of HC/ppm of 2000 at 2500 rpm (over 400 is a fail) and CO% of 11.41 (over 1.5 is a fail), not much better at idle... she is running very rich, probably not just a fiddling with the idle air screw if it fails at 2500 rpm, which is set pretty lean now. The car does foul plugs quickly, running on three until it warms up, especially when cold, but does not visibly smoke.  The car has 52,000 original miles. I fully rebuilt my original carb, which shows no real signs of previous tampering. Does anybody know the correct jet specs for the main versus secondary setup, as I cannot guarantee anybody before me may not have accidently swapped the jets. I know the primaries are smaller than the secondaries, according to the book. The choke does appear to be operating correctly, timing is spot-on according to specs. Half the emission parts and all vacuum hoses have been replaced, the egr valve cleaned and tested. The car really seems to run pretty well, once warmed up. Any input regarding possible causes is truly welcome. Thanks!
Don

Offline dave1987

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Re: 78 Holley 5200 running rich
« Reply #1 on: January 01, 2012, 02:09:33 PM »
My 78 was doing the same thing a couple years ago. I never did figure it out though. My dad hollowed out my cat back in the 80s and I think it was the root cause. I four a way to make it pass though. Shoot me a pm if you can't get. it figiured out.
1978 Ford Pinto Sedan - Family owned since new

Remembering Jeff Fitcher with every drive in my 78 Sedan.

I am a Pinto Surgeon. Fixing problems and giving Pintos a chance to live again is more than a hobby, it's a passion!

Offline bbobcat75

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Re: 78 Holley 5200 running rich
« Reply #2 on: January 01, 2012, 05:26:26 PM »
we had that testing in ohio when i lived there, had a  chevy 1500 that would not pass, but a bottle of rubbing alchol in the gas tank and pulled the pcv and laid it to the side and drove in and passed with flying colors, did better then my moms brand new pt crusier, those test are a waste of time!!!
1975 mercury bobcat 2.8 auto
1978 mercury bobcat wagon 2.3l - soon to have a 88 tc drive line
1975 ford pinto - drag car - 2.3l w/t5 trans - project car

Offline 74WagonMeadowGreen

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Re: 78 Holley 5200 running rich
« Reply #3 on: January 01, 2012, 06:09:57 PM »
Holley 5200 setup for my 1978 non-Calif model 2.3:
Does this look correct?
PRIMARY JETS:
Plug  170
tube  05
Main  167
SECONDARY JETS:
Plug  185
tube  04
Main  219
Should the primary have a "larger" tube than the secondary? So far, nothing indicates why I am running so horribly rich... all choke components sparkling clean and working properly, same with carb internals. ?????

Offline ToniJ1960

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Re: 78 Holley 5200 running rich
« Reply #4 on: January 01, 2012, 06:36:19 PM »
 If you turn the mixture screw in does it to start to die? If you cant get the mixture lean enough to cut the engine, then,as I was told once, it means theres too much gas getting through the `top half` of the carb. Its always, in my case, been the power enrichment valve diaphragm leaking and not allowing the vacuum to hold the piston up off the valve in the carb. It ran ok but the mileage was pretty bad.

Anyway its an easy test turn the scew in a turn or two or until it starts to sound like its going to quit running. If you cant get it to quit, its probably the power valve diaphragm leaking. If it does idle down get rough and start to die just turn it back out some again. I bet thats it.

Offline NMPinto

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Re: 78 Holley 5200 running rich
« Reply #5 on: January 02, 2012, 03:24:14 PM »
2 things worth checking are: Is the float level and fuel pressure correct? If either of these are too high that will
cause rich condition even at idle because if the fuel level in the idle and main circuits is above the design level
you couldn't add enough air though the main and idle air correction jets to compensate. The other is see if you can find the as delivered air, main jet and emulsion tube configuration for the particular carb by tag number if you can to see if it is currently got
the right parts in the right places.

Let us know if that helps.

Phil
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Offline 74WagonMeadowGreen

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Re: 78 Holley 5200 running rich
« Reply #6 on: January 04, 2012, 12:53:59 PM »
If you turn the mixture screw in does it to start to die? If you cant get the mixture lean enough to cut the engine, then,as I was told once, it means theres too much gas getting through the `top half` of the carb. Its always, in my case, been the power enrichment valve diaphragm leaking and not allowing the vacuum to hold the piston up off the valve in the carb. It ran ok but the mileage was pretty bad.

Anyway its an easy test turn the scew in a turn or two or until it starts to sound like its going to quit running. If you cant get it to quit, its probably the power valve diaphragm leaking. If it does idle down get rough and start to die just turn it back out some again. I bet thats it.

The power valve was the ONLY part that was not a correct replacement in my overhaul kit... I didn't think it too critical!! I do now! FANTASTIC suggestion, and the likeliest cause... THANK YOU! I will post a follow-up, hopefully expressing a successful passing of emissions, as well as "normal" running (not so blasted rich)!

Offline ToniJ1960

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Re: 78 Holley 5200 running rich
« Reply #7 on: January 04, 2012, 06:38:51 PM »
 I will be happy too if it helps let us know. I read you said you completely rebuilt the carb,but you just never know. When you do replace the power valve diaphragm, you can press it down and hold your thumb over a little hole on the bottom of the top half of the carb,its near the edge. I used to have an old one if I still did I could take a picture of it. I can look in a book I have too I think that showed it (petersons guide to the Pinto).


If you hold your finger over that hole after you push t he valve plunger in, the plunger should stay in until you remove your thumb from that hole and let air back in. That way you know its working before you put the top back on.

NM was right too it could be the float or something not cutting off the fuel and raw gas `spilling` into the carb. But its so easy to test the power valve by just adjusting the mixture screw to see if it will get lean enough to cut off. I think you would be more likely to smell strong gas odors if it was spilling.

The last time I redid my carn I just replaced the needle and seat set the float replaced the power valve diaphragm and put it back together with new gaskets. The rest I dont see any reason to mess with. The accelerator pump I can always do later.

Offline 74WagonMeadowGreen

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Re: 78 Holley 5200 running rich
« Reply #8 on: January 15, 2012, 08:56:05 PM »
The Pinto passed with flying colors, thank you... it WAS indeed the power valve... it looked like a sieve when held to the light... I have a strong feeling the fuel mileage will improve as well! THANK YOU!!

Offline lugnut

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Re: 78 Holley 5200 running rich
« Reply #9 on: February 01, 2012, 09:10:31 PM »
As much as we ALL like to complain about emission testing, in this case it prompted you to get it fixed, which is a good thing.  I still hate smog checks though!