My old stepvan still isn't firing up. It apperas to have weak spark... atleast to me. This is a '73 300ci, all stock. Should'nt I be getting a nice blue spark? Or am I just used to the newer, hotter ignitions?

It cranks strong and I have plenty of compression. Sometimes, while cranking, it seems like it's going to start but then goes back to just cranking only when the manual choke is on full.

The plugs look dry after trying the above, but I can see gas puddling in the intake and there's a strong gasoline odor. A small amount of gas seem to be wetting the side of the carb. I checked for stuck, sunk float also.

I've checked all wires.. resistor wire, grounds, coil and checked for pulse light on -neg. side of coil while cranking.

It ran, was shut off and never started again.

Basically, should I have a blue spark or is yellow ok?
Does it sound like a carb problem? I have one on order, but I can send it back.

Tomorrow I'm going to check the three vacume lines... for the third time.

Any help will be appreciated.

 

If you have gas pooling in the intake, you have a fuel leak that must be corrected. Without much more information I can't really pintpoint suspect areas, but start or no start this is something that must be corrected immediately. You do not want to be checking for spark on the engine block with a fuel leak.

There is not enough information to justify replacing the carburetor at this point. While a breaker-points ignition system will have less spark energy than its modern counter parts, yellow spark is not OK. Let's start a series of tests, after you correct the fuel leak.

Try this test. Pull the distributor cap off, and make sure that the points are closed. If not, you can turn the motor over until they are. Turn the key to RUN, and measure the voltage from the BATT post of the coil down to ground. Use clean, unpainted metal on the engine block for ground. Report your results. A '73 would have push-style boot connectors on the coil, but there should be a nut exposed at the base that you can get your meter probe on. If not, you can scoot the wire boot a little off the coil terminal to get at some metal; just make sure the coil is still connected for this test.

It is unclear to me what you have done to check the wiring as you described, but suffice to say that visual inspection of wiring will tell you very little. A multimeter is absolutely necessary.

 

I recently purchased it and it did run. It had new plugs and wires, cap, rotor, points and condenser, when purchased. Siince it wont start I have replaced the coil and battery cables (badly needed). Cleaned every ground contact I can find and doubled checked everything I could think of. Checked the resistor wire from plug end to plug end and there is about 2ohms of resistance, so that's probably ok too.

Closed points to ground = 12v. Neg side of coil to ground = 12v.

I have been using an analog meter, but if you prefer I can use my Fluke digital for more exact measurements. I like my analog meter better, though.

If you need any other measurements, just request them. I have measured the voltage, resistance and continuity of many, many of the wires and connections over the last 3 days and haven't found a problem with any.

I ran a direct wire from the battery to + side of coil for a few seconds and still got yellow spark at the coil. (Plug wire attached to coil wire).

 

With the points closed and the key in RUN, the BATT terminal of the coil to ground should be 7-9 volts. The negative terminal of the coil to ground (with the points closed) should be 0 volts. When the points close, the negative terminal of the coil is grounded, so there should be a dead short from the negative terminal to ground. If you're getting 12 volts at the negative terminal of the coil with the points shut, the coil is still open circuit. The fact that you are seeing a full 12 volts on the positive terminal of the coil when the key is in RUN means that no current is flowing through the resistor wire, so there is no voltage drop. This further supports the notion that your coil primary winding is open-circuit with the points shut which is not supposed to be the case. I suspect the points are not grounding.

Trace the following wires and check continuity:

1. Negative terminal of the coil to the points, through the distributor housing.
2. There should be a small jumper wire inside the distributor between the stationary base-plate and the rotating breaker-plate. This wire is responsible for grounding the coil when the points are shut.

 

Thanks. Will do what you asked right now and return with my findiings.

 

Distributor/points/coil findings. To start with, my battery is good though a tad low @11.6v.

With the points closed and key in run, the batt terminal of coil to ground is 5.95v. From the negative terminal of the coil to ground is -.01v (apparently I originally measured while points were open).

As for continuity. Neg terminal of the coil to the points = 0 ohms
The small black jumper wire also has 0 ohms resistance from end to end and to all other parts of points and plate etc.

I did not see any rotating plate in the distributor. The only thing rotating is the distributor shaft with point cam. I checked continuity to every wire and part I could see to one another and to block and there was 0 ohms to all.

Last I checked one other item, but I don't know if it is of revelence. Points open to ground was 73 ohms.

I hope these measurements help.
Thanks!

 

Just where exactly are you checking for spark? At the coil, the cap or at a sparkplug?

And when you say it ran and was shut off. Do mean, you tried to start it recently or it sat for several years in storage?

