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Engine Cranks but will not start

T

taquito971

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Ridgecrest, CA
I've got a 79 GMC K3500 with a 350 and a SM465. I recently got this from my FIL who drove it for the last 20+ years hunting and everywhere else. It was a reliable vehicle for him. It was left sitting for the last two years or so, rarely driven, and I picked it up from there.

Right now my issue is that it cranks but does not start. I have been driving it for weeks without issue (sort of) but this morning it wouldn't start. This isn't necessarily a new issue though, when I got the truck a few months ago nearly every morning it would not start. Mind you this is CA mornings in the summer. Not 30deg mornings, we are talking 60 or 70deg mornings. By lunch time it would start without an issue. At that time I replaced the coil (which I'm not sure was actually bad) and the ignition module (which tested good at Autozone after I replaced it). Neither solved my problem entirely it seems, because today it's not starting.

When it is cranking I can smell fuel, and starting fluid/gas in the carb does not change anything. Pulling a spark plug wire and using the trusty method of sticking a screw driver in there and laying it on the intake shows no spark at all.

Fuel delivery is good, fuel pressure is good, compression is good, but no spark. I've got to be missing something.

Brian
 
Yeah that's what I'm thinkin, too. How bad is the dew inthe morning? It could be that you are getting condensation inside the dizzy in the morning, then by midday it has dried out enough to allow the truck to start. But I dont know much about distributors, so I might be way off on my diagnosis :dunno:
 
cabledawg said:
Yeah that's what I'm thinkin, too. How bad is the dew inthe morning? It could be that you are getting condensation inside the dizzy in the morning, then by midday it has dried out enough to allow the truck to start. But I dont know much about distributors, so I might be way off on my diagnosis :dunno:
Click to expand...
No dew here in the high desert. Humidity level now is 54% and it didn't start all day even when it reached nearly 100*. It sounds like a bad ignition module to me, but I replaced it not that long ago (Like 4-6 weeks ago). Some more digging through the old threads turned up that some ignition modules can fail after being used for a few days or weeks? Is there a brand I can get locally through napa/oreillys/autozone that is considered GTG? When I pulled the old one to replace it I had it tested at Autozone just for fun and it passed, so I'm not sure what to think on that.
 
Just in case someone is searching through the threads like I was and wants to know, I replaced the ignition module (again) and it fired right up. I guess the Autozone modules are complete junk...
 
I would suggest you replace the fuel pump as gas that goes bad will deteriorate the diaphram in the pump and eventually it will leave you stranded and scratching your head AGAIN.
 
I will keep that in mind. I suppose what kept me scratching my head was that this was a part I had already replaced. I'm not really used to buying a part and having it go bad in 3 weeks. Hopefully the Echlin branded stuff from NAPA is better. As for the fuel pump, I don't remember the numbers off the top of my head, but I do recall that it was well within spec when I was checking that for proper operation on the first go around.

How long does gas need to sit to go "bad"? I've heard of bad gas but I'm not sure this truck sat long enough for the gas to go bad. Maybe "sitting" to me means something different. I don't necessarily mean that it was parked in the corner and left for 2 years. I mean he didn't drive it more than a few hundred miles over the course of the last two years. Probably 10 miles a month.

Brian
 
Gas starts to go bad after about 6 months. If the truck never had much gas in it and was driven enough to have to keep adding fresh gas then I wouldn't suspect it to be an issue. If the vehicle had a full tank and was only driven a couple hundred miles in a year then the gas is almost definately bad (or was anyways).
 
Thanks, sounds like a possibility at the very least. The fuel pump appeared to be working fine but I will keep an eye on it.
 
A friend here just bought a car from a family friend, real cheap, they said it had been sitting for about 2 years, not started, anything. I ent to look at it, checked the fluids that were in it, put a battery on it and it fired right up. Smoked alittle from that nasty gas though.

Took it home, dumped about 10 gallons of fresh 91 octane fuel in it, with some fuel additive, replaced all filters, fluids, timing belt, cam seals, water pump, dropped oil pan to clean pick-up screen, new valve cover gaskets, intake gasket.. damn, forgot this was suppose to be a $300 car :doah:

anyways, just thought it odd that this thing started with 2 year old gas in it.

been driving it for a few months now, damn thing runs good now that everything has run through the system and been cleaned.
 
So, it's an old post, but it was mine so whatever. Anyway, I've got the same issue again. This morning it wouldn't start. I ended up pulling the distributor cap and rotor and instead of replacing the module I just tapped on it with the plastic end of my nut driver and decided I would try that. I put it back together and it fired right up. It started at lunch time 6 hours later and a few other times without incident.

As a side note, if I really get on it (it's a 1-ton with a 350, I tend to drive with my foot in it anyway) it will "hesitate" and lose power for a second or so. I have been blaming that on the ignition module as well. Any thoughts?
 
Yeah, keep your foot out of it, it's not a sports car, it's a big heavy truck... :D

anyways, i had that kind of thing happen to me with an old car with the same style dist cap, it wouldn't start, so i'd get out and just out of curiosity one day,i tapped the top of the cap, and it fired up. I don't remember what it was though that i replaxed to make it work :doah:
 
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