Choke Issues

[DaveHess]

I have an '86 Power Ram (D100) with a 360 2bbl. My routine for starting it has been one pedal push to the boards to set the choke, hit the key, wait till she lights and then a quick shot of throttle to smooth her out. This routine would cause the truck to keep dying until she was warmed up. In other words, no high idle.



This past weekend, I tried the one pedal push to the boards, hit the key and see what happens. After some playing around with the high idle adjustment screw, set it at 1500 RPM and she purred great at high idle with the choke closed (or more correctly, barely open). As soon as I give it throttle (still ice cold engine), the choke goes wide open and my high idle goes away, and she struggles to idle until she warms up.



What I don't understand is, what is supposed to keep the chike engaged until the engine comes up in temperature? There is a Vacuum line to a dashpot and a piece of linkage connected to the choke. The linkage I know is driven by a coiled spring in the intake manifold. I thought as it got warmer it moved and opened the choke. Am I wrong? The vacuum I am guessing is designed that as vacuum drops, it allows the choke to open momentarily such as under acceleration.



What am I missing here guys?????

 

[B.G. Smith]

The vac. is to pull the choke open slightly after the engine starts(choke pull off). The rod with the coil down in the well on the manifold should be set so it holds the choke in a high idle poasition untill the coil heats up and opens the choke completely. Note: The choke thermostat will not work correctly if the heat riser in the exhaust manifold is not working correctly (closing when cold, opening slowly as engine warms). I believe it is in the passenger side manifold. bg

 

[DaveHess]

BG: What you said is everything I had suspected. Now, how do I get the coil to hold the choke closed longer for an appropriate warm-up? There is an electrical wire hooked to the choke housing in the intake manifold. I have not checked voltage there yet. When I do, what should I expect to find? Is that coil assembly serviceable?



This pick-up is neat because unlike my 2003 CTD, it has no refinement to it whatsoever. It's like driving a potato buggy with steel wheels. No air (which my bride finds unthinkable), no "fast-glass" (which my two teens find unthinkable), no power locks, AM Radio, but it does have a non-functioning cruise control (which I removed this weekend). Bench seat standard cab long box 4WD. I have a 383 out of a 1971 Road Runner I was thinking about transplanting but the whole transmission/transfer case swap has me thinking twice.

 

[B.G. Smith]

The system you have has a control switch which is activated when the ign. is on, at temps below 58 deg. or so it closes a contact which sends voltage to the heater on the choke rod coil, it de-activates when the switch sees around 110 deg. The rod is not supposed to be adjustable but I think you can get around that. The heater may not be functional and some one may have previously jimmied the rod to keep the choke from being on all the time in cool/cold weather. bg

 

[rscurtis]

You may want to try to adjust the vacuum diaphragm linkage so it doesn't open the choke so far. The vacuum system will always overpower the choke spring, so the adjustment is critical. Since the choke closes with a cold engine, that part of the system is correct.

 

[S.Morris]

The choke setups are pretty tempermental

At best of times.

You need to get adjusted so that after cold start a tap of

Pedal will drop fast idle to lower speed on cam. .

Not completely off.

Vaccuum is to pull choke plate open immediately

After fireup... use pliers to bend S rod for adj.







You ultimately have to run higher rpm than

You would like to get set right. 1500rpm should be step

Down speed after you knock down intial start fast idle.

These things work much better when it is COLD.

Best scenario is to get in gear and go when cold

Hoping first stop is 10min away.

As stated ... make sure heat riser is working freely.

360 were bad to plug up crossover with carbon and not

Make enough heat to pull choke completely off

Even at full OP temp.

Steve

 

[DaveHess]

BG: Where is this control switch???



The vacuum linkage is not making contact with the back inside edge of the choke linkage when the choke is fully open. Let me restate what is happening because all you guys are are great in helping me out here so let's make sure I am saying this right.



One push of the gas pedal on an ice cold engine closes the choke with about . 030 of clearance between the choke blade and the choke tower. The engine starts very nicely and goes to about 1800 RPM and stabilyzes. If I simply blip the throttle, the choke blade comes full open and the engine drops to it's regular idle speed of 950 RPMs (it usually dies since it is cold and the choke does NOT reset to the cold position). At this point I did check the vacuum linkage to see if it was contacting the choke linkage (like as if it was pulling it the choke open open), it was located approximately 1/3 of it's travel to the rear of the choke linkage. As if it had nothing to do with pulling the choke open. Does all this make sense?



So, I see my problem as the choke is receiving some signal to open even if the engine has only been running for several seconds. This only occurs if I touch the gas pedal. The engine will remain at high idle on the choke as long as I don't give it throttle. The last couple of mornings have been in the Thirties and my fix has been to allow the engine to run for two minutes with no throttle input. The RPM climbs in those two minutes to about 1900. I am a bit perplexed.



Keep the ideas coming. Dave

 

[fest3er]

I've always found it easier to install a manual choke in the cab once the automatic system starts acting up. The OEM system is designed for and calibrated to a new system and components. Over time, the components wear and change their characteristics and it just isn't worth the time required to recalibrate the system. Full choke to start and immediately go to 3/4 to 1/2 throttle, depending on the ambient temp; this will keep the engine at mid-throttle. Once you're in gear and driving, turn the choke off completely, unless it's truly frigid (-10 or so).

Years back, I converted my '66 Gutless to manual choke. All the starting problems vanished.

 

[B.G. Smith]

The vac. linkage should be adjusted so when engine starts the vac. pulls the choke open so that the fast idle screw rests on the second highest step on the fast idle cam. Fast idle should be about 1600. Sounds to me like the rod from the choke heater well needs to be bent so the choke closed a little firmer when cold. bg

 

[B.G. Smith]

The vac. linkage should be adjusted so when engine starts the vac. pulls the choke open so that the fast idle screw rests on the second highest step on the fast idle cam. Fast idle should be about 1600. Sounds to me like the rod from the choke heater well needs to be bent so the choke closed a little firmer when cold. Have you checked the heater system for the choke coil yet? You should get voltage to the heater when the engine temp. is below 58 deg. I have an old choke actuating coil and rod with the heater on it. It checks 5. 6 ohms resistance for a reference. The wire is broken off the one I have. bg

 

[DaveHess]

BG: I'll check that resistance. I bought new vacuum line for the vacuum cannister just in case something there is leaking. Although I would expect a vacuum leak and idle problems. If I cannot get this sorted out satisfactorily, I also have a Weiand Action Plus intake manifold and Edelbrock 1406 4bbl with electric choke to go on the engine. I wanted to wait until spring to install these pieces so I would have headers purchased too. We'll see.



Actually, in the Spring this 360 was going to get a Mopar Performance 260 or 268 duration cam and a set of 2. 02 360 heads that came off my 11 second drag car. So the whole top end will be new. This is my daily driver so I don't want to get too crazy before the cold sets in here. Which will be very soon.