Cranks without starting - ignition?

[Hatchet54]

Hey guys,

So I ran into an issue this morning that I am hoping will have an obvious answer.

'77 K15, quadrajet 350.

Some background: drove the truck home on Sunday, running completely normally. On Tuesday, I wired up a new set of fog lamps. I had the battery disconnected as I did this. Wired them to a flip switch beneath my column and attached with a bullet connector. Tested the lights briefly with the motor off, and everything came on strong and looked good. Went to bed.
Today (Thursday) I got up and the truck cranked and cranked but would not start. Lights still came on fine. First thought was that I had overloaded something with my new accessories. So I pulled the bullet connector, effectively shutting the lights off back to stock. Still the same.
I then jumped the battery, thinking maybe I had run it down on my brief test a few days before. Still the same. My guage reads about 10 volts...this is about where it has been normally on startup.
I then checked the fuse box thinking maybe I had shorted something with the lights. Nothing was blown, but I replaced a couple of old looking fuses. Still the same. I noticed that there is an empty plug labeled "Ign" on the block that has no connection. Is this normal? I have not touched it.
The top of the carb smelled like gas. I know there was very little left in the tank when I shut it down, nearly empty. Low pressure in the tank maybe?

After work today, I'm going to start a bit more of a teardown, checking for fuel, spark, etc. But I wanted to let this question simmer in case anyone notices something that I have not.

My question for now is - what should I be looking for that I potentially messed up with my wiring job? I have this weird feeling that I shorted out my ignition somehow. Does anyone have any immediate thoughts? The fact that the truck was running like a top before the lights went on seems hardly coincidental.

Updates soon, thanks!!!

 

[Crispy]

Just curious how you wired the lights. Toggle switch directly to battery and light? Pulling from a fuse as a signal to the lights? Did you use a fuse and relay? What kind of fog lights? Can you be more specific?

Just double check your wiring where it goes through the firewall and check any wires it may be rubbing on to for breaks in the insulation.

Seems like too much of a coincidence for that to happen, it may be, but suspect #1 is the wiring you just intalled.

 

[Hatchet54]

This is embarrassing, but I'm going to be forthcoming about it. Electrical is by faaar my weakest area. This is almost literally the first wiring I've done that wasn't on a motorcycle. So I have zero idea of what I'm doing. I thought I was being a big boy by adding a couple lights onto an existing wire.

Here's a little more detail. The PO had a set of basic aftermarket fog lamps on the bumper. They were wired through the firewall to a flip switch on the dash. The switch had two wires- I'm not totally sure where the second one goes, up in the column somewhere.

I wanted All the lamps to function with the same switch. So all I did was splice my new lights onto the existing wire (all four lights have a single wire btw, no ground), and then replaced a portion of the old wire bear the switch and added a connector there. And like I said, with power turned on, all four of the lights worked great.

But after saying all that, now I'm not even sure it's an electrical issue. This is where it gets weird...
At lunch today I hopped over and looked again. This time I pulled a plug- I'm getting spark.

I also pulled out the entire offending wire loom, so there is no longer anything attaching the lights to the switch...and nothing has changed.

Earlier I mentioned that my tank was low when I shut down. A quick look seemed to indicate that I had fuel, but I didn't get too far inside the carb. I'm starting to think that's the only thing that could be the problem. I'll take a closer look tomorrow and maybe dump a little fuel in there...

 

[Frankenchevy]

Check for voltage on 12ga pink wire and possibly purple wire when cranking. Also a picture of starter solenoid so we have an idea of how it’s wired. Some systems give power to the coil differently when cranking and running.

Edit: disregard, I misread the part about you successfully checking for spark. Obviously getting power to the coil. Agree with checking fuel and the potential for weak spark or other ignition related issue.

If you’ve pulled everything you installed it doesn’t seem like something would be grounding out. Might as well check your fuseable links if your coming up empty handed in your search.

 

[PrairieDrifter]

Put some fuel down the carb and see if it’ll fire. First check if there’s any squirting action down in the primaries of the carb. Get the air cleaner off and look down in the carb then actuate the throttle by hand.

 

[82sbshortbed]

I'm going to be forthcoming about it.

Shoulda done that from the start. You would get better answers to your questions. Good luck on your problem.

 

[Hatchet54]

Check for voltage on 12ga pink wire and possibly purple wire when cranking. Also a picture of starter solenoid so we have an idea of how it’s wired. Some systems give power to the coil differently when cranking and running.

Good idea. I'll test the wires, and depending on how much time I find in the morning tomorrow before work I'll see if I can get some photos too.

Put some fuel down the carb and see if it’ll fire. First check if there’s any squirting action down in the primaries of the carb. Get the air cleaner off and look down in the carb then actuate the throttle by hand.

I'll plan on trying this bright and early tomorrow and report back! I'm hoping that something in the fuel is the problem, I'm a lot more comfortable taking carbs and lines apart than I am wires...lol.
It's just frustrating when I only have an hour of daylight outside of work to mess with stuff, and then sit around tossing it over in my head all day! This might be a slow one...

Shoulda done that from the start. You would get better answers to your questions. Good luck on your problem.

Cool. Thanks?

 

[CoggedBelt75]

I then jumped the battery, thinking maybe I had run it down on my brief test a few days before. Still the same. My guage reads about 10 volts...this is about where it has been normally on startup.
A resting battery should read 12.6 volts. 10 volts is not a good battery.

