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1978 Eldo Cold Start Issue

Started by Jakes, August 19, 2019, 04:02:24 PM

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Jakes

The 425 ci eng. has an M4ME Quadrajet carb.  When the engine is cold, say, from a few days sitting, I start the engine "by the book": floor the pedal to close the choke, floor pedal 2-3 more times, crank engine with foot off pedal, and she starts up in fast idle.  After 30 sec. to a minute I tap the pedal to unload the choke, wait a few minutes more then tap the pedal again to fully unload the choke.  I let it idle for 8-10 minutes more to overcome cold engine bog/sag (some of you may recall my writing about this before in the Forum) and then drive off.

One puzzling thing though.... before fully unloading the choke, the engine will reduce speed and lope for about 5-10 seconds and then resume speed before I fully unload the choke, as described above.  I haven't paid attention to this peculiarity because it's always done it and then "corrected itself".

Now, here's the problem.  Lately, start-up has been erratic.  I go through the steps described above, but instead of going into a vigorous and smooth fast idle, the engine runs very slow and unevenly after starting.  Assuming the fast idle screw is on the highest step of the cam, I tap the pedal after 30 sec. to a minute and the choke seems to unload because the speed reduces, but the engine is idling slower than expected and also unevenly.  I rev the engine up/down a few rpms and after a minute or so the idle speed increases and smooths out to where it seems to be in normal hot idle.  I continue my "anti-bog/sag" idling routine (i.e., waiting a few minutes) and then take off without any problem.

I checked the choke pull-off device, the EFE (heat riser) valve, and the choke thermostatic coil spring (electrically activated) and they all function properly.  This poor cold-engine start-up response is puzzling because it's intermittent -- sometimes it happens and other times the startup procedure is normal, as described in the first para.  Why would that be?  I have a feeling after 41 years the carb. is due for a reconditioning despite my regular 30-mile local/hwy "exercise run" and adding cleaners to the gas such as Sea Foam from time to time (and always use Sta-Bil).

As I'm writing this it occurred to me: could it be the fuel filter?.... I haven't changed that for a while.  But wouldn't a bad filter cause driveability problems?  Once I'm on the road, the car runs perfectly.  Your comments and advice are appreciated.  Many thanks.

Paul Jacobs
Huntington NY
Paul
'78 Eldo. Custom Biarritz Classic

"Cadillac Kid" Greg Surfas 15364

I would start with an external cleaning with carburetor spray to make sure the linkages and the choke components are not sticking.

Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Big Fins

Could it be that it's just sooooo damned hot outside that the choke and fast idle isn't being activated?

That's the case for me and we're cooler here temperature wise, than a lot of the country.
Current:
1976 Eldorado Convertible in Crystal Blue FireMist with white interior and top. (Misty Blue)
1969 Fleetwood Brougham in Chalice Gold FireMist with matching interior and top. (The Old Man) SOLD!

Past and much missed:
1977 Brougham de Elegance
1976 Eldorado Convertible
1972 Fleetwood Brougham
1971 Sedan de Ville
1970 de Ville Convertible
1969 Sedan de Ville
1959 Sedan deVille

Jakes

Here on Long Island temps have been moderate this summer, mostly in the 80s.  Also, the car's in an insulated garage where it's a good 10 deg. cooler than the highest outside daytime temp.  At a couple of times the problem occurred I quickly opened the hood and removed the air cleaner cover and the choke valve appeared to be in its normal position: partially open as the closing force of the thermostat is counter-balanced by the action of the choke pull-off.  But come to think of it, I pushed the choke valve a little toward the closed position and the fast idle speed increased, so, Greg, your suggestion of giving the carb. an external "bath" to free up any binding linkages is a good one. 
Paul
'78 Eldo. Custom Biarritz Classic

cadillacmike68

Break out the gumout. Twice a year at a minimum.
Regards,
"Cadillac" Mike

Big Fins

You 'closing' the choke butterfly and the engine speeding up indicates a possible vacuum leak. EGR valve diaphragm could be torn. Remove that thing anyway and put a delete plate on it. Or that hose from the PCV to the vacuum supply could be disintegrated.
Current:
1976 Eldorado Convertible in Crystal Blue FireMist with white interior and top. (Misty Blue)
1969 Fleetwood Brougham in Chalice Gold FireMist with matching interior and top. (The Old Man) SOLD!

Past and much missed:
1977 Brougham de Elegance
1976 Eldorado Convertible
1972 Fleetwood Brougham
1971 Sedan de Ville
1970 de Ville Convertible
1969 Sedan de Ville
1959 Sedan deVille

76eldo

All of the above comments make sense to me.
Including having your carb rebuilt by a competent shop that knows quadrajets.
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

Jakes

Well, yesterday I gave the carb. a good exterior Gumout bath including the choke shaft and the PCV valve.  The EGR valve and the little thermal valve that's connected to it seem OK as well as all the vacuum hoses.  Not that I noticed any major accumulation of crud on any of the linkages to begin with, but they did seem to operate a bit smoother.  In particular, sprayed liberally around the levers that operate the fast idle mechanism.  Result:  this morning, did my starting routine I described earlier.... but only floored the pedal once to close the choke because the carb was well primed from all the opening/closing of the throttle I did in order to get the spray into all sides of the fast idle mechanism.... and she fired up into her normal, smooth, fast idle mode like a champ.  After a minute tapped the gas and she idled down normally.

Problem solved?... one "test" a trend does not make, but it's encouraging.  So.. many thanks to all of you for your advice.  If the sluggish cold start problem recurs, then as Brian Rachlin suggested, I'll be off to the carb rebuilder.  The carb's never been off the engine in 41 years!
Paul
'78 Eldo. Custom Biarritz Classic

76eldo

Glad to hear there’s some improvement.
After cleaning things up with carb spray I usually follow it up with some CRC lubricant or WD-40 to keep things a little lubed.
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado