Engine and Transmission Tech

Hello to all you four-barrel experts.

So, the new Edelbrock 500 (1404) with its out-of-the-box jettings, is in place on my 3.5 Rover V8, the idle is adjusted with a vac gauge - 11" of vacuum from the Piper 270 cam - distributor run off the timed port, no PCV yet so that's blanked, breathing from the flame trap to the filter, ignition timing is standard, electric fuel pump with 6psi at idle.
Revs cleanly, sounds crisp, and this weekend I hope to take it out and adjust the TV cable.

But.... it's a pig to start from cold. Churns over and over, won't catch, while I move the (manual) choke in and out, then eventually it catches and runs very lumpy, that eight-stroking that sounds as if it's over-rich. Warms up with minimal choke. I increased the fast idle adjustment but haven't finalised it yet.

So, is there a magic way of starting?
The Holley on my AMC just starts right up with half choke.

What's your cold start method?

Ivor

Full rich, ignition off, two revolutions, back off mixture, ignition on, swing the prop.... no wait, that was the Piper Cub...

Jim

"Pay no attention to the man behind the curtain..." (Good one, though, Jim ;-)
Ivor not sure it's applicable, but 6 lbs. of fuel pressure sounds high. Maybe should be closer to three...

Ivor,

When I had that carb I never hooked up the chock, but mine was electric. To start when cold (5C or so) I would give it a partial pump of gas twice then start. Worked welll, never seemed to need the chock. Maybe you are using too much chock.

From the Edelbrock carb manual -

"Avoid extremes in fuel pressure. At IDLE, there should not be any more than 6.0 psi; if the vehicle has
an adjustable fuel-pressure regulator, set it to 5.5 psi. With most fuel pumps the minimum fuel
pressure is encountered at high rpm and WOT. Fuel pressure should not drop below 2.0 psi. If it does,
a fuel pump with more capacity may be required."

Mine is set at 5psi. I have a manual choke Carter. I never hooked up the choke. Been starting it without a choke for over 16 years. Turn on the key, let the pump run for a few seconds, pump the pedal a couple of times, & turn the key, hold the throttle at 1500 or so for a about minute, then back it out of the garage & let it idle in the driveway. Bit harder to start if it has been setting for a few weeks.

When I fitted an Edelbrock 500, I removed its choke mechanism. Instead, I just used the accelerator pump.

I'm gonna take a wild guess that a little less ignition advance (at idle) might help you.

Timing....

Interesting you should say that.
Went out in it today, first time in two years I went any distance even though it was just ten miles.

Hard to start from cold, again. Tried just a couple of pumps at the accelerator, and no choke. No go.

I noticed on previous days it seems to fire just as I shut off the starter. Not the wiring, I already checked that there's no separate ignition feed from the starter. It has a steady 12V, cranking or not. But before it fired, after I'd given it a couple of pumps at the accelerator it sort of backfired and a big puff of smoke/petrol fume came back into the cab.
Then I had to crank it a lot more. And eventually, sure enough, it fired as I released the key.

So I wonder if there is indeed a timing issue.
Although it fires up fine when it's hot. Just some throttle.

I'd better pull the dizzie and have a look. The dizzie is one I put on, I took off the original Opus. Maybe now it has the wrong advance curve.
I could transfer the springs out of the Opus. I wonder if the bob weights are all the same weight.
It gets complicated when one begins modifying things.

Ivor

That thing about starting when you let off the key has me thinking.

Put a test light on the power lead to the coil and watch it while you crank to see if it stays lit the whole time, or if it get brighter when you let off the key. That could be a clue.

Jim

As above, choke removed completely from the carb. Run the electric pump for a few seconds, couple of pumps with the pedal and start. No issues. In fact it was so reliable that when it did not start it was 100 % electrical issue.