I noticed that there is an empty plug labeled "Ign" on the block that has no connection. Is this normal?
Mine is empty also.

The top of the carb smelled like gas. I know there was very little left in the tank when I shut it down, nearly empty.
There could be some gas making it to the carb, but running these old trucks low on fuel risks getting trash in the filter or carb also. Maybe a coincidence your fuel pump happens to be going out? Might throw a fuel pressure gauge on it. If nothing else, you’ll at least know it’s condition.

After work today, I'm going to start a bit more of a teardown, checking for fuel, spark, etc.
Without fuel, spark, and compression there will be no combustion. Like Mason said, visually look down inside the carb to see if there’s a good squirt of fuel while opening the throttle. Pull the coil wire from the distributor and check for a strong spark while cranking.

My question for now is - what should I be looking for that I potentially messed up with my wiring job? I have this weird feeling that I shorted out my ignition somehow. The fact that the truck was running like a top before the lights went on seems hardly coincidental.

Hard to answer the question not actually seeing what you did. Little things usually get left out describing what was actually done. But usually, after making a change and things aren’t what they use to be, then it’s most likely whatever was changed is the culprit. As for the distributor or coil, that can always be pulled and checked at the parts store.

If you do find the problem, keep your thread updated on the fix for future reference.

 

[Jerry phillion]

Squirt some gas in carb. If it don't try to start,
Pull a plug again and ck for a nice BLUE spark. If no spark, it
Might be an ignition module. Mine just quit one day as I was
driving it. It was the module. Update as cogged belt suggested.

 

[Tank6x2]

Well it’s either fuel or ignition, take Cap off clean it, check for wet plugs, do what’s been suggested, keep it simple. Don’t change more than one parameter before reverting it back to the way it was and changing something else. Check resistance of your plug wires with ohm meter, get some starting fluid give it a few squirts, turn it over, if it fires it’s a fuel issue, check the fuel pump for securement, leaks on the lines back to the tank flip valve, if it’s the flip valve(you may not have one)

 

[Hatchet54]

Thanks for the advice you guys. I was definitely beginning to panic yesterday.

This morning I did as was suggested and tested the fuel system. Turns out, it is definitely a fuel problem, not electrical. Apparently the gas I saw in the carb yesterday was left over from the death throes of the fuel pump when I was turning it over? Or maybe I was imagining it, because today, on closer inspection, it was dry.
I dumped a little gas in the top and she fired on the first try and ran great until it burned off. So there's that...

I will track down the problem this weekend further and update/consult this thread more with how things go. It'll be nice to actually have some time and try to figure this out.

 

[PrairieDrifter]

Throw some gas in the tank and try it, if it won’t prime try some gas or spray in the carb to keep it running to prime the pump, if that doesn’t work, spray some compressed air into the fuel tank while cranking the engine, this will push fuel through the lines to prime the pump.

Other than that my best guess is fuel pump. Would be a good idea to replace the rubber lines in the system as well, and install an inline fuel filter.

 

[climb-101]

cracked fuel lines will cause a problem. same goes for a bad fuel pump, plugged fuel filter, no fuel in the tank

 

[Hatchet54]

Got it!

Bad fuel pump was the culprit. Per the advice given here, I tested the fuel system better. Found that gas was only barely weeping from the top line when I pulled it off and cranked it. It was enough that I got fooled the previous day, but not nearly enough gas to run. Definitely explained a lot.
In town I picked up a new pump for $18. Got it installed in about an hour. A little gas poured in the carb to get her started, a little accelerator pedal to clear the sinuses, and she started breathing again. And MUCH better than before! Extremely noticeable improvement in throttle response and overall power. Wow.

Next time I'm in town I'll be getting some new rubber to replace all the lines with, a new filter for the q-jet (I had the wrong size on hand), and additionally a transparent in-line filter so I can see my fuel without taking things apart.

Things I learned from this thread:

1) Don't panic when you're not sure what the problem is. I ended up ripping out my entire wiring job for my lights under the assumption that I had done something wrong with it. I have to put it all in again now, when it was fine to begin with. So effectively doubling my work time for no reason whatsoever.

2) Be thorough with diagnosing. Even when you're pressed for time before work, etc. don't half-ass your diagnosis. I looked in the carb, smelled gas and saw wet spots, so I assumed everything was working. It wasn't until later after a more detailed breakdown that I realized my pump wasn't giving enough fuel. In the long run, I actually would have saved myself time if I'd just looked better in the first place. Instead, I dicked around with the ignition for a day when I didn't need to.

3) ALWAYS remember the basic mantra: Fuel, compression, spark. Fuel, compression spark...and check them. Really check them. LOL. Don't start looking for gremlins until you're sure that you have all three.

Thanks to everyone who gave me the good advice. Hopefully this embarrassing thread will help someone in the future who has a similar problem.

 

[PrairieDrifter]

Technically it’s fuel spark and air, but close enough lol.

Glad you got it figured out! Mechanical pumps are cheap and not a hard repair job. I just did two on the same vehicle in less than 24 hours.

Mine made some rattling noises but that’s all it gave me I thought it was valvetrain but I was driving one day everything all hunky dory and then I leave a stop sign and she bogged twice and crapped out, fuel pump was dead lol.