Car ran perfectly, two weeks later it won't start.

Bmachine

Bmachine

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I have been progressively refreshing my US 74. New plug wires, new dizzy cap and rotor, new ground cables, making sure I restart the car after each step to make sure there is no problem.

Two weeks ago I installed a Pertronix. Everything went well. We took it for a test drive and the car ran great, much smoother than before.

This weekend I am ready to take it for a spin, it cranks healthily as usual but ... that's it. No attempt for the engine to start. Very puzzling. The car was in the garage and nothing was done to it since I ran great with the Pertronix.

I decided to stick a screwdriver in a plug wire and hold it next to one of the front strut bolts which is a good ground to check for spark. I do get a spark but a weak one. Orange color without much of a crack at all.

So I wonder if the Pertronix has something to do with it. So I remove it and replace it with the points and condenser. Same result. The starter does its job but the engine does not start or even attempt to start.

Then I remembered a couple of odd things I noticed before. I have the original black coil but there is no resistor anywhere I can find. The 74 is supposed to have the wire resistor but it is definitely nowhere near the coil. When I measure the resistance across the coil I get 2 ohms. This is within the Pertronix minimum required resistance I did not worry about it. I also measured the voltage on the coil and it was giving me 7.3 volts. The Pertornix instructions require between 6 and 9 so I figure it was safe to hook it up.

But now that I think back I wonder how a black coil could give me 2 ohms resistance and only 7.6 volts without a resistor. Putting this all together, could it be that the coil is no working properly? Would this explain the low voltage and the weak spark? Should I simply buy a new red coil with the resistor and hope that this was the problem?

Thanks for any help.

Bo
 
Hmmm, just had an idea... Maybe I've been barking up the wrong tree.

After I let it crank for 10-20 seconds and press down the accelerator pedal a few times... shouldn't I be able to see some fuel in the carbs when I push open the butterflies? It is totally dry in there...

I still have the mechanical fuel pump and the PO installed Webers 32-36 in there.

???

This might explain why putting the points back in there did not make any difference... But is seems weird that the pump suddenly decided to completely die without any warning, no?
 
2 weeks can allow fuel to drain back out of the carbs into the tank. Check all fuel line connections from tank to carbs to ensure no air leaks. Take off the air cleaners and pour a little gass in there to see if it starts. Some have added a check valve to prevent fuel from draining back. Fuel pump can also be pulling air, you can check by disconnecting the hose from the out side and see if gas flows into a container when cranking. Reinstall the Pertronix.
 
Resistor wire, nor last resistor

Does your car have a blast resistor or ballast wire? The ballast wire looks like speaker cable, but will now be discoloured. The ballast resistor looks like a piece of ceramic about 2 inches long with resistor wire. It is mounted near the coil.

The coil should get more volts when cranking than running, that is the reason for the resistor, but to check the wire voltage (is the loom etc ok) you could hot wire direct from the battery to coil, however if it starts it won't stop on the key, you will need to pull the hot wire off. A fuse is a nice addition to this hot wire.

Is it a carb or injection car? My CSI had this issue, it was the trigger points slightly dirty on one set. This was hard to measure, but with a decent multimeter I turned over the engine and measure the resistance as the points opened and closed, three sets of points, one for sparks and two trigger sets for the injection.

If it is injection is the cold start valve working? Fuel pressure, about 2 bar?

Post us details to help deduce what the issue may be.
Good luck.
C
 
Thanks very much for the replies guys.
It has the original pump between the intake manifolds.
I will disconnect the line coming out of it and see if anything comes out.
Based on other posts on the subject I am thinking more and more about converting to an electric pump. It seems it would be easier to debug.
An anti syphon valve would also be wise.
 
After a two week rest I dump a little gas down the carbs to get it to start. Otherwise it cranks for a very long time to get gas in the carbs.
 
m_thompson said:
After a two week rest I dump a little gas down the carbs to get it to start. Otherwise it cranks for a very long time to get gas in the carbs.
Click to expand...

+1 My mechanical pump works just fine, but if the car sits for a while, which it does, I sometimes have to put a battery charger on it and also a squirt of carb cleaner or WD-40 so it doesn't crank a long time.
 
Bmachine said:
I will disconnect the line coming out of it and see if anything comes out. Based on other posts on the subject I am thinking more and more about converting to an electric pump.
Click to expand...

I would just follow m_thompson's advice (dump a little gas down the carbs to get it to start) - I'll bet that will solve it. As others have written, after a few weeks of non-running, it takes a lot of cranking to get fuel into the carbs again.