As Jim and Jukka are leaning towards, it sure sounds like an electrical fault.
Your first step should be getting a voltage reading at the coil while cold cranking.
Anything less than 10v will be a problem.
Not sure what you replaced the Opus with but most electronic ignitions won't fire at all at 10 volts or less.
The Opus while not very powerful, will fire down to around 9 volts.
If you have a points type ignition now. You may simply have the plugs gapped too large.
The greater power of the electronic ignition would fire them at a reduced voltage but the points type ignition can't deliver enough power at reduced voltage.
The reason that hot starts are ok is that #1 the engine is easier to turn over and does not drag the battery voltage down as much.
#2 is that the battery is at a better advantage as it has just recently been charged.

Hope that helps some.

Cheers
Fred

I give up. What is the fascination with manual choke, or no choke? Is this some macho thing? Automatic chokes have been around for well over half a century. The E-brock 500 on the 215 in my 62 Olds has the stock electric choke. It works great. No drama, no excessive pumping or cranking. No constant messing with a hand choke.

But we like messing with things. Automation is not Us. I also have a manual choke fitted to my AMC. And one on the shopping trolley.

What we don't like is having to correct schoolboy errors in wiring, that leave the power module of the Lumenition Optronic
[autocar-electrical.co.uk]
connected to the output of the ballast.
That meant 5.7V when cranking, and 6V when not. 6V is fine for the 1.5 ohm coil, not so good for the power module. But it started on 6V, which is pretty impressive..
Which of the three garages that has had my car in the last two years committed this faux pas? The three garages that failed to fix everything so I'm having to finish it myself? Well.....

So when I'd corrected my mistake, I found that it starts a whole lot better wired to the input, fed by 12V.
Still won't start by just pulling out the choke. but you are right, with a couple of pumps at the throttle, away it went.
I upped the fast idle so I can use the choke as a hand throttle during warm up. And in the winter, it may need some choke anyway, as it will probably be living outside. I have two garage spaces, one is for the AMC, one is for the wife's shopping trolley.
I know my place,

Thankyou for your assistance. They do say that most carburettor problems are ignition problems.

Now I can start investigating why the oil pressure is not so good. Start with a new gauge. A variation on 'shoot the messenger' perhaps.

Ivor

Excellent work Ivor. We knew you could do it.

Jim

Yes, it starts.
Run the pump awhile, two purposeful squishes at the accelerator, pull out the choke a little - on a learning curve here - then it starts. Then it stops. So I give it another squish, then it starts and keeps going.
Needs to warm up a bit before it will move. Not a start-and-drive setup like the factory carbs.
Could be that some further adjustment of the fast idle would help. What would really help is a hand throttle, then the choke and the fast idle would be independent.
It's an all-year car, so cold start matters.
But it starts. Which is a start.
Thankyou.

Ivor

PS forgot to mention... as regards the low oil pressure, shooting the messenger turned out to be the right call. The (nylon) capillary tube to the gauge was half torn at the engine end. Hardly any oil weepage, but it certainly lowered the pressure reading. The idle pressure has risen from 7.5psi to 20psi.
Unfortunately I obliterated the old 80psi gauge trying to fit it to the new copper capillary, so now I have a 100psi gauge which is not so good. Gauges with a 80psi / 270 degree reading are hard to find.
However, do have oil pressure.



Edited 2 time(s). Last edit at 11/05/2017 06:17AM by 88v8.

Ivor, you should have a fast idle adjust screw.
Also try this trick: Press and hold down the gas pedal, pull the choke all the way out, let the gas pedal up. Now don't touch the gas again, set the choke where it needs to be, and start it. You have set the fast idle cam to it's highest speed and it will drop off as soon as you touch the gas pedal.

HTH,
Jim

Ahhh, yes. That's how one sets the auto choke on the Shadow. Open the throttle full. Then when one touches the throttle, if the engine is warm enough the choke drops off.
Hadn't thought the manual could work the same way. I'll have a look.
Do have a solid choke cable though. A push/pull. And no choke return spring.
I'll report back,

Ivor