Anyone got any ideas? 78 g20 with stock 350. Runs great except that randomly, one of two things will happen. I'll come out to it and it won't start. Starter motor sounds fine. Has a new alternator and battery and belts. It just won't start. Then I'll come out to it 15 mins or an hour later and it'll start right up.

Then the really irritating one: when driving at low speeds, particularly when making tight low speed turns like a u turn, it will just cut off. Loss of power to the engine but not to the lights etc. Again, if I wait and keep trying to start it, it will start again just like normal. Sometimes 5 mins later, sometimes 20, sometimes 2 hours later.

The only thing I can figure is a loose wire somewhere. At some point someone put a security system in it which is not currently hooked up. Any ideas?

Battery cables & ground straps ...

In a points distributor, a bad condenser will cause a no start. I know GM had HEI long before 78. Not sure if there is one in there or not.

Check for spark when it's not starting.
Plus the basics, like frscke1 said.

I know on the later models, there is somd kind of funky failure in the column.
Good Wrenching Nomadgames!

I'll check. It doesn't lose power to the lights or dash or starter tho. Just to the engine.

There is a broken or corroded wire or connection somewhere .... it might look good outside but inside not so much. Start it up go under the hood & move some wires. Check the wiring at the starter.

It may be your fuse box ...

Get a multi meter start pokin around

Will do.

It could be your ing switch .... is the key on the column or dash ? The column has more chance of error than the dash type.

Get a spare coil. When it won't start, check for spark at the plug. if none, wiggle/retighten all wires associated with the coil. If still nothing, swap the coil. THe internal windings can do funny stuff.

Also check for corrosion any where there is a connector.

I’ve chased similar gremlins all over a vehicle only to figure out some moisture got into a group of connectors and corrosion gave it an intermittent problem. Clean the connections and apply dielectric grease.

Dash

To be clear, what happens is: lights turn on, starter works, dash works, battery has power, everything else Works. Starter motor cranks all happy, but engine won't turn over. Testing shows battery as charged, starter sounds like it should. Then randomly it will start as usual. It will work fine for a few days, then suddenly won't start right again.


When it happens when I'm driving, van will run as normal, then when driving at low speed, the engine and accessories (steering and brake booster) will die. Lights etc will still work.

Colin - definitely sounds like something in your spark system. Double check all the connections like everyone says but what I might suggest is putting an HEI set up in there. Gets rid of separate coil and condenser and is a hotter spark. Ive had these same issues in a motorcycle where the ignition system intermittently failed and cut outs but everything else worked fine. Ever since I put this in my van, it starts and runs reliably and is priced very well, only other thing you need is HEI spark plug wires.
Speedway HEI

Starter solenoid .... not the starter its self. .... but that wouldnt explain it cutting off while driving.

that was my initial thought until it cut out while driving. the weird thing is, all three times it cut out while driving, i was in the middle of a tight slow turn. makes me think it's in steering column, but that doesnt make sense with the rest of it.

well, i went and wiggled a bunch of wires and it started up again. BOOOO. i hate chasing electrical demons

Bare or damaged wire in the steering column? When turning the steering shaft is moving and possibly touching a wire in the column, causing a short.

yeah maybe. I need to be a little more methodical in my wire wiggling.


anyway, thanks guys. All the stuff you guys mentioned were the things I was planning on checking. Was mostly just wondering if there was something like the known issue with steering columns in the later models. Vintage vehicles....such a pain sometimes.

issue has been getting worse. Went from happening once, to once about every 3 weeks, to once a week, to once a day, and now it's several times a day. whatever component is failing is doing so in a hurry. Still doesn't happen when driving at speed, only randomly when starting or at very low speed. which makes me think it's something causing it to lose spark temporarily rather than a bad wiring connection.

I started digging into it today to try and figure it out and man, what a mess. original owner had a security system installed in the 80s. toggle switch, sensors on the hood and all the doors. So that wiring was all in there. Ripped that all out. wasn't tied into the ignition system anywhere, just to power. Extra dome lights put in with the conversion interior, direct to power. powered trailer hitch connection, that one was a mess, ripped it out. aftermarket A/C in addition to stock a/c. yes they both work. has a very 70's cup holder tray with lit columns built in to the stock dash, so that wiring is in there too. and a whole bunch more wires, all grey, that go to something that isn't even in there anymore. a stereo system maybe? oh, and an aftermarket cruise control that doesnt work and wasn't hooked up. ripped that out too. f**k. what a mess.