I am thinking more and more about converting to an electric pump
Click to expand...

Yea, that's a good solution for a car that is used infrequently.
 
car ran perfectly...

Suffered these very same symptoms. car sits for sometime weeks, then very difficult to start. blamed fuel pump, tried a few, bought a new one. Discovered as Steve said that putting a check valve in the fuel line, between fuel pump and before line goes back down under car will keep some fuel close to the carbs when you want to start up again. Also, battery must be strong. A failing or weak battery will not have enough strength to give energy for the pump to pull fuel from way back in the tank. Those many cranks get weaker and weaker. Yes, check for any air leaks from tank up to pump. But all solved now. Mike
 
In the winter I always give the carbs a shot of gas to fire it up. Saves a lot cranking to get the fuel to the carbs. Someone here posted a picture on installing a inline primer bulb from a boat gas tank that seem to be a good idea.
 
No gas

is essential. But... orange spark at the plug means something more.

Measure the coil resistance on the secondary side. Probe the positive and the center HT wire to cap center. This controls the spark quality- blue flame.

The HT wire could have been damaged. Measure it. As part of , I don't know who did what to my car last and when, a methodical check of the spark plug wires and their resistance should be part of a tune.

Something more is going on.... 7.6 v with .2 resistance equals 15.2 volts coming into the ignition. So the math says. that means you got nearly an abnormal charging/ running condition.( 14.7 is high)

Regulator going? So start at the battery and check the running and static voltages. Assuming you've got two wires on the positive side of the coil... 15v is bypassed directly to the coil during cranking if it's hooked up right.

.2 resistance is at the high end of the stock coil tolerance range. I'd chuck the coil for new $30 one sometime soon just for reliability. Or keep the one you've got and check the other side- HT.
 
No gas...

Webers notoriously leak at the fuel enrichment cover. On a Zenith it's internal. If there are air leaks, that will contribute to the possibility of fuel drain.

Regardless, yes you should see some fuel evidence if you pumped the accelerator and there's some fuel in the bowl. No fuel, then that's the tale.

It's essential.
 
Wow, fantastic replies everyone! Thanks very much.

Based on all that, I was able to find several other threads which seem to confirm those fuel related suspicions. I took an empty bottle last night and went to the gas station to get a little in there and will squirt some in the weber floats when I get home from work today. I'll post the results.

This being said, I agree with 61porsche. It feels like there may still be something wacko with the iginition part. I am still not finding that resistor wire that a 74 is supposed to have and the numbers around the coil don't seem right.

61porsche, the resistance I am getting between the + and - of the coil is 2 ohms. I'm not sure what you mean by ".2 resistance" but if you mean ohms, it is 2, not 0.2 and from the + to the secondary I get about 13kohms. Based on what I read on the net, this seems pretty high.

So maybe I should get either a new blue coil or a red coil and resistor and put that in just in case...
 
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For reliability I replaced every part of my ignition system whether it needed it or not. I would replace the coil, but not until you have determined whether you have the resistor wire still in use, this will determine which coil to get. Blue if you do, Red with 1.8 ohm ballast if you don't.

Bmachine said:
So maybe I should get either a new blue coil or a red coil and resistor and put that in just in case...
Click to expand...
 
Your

stock resistor coil is below spec. It should be in the 14-16k range. At a measured 13k- it's failed.
 
Thank you Steve. This wire is definitely not anywhere near the coil. See photo. Could it be located upstream where the wiring loom started, on the other side of the engine. I would have thought it would be near the coil...

There are two wires going to the positive, one black and red and the other clear. But the clear one looks like a regular wire and not like a resistor one. Although it does have a half inch strip of brown tape near the spade connector for some reason.
 

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I don't have a resistor wire on my car so I wouldn't know definitively if that is it or not, perhaps other can chime in and verify, but as HBChris said, it sure looks like it.
 
And the winner is...

... the empty fuel line!

After two weeks of chasing the wrong culprit, it turns out, as many suggested, that the mechanical fuel pump could not suck enough gas through the line to get the engine going. I poured a little gas in the carbs and after a couple of tries it started right up! It runs pretty horrible because I had reinstalled the points and they are not setup properly at all of course. But I will reinstall the Pertronix tomorrow which should clean things up nicely.

OK. My next task is to search the forum about the best recommendations for converting to an electric pump. I now I have seen a few threads on the subject before.

Thank you for all the great comments.
 
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