• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Sanity check please!

Share this page

Hi Tom,
This is really getting to be quite the puzzle. If you have spark and gas, it should at least try to start. The fact that it ran not too long ago (albeit roughly) means to me that there's not something seriously wrong. At one point you said it tried to run when fully choked. Maybe the mixture is just not rich enough to start at the cold temperatures that you're having? My Healey will not even try to start if the temperature is below freezing. I can usually get it to fire a few times if I hold my hands over the carbs to richen up the mixture, but the choke by itself just doesn't make the mixture rich enough. Is your garage warm?

Have you tried removing a plug and holding it to the block to see if will spark to the block? That's the best test that I know of for spark. Be sure to hold the plug with insulated pliers and keep it away from any gas that may be around! You should see a nice blue spark.

In my experience, if the battery can turn the starter motor it will have enough juice to spark the plugs, so I don't think it's your battery.

Keith
 
Hey Keith - thanks for the reply.

I haven't done the "hold the spark plug to block" test in several weeks. Back then it sparked just fine - but that's my subjective observation. I'd think if there's any spark at all the fuel should fire - but I'm sure no expert on spark strength.

As I have new coil, new condenser, new points, new wires, new rotor, new dist cap, and new plugs - all which worked about a month ago ... what should I check if I were to discover there's no spark? Even dropping fresh fuel straight into the carb throat doesn't fire.

Thanks.
Tom
 
NutmegCT said:
When I tried starting the engine at noon for the fuel test, it cranked perfectly - but after a few seconds, starter suddenly slowed its rpm's by about 30%. Not a gradual slowdown - but all at once. Checked all wires and cables; engine ground strap is fine. I did a battery load test right afterward and found the load meter said "weak". Is that normal for just after cranking about ten seconds?
Click to expand...
Um, what's the weather like? That would be about right if it was really bitter cold, but at 0F or higher you should be able to get at least 30 seconds or so. Sounds to me like you've got a weak cell (that ran down). What was the open circuit voltage after trying to start?

From previous comments, I assume you are still running points which should still be working even if the motor will just barely turn. However, I have seen electronic ignitions that cut out much higher. Had a strange episode with the Pertronix I installed on my TR3 where, for about 6 months, the engine would only fire right after I released the starter button. That turned out to be a bad battery. I never managed to measure the cranking voltage, but it would spin pretty good and just never fire. Also, one of the Stags has an Allison ignition that apparently won't work at all below about 10.5 volts. I tried limping home once with the alternator not working, and the dash voltmeter was still touching the 11 mark when the engine abruptly quit completely.

For a more severe test of spark voltage, disconnect the wire and hold the end of the wire a short distance from the engine block. The spark should be able to jump at least 1/8" or so (which is several times the gap of a normal spark plug).
 
Thanks Randall. What's left of my sanity tells me the battery is weak, despite the "load test" results. Before cranking today, OCV was about 13. After cranking, OCV was just below 12 (maybe 11.9v). (To be honest, there are so many details circling through my brain right now I sometimes wonder how I can remember any specifics after spending four months with this intermittent problem.)

Battery is 3.5 years old. Temps have been 30 to 50 for the last couple weeks - but very humid. I didn't mean to imply the starter cuts off after ten seconds, but it sure slows down. Started doing that a couple days ago. Battery is always on maintainer unless I'm working on the car.

I thought maybe if I put my charged up 500 amp B&D jump starter in parallel with the battery (box positive to battery positive, box neg to chassis), that would fix the problem. But it didn't change anything. When the nor'easter ends on Saturday maybe I'll give it another shot.

Thanks.
Tom
 
OK, one more crazy thought. Is there a blockage in the exhaust? Any chance some little fuzzy found a nice warm home in the muffer? Even the slowed cranking may be a symptom. How hard is it to disconnect the pipe at the manifold and see if it will start.
It's a long shot, But I've seen that cause a no-start before. Once the nest was blown out by a nice big backfire, the car ran fine.
 
Ben - not so crazy. But seems it should fire at least once or twice even if the lines were totally blocked. (Can't blow those squirrels out if it doesn't fire!)

You can feel some pressure at the tailpipe when the engine cranks. Any thoughts on that strange "dark circle with light brown center" on the wall behind the tailpipe (photo earlier in the thread)?

Thanks.
Tom
 
Just another shot in the dark.... Have you verified that you have the firing order correct? Are the spark plug wires on the distributor cap in the right order?
 
Gliderman8 said:
Just another shot in the dark.... Have you verified that you have the firing order correct? Are the spark plug wires on the distributor cap in the right order?
Click to expand...
Yep - done that. firing order is stamped on the valve cover, and plug #1 fires from the dist cap contact at 5pm.

This is going to be embarrassingly simple - when I finally figure it out. Just can't be so complicated. sheesh

T.
 
I agree Tom... when you finally find the problem I'm sure it will be something simple that was overlooked. Keep at it!
 
Hmm.... That could be the dying smoke ring from the last exhaust gas to get by the blockage. Already had incomplete combustion from poor flow, and low velocity from the same, and she coughed out that puff.
I have seen almost total blockages cause an engine to not even try. There's just not enough vacuum to get a good mix into the bores. It's still only a guess. I'd try loosening the pipe at the manifold. Shoulden't be a huge task.(Famous last words)
 
Thanks gents. Loosening the manifold will be quite a challenge - it's been on there a *long* time.

Before I reach for the blasting caps ... shouldn't I get at least one or two plugs to fire when I first crank the engine? There's plenty of vacuum when I crank; seems the vacuum would be cut way down if the exhaust were plugged. (Not that I understand Otto cycle engines ...)
 
Fixed! Starts and runs! Yeehaa!

(The amazingly simple solution will be revealed when you say the magic word.)

T.
PS - unlike everyone else here, I am an IDIOT!
 
Please....
 
View attachment 26248

When I decided to try another condenser, I removed the old condenser lead and the coil wire from the distributor post. Of course I also had to loosen the condenser bracket so I could slide out the condenser.

When I loosened the condenser bracket screw - WHICH ALSO HOLDS THE DISTRIBUTOR GROUND STRAP - the screw fell down "into the nether regions never to be found again".

After a couple days looking for the missing bracket screw, I found one that fit. I put the new condenser in, and tightened the bracket.

And of course I put the ground strap and other wires back in exactly the right places, because I never ever make mistakes. yeah right

Seems that just afterward, a meteor passed by with a blinding light and deafening roar. I was knocked unconscious and someone sneaked over and moved the ground strap from the condenser bracket screw to ... the distributor positive wire post. Darn kids.

When I regained consciousness, I tried starting the engine and found it wouldn't fire at all. I then spent almost a month troubleshooting the "won't start" issue. Minor detail that I also bought: new plugs, new points, new coil, new ignition wires, new dist cap and rotor.

Onward through the fog.
Thanks again for all the suggestions. They're coming with the little pink pills now - and my padded cell is ready.
Tom
 
Even Mercedes can't always make perfect parts, too much Asian market in everything.
 
Well, at least you know all the other things you 'fixed' won't be a problem in the future. Congrats on getting it running!
Keith
 
Back
Top