Josh

 

I have checked for spark at the coil using a plug wire and a new spark plug then clamping the ground of the plug to a clean section of block.

I have also done the same with the wire attached to the terminal on the cap and the plug grounded to the block.

When I say it was running... it was less than a week ago. It was raining if that makes a difference. It was shut off about an hour or so and never started again.

Just a few minutes ago I discovered a not so good vacume line going to the brake booster. Plugged it at the manifold and attempted to start it. Just cranked, that's it. After about 5 seconds of cranking I stopped and gas spit up out of the carb as usual.

That's it.

 

To me anyways it sounds like all your numbers are good so I would suspect the rotor and cap on down to the wires and plugs.

I assume it's dry inside the cap? It doesn't take much moisture to mess with things.

The rotor looks decent and tang is up and springy?

What are the ohms for the spark plug wires? The standard is usually 8000 ohms per foot.

Josh

 

Okay, your new ignition system numbers sound much more reasonable. Could you be more specific about gas spitting out of the carb? That's not normal.

 

The inside of the cap and distributor is dry and the rotor looks like practically new. I will check the resistance of the wires tomorrow to see if they are up to specs.

The gas spitting out of the carb.

The carb is a Carter YF 6376 1bbl. I felt that the gas spitting from the carb was unusual, that is why I ordered a rebuilt one (not received yet)... It really dumps fuel. I didn't seem to bother with that right now because I still need a good spark. But we can talk carbs too. My truck is a step van so I can remove the doghouse and air filter and watch while cranking it. I pull the manual choke, closes the choke plate, cracks open the throttle and gives a small squirt of gas from the acc. pump. Then I crank the motor for maybe 5 seconds (without touching the acc. pedal). During and especially when I stop I can see a mist/droplets of fuel coming out. It can be seen ON TOP of the choke plate by now. I open the choke and the plate is soaked with gas and there is a puddle down in the manifold. It does it without the choke on too. But if I floor the gas while cranking, it doesn't seem to do it. Day before last I pulled the carb. I removed the top to see if my float sank causing fuel to dump but it floats and I cant hear anything spashing around inside. So I assumed it isn't my float. It looked fairly clean so I hosed it with some carb cleaner and reinstalled it.
I DID notice something that I thought was odd, but it looks like it was made this way. The fuel nozzle located in the venturi has an orfice on the top as well as bottom. Thats all I can say about that.
I have cranked the motor, choke off, while looking inside with a flash lite and see there is quite alot of fuel (Many steady drops) coming from this venturi nozzel. Top and/or bottom of it.

So that's the scoop, sorry to be so long, but I wanted to be as detailed as possible.

Tomorrow I get to work on my son's '73 VW bus... but that's a different forum.

 

The carb is definately flooding out, and it seems the needle and seat is toast.

You seem mechanically inclined, a carb kit to rebuild what you have would have been a better choice than getting a reman carb with a sketchy history.

Either way, I would tend to think that if the van was left to sit for a period of time and you go to start the engine, it should at least run for a bit before the carb floods out.

Way back in the day with a 360 and an Motorcraft 2100 2 barrel, the only way to get the stupid thing to start was to hold the throttle wide open until the engine caught. That engine was quickly replaced with a mild 390 and Carter AFB, but like I said it was pretty much the only way to get it to start unless I had just shut the engine off for only a few minutes.

Josh

Josh

 

Well other than the fuel problem the problem I had on my truck I started it once it ran could not get it to start again. Check your distribuers plate the little metal peice on what you attach your points and condensor too. Make sure that there is no movement from the plate it will cause your points not to fire correctly. If it does move what I found was the problem is two different things. There are three little plastic nubs on the bottom of the plate. Also the vaccum advance arm the attachment point under the cap had worn out and was loose allowing movement in the plate. Check those and that should fix any problems you ave with power.

 

I've rebuilt a couple carbs and had good luck. They wanted 49.95 for a rebuild kit or $120 for the whole carb. I figured with a warranty, if it's no good I'll just take it off and get another. It's a Champion Rebuild, so hopefully there is some quality. But I can always send it back and rebuild mine. They don't know if the new one is a manual choke or not. If it isn't, I don't want it.

Occaisionally it will sputter while cranking, but it never starts, but only with the choke on full. If the choke is off and the pedal to the floor, it won't even sputter. I have tried variations of choke-throttle settings and nothing.

But with that much fuel and weak spark, I don't see it starting.

 

That is more or less the problem i had with my truck the only difference i had was my fuel pump was sending enough fuel so I replaced it with an electrical thats when i found the ignition problem