anyway, it's back down to almost stock wiring and the wiring harness actually looks pretty good and clean. battery connections are good. everything else looks good so far. turning steering wheel makes no difference. no wiggling of any wires makes a difference. as far as I can tell at this point it's totally random. I didn't test every single wire but it's not really looking like a wiring problem yet. The one thing I did notice is that the starter switch socket has one cut wire sticking out. it's exactly like this, including the yellow sleeves:



except that one of the wires is cut right next to the socket.

blah. what a fiasco. going to open up the doghouse and see what I can figure out about the coils and distributor next.

so, this guy gave me a very lengthy, very detailed, and very convincing argument that the problem is vapor lock at the fuel pump due to sediment. I've been treating it as such, and the behavior has been as he predicted. So for now, I'm going to test the spark to make sure (been too busy to open it up), and if it's not that, i'll throw a filter in the fuel line and see if that fixes it.


not that anyone cares, but hey, there's the update. ;)

well, now it's just dead. goofing around and poking and half assing my investigation is over. Gotta actually fix it. womp womp.

Pull the rotor cap, under there is a black box. That is your coil. Very cheep, like $10. Pull it, get another & install it. You can even get one for a dollar at the yard. If it fixes it get a new one.

I guess that rules out the vapor lock cause so. Try what frske1 mentions above, I have heard of coils breaking down like this. As regards whether anyone cares, you'll find they're a very caring bunch on here. Intermittent faults can be a PITA to fix and even harder to diagnose when your not in front of the machine.

Prezz, it's a 78. I think it's the GM HEI, but didn't they run a conventional coil on top of the intake? Or not. Lol. I may be incorrect after looking at the link.
I was a Plumber in 1978, and you know what they say...

Nomad, Type of coil? If its dead, does it have spark, or 12 volts at the coil with the key on? Power to the Ignition switch? Fuse block? Starter solenoid?

Fusible link? You need a factory service manual and a wiring diagram, or better yet, a GVan electrical manual.

We totally feel your pain. You are Totally on the right track. Good job Nomad! Good Hunting!

Sry I just saw G20 w/ 350 ...

The HEI setup in the link has the coil under the cap. My 327 was from a 69 Impala. I do remember it did not have a points distributor. So I do believe IDK for sure.

The Truth is out there....

Lol. Cheers!

Thanks guys. I haven't had a chance to look at it yet with thanksgiving and all that. I'll dig into it tomorrow. Gonna start with checking for spark and fuel pump failure and go from there. Ain't got nothing else to do tomorrow so hopefully can get it going. Fun part is my motorcycle has a bad crank bearing too, so both of my vehicles are sad. unfortunately I have to head back to NYC for a project for all of December. May end up buying a newer FI DD truck when I get back and moving the van into part time fun vehicle/project status.

Appreciate the help. Btw, the "no one cares" comment was more about poking fun at myself for putting my vehicle woes on the internet.

Well, I finally did some actual testing but still no idea what's going on.

Turned van on and pumped the gas pedal with the air filter off, could see it pumping gas into the carb just fine.

Checked for spark... no spark at all. Starter still cranking happy, battery showing a perfect charge. No spark. Distributor is HEI already. Power wire to distributor sending power fine. Coil showing 12 volts with key on. Took distributor apart to make sure connections were ok inside. Couldn't see anything wrong. Plugged every thing back in and put the distributor back together and suddenly it fires up first turn of the key. No f**king clue. I hate electrical gremlins like no other. I'm going to go drive it around but my assumption at this point is that it's going to do it again. I have no idea.

Well, knock on wood, but for whatever reason taking my distributor apart and putting it back together seems to have fixed the intermittent dead engine problem. Although now it's idling really high in park or neutral, and doing an old man sputter, cough, and die a few full revolutions after I turn the key to off. And the master cylinder is going going gone. Love driving a 39 yr old van as a DD. ;)

Good you already have an HEI. Make sure your vacuum advance hose to the distributor is still in good shape. No cracks, etc. Check to make sure that the small metal tab that contacts the cap inside is not loose or poorly adjusted, you obviously want a solid connection to all the plug wires. Confirm your timing is correct as well. A new master is not too expensive, you can easily bench bleed it prior to install. May be worth replacing the booster, I think I'm gonna be there soon myself.

I got a reman master for $25, i'm not worried about that part, have done plenty of brake work. will prob do the booster as well just because. I'm in NYC for a month for a project though, nothing's happening on it right now. It's also developing brake dive and shake pretty hard. I think after putting 10k miles on it in about 2.5 months, all the parts that might have needed replacement have accelerated to definitely needing replacement.

My 92 Chevy conversion was losing power but not electrical, it ended up being the coolant temperature sensor. They said it was telling the fuel pump to shut down due to faulty sensor readings. Replaced it & back to normal for the rest of the trip.